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a Hollow flight augers are used when drilling through collapsible soils, voids, or running sands, where the hole may not otherwise remain open. b The active components of a typical split barrel drive sampler are shown (Federal Highway Administration)
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Naturally occurring landslides can be difficult to characterize and often exhibit anomalies in controlling geometry and consistency. The characterization of landslides in engineering geology practice is usually based on program of subsurface exploration; focused on identifying subsurface materials, structure and stratigraphy, hydrologic conditions,...
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... Although this procedure is very effective and allows for the retrieval of undisturbed samples that may be tested in laboratory to estimate geotechnical properties of the materials affected by instability, it may become prohibitive when landslide mass is very large because the number of boreholes needed is too high. For these cases, geophysical methods represent an interesting solution because they allow for the fast coverage of wide areas at a reasonable cost, and they do not disturb the area under study [3][4][5]; this last characteristic is of special interest when the landslide affects urban areas. At present, electromagnetic [6,7], electrical [8,9] and seismic methods [10][11][12] are among the most used geophysical techniques applied to landslide studies. ...
The urban area of Albuñuelas, a small town located to the south of Granada (S Spain), has been developed in terrain affected by a large-scale rotational landslide with very slow rate of movement. Despite this situation, the internal structure of the landslide and how it has evolved to its present state has not been analyzed in depth up to now. In this paper, we present the first study performed on this landslide to define its configuration and characteristics. For this purpose, ambient noise single-station and array measurements were carried out along several cross-sections of the landslide. The inversion of the measurements has allowed for the estimation of the soil stratigraphy at each site of measurement. These geophysical results have been constrained by data from a borehole drilled in the zone and from field observations of the local geology, allowing for the reduction in uncertainties in the results. A geological–geophysical model of the landslide has been built from these data, showing that the landslide thicknesses is greater than 50 m in its central parts and above 60 m in the upper ones. This model reveals that the evolution of the landslide was complex, with several dislodged elements (blocks) that moved in sequence (retrogression) and were partially eroded in order to explain present morphology. The future evolution of this landslide will be controlled by the composition of the materials surveyed along the foot of the valley, being the western part where there are more erodible materials according to the obtained results.
... Overall, detailed geological studies of these large landslides should be performed to understand better their internal structure and kinematics and to model possible evolution scenarios for a correct hazard assessment (Soldati 2013;Spreafico et al. 2021). Similarly, in situ monitoring such as inclinometers or extensometers (Corominas et al. 2000), Global Positioning Systems (GPS) (Brunner et al. 2003) or the exploration drilling and geophysical techniques (Rogers and Chung 2017) should also be carried out for a precise subsurface characterisation of the landslides. In this work, we produced an updated and more accurate landslide inventory that is the starting point to assess the landslide hazard over an area (van Westen et al. 2008). ...
An updated and complete landslide inventory is the starting point for an appropriate hazard assessment. This paper presents an improvement for landslide mapping by integrating data from two well-consolidated techniques: Differential Synthetic Aperture Radar (DInSAR) and Landscape Analysis through the normalised channel steepness index ( k sn ). The southwestern sector of the Sierra Nevada mountain range (Southern Spain) was selected as the case study. We first propose the double normalised steepness ( k snn ) index, derived from the k sn index, to remove the active tectonics signal. The obtained k snn anomalies (or knickzones) along rivers and the unstable ground areas from the DInSAR analysis rapidly highlighted the slopes of interest. Thus, we provided a new inventory of 28 landslides that implies an increase in the area affected by landslides compared with the previous mapping: 33.5% in the present study vs. 14.5% in the Spanish Land Movements Database. The two main typologies of identified landslides are Deep-Seated Gravitational Slope Deformations (DGSDs) and rockslides, with the prevalence of large DGSDs in Sierra Nevada being first revealed in this work. We also demonstrate that the combination of DInSAR and Landscape Analysis could overcome the limitations of each method for landslide detection. They also supported us in dealing with difficulties in recognising this type of landslides due to their poorly defined boundaries, a homogeneous lithology and the imprint of glacial and periglacial processes. Finally, a preliminary hazard perspective of these landslides was outlined.
