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Liquefaction assessment using microtremor measurement, conventional method and artificial neural network (Case study: Babol, Iran)
Abstract
Recent researchers have discovered microtremor applications for evaluating the liquefaction potential. Microtremor measurement is a fast, applicable and cost-effective method with extensive applications. In the present research the liquefaction potential has been reviewed by utilization of microtremor measurement results in Babol city. For this purpose microtremor measurements were performed at 60 measurement stations and the data were analyzed by suing Nakmaura’s method. By using the fundamental frequency and amplification factor, the value of vulnerability index (K
g
) was calculated and the liquefaction potential has been evaluated. To control the accuracy of this method, its output has been compared with the results of Seed and Idriss [1] method in 30 excavated boreholes within the study area. Also, the results obtained by the artificial neural network (ANN) were compared with microtremor measurement. Regarding the results of these three methods, it was concluded that the threshold value of liquefaction potential is K
g
= 5. On the basis of the analysis performed in this research it is concluded that microtremors have the capability of assessing the liquefaction potential with desirable accuracy.
... In addition, stiff deposits are dangerous for short structures and near-field earthquakes due to the amplification of ground motion. In other words, it can be stated that soil acts like a filter and changes the characteristics of ground motion during earthquake [22][23][24][25]. Density, age, thickness and other geotechnical properties of soil can alter the characteristics of seismic waves so that site effect can increase intensity up to 3 degrees in Mercalli scale [26][27][28][29][30][31][32]. ...
... This city is situated in a high seismic area due to its location in front of Alborz Mountain, which is tectonically an active region. The tectonic of Alborz Mountain is controlled by boundary conditions due to convergent motion between Arabia and Eurasia, which probably started in the Cretaceous [16,24]. The texture and thickness of deposits in Babol city are mainly affected by the sedimentation of Babolrood River and the coastal deposits of Caspian Sea. ...
... Characteristics of faults around the study area[24].February 958), Damavand-Shemiranat (27 March 1830), Ah-Mubarakabad (2 October 1930), Kusut (11 April 1935), Bandpay (2 July 1957), Babol Kenar (2 August 1971), Kojoor (28 May 2004), Marzi Kola (16 January 2012), Kiasar (21 March 2013), Surak (20 March 2017) and Juybar (23 September 2018). ...
Site effect is known as one of the important issues in geotechnical earthquake engineering. The site effect can change the characteristics of seismic waves and amplify the vibrations which results in the casualties and financial damages. Nonlinear method is an appropriate numerical method for site effect analysis due to its accuracy and its close results compared to the actual soil behavior. Thus, in this research, nonlinear analysis was applied for evaluation of site effect and for achievement of a suitable design spectrum in Babol city located in the north of Iran. For this purpose, first, seismic, geophysical and geotechnical data of Babol city were provided. Then, by modeling the subsurface conditions, the tripartite response spectra were found for different areas of Babol. According to the obtained results, the behaviors of tripartite response spectra are fundamentally different in some frequency ranges. In addition, the shape factors obtained from site analysis for different parts of Babol city were compared with the shape factor of the design spectrum presented by Iranian seismic code. This comparison indicated that the response spectrum obtained through analysis differs from the Iranian seismic code design spectrum. Finally, it can be concluded that the structures designed according to Iranian seismic code are neither safe nor economic in some areas. This issue shows the necessity for more serious consideration of site effect phenomenon in Iranian seismic code.
... The analysis of soil liquefaction can be conducted using different techniques such as standard penetration test (SPT) (Seed and Idriss, 1971;Tunusluoglu and Karaca, 2018), cone penetration test (CPT) (Robertson and Campanella, 1985;Moss et al., 2006;Papathanassiou et al., 2015), and shear wave velocity (V S ) (Andrus and Stokoe, 2000;Youd et al., 2001). Apart from these, ambient vibrations and artificial neural network techniques have begun to be used in liquefaction analysis in recent years (Huang and Tseng, 2002;Beroya et al., 2009;Rezaei and Choobbasti, 2014;Abbaszadeh Shahri, 2016). The primary purpose of this paper is analysing the liquefaction potential using geophysical data. ...
... With this method, the predominant frequency and amplification of the soil can be calculated and, then, soil classification can be carried out. Moreover, in recent years, many studies have been performed to assess the soil liquefaction potential using vulnerability index (Kg) calculated from microtremor data (Huang and Tseng, 2002;Beroya et al., 2009;Rezaei and Choobbasti, 2014). Mokhberi and Fard (2018) stated that the Kg value can be used as a parameter to evaluate the liquefaction potential of a soil. ...
... The use of the ANN method in different areas of Earth sciences has increased in recent years (Gelisli et al., 2015;Kilic and Eren, 2018). Moreover, many researchers have used the ANN method to evaluate liquefaction potential (Goh, 1996;Juang et al., 2003;Rezaei and Choobbasti, 2014;Abbaszadeh Shahri, 2016). ...
This study focuses on demonstrating how a holistic approach based on geophysical, geotechnical, and Artificial Neural Network (ANN) methods in a region where urban development is intense will crucially contribute to the assessment of liquefaction potential. The liquefaction potential of the coastal part of the Araklı district of Trabzon has been evaluated. First, earthquake scenarios for different magnitudes, which may affect the study area, were produced. Maximum acceleration values to use in liquefaction analysis were calculated from the scenarios. Second, geophysical
data were collected using seismic refraction, multichannel analysis of surface waves, electrical resistivity tomography, and ambient vibrations measures. In addition, results of standard penetration test were taken from the drillings in the region. The liquefaction potential using these data was also determined by ANN. The results show
that the studied area has a serious risk of liquefaction and the more reliable liquefaction estimates are performed in the study area with the holistic approach. The results of this study will be of great importance for taking necessary measures in constructing
engineering projects in the region, especially along the coastline.
... There are two general categories of ambient noise sources: natural sources (such as wind and collision of sea and ocean waves to the coast) and artificial sources (such as human activities, traffic and vibration of industrial vehicles) [11,12]. Today, various ambient noise measurements methods are utilized in many studies due to their simplicity, low cost, fast data collection operation and reliable results [3,[13][14][15][16][17][18][19]. ...
... Once finished with ambient noise measurements, the acquired data should be analyzed. For analysis of the data, the method presented by Nakamura [14] called H/V spectral ratio (HVNR) was implemented. The Nakamura method shows that using a single seismograph one could derive the transfer function of surface layer from the ground surface measurements [14,18,[21][22][23][24]. Numerous research and field investigations indicate that the spectral ratio obtained by this method can provide a reasonable estimate of the site fundamental frequency. ...
... For analysis of the data, the method presented by Nakamura [14] called H/V spectral ratio (HVNR) was implemented. The Nakamura method shows that using a single seismograph one could derive the transfer function of surface layer from the ground surface measurements [14,18,[21][22][23][24]. Numerous research and field investigations indicate that the spectral ratio obtained by this method can provide a reasonable estimate of the site fundamental frequency. ...
One major step in evaluating the site response is estimation of the shear wave velocity and fundamental frequency. Various methods are available for evaluating the site effect, of which the ambient noise measurement method is a prevalent one. The method is quick with low cost; it is nondestructive and gives precise results. In the present research, to assess the site response in Babol City, measurements of ambient noise were performed at 60 points and the data were analyzed by Nakamura method. Also, at 8 sites, measurements of the ambient noise were done by applying SPAC method and the data were analyzed to obtain the shear wave velocity. In addition, equivalent-linear method was performed using the shear wave velocity as well as geotechnical and geological data of those 8 sites. Furthermore, the artificial neural network (ANN), with different input data, was trained and then was utilized to predict the fundamental frequency. The fundamental frequencies acquired from ambient noise, ANN and equivalent-linear method were compared to each other to investigate reliability of the results. The results showed that most parts of the study area have a fundamental frequency less than 1 Hz, while higher frequencies could be observed in some northwestern and southern parts of the city. Finally, it is shown that, the ambient noise measurements were highly useful for evaluating the site effect and estimating important seismic parameters (fundamental frequency and shear wave velocity).
... Although some researchers conducted studies about soil liquefaction potential of Babol city [31,32], the obtained results were different because they applied only one method in their investigations. Therefore, in this paper, a focus is made on the most widely accepted methods utilized for estimating liquefaction. ...
... Andrus and Stokoe-based factor of safety curve is more conservative than factor of safety curves based on Idriss and Boulanger [33] and Moss et al. [35] methods. The obtained results in this study were compared with the results of Rezaei and Choobbasti [32] research. They studied Babol soil liquefaction potential using artificial neural networks (ANN). ...
... Figure 13. Liquefaction microzonation of Babol by artificial neural networks [32] Liquefaction microzonation of Babol city using Andrus and Stokoe [34] method ( Figure 10) and the average results ( Figure 12) have good compatibility with Figure 13. These results show that although the Cone Penetration Test (CPT) and Standard Penetration Test (SPT) are the two most widely used indices for evaluating the liquefaction characteristics of soils, the standard penetration number (N) and cone tip resistance (q c ) are not evaluated accurately and the test apparatus can be in error. ...
... Ambient seismic noise or micro-tremors are slight ground motions with displacement amplitudes of about 0.1 to 1 μm and period range of 0.1 of a second to 10s (Kanai and Tanaka 1961). Recently, to assess potential hazards associated with ground failure or liquefaction, the vulnerability index (or Kg value) that is derived from micro-tremor data may be evaluated and used as a key value (Akkaya 2020;Choobbasti et al. 2015;Khalqillah et al. 2019;Rezaei and Choobbasti 2014;Sunaryo 2017). ...
... In this way, it can be seen that the most liquefied points are those that are above the high vulnerability index Kg (in our case Kg=11.93), this method is used in several studies after Nakamura to evaluate liquefaction factors (Rezaei and Choobbasti 2014;Saita et al. 2012). We compute the strains of ground (γ) from the vulnerability index Kg by the following expression: ...
The purpose of this investigation is to compute the seismic vulnerability in the Rif area in order to estimate the occurrence susceptibility to liquefaction sites. In addition to that, evaluating the liquefaction potential is one of the most useful investigations for risk mitigation and seismic hazard zonation and assessment. The parameter of the seismic vulnerability can be quantified and expressed by Kg index which is derived from the well-known ambient noise horizontal-to-vertical spectral ratio (HVSR) method of Nakamura. In this paper, the depicted analysis involves 15 broadband stations extended across the Rif region. The HVSR method was conducted on the whole micro-tremor data of 2014. By extracting the fundamental frequency F0 and the amplification factor A0 from the micro-tremor data, the Kg index was calculated, and the liquefaction potential was evaluated. The lowest estimated Kg value was about 0.19 (34.97° N–3.32° W), while the highest value reached 11.93 (35.33° N–4.96° W) which refers to the station situated near the Bou-Ahmed river branch north Morocco. Accordingly, the low Kg values exhibit a dominance in the Rif area, which can be related to minor water content, thus unsaturated ground granules.
... However, the inability of traditional statistical methods to handle missing or noisy data, as well as to manage nonlinearities and to identify certain behavior patterns, opens up space to the use of innovative computer-based solutions. In the last couple of years, the use of Artificial Neural Networks (ANNs) is becoming increasingly popular in many civil engineering applications [4][5][6], namely in the field of earthquake engineering [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Traditionally, ANNs are used as "black boxes" to obtain a problem solution without a clear understanding about the mathematical relations between the inputs and the outputs, which are often considered as being a handicap for engineering purposes. ...
... However, the inability of traditional statistical methods to handle missing or noisy data, as well as to manage nonlinearities and to identify certain behavior patterns, opens up space to the use of innovative computer-based solutions. In the last couple of years, the use of Artificial Neural Networks (ANNs) is becoming increasingly popular in many civil engineering applications [4][5][6], namely in the field of earthquake engineering [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Traditionally, ANNs are used as "black boxes" to obtain a problem solution without a clear understanding about the mathematical relations between the inputs and the outputs, which are often considered as being a handicap for engineering purposes. ...
