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An earthquake fault rupture generates two types of ground motion: permanent quasi-static dislocations and dynamic oscillations, characterized by strong pulses. This study investigates tunnel’s response to two different conditions using a 2D finite element program; the first one has a static dislocation corresponding to different earthquake magnitud...
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A Mw7.8 earthquake struck Turkey on February 6, 2023, causing severe casualties and economic losses. This paper investigates the characteristics of strong ground motion and seismogenic fault of the earthquake. We collected and processed the strong ground motion records of 379 stations using Matlab, SeismoSignal and Surfer software, and obtained the...
Citations
... Varnusfaderani et al. [21] studied the effects of initial seismic excitations near the fault and subsequent reverse fault rupture on cylindrical tunnels. ey concluded that the pulse type determined by SVMax and PGV (indicating pulse intensity) and pulse period (TP) play a crucial role in the final response of the tunnel lining. ...
In this study, the e ect of urban subway tunnels with a circular cross section on the spectral velocity of the ground surface in alluvial soils was investigated. By changing the soil characteristics of the tunnel construction site and the geometric characteristics of the tunnel section (such as the radius and thickness of the lining and the depth of its placement), the frequency of the soil-tunnel system was changed. en, the maximum velocity values were extracted for di erent parts of the ground surface. By averaging the data for each model, the amount of spectral velocity for di erent parts of the ground surface was extracted. e results show that the spectral velocity of the ground surface decreases by increasing the tunnel radius by 92% to a maximum of 12.3% in the tunnel center image on the ground's surface. Also, by increasing the doubling of the depth of the tunnel, the spectral velocity of the ground surface at a distance approximately equal to the radius of the tunnel is reduced to a maximum of 4.42%. e increase in the spectral velocity of the ground surface due to the increase in the depth of the tunnel is a maximum of 12.13% and occurs at a distance approximately equal to the tunnel radius. In a small number of reviewed models, increasing the depth of the tunnel placement increases the spectral velocity of the ground around the tunnel. e e ect of increasing the thickness of the tunnel lining on the spectral velocity of the ground surface was also investigated. In tunnels with greater overhead depth, the spectral velocity of the ground surface increases by a maximum of 10.86% with increasing thickness of the tunnel lining and occurs in the image of the center of the tunnel on the ground surface. In tunnels with less overhead depth, the spectral velocity of the ground surface decreases by a maximum of 7.56% with increasing thickness of the tunnel lining and occurs approximately at a distance equal to the diameter of the tunnel from the image of the tunnel center to the ground surface. e study was performed using PLAXIS 2D and Ansys nite element software.
... As to lifelines, tunnels are vulnerable structures, and the studies run of them are limited. Most of the experimental and numerical studies in this field have been and are mainly focused on the behavior of parallel tunnel faults (Lin et al., 2007;Baziar et al., 2014;Varnusfaderani et al., 2015Varnusfaderani et al., , 2017Azizkandi et al., 2019). ...
Although tunnels are vulnerable to Permanent Ground Displacement (PGD) due to a fault crossing, studies in assessing this intersection are limited, and most of the existing studies have focused on fault movement parallel to the tunnel. A series of numerical models with the Finite Element Method is applied here to evaluate the behavior of tunnels and reverse faults intersections. The numerical modeling results of 60° reverse faulting in free-field and tunnel mode are validated through centrifuge tests. These models are applied as reference models for the parametric study. The effects of geometrical properties, including fault angle, faulting displacement, tunnel diameter, tunnel lining thickness, and overburden soil height on the reverse fault-tunnel crossing is studied. Increasing the tunnel diameter increase the tunnel's vulnerability. The 60° fault angle causes the most damage to the tunnel. Any fluctuation in fault angle from this specific value reduces the tunnel lining bending moments.
... They also reported that failure of segmental tunnels does not occur suddenly and can withstand a certain amount of displacement without complete failure. The focus of other studies in this area, in particular physical modeling, is on assessing the interaction of soil and tunnel parallel to the fault in earthquake [31][32][33][34]. Avoidance of an intersection is impossible if the tunnel is perpendicular to the fault line, thus, the most severe damage. ...
Tunnels extend in large stretches with continuous lengths of up to hundreds of kilometers which are vulnerable to faulting in earthquake-prone areas. Assessing the interaction of soil and tunnel at an intersection with an active fault during an earthquake can be a beneficial guideline for tunnel design engineers. Here, a series of 4 centrifuge tests are planned and tested on continuous tunnels. Dip-slip surface faulting in reverse mechanism of 60-degree is modeled by a fault simulator box in a quasi-static manner. Failure mechanism, progression and locations of damages to the tunnels are assessed through a gradual increase in Permanent Ground Displacement (PGD). The ground surface deformations and strains, fault surface trace, fault scarp and the sinkhole caused by fault movement are observed here. These ground surface deformations are major threats to stability, safety and serviceability of the structures. According to the observations, the modeled tunnels are vulnerable to reverse fault rupture and but the functionality loss is not abrupt, and the tunnel will be able to tolerate some fault displacements. By monitoring the progress of damage states by increasing PGD, the fragility curves corresponding to each damage state were plotted and interpreted in related figures.
... In this study, the selected intersection angle is 90°. The focus of studies in this field, especially the physical modelings, have assessed the soil and tunnel and fault line interactions in their parallel sense [40][41][42]. ...
