Moderate-size earthquakes, and the presence of water saturated soil in the near surface can trigger the liquefaction geohazard causing buildings to settle / tilt or collapse, damaging bridges, dams, and roads. A number of paleo-seismic research have focused on the Himalayan area as a potential site for liquefaction. The present study site is in the south of the tectonically active Himalayan foothills and lies in earthquake Seismic Zone III. Therefore, the region can experience earthquakes from nearby regions and can potentially damage civil infrastructures due to liquefaction. The objective of this paper is to determine the susceptibility of alluvial soil deposits to liquefaction for seismic hazard and risk mitigation. Liquefaction geohazard study of alluvial deposits was carried out using shear wave velocity (Vs) profiling. Preliminary assessment of the soil is made by building the average shear wave velocity map up to 30 m depth (Vs30) and by constructing the corrected shear wave velocity (V-s1) maps. It was observed from the Vs30 map that a major portion of the studied area lies in Site Class CD and only a small portion lies in Site Class D. Moreover, it is also noticed from the V(s1 )map that a smaller of the area has V(s1 )lower than the upper limit of V-s1(& lowast; )(215 m/s) below which liquefaction may occur. The region showing lower values of V(s1 )is further examined for liquefaction hazard as per the guidelines given by Andrus et al. (2004). Resistance of the soil to liquefaction, stated as cyclic resistance ratio (CRR), and the magnitude of cyclic loading on the soil induced by the earthquake shaking, stated as cyclic stress ratio (CSR) are computed for the area. Several maps of factor of safety (FS) for different depths are prepared by taking the ratio of CSR and CRR. When FS < 1, the soil is considered prone to liquefaction. Furthermore, susceptibility of soil to liquefaction against different peak horizontal ground surface acceleration (PHGSA) and varying depth of water table is also evaluated in terms of factor of safety. It is observed from this study that for lower levels of PHGSA (up to 0.175 g) the soil can be considered safe. However, the soil becomes more vulnerable to liquefaction when PHGSA is above 0.175 g and with rising water table. The comparison of the factor of safety (FS) obtained using the SPT-N method and the Vs-derived approach shows consistent results, with both methods confirming the absence of liquefaction in the studied soil layers.

Accurately capturing the seismic response of underground structures subjected to obliquely incident seismic waves, particularly when the angle of incidence surpasses the critical value, remains a challenging task in earthquake engineering. To address this gap, this paper presents a three-dimensional (3D) nonlinear seismic analysis of subway stations embedded in a layered site, specifically in response to obliquely incident shear (SV) waves at arbitrary angles. An innovative procedure, termed the coupled dynamic stiffness matrix-finite element method (DSM-FEM), is introduced to enable seismic input by transforming responses induced by arbitrarily incoming SV waves into equivalent nodal loads. To accurately simulate wave propagation within the site, a viscous-spring artificial boundary is utilized, while a nonlinear generalized Masing model that incorporates modified damping is employed. Using the Daikai subway station as a benchmark, the research examines the effects of varying oblique incident angles on the structural response, taking into account dynamic soil-structure interaction. The results reveal that the maximum response, including peak deformation, internal forces, Mises stress, occurs when the incident angle approaches the critical value. Beyond this critical angle, the seismic response notably diminishes. Additionally, the influence of horizontal incident angles is found to be noticeable, leading to variations in deformation patterns and internal forces across different structural components. Specifically, it has been observed that the drift ratio, displacement, shear force, acceleration, and Mises stress exhibit a decreasing trend as the horizontal incident angles increase. These findings highlight the significance of considering non-vertical input ground motion in seismic analysis, and offer valuable insights for the structural design and safety evaluation of underground structures.

This study aims to assess the effectiveness of inter-storey isolation structures in reducing seismic responses in super high-rise buildings, with a focus on analyzing the impact of soil-structure interaction (SSI) on the dynamic performance of the buildings. Utilizing the lumped parameter SR (Sway-Rocking) model, which separately simulates the overall displacement of the super high-rise structure and the rotational motion of the foundation, the dynamic characteristic parameters of the simplified model are derived. The natural frequencies of the system are calculated by solving the equations of motion. The study examines the influence of parameters such as soil shear wave velocity and structural damping ratio on the dynamic response of the structure, with particular emphasis on displacement transfer rates. The findings indicate that inter-storey isolation structures are highly effective in reducing displacement responses in super high-rise buildings, especially when considering SSI effects. Specifically, for high-damping inter-storey isolation structures, modal frequencies decrease as soil shear wave velocity decreases. In non-isolated structures, the damping ratio increases with decreasing soil shear wave velocity, whereas for isolated structures, the damping ratio decreases, with a more pronounced reduction at higher damping ratios. Increasing damping significantly reduces inter-storey displacement and damage indices. However, under low shear wave velocity conditions, inter-storey isolation structures may experience increased displacement and damage.