This paper discusses the adoption of Artificial Intelligence-based techniques to estimate seismic damage, not with the goal of replacing existing approaches, but as a mean to improve the precision of empirical methods. For such, damage data collected in the aftermath of the 1998 Azores earthquake (Portugal) is used to develop a comparative analysis between damage grades obtained resorting to a classic damage formulation and an innovative approach based on Artificial Neural Networks (ANNs). The analysis is carried out on the basis of a vulnerability index computed with a hybrid seismic vulnerability assessment methodology, which is subsequently used as input to both approaches. The results obtained are then compared with real post-earthquake damage observation and critically discussed taking into account the level of adjustment achieved by each approach. Finally, a computer routine that uses the ANN as an approximation function is developed and applied to derive a new vulnerability curve expression. In general terms, the ANN developed in this study allowed to obtain much better approximations than those achieved with the original vulnerability approach, which has revealed to be quite non-conservative. Similarly, the proposed vulnerability curve expression was found to provide a more accurate damage prediction than the traditional analytical expressions.
... A cada ventana se le hizo corrección de línea base y se transformó al dominio de la frecuencia empleando la transformada rápida de Fourier (FFT). Luego, se combinaron las componentes horizontales ( : horizontal Norte -Sur y : horizontal Este -Oeste) de cada ventana utilizando la media cuadrática (Ecuación 1) según lo recomendado por el proyecto SESAME (Bard & SESAME-Team, 2005) y Rezaei & Choobbasti (2014). Luego se realizó la relación espectral entre la combinación de componentes horizontales ( ) con su respectiva componente vertical ( ), obteniendo la función de transferencia HVSR ( ) de cada ventana (Ecuación 2). ...
... Sin embargo, los periodos predominantes identificados en la PTAP son superiores a 1 s, por lo que puede inferirse que la respuesta del suelo en esta zona está dominada por la profundidad del depósito de suelo y no por la rigidez de los estratos (Kramer, 1996). Esto es consistente con lo reportado en otros estudios de caracterización dinámica de llanuras aluviales (Hardesty, et al., 2010;Rezaei & Choobbasti, 2014;Sathyaseelan, et al., 2017). ...
Los depósitos de suelo de la llanura aluvial del río Cauca en Santiago de Cali (Colombia) presentan una estratigrafía conformada por una capa de arcilla superficial seguida de una capa de arena licuable. Sobre estos depósitos de suelos se encuentra ubicada la Planta de Tratamiento de Agua Potable Puerto Mallarino (PTAP Puerto Mallarino), la cual es una estructura de gran importancia para la ciudad puesto que abastece más del 50% del agua de la población. Según el Reglamento Colombiano de Construcción Sismorresistente (NSR-10), el perfil de suelo de la PTAP es de Tipo F, por lo que requiere, además de los estudios geotécnicos convencionales, de un análisis de amplificación de ondas sísmicas. De acuerdo con lo anterior y pensando en construcciones futuras dentro de la PTAP Puerto Mallarino, se realizó la caracterización dinámica de la zona mediante el análisis de vibraciones ambientales y registros sísmicos medidos en la zona y en un afloramiento rocoso cercano. Asimismo, se determinó el perfil de velocidad de onda cortante hasta 28 m de profundidad a través del ensayo Up-Hole. El análisis de las vibraciones ambientales muestra que el periodo predominante de la PTAP Puerto Mallarino se encuentra en un rango entre 1.4 y 1.7, s con factores de amplificación entre 3.5 y 5.2. En contraste, el análisis de registros sísmicos muestra que el periodo predominante se encuentra en un rango entre 1.6 y 2.2 s, con factores de amplificación entre 7.5 y 34.4. Las diferencias en estos resultados se atribuyen a los posibles efectos de la no linealidad del suelo durante la ocurrencia de los sismos. Finalmente, basado en los resultados del perfil de velocidad de onda cortante y los periodos predominantes, es posible concluir que los altos contrates de rigidez entre los estratos superficiales y la profundidad del depósito dificultan la identificación de sus propiedades dinámicas con vibraciones ambientales.
... Según Nakamura (2000) Kg (() es un valor correspondiente al sitio y es considerado como un índice de vulnerabilidad que puede ser de utilidad para encontrar puntos débiles en el suelo, mientras que es esperado que el coeficiente (() sea aproximadamente constante para una zona de trabajo relativamente amplia. Según lo hallado en la literatura, la susceptibilidad a licuación crece a medida que el valor de Kg aumenta (Rezaei & Choobbasti, 2014). ...
... Rango dinámico (a 1 Hz) >132 dB Factor de transducción 400 V/m/s Umbral de saturación ± 0.0125 m/s Cada paquete de registro se dividió en ventanas de 30 segundos traslapadas al 50%, obteniendo un total de 39 subregistros por paquete, a los que se le hizo corrección de línea base. Cada subregistro se transformó al dominio frecuencial utilizando la transformada rápida de Fourier (FFT), y luego se combinó sus componentes horizontales ( : horizontal Norte-Sur y : horizontal Este-Oeste) utilizando la media cuadrática (() según lo recomendado por el SESAME Project (2004) y Rezaei & Choobbasti (2014). Cada subregistro de componentes horizontales combinadas ( ), se relaciona con su respectivo sub-registro de la componente vertical ( ) ((), obteniendo una función de transferencia aproximada ( ) (Figura 5.a), que se promedia con sus correspondientes en cada punto de muestreo (Figura 5.b). ...
RESUMEN
La licuación cíclica es un fenómeno en el cual depósitos de suelo conformados por arenas poco consolidadas y saturadas, pierden su resistencia al esfuerzo cortante debido a la acción de cargas dinámicas como sismos, ocasionando en el peor de los escenarios el colapso de las estructuras que soporta. En Colombia hay municipios que están expuestos a la ocurrencia de este fenómeno, como en Santiago de Cali, donde la zona oriental de la ciudad se encuentra urbanizada sobre depósitos aluviales del Río Cauca. En la actualidad, el potencial de licuación se evalúa en campo a través de: I) ensayo de penetración estándar (SPT), II) el ensayo de penetración de cono (CPT) y III) ensayos geofísicos, los cuales tienen un alto costo monetario y/o pueden ser difíciles de ejecutar en lugares densamente urbanizados. Debido a esto se plantea en este trabajo aplicar la técnica desarrollada por Nakamura en 1997, la cual consiste en determinar a través de la relación espectral H/V, el Índice de Vulnerabilidad Kg-parámetro que cuantifica el daño probable producido debido a eventos sísmicos, y en el caso de depósitos de arenas, puede correlacionarse a su potencial de licuación. El presente artículo hace parte de los recientes aportes que buscan validar esta metodología, a través del análisis compa-rativo de los resultados obtenidos entre el método propuesto por Nakamura y los métodos convencionales de campo, aplicados en la evaluación del potencial de licuación de los suelos del oriente de Cali. Palabras clave: Licuación de suelos, índice de vulnerabilidad, vibración ambiental, relación espectral H/V.
ABSTRACT
Liquefaction is a phenomenon in which soil deposits formed by poorly consolidated and saturated sands lose their shear resistance due to the action of dynamic loads like earthquakes, causing in worst scene the collapse of structures that supports. In Colombia there are municipalities that are exposed to the occurrence of this phenomenon, as in Santiago de Cali, where the eastern part of the city is urbanized above alluvial deposits of Cauca river. At present, liquefaction potential is evaluated in field through: I) Standard Penetration Test (SPT), II) Cone Penetration Test (CPT) and III) geophysical tests, which have a high monetary cost or can be difficult to execute in densely urbanized places. Due this it's proposed in this paper to apply the technique developed by Nakamura in 1997, which consists in determining through the H/V spectral relation, the Vulnerability Index Kg-parameter that quantifies the probable damage produced due to seismic events, and in the case of sand deposits, can be correlated to its liquefaction potential. The present article is part of the recent contributions that seek to validate this methodology, through the comparative analysis of the results obtained between the method proposed by Nakamura and the conventional field methods, applied in the evaluation of the soil liquefaction potential of the east of Cali.
... Ambient noise is a low-frequency ground vibration generated due to geological background, river, wind, traffic, and human activities. These ambient noises have very low displacement amplitude (0.1 µ) and velocity amplitude (0.001 to 0.01 cm/s; Rezaei and Choobbasti 2014). The method of ambient noise measurements is cost-effective and convenient with the advantage of its accuracy and flexibility to be employed in areas where getting geological data is very difficult and expensive. ...
The Soldha slide zones have been evaluated using ambient noise measurements from 30 sites to obtain predominant frequency, HVSR amplification factor, and azimuthal site response. The result shows that the resonance frequency ranges from 1.66 to 19.97 Hz, and the amplification factor ranges from 3 to 5, indicating the presence of thick debris deposits in the centre of the slide zone. Moreover, the directional response analysis shows that the site directional response was parallel to the landslide movement indicating that the site directional response followed the landslide direction and the slide zone is multidirectional in nature. Further, the geometry of the slip surface has been derived using shear wave velocity (Vs) analysis which reveals that the slide was rotational. The 1-D Vs profile indicated variation from 140 to > 320 m/s at depth. The slope angle varied from 60° near the second detachment zone to 78° near the first detachment zone and 26° near the toe. Grain size analysis showed that the soil is sandy with large pore spaces but the fine size samples (sieve size < 0.42 mm) have a cohesion of 74 kPa and an internal frictional angle (19.36°) indicating that the fine size of soil samples decreases the pore space at depth and increases the water-holding capacity and volumetric expansion at the subsurface, thus increasing the pore water pressure and reducing the cohesion, and finally leading to slope failure. The study signifies that ambient noise measurements are an effective technique for estimating slip geometry and soil dynamic behaviour.
... and Farakhak Pishro companies ( Fig. 2a and b). The soils in the north of Iran are known to be susceptible to liquefaction (Rezaei & Choobbasti, 2014;Taghavinezhad et al., 2021). The site investigation activities for this study were conducted in the Rudbar and Amirabad port areas. ...
In this study, a new web-based platform was developed for fast estimation of soil liquefaction potential (SLP). The geotechnical results from 47 boreholes in the north of Iran were collected over three years to create an estimator model. The dataset included information on SPT, soil type, strength parameters, and water content. Python libraries Pycaret and Gradio were used to develop the model for SLP. A set of pipeline codes were applied to base classifiers, including 13 different machine learning models such as the Ada boost classifier ( ad ), decision tree classifier ( dt ), gradient boosting classifier ( gb ), the k-neighbors classifier ( knn ), light gradient boosting machine ( lightgbm ) and random forest classifier ( rf ). The results show that the lightgbm model outperformed the other applied machine learning classifiers with accuracy = 0.946, AUC = 0.982, and F1-score = 0.9. The proposed model was then used as the primary element of the web-based application, providing a helpful tool for geotechnical engineers to determine SLP.
... Liquefaction usually occurs due to changes in soil conditions. It begins from a drained condition in the soil to an undrained condition, so that the pore pressure increases and is greater than the effective soil stress (Rezaei and Choobbasti 2014) . ...
An earthquake can trigger other disasters. Liquefaction is one of them and it occurs due to the reduction or loss of effective stress in soil due to cyclic loads. Liquefaction may cause the ground to act as a flowing liquid and become harmful to the building above it. Damage to a building’s structure can occur because of the strong surface waves from soil thrust and flow. Thus, an evaluation of the liquefaction potential is needed to prevent building damage. This study aims to determine the vulnerability of Padang City to liquefaction disasters and proposes a liquefaction potential based on the natural frequency at the surface. The study was conducted by analysing soil investigation data (54 CPT and SPT), using earthquake acceleration to obtain the value of the safety factor (SF), and single microtremor observations, to determine the natural frequency of the soil at these points. The results show that the form of liquefaction potential in Padang City varies depending on the depth of the reviewed soil. At a depth of 1 m, almost the entire research area has liquefaction potential. The coastal area has a very high level of vulnerability. In general, the liquefaction potential decreases with increasing depth. The liquefaction potential and the natural frequency of the soil ( f 0 ) are related; soil with an f 0 value of more than 0.432 Hz does not have a liquefaction potential.