... Various methods exist to describe the development of structural damage. A very efficient model using the Uzawa algorithm, (Gharizade Varnusfaderani et al., 2017;Gharizade Varnusfaderani et al., 2015;Procházka and Šejnoha, 1995), is suitable for cases where location of damage is a priori known. In the case that the site of the damage is not known it is advisable to use discrete elements. ...
... Blast operations done during driving tunnels or in the surroundings of quarries are the most frequently evaluated technical vibrations. Special measurements were realised in a near zone to determine a vibration effect on the temporary or final lining (for example, Qiu et al., 2008;Kaláb et al., 2013Kaláb et al., , 2014Kaláb and Hrubešová, 2015;Varnusfaderani et al., 2015Varnusfaderani et al., , 2017. The effect of technical seismicity (industry, traffic, forging shop, vibration roller, etc.), excluding blasts, is usually at a lower limit of a possible negative impact on underground structures (for example, according to Czech Technical Standard 73 0040). ...
This paper deals with a summary of possible seismic loading of shallow geotechnical structures. It is known that seismic loading influences the underground structures much less than the structures on the surface, therefore, it is not usually taken into account. However, cracks or damage in lining occur due to vibration from time to time. Two effects of earthquakes are documented on these structures: an effect due to faulting and an effect due to vibration. At present, FEM is the most popular method to solve the above problems. Integrated earthquake simulation is the most frequent task that has a significant impact on seismic hazard and seismic risk estimations, and human actions against earthquake disasters. Three types of rock massif were defined for this study: soft rock, medium hard rock, and hard rock. More detailed description and sensitivity analysis are performed for circle cross-section of those structures. Sensitivity analysis was performed using soil interaction method according to Wang´s methodology; change of lining diameter and elastic modulus of lining were tested. Thrust force must also be calculated for the no-slip condition. Graphs presented in this paper document individual relations between individual studied parameters. These results can be used as sufficient accurate final analysis while idealised conditions can be accepted.
Tunnels built in geologically active areas are prone to severe damage due to fault dislocation and subsequent earthquakes. Using the Ngong tunnel in the East African Rift Valley as an example, the dynamic response of a fault-crossing tunnel and the corresponding sensitivity are numerically simulated by considering four factors, i.e., tunnel joint stiffness, isolation layer elastic modulus, strike-slip fault creep-slip and earthquakes. The results show that a valley-shaped propagation of peak displacement at the tunnel invert occurs in the longitudinal axis direction under an earthquake alone. Then, it transforms into an S-shaped under strike-slip fault creep-slip and subsequent seismic shaking. The tunnel invert in the fault zone is susceptible to tensile and shear failures under strike-slip fault creep-slip movements of less than 15 cm and subsequent seismic shaking. Furthermore, the peak tensile and shear stress responses of the tunnel invert in the fault zone are more sensitive to fault creep-slip than earthquakes. They are also more sensitive to the isolation layer elastic modulus compared to the joint stiffness of a segmental tunnel with two segments. The stress responses can be effectively reduced when the isolation layer elastic modulus logarithmic ratio equals −4. Therefore, the isolation layer is more suitable to mitigate the potential failure under small strike-slip fault creep-slip and subsequent seismic shaking than segmental tunnels with two segments. The results of this study can provide some reference for the disaster mitigation of fault-crossing tunnels in terms of dynamic damage in active fault zones.
The failure mechanism of tunnels crossing faults is a critical issue for tunnels located in seismically active regions. This study aims to investigate the nonlinear response of rock tunnels crossing inactive faults under obliquely incident seismic P waves. Based on the equivalent nodal force method together with the viscous-spring boundary, an incident method for the site, which contains fault and is subjected to obliquely incident seismic P waves, is developed first. Then, based on the proposed incident method, the nonlinear response and the failure process of the tunnel crossing inactive fault are numerically studied. The numerical results show that the failure mechanism of the tunnel crossing inactive fault can be attributed to the combined action of the seismic waves and its associated fault slippage. Finally, parameter studies are conducted to investigate the effects of the wave impedance ratio of the fault to the surrounding rock and the incident angle of P waves. By the parameter analysis, it can be concluded that: (1) with decreasing the wave impedance ratio of the fault to the surrounding rock, the seismic response of the tunnel increases significantly; (2) the seismic response of the tunnel increases first and then decreases with the increasing of the incident angle of P waves. This study offers the insight for further research on the seismic stability of tunnels crossing inactive faults.
With the rapid development of underground space, more adverse site conditions are occurring in the construction of underground structures. For example, a subway station passes through longitudinally inhomogeneous geology. When the subway station crosses the interface of soft soil and hard soil, this may lead to the destruction of underground structures. In this paper, three-dimensional (3D) nonlinear seismic response analysis of subway stations crossing longitudinally inhomogeneous geology subjected to obliquely incident P waves is presented based on actual engineering background. The earthquake input method for the longitudinally inhomogeneous site that transforms the site seismic response into an equivalent nodal load is first developed and verified. The viscous-spring artificial boundary is used to simulate the radiation damping effect of infinite domain media. Subsequently, the topographic and geological effects on seismic response of engineering site are investigated. Finally, the failure mechanism of the subway station structure crossing longitudinally inhomogeneous geology under the obliquely incident P waves is revealed. The investigation demonstrates that the plastic zone of site usually appears along the interface between the hard and soft soil media, and appears on the side of the soft soil. The sidewall and bottom slab of the structure experience obvious tensile damage at the interface location between the hard and soft soil media. The results show that topographic and geological effects should be considered in seismic analysis and design of underground structures when the topography and geology change significantly.
