A utility tunnel is an infrastructure that consolidates multiple municipal pipeline systems into a shared underground passage. As long linear structures inevitably cross different soils, this paper aims to accurately assess the seismic damage to a shallow-buried utility tunnel in a non-homogeneous zone by employing a viscous-spring artificial boundary and deriving the corresponding nodal force equations. The three-dimensional model of the utility tunnel-soil system is established using finite element software, and a plug-in is developed to simulate the three-dimensional oblique incidence of SV waves with a horizontal non-homogeneous field. In this study, the maximum interstory displacement angle of the utility tunnel is used as the damage indicator. Analysis of structural vulnerability based on IDA method using PGA as an indicator of seismic wave intensity, which considers the angle of oblique incidence of SV waves, the type of seismic waves, and the influence of the nonhomogeneous field on the seismic performance of the utility tunnel. The results indicate that the failure probability of the utility tunnel in different soil types increases with the incident angle and PGA. Additionally, the failure probability under the pulse wave is higher than that under the non-pulse wave; Particular attention is given to the states of severe damage (LS) and collapse (CP), particularly when the angle of incidence is 30 degrees and the PGA exceeds 0.6g, conditions under which the probability of failure is higher. Additionally, the failure probability of the non-homogeneous zone is greater than that of sand and clay; the maximum interlayer displacement angle increases with the incident angle, accompanied by greater PGA dispersion, indicating the seismic wave intensity. The maximum inter-layer displacement angle increases with the incident angle, and the dispersion of the seismic wave intensity indicator (PGA) becomes greater. This paper proposes vulnerability curves for different working conditions, which can serve as a reference for the seismic design of underground structures.

Depth to bedrock (DTB) is a critical factor for rainfall-induced slope failures. However, the influence of uncertainties in these measurements, particularly at a small-scale, has not been fully understood. Numerical modeling was conducted to assess the impact of a variable bedrock topography on the stability of a real-world unsaturated slope. The simulations included a three-dimensional pore-water pressure estimation, derived from the numerical solution of the Richards equation, coupled with a slope stability assessment using numerical limit analysis. The study explored the potential of incorporating random fields (RFs) into an established DTB model to improve the understanding of rainfall-triggered landslides. The proposed methodology was applied to the analysis of a small watershed within the Papagaio River basin in Brazil, an area historically subjected to landslides triggered by rainfall events. Our main findings reveal that small variations in DTB can significantly impact the safety factor and probability of failure estimations. Furthermore, they influence the shape, location and failure volume associated to predicted landslides. The incorporation of RFs effectively addresses small- scale uncertainty in DTB, controls bedrock morphology, and enhances the assessment of probabilistic numerical modeling for landslide susceptibility. This study highlights the importance of accurate and comprehensive DTB characterization for assessing rainfall-induced landslides at local slope scale.

Electric transformers are major components of electrical systems, and damage to them caused by earthquakes can result in significant financial loss. The current study modeled a three-dimensional (3D) isolated electrical transformer under horizontal and vertical records from different earthquakes. Instead of using fixed coefficients, an improved wavelet method has been used to create the greatest compatibility between the response spectra and the target spectrum. This method has primarily been used for dynamic analysis of isolated structures with spring-damper devices because it has shown greater accuracy in predicting the response of such structures. The effect of the nonlinear soil-structure interaction on the probability of transformer failure also has been investigated. Soil and structure interaction modeling was carried out using a beam on a nonlinear Winkler foundation. The effect of the nonlinear soil-structure interaction during dynamic analysis of transformers revealed that the greatest increase in the probability of transformer failure was in the fixed-base condition when the structure was located on soft soil. This intensified the response of the structure and increased the probability of transformer failure by up to 27% for far-field and up to 95% for near-field ground motions. A comparison of the results indicates that the use of 3D isolation systems in transformers in areas with soft clay that are subject to near-field ground motions can strongly reduce the probability of failure and improve the seismic performance of the transformer.

The present study focuses on investigating the effects of soil rotated anisotropy and spatial variability on slope failure in seismic conditions. The random finite element method aided by subset simulation is implemented, which ensures an efficient quantification of both the probability of failure and its associated consequence of failure. Several slope angles of gentle and steep slopes and soil properties that lead to a low probability of failure were selected for parametric studies. The comprehensive parametric studies of seismic slope stability analysis consider various factors such as slope inclinations, seismic coefficients, scales of fluctuation, and orientations of the major principal scale of fluctuation (i.e., the rotation angle of random field). The results underscore the importance of considering the combined effects of soil anisotropy and the orientation of the major principal scale of fluctuation for designing both gentle and steep slopes under seismic conditions and emphasize that care must be given to ensure the worst-case scenario is considered. Visual observations of failure mechanisms of gentle and steep slopes under seismic conditions were also shown to be very helpful in interpreting the variation of probability of failure due to soil spatial variation.

Soil is a complex material that exhibits both spatial variability and anisotropy. For simplicity, the traditional approach for analyzing slope stability often assumes that soil is homogeneous or isotropic, which can lead to an overestimation of slope stability and reliability. To address this issue, a novel approach is proposed in this study that uses an anisotropic yield criterion based on the random finite-element method to evaluate the influence of strength anisotropy on slope stability, while accounting for the influence of spatial variability on reliability. The proposed approach is applied to a typical case of slope reliability analysis. It is shown that the results of the proposed approach are consistent with those of previous studies and OPTUM G2 outcomes. The assessment involves determining the safety factors for both homogeneous and anisotropic conditions, while also taking into account the probability of failure in the presence of spatial variability. It is found that strength anisotropy significantly affects slope stability and reliability, as the factor of safety decreases from 1.255 to 1.037 and the probability of failure increases from 3.5% to 52.1% when considering strength anisotropy (n=0.707, xi=11.25 degrees). In addition, a sensitivity analysis is performed to investigate the influence of slope geometric parameters, strength anisotropic parameters, and spatial variability parameters on slope stability and reliability.