... ANN was also used to predict soil liquefaction in a number of studies (Erzin and Ecemis, 2015;Hanna et al., 2007;Jirdehi et al., 2014;Tang et al., 2018;Venkatesh et al., 2013;Yang et al., 2020). Depth of the water table, standard penetration test (SPT) value and cone penetration test (CPT) value were taken as inputs (Hu et al., 2015;Kumar et al., 2012;Rezaei and Choobbasti, 2014). A small number of studies used SVM as well (Hoang and Bui, 2018;Kaveh et al., 2018). ...
Geotechnical engineering deals with soils and rocks and their use in engineering constructions. By their nature, soils and rocks exhibit complex behaviours and a high level of uncertainty in material modelling. Artificial intelligence (AI) methods have been developed and used by an increasing number of researchers in the field of geotechnical engineering in the last three decades. These methods have been considered due to their ability to predict complex nonlinear relationships. Based on more than one thousand (i.e. 1235) published literatures, this paper presents a detailed review of the performance of AI methods and algorithms used in geotechnical engineering. Nine key areas where the application of AI methods is prominent were identified: frozen soils and soil thermal properties, rock mechanics, subgrade soil and pavements, landslide and soil liquefaction, slope stability, shallow and piles foundations, tunnelling and tunnel boring machine, dams, and unsaturated soils. Artificial Neural Network (ANN) emerged as the most widely used and preferred AI method with 52% of studies relying on it. Other methods that were used to a lesser extent were FIS, ANFIS, SVM, LSTM, CNN, ResNet and GAN. The analysis shows that the success and accuracy of AI applications depends on the number and type of datasets and selection of input parameters. The paper also provides statistical information on research incorporating AI methods and discusses the opportunities and challenges for future research and practical applications in geotechnical engineering.
... Geophysical surveys as rapid, inexpensive, and nondestructive tools allow to obtain valuable information about the subsoil structure in the form of vertical and horizontal variations of physical parameters, which can be used to determine the depth of the rupture surface and its geometry, as well as the thickness of the landslide body (Jongmans et al. 2009;Rezaei and Choobbasti 2014;Rezaei and Choobbasti 2017). However, contrary to the borehole and inclinometric surveys, which constitute so far the most reliable method for the detection of a landslide's slip surface, geophysical in situ analysis can only be accurately used in cases where a clear geophysical contrast exists between the landslide body and the underlying nondisplaced layers (Jongmans et al. 2009;Pilz et al. 2014). ...
During many decades, the town of Moulay Yacoub underwent an important urban expansion to meet the high demand on housing fuelled by tourism activities, which constitute the backbone of the town’s economy. Unfortunately, the majority of buildings, both private and public, suffer from varying levels of damage related to the lithological, climate, and geomorphic settings of the area. In fact, the town is built on a marly hill prone to various types of mass movements, ranging from shallow soil creep to large slides. In addition, vertical displacement related to swelling/shrinkage behaviour of these Miocene marls is widespread in the area. The present paper presents a multi-disciplinary approach to investigate the activity and the interaction between slow-moving urban landslides and expansive soils within the urban perimeter of Moulay Yacoub. In fact, the severe seasonal contrast characterised by intense rainfall over short periods constitutes the main triggering factor of the instability phenomena in the region. Moreover, the desiccation cracks affecting marly soils are indicators of their expansive behaviour, which is very obvious in geotechnical tests results. The other geotechnical parameters obtained from laboratory tests show that the shallow marl samples are severely weathered compared with those of the compact material extracted at greater depth. The borehole data and seismic noise survey allows the detection of several impedance contrasts corresponding to the weathered layer – bedrock boundary, which in some cases corresponds to the rupture surface of the inventoried landslides. The very slow but perennial activity of the later processes is well documented by the inclinometers, the PS-InSAR monitoring, and building damage assessment surveys. Indeed, this case study highlights the complementarity of techniques used in this multi-disciplinary approach that give a multi-faceted understanding of slope instability processes and should provide a blueprint for future site-specific studies in the region.
... After Nakamura, some scientists have used microtremor to liquefaction evaluation [7][8]. ...
According to historical documents and Moroccan earthquakes catalogs, the coastal zone has suffered in the past from several earthquakes. Understanding how sedimentary basins respond to seismic-wave energy generated by earthquake events is a significant concern for seismic-hazard estimation and risk analysis. The main goal of this study is to determine the distribution of the natural frequency value (F), the amplification factor value (A), and the soil vulnerability index (Kg) were carried out as an indicator for liquefaction potential sites in the Martil city based on the microtremor measurements. Liquefaction assessment was done at 96 stations using the HVSR approach provided by Nakamura (1989). According to the analysis results, the predominant frequency values range from about 0.31 to 5.63 Hz, and the amplification factor values range from 3 to 15. Based on these parameters, the vulnerability index Kg is determined, which can be used as a parameter in calculating the liquefaction potential of an area. This study shows supporting evidence for the first time that the HVSR of microtremors can be an excellent alternative indicator for an area's potential for liquefaction.
... Nakamura and Takizawa [17] found, from experimental studies using HVSR, that the surface manifestations of liquefaction in the San Francisco Bay (USA) during the Loma Prieta Earthquake (1989), was correlated to the amplification factor (A g ) corresponding to the fundamental frequency obtained by HVSR. Similar results were reported for other locations such as Yuan-Lin (Taiwan) [18], Babol (Iran) [19], Nuevo Madrid (USA) [20], and Doon Valley (India) [21], where a match between A g and liquefaction susceptibility of soils was found. ...
Nakamura and Takizawa (1990) proposed a shear strain model from experimental studies using the horizontal-to-vertical spectral ratio (HVSR) in potentially liquefiable sites. This model allows estimating the maximum surface layer shear strain during an earthquake. In this paper, the model's experimental verification is performed by analyzing more than 130 earthquakes in two monitoring centers with potentially liquefiable soils. It is concluded that the model may be used to estimate the maximum soil shear strain for earthquakes with peak ground acceleration greater than 5 cm/s2 and when the soil deposit has a soft surface layer over a rigid layer. A methodology to identify potentially liquefiable sites based on this model was proposed and tested in an alluvial soil deposit in Santiago de Cali (Colombia). The results are compared with those obtained from the liquefaction assessment using CPT and Vs, and a good match between the methodologies is observed.
... In addition, engineers can decide about the types of new structures that are most appropriate to be constructed in a specific region using liquefaction map. [44]. In their study, Babol soil liquefaction potential was evaluated using artificial neural networks (ANN). ...
During earthquakes, ground failure is commonly caused by liquefaction. Thus, assessment of soil liquefaction potential in earthquake-prone regions is a crucial step towards reducing earthquake hazard. Since Babol city in Iran country is located in a high seismic area, estimation of soil liquefaction potential is of great importance in this city. For this purpose, in the present research, using field-based methods and geotechnical data (such as unit weight of soil, relative density, SPT number, shear wave velocity and cone tip resistance) of 60 available boreholes in Babol, three liquefaction maps were provided. Finally, one comprehensive liquefaction map was presented for soil of Babol city. The obtained results in this paper are well in line with the previous investigations. Based on the results, the factor of safety in 45% of the study area is less than one (liquefaction occurrence). In addition, the results indicate that since each field-based method requires particular data, applying various field tests is necessary for a more accurate liquefaction assessment.
... Recently, the practicability of using ANN in geotechnical construction has been confirmed [37,38], particularly in nonlinear situations that are similar to the liquefaction phenomenon. ...
Lateral displacement due to liquefaction (DH) is the most destructive effect of earthquakes in saturated loose or semi-loose sandy soil. Among all earthquake parameters, the standardized cumulative absolute velocity (CAV5) exhibits the largest correlation with increasing pore water pressure and liquefaction. Furthermore, the complex effect of fine content (FC) at different values has been studied and demonstrated. Nevertheless, these two contexts have not been entered into empirical and semi-empirical models to predict DH This study bridges this gap by adding CAV5 to the data set and developing two artificial neural network (ANN) models. The first model is based on the entire range of the parameters, whereas the second model is based on the samples with FC values that are less than the 28% critical value. The results demonstrate the higher accuracy of the second model that is developed even with less data. Additionally, according to the uncertainties in the geotechnical and earthquake parameters, sensitivity analysis was performed via Monte Carlo simulation (MCS) using the second developed ANN model that exhibited higher accuracy. The results demonstrated the significant influence of the uncertainties of earthquake parameters on predicting DH.
... Popular geophysical methods include seismic refraction, seismic reflection, multichannel analysis of surface waves (MASW), electrical resistivity and ground penetrating radar etc. These techniques are rapid, cost effective and, nondestructive [2][3][4]. Among these methods, electrical resistivity test (ERT) is emerging as an attractive technique for subsurface characterization [5]. ...
The paper develops the resistivity correlations with standard penetration test (SPT)-N and shear wave velocity (Vs) for the soil in Patna region in India. As part of the investigation, 16 numbers of each SPTs and electrical resistivity tests (ERTs) were conducted in the study area of 500 acres. The field tests were conducted up to a depth of 20 m, uniformly spanning across the study area. During the SPT, soil samples were collected at selected depths for the laboratory investigation. ERTs were performed using the Schlumberger array. Field test results were used to develop the correlation between resistivity and SPT-N. Previously available shear wave velocity data of the area were used for the developing the correlation between resistivity and shear wave velocity. The results revealed the existence of a strong linear correlation between resistivity and SPT-N. A relatively weak linear correlation was observed between resistivity and shear wave velocity. Further, the resistivity correlations were extended to corrected SPT-N and moisture content for the given soil. In overall, the developed correlations are useful for the quick determination of the soil design parameters solely performing electrical resistivity tests, saving the time and effort required by conventional tests.
... Using the microtremor method, soil amplification and dominant vibration frequency can be determined and then soil classification can be done using this data. In recent years, evaluation of soil liquefaction potential has been made using data obtained from microtremor measurements (Huang and Tseng, 2002;Beroyaet.al.2009;Rezaei and Choobbasti, 2014;Choobbasti et.al.2015;Fergany and Omar, 2017). For this purpose, the soil liquefaction potential was assessed using the microtremor records taken in the Araklı, Trabzon. ...
Determination of the characteristics of the soils on which constructions will be built before earthquakes or similar disasters are among the most important topics of geotechnical engineering. One of the most important soil problems that cause damage to buildings during an earthquake is liquefaction. Liquefaction is a usually viscous liquid behavior instead of solid losing the strength of saturated sandy soils under dynamic loads such as earthquakes. In recent years, researchers have begun to use the microtremor method, which is one of the fast, easy to apply and low cost geophysical methods, especially in large scale studies. In this study, the liquefaction potential in Araklı district of Trabzon province was evaluated by using microtremor measurement results. For this purpose, measurements were taken at 14 points by single station microtremor method and data were analyzed using Nakamura method. Vulnerability index (Kg) values were calculated by using the amplitudes of the H/V ratio and the dominant frequency values and the liquefaction potential of the study area was evaluated by considering the threshold values given by Nakamura (1997). As a result, it has been determined that there is a high risk of liquefaction in a significant part of the study area according to the calculated Kg values.
... Due to the serious noise interference in an urban environment, it is hard to carry out geophysical exploration by using active-source seismic methods. On the contrary, the microtremor survey method can overcome these restrictions by taking advantage of the high level of ambient noise, which has gained wide applications such as in mapping deeply buried geothermal faults (Xu et al. 2012;Tian et al. 2016Tian et al. , 2017, investigating the strata structure of landslides (Du et al. 2018), seismic microzonation (Bonnefoy-Claudet et al. 2009) and liquefaction evaluation (Rezaei & Choobbasti 2014). ...