... Chae et al., 2017;Prokop and Panholzer, 2009;Stumvoll et al., 2021). For subsurface landslide investigation, both static (soil type, subsurface structure, regolith thickness) and dynamic parameters (groundwater, soil moisture, slope movement) are of interest (Rogers and Chung, 2017). The aim of subsurface investigation in relation to landslide processes is to detect depths of potential shear surfaces (e.g. ...
Complex, slow-moving landslides are common in deeply weathered soils with clay-rich layers, as can be found in the Flysch Zone of Lower Austria. Complex process behaviour on differing spatio-temporal scales calls for long-term measurement series on both surface and subsurface parameters. Only then, dynamics and interrelations with possible triggering mechanisms might be further understood. This study investigates a small, slow-moving earth slide - earth flow system.
Information on surface changes, based on digital elevation models (DEMs) of Difference (DoDs) using terrestrial laser scanning (TLS), is available since 2015 (2009, including ALS). Subsurface monitoring started in 2018. Data was analysed comparatively for overlapping periods: A conceptual subsurface model was generated with geotechnical information (penetration tests/ drill core samples), incorporating regolith thickness and potential shear surfaces. For four periods between 2018-11-14 and 2020-11-18 (∼2 years), interrelations of hydro-meteorological input data (precipitation/ temperature), changes in the spatio-temporal development of subsurface hydrology (piezometers), subsurface dynamics (inclinometer) and surface dynamics (DoDs) were analysed in detail.
Total dynamics in the 2-year period were marginal. Total inclinometer displacements were max. ∼1.65 cm; these changes were too small to be depictable on the surface with TLS based DoDs. Nonetheless, several relations of present state and known former dynamics were found: Regolith thickness could be reasonably described via penetration tests, being relatively shallower in areas of known process activity. Interpolated shear surfaces based on drill core analyses, penetration tests and inclinometer data are highly simplified; nevertheless, they depict relations to locations of known activity with respect to depth and geometry. Locations of shallowest groundwater levels and highest fluctuations correspond with areas of recent minor and former larger dynamics. Inclinometer displacement rates exhibit relations to hydro-meteorological input data and are in locations known from former bigger process magnitudes.
... Data integration provides complementary knowledge to reduce the uncertainties associated with the properties of a landslide area. Intrusive and direct methods, such as trial pits and boreholes, are used to recover samples for the identification of the properties of a landslide mass at discrete locations (Uhlemann et al. 2016;Rogers and Chung 2017). However, these methods are not always adequate in providing a wider view of the landslide system because of the subsurface complexity of the landslide settings (Whiteley et al. 2019). ...
The Isiklar paleo-landslide area was reactivated in 1952, and today the spatial dimension of scarps is significantly different across the area. However, the steep slopes hamper the application of detailed in-situ methods, and the limited surficial field observations could not explain the complexity of the area so far. This paper aims to determine the origins of different displacements on two adjacent fields (Field-1 and Field-2) separated by woodland in the paleo-landslide area. The fields were imaged and monitored by multiple geophysical methods including seismic refraction and electrical resistivity tomography, surface waves analysis, and microtremors. Unified soil classification of six disturbed samples was carried out to define texture and grain size distribution. Up-to-date geographic maps were generated by GNSS measurements. The main findings show that the favorable conditions for the variation of displacements are controlled by the dissimilarity of landslide materials in terms of geological setting, S-wave velocity, and layer thickness. Also, the slope values higher than 30% are distinctive in fields regarding the development of scarps. Conversely, the seasonal changes and ground-water conditions do not influence the variability in displacements. The results suggest that the neighboring areas have been evolving differently on the same main-rock and the border of deforested woodland for agricultural purposes plays a crucial role in this process. The combination of different geophysical methods allowed imaging the subsurface at different spatial resolutions with various physical properties. Additionally, the integration of geophysical outcomes with geological and geodetic findings made it possible to restrict the spectrum of causal factors.
... The complete characterization of a landslide requires a good understanding of the conditioning and triggering factors, accurate measurements of its historic and current activity and precise modelling of the slip surface (Carter and Bentley 1985;Baldi et al. 2008;Eberhardt et al. 2008;Antronico et al. 2013;Grana and Tommasi 2014;Gullà 2014;Maiorano et al. 2015;Rogers and Chung 2017). The multidisciplinary approach proposed in this study applies modern field investigation, remote sensing, and in situ geophysical and geotechnical techniques to achieve this goal (Fig.45). ...