This paper proposes a performance-based damage assessment procedure for reinforced concrete (RC) box tunnels subjected to earthquakes, employing a pseudostatic approach and a ductility-based damage index that incorporates the relative stiffness between the structure and surround soil, widely denoted as flexibility ratio (F). Distributed plasticity frame elements and discretized spring elements were used to model tunnel structures (slabs, walls, and columns) and the reactions of surrounding soil, respectively. Two damage-state descriptors were investigated: one based on the number of yielding in the tunnel members and another on the material state. Results show that the number-of-yielding based descriptor captures global structural capacity only for specific F ranges, while drift ratio lacks consistency as a damage index across all F ranges. In contrast, the material-state descriptor and damage indexes based on curvature ductility provide effective capacity estimation and are independent of F. Therefore, combining both descriptors is recommended for seismic performance evaluation of RC box tunnels. Additionally, higher F leads to brittle failure due to better load distribution and increased yielding before the strength degradation, while lower F results in concentrated damage with less yielding. These findings highlight the necessity of seismic design considering flexibility ratio for earthquake-resistant tunnels.

Moisture intrusion into the subgrade can significantly increase its moisture content, leading to a decrease in stiffness and strength, thereby compromising the serviceability performance of the pavement. Electro-osmosis has been used as an effective method for reducing moisture content and improving subgrade mechanical properties. However, its impact on mechanical properties has not been well understood. This study evaluated the mechanical behavior of electro-osmosis-treated subgrade soil through laboratory experiments that included bender element and cyclic triaxial tests. The study analyzed the effects of supply voltage and soil compaction degree on electro-osmosis treatment. The results showed that after treatment, the shear wave velocity increased by 26.0 to 59.2%, and the dynamic resilient modulus improved by a factor of three. Increasing the supply voltage and degree of compaction was found to lead to more significant improvements. Further analysis revealed that the reduction in moisture content alone was insufficient to contribute to the improvement. Cementation of colloids generated by the electrochemical reaction between soil particles also contributed to the improvement. It is worth noting that the nonuniform distribution of moisture and colloid in electro-osmosis-treated soils resulted in heterogeneity, with soil close to the anode being the weakest in terms of mechanical strength. Chemical injection or polarity reversal was suggested to enhance the uniformity of distribution and improve the overall treatment effectiveness. Overall, the study highlights the potential of electro-osmosis as a viable method for improving the mechanical properties of subgrade soil, but further research is required to investigate the heterogeneity of the distribution of moisture and colloid.

The inclusion of calcite precipitates (CaCO3) in soft soil can improve the mechanical properties. Understanding the variability in sand stiffness due to heterogeneous precipitates is crucial for stiffness evaluation and prediction. A novel discrete element-Monte Carlo (DE-MC) method was proposed to quantify the sand stiffness variability induced by stochastic distributions of calcite precipitates, specifically focusing on shear wave velocity (Vs) as an indicator of soil stiffness. A total of 1972 samples were constructed to simulate stochastic spatial distributions of calcite precipitates. Through joint stochastic analysis, the preferential paths formed by calcite clusters were identified as significant contributors to Vs variability. The normalized connectivity per unity distance contact weight (Cd,n) exhibited the most correlated relation with Vs. Two weight selection methods were applicable for using Cd,n to characterize and predict Vs. The results suggest that the DE-MC method has the potential to assess the variability in sand stiffness quantitatively.