To explore and utilize the urban underground space, it is important for us to accurately obtain information on the near surface structures. Microtremor signals play a vital role in that they carry abundant information about the subsurface structure and can be easily observed under disturbance of human activities in urban areas. We collected microtremor signals at 24 sites along a survey line in central Jinan city, obtained the dispersion curves by using the Extended Spatial Autocorrelation method and the resonance frequencies by using the horizontal-to-vertical spectral ratio method, and inverted the near surface structures by using the forking genetic algorithm. The lateral variation of the soil–rock interface was delineated at a maximum depth of 33 m and a large fracture zone was determined at a width of approximately 300 m. The frequency peaks changed from 2.5 to 7.3 Hz for the fracture and stable zones. A frequency-dependent model of the sediment thickness was obtained as $h = 101{f_r}^{ - 1.13}$, where h is the depth with a unit of m and fr is the resonance frequency. These results may be useful for understanding near surface structures and then benefit exploration of urban underground space.
... Nowadays, such methods as ambient noise measurement and electrical resistivity tomography (ERT) are widely applied in a landslide area. Geophysical methods are mostly inexpensive, fast, and non-destructive (Choobbasti et al. 2013, Rezaei and Choobbasti 2014, Rezaei and Choobbasti 2017b. Furthermore, one can examine a larger area of a landslide using geophysical investigations. ...
Today, geotechnical and geophysical techniques are used for landslide evaluation. Geotechnical methods provide accurate data, but are time consuming and costly. Geophysical techniques, however, are fast and inexpensive, yet their accuracy is lower than that of the geotechnical methods. Therefore, simultaneous use of geotechnical and geophysical methods provides a suitable solution for landslide evaluation. Availability of geotechnical and geophysical data makes it possible to investigate correlation between different parameters. Correlating geotechnical and geophysical parameters ends up lowering field investigation costs and enhancing subsurface survey speed in a landslide zone. In the present study, in order to evaluate Nargeschal landslide in Iran, ambient noise measurement, ERT survey, and geotechnical investigations were used. Once finished with data processing, the data obtained from geotechnical and geophysical investigations were correlated. These included SPT-N – electrical resistivity, soil moisture content – electrical resistivity, and SPT-N – shear wave velocity correlations. The correlations were examined using two methods, namely Spearman’s coefficient test and least square regression analysis. The results obtained from the two methods were in good agreement with one another. The correlations obtained in this study were of moderate to very strong strength and fell in the range of the results of previous studies. Investigation of the results indicated significant influences of ground water on electrical resistivity and soil stiffness on shear wave velocity. Results of this study can be used for soil classification and determination of mechanical and seismic characteristics of soil across various areas.
... In recent decades, geophysical methods have been widely used in landslide investigations. These methods are applied to determine the thickness of alluvial deposits, shear wave velocity, fundamental frequency, depth of bedrock, groundwater level, slip surface, etc. in landslide areas (Choobbasti et al. 2013;Rezaei and Choobbasti 2014;Akpan et al. 2015;Rezaei et al. 2015;Fressard et al. 2016;Rezaei and Choobbasti 2017a;Rezaei and Choobbasti 2017b;Rezaei et al. 2018). Geophysical methods are fast, low cost, and nondestructive compared to geotechnical methods and they can investigate vast areas; hence, general interest in these methods is increasing (Oh and Sun 2008;Sudha et al. 2009;Siddiqui and Osman 2013;Devi et al. 2017). ...
Landslides are natural hazards that cause severe casualties and financial losses. There are various methods used to analyze landslides; among these, geotechnical and geophysical methods are widely used due to their accuracy and low cost, respectively. In this study, 2D electrical resistivity tomography (ERT) surveys, geotechnical, and field data are used to define the subsurface structure and the geometry of the Nargeschal landslide. To determine the most appropriate array, ERT measurements were performed by Wenner-alpha (Wa), Wenner-Schlumberger (WS), and dipole-dipole (DD) arrays. Furthermore, the relationship between electrical resistivity with change in the degree of saturation and landslide hydrology was investigated by completing multiple surveys at the same location, at different times. Landslide 3D geometry and hydrology were identified by ERT results. Moreover, geotechnical data was used to investigate the Nargeschal landslide and to interpret the ERT pseudo sections. The data from boreholes were used to constrain the depth and consequently the resistivity range that characterize the basal slip surface of the landslide in the ERT pseudo sections. The results of geotechnical investigations indicated that the landslide material had moisture content very close to the plastic limit, with a higher clay fraction and low shear strength at the slip surface. Finally, it must be noted that the simultaneous use of the ERT survey, geotechnical methods, and field investigations led to a complete and accurate characterization of the Nargeschal landslide.
... For personal use only; all rights reserved.recommended by the SESAME project(Bard & SESAME-Team, 2004;Albarello & Lunedei, 2013;Rezaei & Choobbasti, 2014). The spectral ratio between the combined horizontal component ( f H ) and the vertical component ( ...
Cyclic liquefaction is a phenomenon in which soil deposits formed by loose and saturated sands, lose their shear resistance due to dynamic loads, as earthquakes, sometimes causing the collapse of structures. This phenomenon is a hazard in different cities of the world, as is the case of Santiago de Cali (Colombia), a city that has large alluvial deposits due to its seven rivers. Currently, the liquefaction potential is evaluated by field tests that can be expensive and difficult to perform in densely urbanized areas. Due to this drawbacks, this paper proposes a simple and versatile methodology to evaluate the liquefaction potential in large areas based on the vulnerability index (Kg) proposed by Nakamura in 1997 (hereinafter Nakamura Methodology). This methodology consists of calculating the vulnerability index using the fundamental frequency (Fg) and amplification factor (Ag) determined using HVSR method. The Kg index quantifies the probable damage in the soil produced by earthquakes, and for sand deposits, Kg can be correlated with liquefaction potential. For this research, the liquefaction potential was evaluated using Nakamura methodology in 34 points of Santiago de Cali, within an approximate area of 12 km². The results were compared with those of SPT and CPT tests performed in the same area. The methodology showed a match of up to 82% compared to conventional methods. In conclusion, Nakamura methodology is a viable alternative for liquefaction hazard mapping of large areas and could be very useful in places where there are limited funds or the conditions for more robust testing are not available.
... The horizontal components (í µí°» í µí±í µí± y í µí°» í µí°¸í µí± ) were combined using the quadratic mean (Eq. 8) as recommended by the SESAME project (Bard & SESAME-Team, 2004;Albarello & Lunedei, 2013;Rezaei & Choobbasti, 2014). The spectral ratio between the combined horizontal component (í µí°» í µí± ) and the vertical component (í µí± í µí± ) was then performed to obtain an approximate transfer function (í µí±) (Eq. ...
Cyclic liquefaction is a phenomenon in which soil deposits formed by loose and saturated sands, lose their shear resistance due to dynamic loads, as earthquakes, sometimes causing the collapse of structures. This phenomenon is a hazard in different cities of the world, as is the case of Santiago de Cali (Colombia), a city that has large alluvial deposits due to its seven rivers. Currently, the liquefaction potential is evaluated by field tests that can be expensive and difficult to perform in densely urbanized areas. Due to this drawbacks, this paper proposes a simple and versatile methodology to evaluate the liquefaction potential in large areas based on the Vulnerability Index (í µí°¾ í µí±) proposed by Nakamura in 1997 (hereinafter Nakamura Methodology). This methodology consists of calculating the vulnerability index using the fundamental frequency (í µí°¹ í µí±) and amplification factor (í µí°´íµí°´í µí±) determined using HVSR method. The í µí°¾ í µí± index quantifies the probable damage in the soil produced by earthquakes, and for sand deposits, í µí°¾ í µí± can be correlated with liquefaction potential. For this research, the liquefaction potential was evaluated using Nakamura methodology in 34 points of Santiago de Cali, within an approximate area of 12 km 2. The results were compared with those of SPT and CPT tests performed in the same area. The methodology showed a match of up to 82% compared to conventional methods. In conclusion, Nakamura methodology is a viable alternative for liquefaction hazard mapping of large areas and could be very useful in places where there are limited funds or the conditions for more robust testing are not available.
... Duman et al. (2014) published an article about the estimation of the soil liquefaction potential index using SPT data in the Erzincan, Turkey. Rezaei and Choobbasti (2014) This paper will present to estimate potential of liquefaction related to SPT values and laboratory results for the military residential area in Marmara region (TURKEY). The potential of liquefaction was calculated by using Matlab software with the Seed-Idriss method. ...
Istanbul is the most populous and biggest city in Turkey. Its construction plans increase
day by day. Large earthquakes of high magnitudes occurred along the North Anatolian Fault
(NAF) in this city. İstanbul has seperated two parts as Europe and Asia, includes various types of
rocks and soils. This study aimed at determining liquefaction analyses at the North Turkish Naval
Forces site (Kasımpaşa, İstanbul) in İstanbul province. Military buildings were damaged by the
Gölcük earthquake 7.4 magnitude in 1999. In-situ tests were done at opened boreholes and
laboratory experiments were carried out by taking samples for this purpose. The liquefaction
hazard of soils in Kasımpaşa district of Istanbul was investigated by Cyclic Stress Resistance
approach. Matlab software was written by using the Seed-Idriss method for liquefaction analysis.
The input parameters such as Standart Penetration Test-N (SPT-N) values taken from various
depths, fine contents (FC), ground water levels (GWL) and liquid limits were used for all layers
within 5.0 m from the surface. The magnitude and acceleration values of a scenario earthquake in
the analysis for İstanbul were selected 7.5 (magnitude) and 0.4g, 0.5g (accelerations). Calculated
the Cyclic Stress Ratio (CSR) and the Cyclic Resistance Ratio (CRR) were presented. The safety
factor against liquefaction was also estimated. Geographic Information Systems (GIS) maps of
groundwater level and liquefaction potential were established with the help of the necessary data
parameters on survey area. The presences of liquefiable regions were determined by the results
obtained. The results in this region are important for human security on the construction site.
The seismic vulnerability index (Kg) is based on soil dynamic properties. To create a seismic vulnerability index map, horizontal-to-vertical spectral ratio (HVSR) microtremor measurements were taken at over 260 locations throughout the Makkah Al-Mukarramah urban region. The fundamental resonance frequency and accompanying maximum relative amplification maps have been developed based on the H/V results. According to these maps, portions of the wadis in Makkah have fundamental resonance frequencies ranging from 0.26 and 17.27 Hz and may amplify bedrock ground motion by up to 14 times with the estimated amplification factor of 0.87 to 14.68 for the studied sites. The vulnerability index reveals the structural damage before destructive earthquakes. The values of the vulnerability index range from 0.13 to 284, with a high value of vulnerability indicating that the area in this value is located on the thickest layer of soft soil, posing the greatest risk. In the Al-Sharai’a, Ar Rashidiyyah, Al Khadra, AN Nassem, Al Shoqiah, and AZ Zahir districts, in the An nuzah, Batha Quraish, and Umm Al Qura University districts, a moderate result of the vulnerability index indicates that the location is located in stiff soil, which poses a moderate risk. The Makkah Al-Mukarramah municipality’s civil engineers and urban designers will benefit from these findings. In addition, these results can be used to improve the Saudi Building Code.