Landslides are among the most widespread natural hazards worldwide. In the province of Tetouan, previous studies have shown that the region is marked by an abundance of landslide processes that are still not fully characterized. In this regard, this research is conducted with the aim of answering a number of important questions concerning the relationship between the distribution of mass movements in relation to that of their main predisposing factors, as well as the quantification of the real impact of these natural hazards on the socio-economic development of the region. This work follows a multi-scale strategy to characterize landslides in the light of old and new techniques and data. To do so, a multidisciplinary approach is used to conduct three case studies, representing three different geological contexts. In all three sites, fieldwork, remote sensing techniques, geotechnical and geophysical characterization methods and numerical modeling tools are integrated to reach a good understanding of the investigated phenomena. Then, studies at the communal scale are attempted, allowing characterizing the slope dynamics at the local scale. To do so, multidisciplinary approaches are used to conduct landslide susceptibility assessment efforts of Ain Lahcen and study the interaction between landslides and human activities in the city of Chefchaouen. Finally, a regional scale analysis is conducted with the aim of understanding the link between regional geology and landslides, and building a landslide susceptibility (spatial prediction) map.
Geophysical, geotechnical and field investigation results show that on a small scale, tectonic structures seem to influence the geometry of landslides. This is clearly perceptible in the 2D profiles of the Tamegaret landslide of the internal domain and the Seikha landslide of the external domain. Regarding remote sensing and field surveys, they allowed identifying the major landslides triggers. In fact, in the absence of significant seismic events, extreme rainfall events seem to have the most correlated with landslide occurrences, especially shallow landslides. Anthropogenic activities are also found to be of significant impact especially road construction work which introduces great topographic changes in some areas. With respect to rockfalls, the example of Bouanane shows the potential danger of such phenomena, with a risk of wedge sliding. This detachment mechanism explains the wedge-like morphology of most boulders deposited at the site..
On a communal scale, the investigations carried out highlight the impact of landslides on the socio-economic development of certain communes in the region. This situation is more pronounced near major tectonic contacts that promote significant multi-generational slope dynamics. Analyses on a regional scale confirm these results. Indeed, they show that major tectonic contacts favor the development of large landslides for both the internal and external domains of the Rif Range. For the former domain, it has been shown that high-angle normal faults play a passive role manifested by the creation of weakness planes, easily exploitable by gravitational forces. For the external domain, differential erosion and topographic growth seem to push the slopes close to their stability threshold, thus favoring the generation of landslides. In terms of susceptibility assessment on a regional scale, it can be said that lithostructural and morphostructural control on the spatial distribution of high susceptibility areas proves to be of great importance. This is due to the interaction between the natural mechanisms mentioned above as well as the tendency of road builders to follow the sinusoidal morphology of tectonic contact areas, characterized by gentler slopes due to the development of piedmont landforms. 4
From a socio-economic point of view, the results of this work suggest that the landslide phenomena is capable of hindering the socio-economic development of the region. Their effects range from destabilizing important road segments such as RN2 and N16, which seem to be the most exposed, to decreasing the value of property. In addition to the direct impact of landslides, which could be in the millions as shown in the case of Chefchaouen commune (25 million dirhams), the stabilization of landslides necessitates more capital investment and thus increases the cost of major infrastructure projects. Despite the fact that avoiding landslide affected areas is still the best solution so far, the demographic boom that the region knows pushes towards exploring more hazardous terrain.
... In this study weighted overlays, analytical hierarchy processes (AHP), and fuzzy logic methods (available in ArcGIS software version 10.5) were employed to generate landslide hazard maps of the Hunza River watershed. The weighted overlay method is a simple, and straight forward way to evaluate probable landslide areas on a regional basis (Erener and Duzgun 2012;Intarawichian and Dasananda 2010;Bachri and Shresta 2010;Rogers and Chung 2017). Fuzzy logic is another simple and inexpensive semiquantitative method developed as a GIS tool for regional-scale landslide hazard mapping. ...