In this research, we look at the variation of cross anisotropy as a result of the application of vacuum-assisted consolidation in very soft clays that underlie a trial embankment that was built at a site in the former Texcoco Lake, some 11 km north-east of central Mexico City. Cross-anisotropy was evaluated by referring to the cross-anisotropy index, VSH/VSV. It was used shear waves propagated horizontally (VSH) from cross-hole tests, and shear waves transmitted vertically (VSV) from seismic dilatometer and suspension logging tests. These tests were performed two months after the vacuum pumps were shut down thus, the changes induced by the vacuum-assisted consolidation of soil properties were observed from the shear wave velocities measurement. Moreover, the VSH/VSV ratio was evaluated from resonant column tests performed on soil specimens retrieved from a site near the trial embankment. These samples were trimmed horizontally and vertically and tested in the resonant column device. Field and laboratory test results showed that cross-anisotropy of the studied soft lacustrine soils is barely affected by the stress state variation induced by vacuum-assisted consolidation or by loading direction, as observed in the resonant column tests. Laboratory tests also showed that the VSH/VSV is related to the liquidity index through an empirical equation that can be used to estimate fairly well field values of VSH/VSV.

The seismic performance of underground structures is strongly influenced by the characteristics of both the surrounding soil and the earthquake. In contrast to traditional deterministic analysis methods, this study uses a stochastic analysis approach to investigate the effect of uncertainties in nonlinear soil characteristics, shear wave velocity, density, and earthquake randomness on the response of underground stations. The equivalent linearization method is employed to approximate the nonlinear behavior of the soil. The soil was modeled using a linear elastic constitutive model combined with Rayleigh damping in the finite element model. Inter-story displacements are used to determine structural damage. Probabilistic analysis methods are used to obtain their statistical characteristics, and the probability of failure is calculated. The results show that, according to single parameter analysis, random ground motion results in the greatest probability of exceeding the threshold (PET), while ground shear wave velocity significantly affects the coefficient of variation (COV), and the effect of density is the smallest. The study also found that when soil nonlinearity, shear wave velocity, and random ground motion are considered simultaneously, the range, mean, standard deviation, and COV of interstory displacement all increase significantly, but the PET slightly decreases. In summary, the analysis results indicate that random ground motion has the greatest impact on interstory displacement, followed by shear wave velocity, with nonlinear soil characteristics having a smaller effect, and density the least. Therefore, the impact of various uncertainties should be fully considered in the analysis of underground structures, especially random ground motion and shear wave velocity.

This paper investigates the anisotropic characteristics of Champlain marine clay soil using a combination of laboratory techniques. A modified oedometer cell with a piezoelectric ring actuator technique was used to measure shear wave velocity during consolidation stages. The axisymmetric design of the oedometer allowed for the determination of shear wave velocity in both the vertical and horizontal planes. The preliminary findings reveal that the sensitive marine clay is inherently anisotropic, with lower preconsolidation pressure for horizontally consolidated specimens and faster propagation of shear waves in the plane parallel to the bedding layer. High-precision strain gauges integrated into the consolidation ring were used to evaluate horizontal stress during the one-dimensional consolidation test. The ability to determine mean effective stress enables the normalization of shear wave velocities using this stress, providing more coherent empirical correlations in terms of shear wave velocity. Scanning electron microscopy was used to examine the microstructure of clay specimens, providing qualitative and quantitative insight into the restructuring and reorientation of clay platelets under consolidation stress. The consistency of the results through both micro and macro-scale analyses confirms the reliability of the experimental approach, highlighting its potential for future studies on the anisotropy of Champlain marine clay fabrics.

Shear wave velocity (Vs) is an important soil parameter to be known for earthquake-resistant structural design and an important parameter for determining the dynamic properties of soils such as modulus of elasticity and shear modulus. Different Vs measurement methods are available. However, these methods, which are costly and labor intensive, have led to the search for new methods for determining the Vs. This study aims to predict shear wave velocity (Vs (m/s)) using depth (m), cone resistance (qc) (MPa), sleeve friction (fs) (kPa), pore water pressure (u2) (kPa), N, and unit weight (kN/m3). Since shear wave velocity varies with depth, regression studies were performed at depths up to 30 m in this study. The dataset used in this study is an open-source dataset, and the soil data are from the Taipei Basin. This dataset was extracted, and a 494-line dataset was created. In this study, using HyperNetExplorer 2024V1, Vs prediction based on depth (m), cone resistance (qc) (MPa), shell friction (fs), pore water pressure (u2) (kPa), N, and unit weight (kN/m3) values could be performed with satisfactory results (R2 = 0.78, MSE = 596.43). Satisfactory results were obtained in this study, in which Explainable Artificial Intelligence (XAI) models were also used.