The purpose of this study is to investigate soil liquefaction in Jizan city using the horizontal-to-vertical spectral ratio (HVSR) microtremor measurements which were taken at 140 locations across the city. In Jizan, evaluating liquefaction probability is critical for land use planning. Jizan ground surface is made up of soft sand to silty clay deposits, and the groundwater level is less than 2 m deep. Moreover, Jizan is located in an earthquake-prone area of the southern Red Sea earthquake-active zone and has been impacted by earthquakes throughout history. As a result, earthquakes with magnitudes greater than 5 on the Richter scale can cause liquefaction in these soils. The fundamental frequency (f0) and accompanying amplification factor (A0) of this data were calculated utilizing international software. The vulnerability index, Kg, and ground shear strain γ were used to assess the likelihood of soil liquefaction. The peak frequencies of HVSR range from 0.25 to 3.3 Hz, with corresponding peak amplitudes ranging from 1.0 to 17.75. While Kg and γ range from 2.46 to 655.72 and 0.75 × 10−4 to 2.56 × 10−4, respectively. The findings imply that the city of Jizan’s near-surface saturated sediments (down to a depth of 10 m) are very susceptible to liquefaction, particularly in the city’s northern urban extensions along the coastal plain. These results should be considered by policymakers in Jizan Municipality to mitigate the liquefaction hazardous impacts on the important facilities and infrastructures in the Jizan city.
We present a novel approach to mapping the storage coefficient (Sk) from InSAR-derived surface deformation and S-wave velocity (Vs). We first constructed a 3D Vs model in the Kumamoto area, southwest Japan, by applying 3D empirical Bayesian kriging to the 1D Vs profiles estimated by the surface-wave analysis at 676 measured points. We also used the time series of InSAR deformation and groundwater-level data at 13 well sites covering April 2016 and December 2018 and estimated the Sk of the confined aquifer. The Sk estimated from InSAR, and well data ranged from ~0.03 to 2 × 10−3, with an average of 7.23 × 10−3, values typical for semi-confined and confined conditions. We found a clear relationship between the Sk and Vs at well locations, indicating that the compressibility of an aquifer is related to the stiffness or Vs. By applying the relationship to the 3D Vs model, we succeeded in mapping the Sk in an extensive area. Furthermore, the estimated Sk distribution correlates well with the hydrogeological setting: semi-confined conditions are predicted in the Kumamoto alluvial plain with a high Sk. Our approach is thus effective for estimating aquifer storage properties from Vs, even where limited groundwater-level data are available. Furthermore, we can estimate groundwater-level variation from the geodetic data.
Engineers use various soft computing techniques for solving different problems in geotechnical earthquake engineering. This paper will investigate the application of different soft computing techniques {artificial neural network (ANN), support vector machine (SVM), least square support vector machine (LSSVM), genetic programing (GP), relevance vector machine (RVM), multivariate adaptive regression spline (MARS), extreme learning machine (ELM), adaptive neurofuzzy inference system (ANFIS), minimax probability machine regression (MPMR), Gaussian process regression (GPR), adaptive neurofuzzy inference system (ANFIS)} in different fields of geotechnical earthquake engineering such as liquefaction, lateral spreading, seismic slope stability and reliability. The advantages of different soft computing techniques will be described.
Evolutionary computation (EC) is a widely used computational intelligence that facilitates the formulation of a range of complex engineering problems. This study tackled two hybrid EC techniques based on genetic programming (GP) for ground motion prediction equations (GMPEs). The first method coupled regression analysis with multi-objective genetic programming. In this way, the strategy was maximizing the accuracy and minimizing the models’ complexity simultaneously. The second approach incorporated mesh adaptive direct search (MADS) into gene expression programming to optimize the obtained coefficients. A big data set provided by the Pacific Earthquake Engineering Research Centre (PEER) was used for the model development. Two explicit formulations were developed during this effort. In those formulae, we correlated spectral acceleration to a set of seismological parameters, including the period of vibration, magnitude, the closest distance to the fault ruptured area, shear wave velocity averaged over the top 30 meters, and style of faulting. The GP-based models are verified by a comprehensive comparison with the most well-known methods for GMPEs. The results show that the proposed models are quite simple and straightforward. The high degrees of accuracy of the predictions are competitive with the NGA complex models. Correlations of the predicted data using GEP-MADs and MOGP-R models with the real observations seem to be better than those available in the literature. Three statistical measures for GMPEs, such as E (%), LLH, and EDR index, confirmed those observations.
One of the most important steps for the evaluation of landslide is the investigation of ground dynamic characteristics. The determination of ground dynamic characteristics significantly helps to evaluate site effects and identify critical areas on the slope. One of the most important ground dynamic characteristics is the shear wave velocity. It is possible to detect the seismic impedance, slip surface, and depth to the bedrock using shear wave velocity profiles. There are various methods for calculating the shear wave velocity, among which single-station ambient noise measurement is one of the least costly and fastest. Hence, single-station ambient noise measurements are taken at 30 points in order to determine ground dynamic characteristics and estimate the shear wave velocity in Nargeschal landslide area. At first, ambient noises are analyzed using the H/V method and the fundamental frequency is calculated. Then, Rayleigh wave ellipticity is determined by RayDec method in order to estimate the 1D shear wave velocity profiles. A 3D shear wave velocity model is developed by interpolation between 1D shear wave velocity profiles in the study area. The slip surface, depth to the bedrock, and, generally, subsurface conditions and ground dynamic characteristics are estimated in the landslide area using the 3D shear wave velocity model. Investigations show good agreement between the results of ambient noise measurements and geotechnical, geological, and geophysical data in the study area.
Iran is located on the Alpide earthquake belt, in the active collision zone between the Eurasian and Arabian plates. This issue makes Iran a country that suffers from geotechnical seismic hazards associated with frequent destructive earthquakes. Also, according to the rapid growth of population and demands for construction lifelines, the risk assessment studies which should be carried out in order to reduce the probable damages is necessary. The most important destructive effects of earthquakes on lifelines are transient ground displacements and permanent ground deformations. The availability of the map of the displacements caused by liquefaction, landslide, and surface fault rupture can be a useful reference for researchers and engineers who want to carry out a risk assessment project for each specific region of the country. In this study, the mentioned precise maps by using a considerable number of GIS-based analyses and by employing HAZUS methodology, are produced and presented. It is important to note that a required accuracy for risk assessment is approximately around the macro scale. So, in order to produce a suitable map for risk assessment goals, in terms of accuracy, the GIS-based analyses are employed to mapping all spread of Iran.
Abstract. Iran is located on the Alpide earthquake belt, in the active collision zone between the Eurasian and Arabian plates. This issue makes Iran a country that suffers from geotechnical seismic hazards associated with frequent destructive earthquakes. Also, according to the rapid growth of population and demands for construction lifelines, the risk assessment studies which should be carried out in order to reduce the probable damages is necessary. The most important destructive effects of earthquakes on lifelines are transient ground displacements and permanent ground deformations. The availability of the map of the displacements caused by liquefaction, landslide, and surface fault rupture can be a useful reference for researchers and engineers who want to carry out a risk assessment project for each specific region of the country. In this study, the mentioned precise maps by using a considerable number of GIS-based analyses and by employing HAZUS methodology, are produced and presented. It is important to note that a required accuracy for risk assessment is approximately around the macro scale. So, in order to produce a suitable map for risk assessment goals, in terms of accuracy, the GIS-based analyses are employed to mapping all spread of Iran.
A landslide is a destructive phenomenon that often takes hundreds of lives and causes serious financial damage each year. So, evaluation of landslides and identification of their complexity are of great importance. Ambient noise measurements provide a practical way to evaluate the geometry of landslides. Ambient noises are weak, small-amplitude vibrations recorded on the ground surface. This method is fast, low-cost, and nondestructive, and the accuracy of its results is appropriate. This study used ambient noise measurements at 30 sitesand analyzed them by the HVNR method to identify the fundamental frequency, amplitude, and directional resonance. Then, the results of the ambient noise measurements were compared and verified using geological and geotechnical data in the study area. The results establish that the simultaneous use of ambient noise measurements and conventional geotechnical methodsis an ideal combination for comprehensive landslide evaluation.
Every year, numerous casualties and a large deal of financial losses are incurred due to earthquake events. The losses incurred by an earthquake vary depending on local site effect. Therefore, in order to conquer drastic effects of an earthquake, one should evaluate urban districts in terms of the local site effect. One of the methods for evaluating the local site effect is microtremor measurement and analysis. Aiming at evaluation of local site effect across the city of Babol, the study area was gridded and microtremor measurements were performed with an appropriate distribution. The acquired data was analyzed through the horizontal-to-vertical noise ratio (HVNR) method, and fundamental frequency and associated amplitude of the H/V peak were obtained. The results indicate that fundamental frequency of the study area is generally lower than 1.25 Hz, which is acceptably in agreement with the findings of previous studies. Also, in order to constrain and validate the seismostratigraphic model obtained with this method, the results were compared with geotechnical, geological, and seismic data. Comparing the results of different methods, it was observed that the presented geophysical method can successfully determine the values of fundamental frequency across the study area as well as local site effect. Using the data obtained from the analysis of microtremor, a microzonation map of fundamental frequency across the city of Babol was prepared. This map has numerous applications in designing high-rise building and urban development plans.
Earthquake has left much life and property damages. The occurrence of such events necessitates the execution of plans for combating the earthquakes. One of the most important methods for combating earthquakes includes assessing dynamic characteristics of soil and site effect. One of the methods by which one can state dynamic characteristics of the soil of an area is the measurement of microtremors. Microtremors are small-scale vibrations that occur in the ground and have an amplitude range of about 0.1–1 microns. Microtremor measurement is fast, applicable, cost-effective. Microtremor measurements were taken at 15 stations in the Babol, north of Iran. Regarding H/V spectral ratio method, peak frequency and amplification factor were calculated for all microtremor stations. According to the analysis, the peak frequency varies from 0.67 to 8.10 Hz within the study area. Also, the authors investigated the validity of the results by comparing them with SESAME guidelines and geotechnical conditions of study area. The microtremor analysis results are consistent with SESAME guidelines and geotechnical condition of study area. The results show that the microtremor observations are acceptable methods for assessing dynamic characteristics of soil and site effect in the Babol City.
In the two last decades the microtremor H/V spectral ratio method has been widely used for site effect studies. Straightforward estimate of the site effect of sediments and low-cost measurements are the main advantages of mentioned method. In this research the use of microtremor measurements in estimation of site response have been investigated. In order to assessing the accuracy of the measurements and its application in site effect evaluation, a preliminary site response modeling was carried out using the numerical methods. The results showed that the H/V spectral ratio approach provides an acceptable means of site effect evaluation in study area.
We have used portable 5-sec period seismometers to record ambient noise across a glacially cut valley filled with unconsolidated Holocene sediments. The valley, located in Flushing Meadows, New York City, is surrounded by a densely populated urban environment. Microtremors were recorded at several sites on and adjacent to the valley. The frequency of the predominant peak remains constant across the valley width, while the relative amplitude decreases systematically from a maximum at the valley center to background levels near the valley edge. Resonant frequencies predicted by one-dimensional modeling of the valley center site response show excellent agreement with observations. The 0.8-Hz peak is interpreted as the fundamental resonance mode, and the 2.4-Hz peak is interpreted as the first harmonic of the region above the base of an organic clay layer observed in borehole data. -from Authors
The main objective of the present work is to utilize feedforward multi-layer perceptron (MLP) type of artificial neural networks (ANN) to find the combined effect of nano-silica and different fibers (steel, polypropylene, glass) on the toughness, flexural strength and fracture energy of concrete is evaluated. For this purpose, 40 mix plot including 4 series A and B and C and D, which contain, respectively, 0, 2, 4 and 6% weight of cement, nano-silica particles were used as a substitute for cement. Each of series includes three types of fibers (metal: 0.2, 0.3 and 0.5% volume and polypropylene: 0.1, 0.15 and 0.2 % volume and glass 0.15 and 0.2 and 0.3% by volume) were tested. The obtained results from the experimental data are used to train the MLP type artificial neural network. The Results of this study show that fibers conjugate presence and optimal percent of nano-silica improved toughness, flexural strength and fracture energy of concrete of Self-compacting concrete (SCO). Results of this study show that fibers conjugate presence and optimal percent of nano-silica improved toughness, toughness, fracture energy and flexural strength of SCC.