Landslides pose a significant hazard to life and property in areas vulnerable to mass movements. Qualitative landslide susceptibility maps offer a preliminary means of screening locations likely susceptible to slope instability. In this study, attempts have been made to identify various landslide hazard zones within the Hunza River watershed (varying from very high to low hazards) by considering geomorphic and geological conditions and employing common trigger factors into GIS data layers. Three different approaches were selected: the weighted overlay, fuzzy logic, and analytical hierarchy processes. These approaches allowed the compilation of preliminary landslide hazard maps for the 8,000 km 2 Hunza River watershed area. This study utilizes the information layers related to geomorphological and geological risk factors such as elevation, slope angle, slope aspect, curvature, the normalized difference vegetation index (NDVI), lithology, distance to major faults, and drainage. Assumed triggering factors included seismic excitation and precipitation, expressed in raster files. These thematic map overlays were employed as input layers to compile landslide hazard maps. Each of the methods used to construct hazard maps produced satisfactory results when compared with existing landslide inventories, even those accompanied by field validation surveys. For the very high hazard zones in Chalt and the upper Hunza Valley, the trigger variable appears to be the Main Karakorum Thrust (MKT), where shattered lithologic units are most susceptible to landslides. These comparisons suggest that majority of documented rockslides fall in high and very hazard zones in the Hunza River watershed. Our findings also suggest that the employment of off-the-shelf GIS software may become a cost-effective means of assembling similar hazard maps on a regional scale elsewhere.
... It is a highly localized approach because of the requirements for detailed data and relies on expert knowledge. Some reports with this approach can be found in Amoroso, Totani, andTotani (2011), Riquelme, Cano, Tomás, andAbellán (2016), Saade, Abou-Jaoude, and Wartman (2016) and Rogers and Chung (2017). The second approach depends on measuring the relevance of causative factors by establishing correlations between previous landslides and geoenvironmental variables to predict areas of landslide initiation with a similar combination of factors from local to regional scales (Baeza, Lantada, & Amorim, 2016;Vorpahl, Elsenbeer, Märker, & Schröder, 2012). ...
This study demonstrated the potential of methods derived from geomorphometry and regression models to evaluate landslide susceptibility in a study area located in southern Colombia. From a morphometric stance, the first step was to evaluate the quality of DEM sources by comparison to control points obtained by static-mode GPS. The PALSAR_RTC_hi data was selected for having the best accuracy of heights and was used to derivate terrain parameters at SAGA software. Then, the Principal Component Analysis selected variables with low collinearity, and we classified twelve landforms using fuzzy k-means algorithm, which was compared to a geomorphological map by using the multinomial logistic regression method in R software. We got a Kappa coincidence index of about 30%. The resulting landslide susceptibility mapping took dependent (a mask with unstable-stable cells from an existing landslide inventory) and independent variables (selected morphometric ones). The binary logistic regression showed the propensity of the area to be adversely affected by landslides. This model’s performance was tested with a ROC curve over a sample, with 20% of landslide database resulting in an Area Under the Curve of 0,55. This result was contrasted with a spatial prediction model of debris flow, explaining the high frequency of avalanches.
On April 2-4, 2021, severe cyclone Seroja occurred in Kupang City, resulting in a landslide hazard. Landslide disaster management is essential for disaster mitigation. However, the susceptibility landslide map for the cyclone Seroja in Kupang City has not yet been done. In this paper, we map landslide locations using remote sensing. We used free remote sensing data. The data are Landsat 8 imagery, Digital Elevation Model (DEM), and rainfall. To create a landslide map in Kupang City, we overlaid three maps. Those are landcover, slope and rainfall maps. We created a landcover map using the Landsat 8 imagery. The landcover types were classified using the Supervised Classification method of Support Vector Machines (SVM) in the QGIS software. Each land cover type was determined based on training sites taken in the field using GPS. DEM was used to create a slope map. We used the accumulative rainfall data for three days to map the rainfall. For data validation, we took GPS points from the landslide locations. The study result shows a landslide map in Kupang City after cyclone Seroja. This work informs that remote sensing can be used to determine the location of landslides in inaccessible areas. Remote sensing can also be used to map landslide areas with a limited budget and limited data.