This paper describes the results of the study of seismic microzonation at Yenisehir-Bursa which is located at the Northwestern part of Turkey. Seismic noise measurements have been made at 151 sites. Short periods (less than 1 second) were taken into account at the main peak in the spectral ratio between the horizontal and the vertical components. At the investigated area, two maps were prepared that show the spatial variations of the predominant period and seismic amplification according to Nakamura's technique. The analysis shows that the north and south edges of the Yenisehir basin have relatively high predominant periods and high seismic amplification compared to the centre of the basin. This result is in line with the theory of topographic effects on seismic amplification and also confirmed the suitability of the H/V spectral ratio of ambient noise as a geophysical exploration tool in seismic hazard assessment.
Many geotechnical problems lack a precise analytical theory or model for their solutions because of an inadequate understanding of the phenomena involved and the factors affecting them, as well as the limited quantity and inexact quality of information available. This study presents a practical example to illustrate the potential of neural networks to improve the synthesizing of the information for the development of empirical design aids. In the example, the back-propagation approach is used to evaluate the friction capacity of driven piles in clay from actual field records.
Following disastrous earthquakes in Alaska and in Niigata, Japan in 1964, Professors H. B. Seed and I. M. Idriss developed and published a methodology termed the ''simplified procedure'' for evaluating liquefaction resistance of soils. This procedure has become a standard of practice throughout North America and much of the world. The methodology which is largely empirical, has evolved over years, primarily through summary papers by H. B. Seed and his colleagues. No general review or update of the procedure has occurred, however, since 1985, the time of the last major paper by Professor Seed and a report from a National Research Council workshop on liquefaction of soils. In 1996 a workshop sponsored by the National Center for Earthquake Engineering Research (NCEER) was convened by Professors T. L. Youd and I. M. Idriss with 20 experts to review developments over the previous 10 years. The purpose was to gain consensus on updates and augmen- tations to the simplified procedure. The following topics were reviewed and recommendations developed: (1) criteria based on standard penetration tests; (2) criteria based on cone penetration tests; (3) criteria based on shear-wave velocity measurements; (4) use of the Becker penetration test for gravelly soil; (4) magnitude scaling factors; (5) correction factors for overburden pressures and sloping ground; and (6) input values for earthquake magnitude and peak acceleration. Probabilistic and seismic energy analyses were reviewed but no recommen- dations were formulated. a
Microtremor measurements are one of the most popular world-wide tool for estimation of site response especially within the urban area. This technique has been applied over 85 sites distributed regularly through Yanbu metropolitan area with an ultimate aim of seismic hazard microzonation for ground-shaking site effects. The horizontal to vertical spectral analysis (H/V) was carried out over all the sites to estimate both the fundamental resonance frequency and its corresponding amplification for the ground vibration. In most sites, H/V curve for amplitude spectra display a clear peak suggesting the presence of a soil-bedrock impedance contrast. Other sites, however, show more than one peak indicating the presence of more than one impedance contrast through sedimentary cover. The estimated values of fundamental frequency range from 0.25Hz up to 7.9Hz increases with decreasing depths of basement rock. It has lower values at the central zone extending from north to south compared to the eastern and western parts of Yanbu area. On the other hand, the estimated values of amplification factor ranges from the value of 2 to 5, where the higher values prevailing through the central zone with increasing thickness of sediments. Analyses of the acquired data set have clearly shown that, both of two parameters vary considerably through Yanbu city. This could be due to lateral variations in soil thickness and/or variations in the soil type at Yanbu area. These results show the 2D and 3D effect of basin geometry. The estimated values for the fundamental frequency from microtremor data are compared with that from shear-wave velocity structure within the area of interest and show an excellent agreement.
In order to gather earthquake information at an early stage and to establish an efficient traffic control just after an earthquake, Japan Highway Public Corporation (JH) has been developing the new seismometer network along their expressways since the 1995 Kobe Earthquake. However variation of earthquake records was found, comparing with the records from the nearest stations of K-NET. In this study, the horizontal-to-vertical (H/V) Fourier spectrum ratios were calculated for microtremors observed at four JH seismic stations and four K-NET stations. The H/V ratios for the earthquake motions observed at these seismic stations were also calculated. It was observed that the H/V Fourier spectrum ratios for the microtremor and seismic motion are similar. Hence, using the H/V ratios for microtremor as quasi transfer functions, the earthquake records at the microtremor observation points can be predicted. This idea can be applied for the estimation of seismic motion along the expressway networks in Japan.
This paper evaluates and compares two comprehensive cone penetration test (CPT) based methods for evaluating liquefaction resistance of sandy soils. The comparison is made based on the results obtained from artificial neural network (ANN) analyses. Two methods are compared, one by Olsen and his colleagues at the Waterways Experiment Station and one by Robertson and his colleagues at the University of Alberta. ANN models are created to approximate the two CPT-based methods so that they can easily be compared using a large database. The results show that ANN models can approximate both Robertson and Olsen methods well, and that both methods are fairly accurate in predicting liquefaction resistance. The Robertson method has a success rate of 89% in predicting liquefied cases, a success rate of 76% in predicting nonliquefied cases, and an overall success rate of 84%. The success rates for the Olsen method are 68%, 89%, and 77%, respectively, in predicting liquefied cases, nonliquefied cases, and all cases. Both methods are considered accurate in predicting liquefaction resistance of sandy soils. The Robertson method is slightly more accurate than the Olsen method. The issue of the propagation of potential uncertainties in the soil parameters and solution model is also discussed.
This paper presents an artificial neural network (ANN) model that predicts the efficiency of pile groups installed in cohesionless soil and subjected to axial loading. The model accounts for the planar geometry of the group (pile diameter, pile spacing, and pile arrangement) and incorporates the effect of pile installation, pile length, cap condition, soil condition, and type of loading on the group efficiency. The results produced by the proposed ANN model compared well with the available results of laboratory and field tests. The ANN model is a viable design tool that assists foundation engineers in predicting the pile group efficiency in an accurate and realistic manner. In addition, this model can be easily updated to incorporate new data and accommodate new design parameters.Key words: axial load, pile foundation, group efficiency, cohesionless soil, artificial neural networks.
The area of interest represents the industrial part of Ain El-Sokhna new port, located in the northwestern part of the seismically active Gulf of Suez zone. The main objective of the current study is to estimate the site characteristics of the area of interest in terms of the fundamental frequency and the corresponding peak amplitude using noise measurements. The microtremor measurements were performed at 44 sites distributed over the study area in order to calculate the horizontal-to-vertical (H/V) spectral ratio. The standard spectral ratio (SSR) is used in addition to the numerical modelling of horizontal shear (SH) waves in soil at selected sites in order to have a comparison with the H/V spectral ratio. The required 1D soil models for the numerical modelling of SH-waves were derived from 220 P-wave shallow seismic refraction profiles in addition to 30 SH-wave profiles. Maps of the fundamental frequency (f0) and its corresponding H/V peak amplitude (A0) were provided, and a range of site conditions in the area were shown. The amplification factor results derived from the SSR technique are very similar to those derived from the H/V spectral ratio. In most cases, the H/V spectral ratio proved to be suitable for calculating the fundamental resonance. Results were found to be compatible with the surface geology of the area of interest.
Microtremor studies were originated in Japan and have gained broader recognition in studying the site effect in earthquake strong ground motion. In recent years, microtremors have also been used in investigating the subsurface structures of a basin. There are also many reports of using array observation to invert the crustal structure; it is particularly popular in Japan. However, to our knowledge, there has been no report on using the spectral ratios between the horizontal components of a microtremor relative to the vertical component, H/V, to deduce the basin's structure, whose thickness could reach a few kilometres, through dense microtremor observation independently. This paper reports the results from a microtremor observation profile crossing the Yinchuan City to study the crustal structure of the Yinchuan Basin, which is the west border of the Ordos block. This basin is a continent graben-basin. The sedimentary layer is very deep; the Quaternary alone is reaching 1600 m. We used the long-period velocity seismometer in this study. The auto-correlation function analysis is used to get the H/V spectral ratio, and to investigate the crustal structure based on the fundamental frequency obtained from the H/V spectra. We have used two methods to verify the computation results. The first one is to compare the crustal structure results with those obtained from seismic explorations. The two results are highly consistent. The second method is to compare the theoretical prediction of the microtremor characteristics using the deduced basin model with real observations. It is shown that it is practical and economical to use densely distributed single-point microtremor observations to study the basal structure of deep basins with decent precision.
Liquefaction microzonation is a process that involves incorporation of geologic, seismologic and geotechnical concerns into economically, sociologically and politically justifiable and defensible land-use planning for earthquake effects so that engineers can site and design structures that will be less susceptible to damage during earthquakes.The scope of present study is to prepare the liquefaction microzonation map for the Babol city based on Seed and Idriss (1983) method using artificial neural network.Artificial neural network (ANN) is one of the artificial intelligence (AI) approaches that can be classified as machine learning. Simplified methods have been practiced by researchers to assess nonlinear liquefaction potential of soil. In order to address the collective knowledge built-up in conventional liquefaction engineering, an alternative general regression neural network model is proposed in this paper.To meet this objective, an effort is made to introduce a total of 30 boreholes data in an area of 7 km2 which includes the results of field tests into the neural network model and the prediction of artificial neural network is checked in some test boreholes, finally the liquefaction microzonation map is produced for research area.Based on the obtained results, it can be stated that the trained neural network is capable in prediction of liquefaction potential with an acceptable level of confidence. At the end, zoning of the city is carried out based on the prediction of liquefaction potential variations in the study area.
A method which employs microtremor has been introduced for estimating dynamic characteristics of surface layers, in early 1950. Then usage of this method has received lots of criticism considering uncertainty about source of microtremor. After an introduction of the Nakamura's technique (H/V or QTS technique; Nakamura, 1989), many people have paid a renewed great attention for estimating dynamic characteristics of ground and structures using microtremor, since clear and reliable information was provided by very simple and inexpensive noise measurements. In recent years, although several researchers claimed that theoretical ground of this technique is not clear and consensus based on experiment couldn't be reached, there have been many successful experimental studies based on these technique. Many theoretical studies have been performed, for explaining the amount of types of waves included in microtremor and checking the applicability of the QTS technique. And some of them are suggested that the peak on H/V ratio can be explained with the fundamental peak of Rayleigh waves. From the output of these researches, explanation of microtremor with Rayleigh waves caused some confusion between users and the author decided to clear out this problem. The basic idea and the main goal of QTS technique are tried to be re-explained in present paper. The author's explanation about the effects of contents of Rayleigh waves in microtremor is also given. Other possible usage of products from QTS technique (predominant frequency and amplification factor) for hazard estimation is also given. As it is well known, occurrence of earthquake damage depends upon strength, period and duration of seismic motions. And these parameters are strongly influenced by seismic response characteristics of surface ground and structures. This reality makes investigation of vulnerability of ground and structures an important issue, before the earthquake occurs. For this purpose, vulnerability indices called K values were proposed by Nakamura (1996). K values are simply derived from strains of ground and structures. Formulation of K values for ground (Kg) and some application examples are also given in present paper. These new values give a chance to estimate vulnerabilities of all types of structures and ground, before the real damage occurs.
Experimental methods involving microtremor recordings are useful for determining site effects in regions of moderate seismic activity where ground motion records are few, and in urban or industrial contexts where the noise level is high. The aim of this study is to establish a microzonation by using the Nogoshi–Nakamura method, and a simple experimental technique based on microtremor recordings. Since the physical phenomena underlying the method are only partially understood, the spectral responses obtained cannot be used alone. We, therefore, complete our experimental results by comparing them with the solutions of a one-dimensional numerical simulation (SHAKE91). and The experimental programme was carried out on a plain near the Rhone Delta (South of France). H/V spectral ratios were calculated at 137 noise measurement points. In addition, we were able to compute the numerical transfer functions from soil columns defined by geotechnical characteristics inside the studied region. A comparison of the results obtained by the experimental and numerical methods showed that the fundamental frequencies are in good agreement, but that the amplitudes obtained by the two techniques are sometimes different. The analysis of H/V spectral ratios enabled us to establish maps to characterize the region: a resonance frequency map and maps of amplification levels as a function of frequency range, leading to a seismic microzonation for the whole of the region.
Thesis (Ph. D.)--Harvard University, 1975. Includes bibliographical references.
The liquefaction potential of a soil mass during an earthquake is dependent on both seismic and soil parameters. The impact of these soil and seismic variables on the liquefaction potential of soil is investigated through computational and knowledge based tools called neural networks. A back-propagation neural network model is utilized. The back-propagation learning algorithm is a developing computational technique that assists in the evaluation of experimental and field data. The artificial neural network is trained using actual field soil records. The performance of the network models is investigated by changing the soil and seismic variables including earthquake magnitude, initial confining pressure, seismic coefficient, relative density, shear modulus, friction angle, shear wave velocity and electrical characteristics of the soil. The most efficient and global model for assessing liquefaction potential and the most significant input parameters affecting liquefaction are summarized. A forecast study is performed for the city of Izmir, Turkey. Comparisons between the artificial neural network results and conventional dynamic stress methods are made.
Liquefaction is a process by which sediments below the water table temporarily lose strength and behave as a viscous liquid rather than a solid. This causes a great damage to the structures constructed on those sediments. To assess the liquefaction potential, many models have been proposed. Earlier regression models were used to predict the liquefaction of sand deposit but those models were not consistent. Recently neural networks were used for such problems. In this paper an existing Instance Based Learning (IBL) is explored to predict the liquefaction potential. This is a machine learning approach, which creates an instance base of previous case records and predicts the result on the basis of its nearest(s) instance from the base. The IBL model is tested on Cone Penetration Test (CPT) dataset. The IBL performance showed improvement in case of CPT dataset over existing neural networks model.
The characteristics of soil liquefaction were investigated using the H/V ratios of microtremors in the Yuan-Lin area. Liquefaction at Luen-Ya-Li, Yuan-Lin in central Taiwan was clearly observed with serious sand boils bringing about massive damages during the Chi-Chi earthquake. Based on the H/V ratios calculated from microtremor measurements at 42 points distributed in this area, the predominant frequencies appeared between 0.8-0.9 Hz for the liquefied area, with higher relative amplification factors compared to other areas. In the study, the ground vulnerability index (Kg) values (Nakamura 1996) in the liquefied areas were higher than those in the neighboring areas without liquefaction. This study shows supporting evidence for the first time that the H/V ratios of microtremors can be a good alternative indicator for an area's potential for liquefaction.
This paper evaluates and compares two comprehensive cone penetration test (CRT) based methods for evaluating liquefaction resistance of sandy soils. The comparison is made based on the results obtained from artificial neural network (ANN) analyses. Two methods are compared, one by Olsen and his colleagues at the Waterways Experiment Station and one by Robertson and his colleagues at the University of Alberta. ANN models are created to approximate the two CPT-based methods so that they can easily be compared using a large database. The results show that ANN models can approximate both Robertson and Olsen methods well, and that both methods are fairly accurate in predicting liquefaction resistance. The Robertson method has a success rate of 89% in predicting liquefied cases, a success rate of 76% in predicting nonliquefied cases, and an overall success rate of 84%. The success rates for the Olsen method are 68%, 89%, and 77%, respectively, in predicting liquefied cases, nonliquefied cases, and all cases. Both methods are considered accurate in predicting liquefaction resistance of sandy soils. The Robertson method is slightly more accurate than the Olsen method. The issue of the propagation of potential uncertainties in the soil parameters and solution model is also discussed.
Significant factors affecting the liquefaction (or cyclic mobility) potential of sands during earthquakes are identified, and a simplified procedure for evaluating liquefaction potential which will take these factors into account is presented. Available field data concerning the liquefaction or nonliquefaction behavior of sands during earthquakes is assembled and compared with evaluations of performance using the simplified procedure. It is suggested that even the limited available field data can provide a useful guide to the probable performance of other sand deposits, that the proposed method of presenting the data provides a useful framework for evaluating past experiences of sand liquefaction during earthquakes and that the simplified evaluation procedure provides a reasonably good means for extending previous field observations to new situations. When greater accuracy is justified, the simplified liquefaction evaluation procedure can readily be supplemented by test data on particular soils or by ground response analyses to provide more definitive evaluations.
The use of the cone-penetration-test (CPT) resistance data as a field index for evaluating the liquefaction potential of sands is receiving increased attention because of the popularity of this in situ test method for the site characterization. This paper examines the feasibility of using neural networks to assess liquefaction potential from actual CPT field data. A back-propagation neural-network algorithm was used to model actual field-liquefaction records. The study indicated that neural networks can successfully model the complex relationship between seismic parameters, soil parameters, and the liquefaction potential. The neural-network model is simpler than and as reliable as the conventional method of evaluating liquefaction potential. No calibration or normalization of the cone resistance q c is required, unlike with the conventional method. As additional field case records become available, these data can be readily included in the neural-network training and testing data for further improvements of modeling of liquefaction potential.
In this the present study, an attempt has been made to evaluate the seismic hazard considering local site effects by carrying out detailed geotechnical site characterization in Babol, Iran. Use of geotechnical data and synthesis of drilling data extracted from the Babol’s subsurface database have enabled authors to determine the geotechnical properties of each site. These data are consisted of twenty five boreholes up to depth of 40 m. Based on the obtained data from geotechnical investigation the study area is divided to five zones. Dynamic analysis was performed in time domain, using fully nonlinear model by PLAXIS. A series of analysis in the study area showed the site period, ranging from 0.4 to 0.8 s. Finally the obtained response spectra from fully nonlinear method were compared with site response spectra of Iran’s 2800 (earthquake) code.
Site effect assessment is an important procedure for a reliable site-specific hazard assessment. Fundamental frequency is a very important factor that must be considered in a construction site for examining the potential damage resulting from earthquake. In the two last decades, the microtremor H/V spectral ratio method has been widely used for site effect studies. Microtremor measurement is fast, applicable, and cost-effective. Microtremor measurement was undertaken at 60 stations in the Babol, north of Iran, during 2011 and 2012. Regarding Nakamura’s method, H/V spectral ratios, fundamental frequency, and amplification factor were calculated for all microtremor stations. The obtained results were controlled with SESAME guidelines. In order to assess the accuracy of the microtremor measurements and its application in site effect evaluation, a preliminary site response modeling was carried out using the equivalent linear methods at some stations. More than 18 boreholes in the study area were modeled as multilayer column, overlaid on bedrock. Also, the artificial neural networks (ANN) with different inputs including thickness, type of soil, unit weight, shear wave velocity, and max shear modulus of soil layer were trained. Then, the trained ANN predicts the fundamental frequency, and the output results were compared with microtremor measurement. The results showed that microtremor measurement approach provides an acceptable means of site effect evaluation in the study area.
We report a site effect study carried out in a small alluvial valley, Nari basin, in Ulleung island, Republic of Korea. In that small valley a permanent, broad-band array of five stations records ground motion continuously. In addition, we performed microtremor measurements using two arrays of stations; a small aperture array (60 m) and a medium aperture one (500 m). Ambient vibration was also recorded at 38 points inside the basin. The records were analyzed using horizontal-to-vertical spectral ratios (HVSR), to estimate dominant frequency and maximum amplification, and the spatial autocorrelation (SPAC) method, to estimate the subsoil structure via phase velocity dispersion curves. Nari basin is clearly a 3D structure but it was expected that a laterally irregular model might be built from the interpolation of several 1D models. Dominant frequency maps based on results from HVSR suggest a simple sedimentary structure with mostly smooth lateral variations. In contrast, maximum amplification distribution is very irregular and shows no correlation with dominant frequency. In the case of Nari, it seems that the complexity of the basin structure cancels the usefulness of HVSR. We could estimate a phase velocity dispersion curves for 81% of the station pairs recording simultaneously ambient vibration in our arrays. In all the cases, the resulting dispersion curve had a simple shape, suggesting that the subsoil structure consists of a single layer over a half space. However, the dispersion curves are incompatible among them, even for different station pairs covering the same path, something impossible if the subsoil structure were 1D. It seems that the passive methods we have used in Nari basin are not adapted to its structure. This makes a tomography unfeasible and we are unable to propose a subsoil structure for Nari basin. Our results show that surface wave dispersion may be estimated using the SPAC method even when the medium is far from 1D. We believe that this problem is enhanced by the small size of this basin, which amplifies the effect of lateral heterogeneities.
The effect of the chain length, the temperature and the strain rate on the yield stress and the elastic modulus of glassy polyethylene is systematically studied using united-atom molecular dynamics (MD) simulations. Based on our MD results, a sensitivity analysis (SA) is carried out in order to quantify the influence of the uncertain input parameters on the predicted yield stress and elastic modulus. The SA is based on response surface (RS) models (polynomial regression and moving least squares). We use partial derivatives (local SA) and variance-based methods (global SA) where we compute first-order and total sensitivity indices. In addition, we use the elementary effects method on the mechanical model. All stochastic methods predict that the key parameter influencing the yield stress and elastic modulus is the temperature, followed by the strain rate.
This paper is concerned principally with the application of Artificial
Neural Networks (ANN) in geotechnical engineering. In particular the
application of ANN is discussed in more detail for subsurface soil
layering and landslide analysis. Two ANN models are trained to predict
subsurface soil layering and landslide risk using data collected from a
study area in northern Iran. Given the three-dimensional coordinates of
soil layers present in thirty boreholes as training data, our first ANN
successfully predicted the depth and type of subsurface soil layers at
new locations in the region. The agreement between the ANN outputs and
actual data is over 90 % for all test cases. The second ANN was designed
to recognize the probability of landslide occurrence at 200 sampling
points which were not used in training. The neural network outputs are
very close (over 92 %) to risk values calculated by the finite element
method or by Bishop's method.
Kathmandu Valley, an intermontane basin of the Himalaya, has experienced many destructive earthquakes in the past. The observations of the damage pattern during the 1934 Earthquake (Mw = 8.1), in particular, suggest that the spectral ground amplification due to fluvio-lacustrine sediments plays a major role in intensifying the ground motion in the basin. It is, therefore, imperative to conduct a detailed study about the floor variation of sediments in the basin. In this paper, a preliminary attempt was made to estimate the thickness of soft sediment in the Kathmandu Basin using microtremor observations. The measurements of microtremors were carried out at 172 sites spaced at a grid interval of 1 km. The results showed that the predominant frequency varies from 0.488 Hz to 8.9 Hz. A non-linear regression relationship between resonance frequency and sediment depth was proposed for the Kathmandu Basin. The thickness of lacustrine sediments at various points in the basin was estimated using the proposed equation, and then the estimated thickness was used to plot a digital elevation model of the basement topography and cross profiles of the sediment distribution in the basin. The results were validated by correlating the estimated sediment thickness with geology and geomorphology of the study area.
Two geologic profiles of Kofu basin, Japan, are estimated by making use of microtremor observations. Microtremors in horizontal and vertical components were recorded at 209 points which constitute two perpendicular lines: one N-S line and the other E-W line. From the records, horizontal to vertical spectral ratios were obtained. The spectral ratios are depicted like a running-spectrum diagram manner, the horizontal axis of the diagram is an observation line and the vertical one is period. Because the horizontal to vertical spectral ratio of microtremors peaks at the resonance period of the ground, the spatial variation of the predominant peak shows that of the sediment thickness when shear-wave velocity of the sediment is laterally homogeneous. The spatial distribution of the predominant period along the N-S line suggests that the sediment is thin in the north and thick in the south. In the E-W line, on the other hand, the variation of the predominant period is less noticeable. The results quite agree with seismic-reflection profiles that were conducted along the lines.
A review of probabilistic and deterministic liquefaction evaluation procedures reveals that there is a need for a comprehensive approach that accounts for different sources of uncertainty in liquefaction evaluations. For the same set of input parameters, different models provide different factors of safety and/or probabilities of liquefaction. To account for the different uncertainties, including both the model and measurement uncertainties, reliability analysis is necessary. This paper presents a review and comparative study of such reliability approaches that can be used to obtain the probability of liquefaction and the corresponding factor of safety. Using a simplified deterministic Seed method, this reliability analysis has been performed. The probability of liquefaction along with the corresponding factor of safety have been determined based on a first order second moment (FOSM) method, an advanced FOSM (Hasofer–Lind) reliability method, a point estimation method (PEM) and a Monte Carlo simulation (MCS) method. A combined method that uses both FOSM and PEM is presented and found to be simple and reliable for liquefaction analysis. Based on the FOSM reliability approach, the minimum safety factor value to be adopted for soil liquefaction analysis (depending on the variability of soil resistance, shear stress parameters and acceptable risk) has been studied and a new design safety factor based on a reliability approach is proposed.
The purpose of this paper is to clarify the meaning of the values of standard penetration resistance (SPT) used in correlations of field observations of soil liquefaction with values of N//1 measured in SPT tests. The field data are reinterpreted and plotted in terms of a newly recommended standard, (N//1)//6//0, determined in SPT tests where the driving energy in the drill rods is 60% of the theoretical free-fall energy. Energies associated with different methods of performing SPT tests in different countries and with different equipment are summarized and can readily be used to convert any measured N-value to the standard (N//1)//6//0 value. Liquefaction resistance curves for sands with different (N//1)//6//0 values and with different fines contents are proposed.
This study shows how microtremor measurements can be used as an aid to liquefaction hazard mapping and zonation, as demonstrated in Laoag City, Northern Philippines. From microtremor measurements, qualitative information on subsoil conditions was obtained and a site classification map was generated. The map was combined with the geomorphology-based liquefaction susceptibility map to produce an integrated liquefaction hazard zonation map. This integrated map is deemed to be more accurate in depicting relative liquefaction susceptibility since it combines information on the distribution of potentially liquefiable soils in terms of geology and grain characteristics with information on the stiffness and thickness of these soils. With information about the thickness of the deposits, an idea of the severity of liquefaction-related damage can also be gathered since thicker deposits relate to more serious damage. Plots of historical liquefaction cases, as well as borehole data and resistivity profiles in the study area, support the validity of the integrated map. The use of microtremor, therefore, constitutes an effective and inexpensive approach to liquefaction hazard zonation, and as such is very useful in less-developed countries like the Philippines and other areas where funds for more rigorous investigations are not always available.
The Talchir Basin, one of India's oldest basins, has been a subject of interest because of its rich coal deposits. The maximum thickness of the basin is about 1500 m. Beyond the basin is the hard metamorphic rocks of Precambrian age. The ambient noise survey data have been analyzed for the Talchir Basin using Nakamura's technique of horizontal–vertical-spectral-ratio (HVSR) to ascertain the basin structure in terms of the predominant frequency. The predominant frequency varies from 0.25 Hz to 7.8 Hz but a major portion of the basin comes under the range of 0.3 Hz–2.4 Hz while on the metamorphic rocks it is as high as 7.8 Hz. The variation in predominant frequency shows a good correlation with the sediment thickness of the basin. The results have been compared with the previous studies by other researchers and it shows consistency with the northerly dip of the basin. The present study has also been compared with the results of the synthetic seismogram that was performed for the Talchir Basin. The predominant frequency obtained from HVSR technique complements well with the frequency at which the peak response spectra ratio is observed. The present study of the predominant frequency identifies quite well the characteristics of Talchir Basin and is in good agreement with the synthetic ground motion modeling of the region.
Purpose
In the literature, several empirical methods can be found to predict the occurrence of nonlinear soil liquefaction in soil layers. These methods are limited to the seismic conditions and the parameters used in developing the model. This paper seeks to present General Regression Neural Network (GRNN) model that addresses the collective knowledge built in simplified procedure.
Design/methodology/approach
The GRNN model incorporates the soil and seismic parameters of the region. It was developed in four phases; identification, collection, implementation, and verification. The data used consisted of 3,895 case records, mostly from the cone penetration test (CPT) results produced from the two major earthquakes that took place in Turkey and Taiwan in 1999. The case records were divided randomly into training, testing and validation datasets. Soil liquefaction decision in terms of seismic demand and seismic capacity is determined by the stress‐based method and strain‐based method, and further tested with the well‐known Chinese criteria.
Findings
The results produced by the proposed GRNN model explore effectively the complex relationship between the soil and seismic input parameters and further forecast the liquefaction potential with an overall success ratio of 94 percent. Liquefaction decisions were further validated by the SPT, confirming the viability of the SPT‐to‐CPT data conversion, which is the main limitation of most of the simplified methods.
Originality/value
The proposed GRNN model provides a viable tool to geotechnical engineers to predict seismic condition in sites susceptible to liquefaction. The model can be constantly updated when new data are available, which will improve its predictability.
Simplified techniques based on in situ testing methods are commonly used to assess seismic liquefaction potential. Many of these simplified methods are based on finding the liquefaction boundary separating two categories (the occurrence or non-occurrence of liquefaction) through the analysis of liquefaction case histories. As the liquefaction classification problem is highly nonlinear in nature, it is difficult to develop a comprehensive model taking into account all the independent variables, such as the seismic and soil properties, using conventional modeling techniques. Hence, in many of the conventional methods that have been proposed, simplified assumptions have been made. In this study, a probabilistic neural network (PNN) approach based on the Bayesian classifier method is used to evaluate seismic liquefaction potential based on actual field records. Two separate analyses are performed, one based on cone penetration test data and one based on shear wave velocity data. The PNN model effectively explores the relationship between the independent and dependent variables without any assumptions about the relationship between the various variables. Through the iterative presentation of the data (the learning phase), this study serves to demonstrate that the PNN can "discover" the intrinsic relationship between the seismic and soil parameters and the liquefaction potential. Comparisons indicate that the PNN models perform far better than the conventional methods in predicting the occurrence or non-occurrence of liquefaction.Key words: cone penetration test, neural networks, prediction, probabilistic neural network, sand, seismic liquefaction, shear wave velocity.
As methods for dynamic characteristics estimation of surface layers, investigation of boreholes and a method which employs microtremors are well known. Borehole investigation, one of the most accurate methods, is costly and time-consuming and is not available all the time. The method that employs microtremors is handy but has not produced satisfactory results to this day. This paper describes a new processing method that employs microtremor observations yet produces accurate estimates of the characteristics of the ground motion. The method uses a vertical component and horizontal components. As a result, the spectrum ratio of the horizontal components and the vertical component of the microtremors bears a resemblance to the transfer function for the horizontal motion of the surface layers.
Earthquake disaster never occurs whenever seismic force does not surpass durability of ground and structures. Thus continuous watch of earthquake motion is first of all necessary, in order to predict and monitor the occurrence of earthquake disaster. For the ground and structures exposed to earthquake motion, it is necessary to grasp their durability precisely by executing investigations in advance. From the view point of earthquake disaster prevention, to grasp the durability of ground and structures is even more important than to monitor the earthquake motion. In this paper, a new technique to investigate rapidly with precision durability against earthquake of various structures and surface ground by using microtremor. Validity of the proposed method has been examined by comparing the results of investigations by the new technique in the earthquake damaged areas (before or after the event) with actual earthquake damage experienced. If weak points of structures can be detected in advance by investigating the durability of various structures and ground, damage of structures can be decreased by taking appropriate countermeasures. Besides, secondary disaster can be also decreased very much by adopting precise immediate measures based upon accurate damage estimation when earthquake occurs.
The microtremor spectral ratio proposed by Nakamura (A method for dynamic characteristics estimation of subsurface using microtremor on ground surface. QR of RTRI, 1989, 30(1), 25–33.) developed a new interest on the use of microtremor measurements for the estimation of site effects. The Lisbon region is an earthquake-prone area and several descriptions of destructive earthquakes are reported in the historical data, which suggest the existence of site effects in the town of Lisbon. Several seismic hazard studies were already performed, as well as some microzonation studies based on records from blasts. In order to characterize the seismic behaviour of alluvium layers existing in the town, two sets of microtremor measurements were performed. The data were processed according to the Nakamura technique and the results are presented here. These results were correlated with the thickness of the alluvium deposits and compared with the spectral ratios obtained using records from blasts, as well as with 1D theoretical models and with 2D theoretical simulations obtained by the use of the Aki-Larner technique. These comparisons seem to prove that the use of microtremor measurements could give a good contribution for the microzonation techniques, specially in urban zones, due to the simplicity and rapidity of their acquisition.
In the last few decades, considerable efforts have been devoted to the phenomenon of wave-induced liquefactions, because it is one of the most important factors for analysing the seabed and designing marine structures. Although numerous studies of wave-induced liquefaction have been carried out, comparatively little is known about the impact of liquefaction on marine structures. Furthermore, most previous researches have focused on complicated mathematical theories and some laboratory work. In the present study, a data dependent approach for the prediction of the wave-induced liquefaction depth in a porous seabed is proposed, based on a multi-artificial neural network (MANN) method. Numerical results indicate that the MANN model can provide an accurate prediction of the wave-induced maximum liquefaction depth with 10% of the original database. This study demonstrates the capacity of the proposed MANN model and provides coastal engineers with another effective tool to analyse the stability of the marine sediment.
The Bovec basin, which is filled with glacial and fluvial sediments, has recently been struck by two strong earthquakes (1998 and 2004) which caused extensive damage (VII–VIII EMS-98). Strong site effects resulted in large variations in damage to buildings in the area, which could not be explained by the surface variations in Quaternary sediments. The microtremor horizontal-to-vertical-spectral ratio (HVRS) method was therefore applied to a 200 m dense grid of free-field measurements to assess the fundamental frequency of the sediments. Large variations in the sediment frequency (3–22 Hz) were obtained, with most of the observed values in the range 6–12 Hz. The observed frequencies cannot be related to the total thickness of Quaternary sediments (sand, gravel), but can be explained by the presence of conglomerate or lithified moraine at shallow depths. The results were compared also with the velocity structure derived from seismic refraction data. Microtremor measurements performed in several two and some three- and four-storey houses (masonry with RC floors), which prevail in the Bovec basin, have shown that the main building frequencies in the area are in the range 7–11 Hz. This indicates that damage to houses in both earthquakes in some parts of the basin was enhanced by site amplification and soil-structure resonance. Areas of possible soil-structure resonance were identified in the settlements Bovec–Brdo, Bovec–Mala vas, Čezsoča and Kal-Koritnica. Considerable changes in fundamental frequencies within short distances were established in the town of Bovec. Their values are as high as 22 Hz in the central part of the town, but diminish to 6–11 Hz in the adjacent Brdo and Mala vas districts. This is in agreement with the distribution of damage in both earthquakes, which was considerably higher in Brdo and Mala vas, although the houses in the central part of the town are older.
Numerical simulation of liquefaction. Dissertation for the Doctoral Degree
- A Choobbasti
- A J Choobbasti
Choobbasti A J. Numerical simulation of liquefaction. Dissertation
for the Doctoral Degree. Manchester: University of UMIST, 1997
Real-time information systems for hazard mitigation
- Y Nakamura
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In: Proceedings of the 10th World Conference in Earthquake
Engineering. Spain, Madrid, 1996
On microtremors. VIII. Bull Earth Research Int
- K Kanai
- Takana
Kanai K, Takana T. On microtremors. VIII. Bull Earth Research Int, 1961, 39: 97–114