This study evaluates the impact of varying bedrock depths on local site amplification factors and their consequent influence on the vulnerability of buildings under seismic actions. An index-based methodology is implemented to analyze the seismic vulnerability of old masonry buildings in the historic center of Galata, & Idot;stanbul. As part of a site-specific analysis, soil models are developed to replicate a dipping bedrock at six different depths varying between 5 and 30 m beneath the ground surface. Consequently, potential damage scenarios are generated employing a seismic attenuation relation and damage distributions are compared for the cases with/without amplification effects. The findings point out that, the structural response undergoes the greatest amplification at a bedrock depth of 20 m, exceeding 1.6 and attaining its maximum value of 2.89 at the structural period of 0.22 s. The maximum shift in damage grades occurs for buildings with natural periods between 0.16 and 0.20 s on 15 m bedrock depth, whereas, for longer periods, the greatest increase occurs at 20 m bedrock depth compared to the scenarios without site amplification. As a result, this study emphasizes the significance of site-specific conditions that might amplify structural response and consequently, increase the seismic damage level in assessing the vulnerability of built heritage. By integrating geo-hazard-based evaluation into the large-scale seismic assessments, this study offers a framework for more accurate damage forecasting and highlights the need to include local site amplification effects in seismic risk mitigation plans, enhancing strategies for preserving built heritage.

In this study, the anisotropic nature of the medium is used to simulate the stratigraphic conditions. Taking the embankment of a high-speed railway as the object of study, the wave function expansion method is used to obtain the level solution for inverse plane shear wave scattering of the anisotropic half-space medium-waisted ladder form of the embankment. Then, by changing the anisotropy parameter of the soil medium, the effects of different incidence angles, dimensionless frequencies, embankment slopes, and anisotropic parameters on the isosceles trapezoidal form of the embankment structure are investigated. The results show that the anisotropy of the medium not only has a significant effect on the surface displacement of the embankment site but also makes other parameters more sensitive to the site effect, as manifested by the larger amplitude of the surface displacement caused by the incident wave along a certain angle at a certain dimensionless frequency compared to that of the isotropic medium. The embankment structure plays an important role in vibration damping and isolation during the propagation of vibration waves in the horizontal direction, and this phenomenon becomes less obvious with larger dimensionless frequency.

On December 18, 2023, the Jishishan M(S)6.2 earthquake caused serious damage to Jishixiongguan, China, which is a rammed-earth city wall, and was about 14 km away from the epicenter. There was a large area of collapse and part of the vertical ramming overlap separation phenomenon. Based on the results of earthquake field investigation, the dynamic response of Jishixiongguan under the earthquake was studied by analyzing the maximum displacement, peak acceleration (PA) and stress-strain distribution characteristics of wall measuring points at different locations, and the mechanism of Jishixiongguan failure induced by Jishishan M(S)6.2 earthquake was given. The results show that the plastic zone initially develops from the bottom erosion of the wall and the transverse through crack at the top of the right-end, and it rapidly extends downward along the slope into the interior of the wall, resulting in destructive permanent displacement shortly after the peak ground acceleration (PGA) is reached, the maximum plastic strain and maximum displacement occur at transverse through cracks of the right-wall top. Owing to the wall being constructed against a mountain slope, the amplification effect (AE) of the slope on the displacement of the wall is obvious, and the closer the wall is to the higher parts of the slope, the more significant the AE of the displacement is due to the combined effect of the mountain slope and the wall height. Pre-existing defects in the wall will weaken the AE of the slope and the wall height on the acceleration, however, the transverse through cracks will enhance the AE of the wall height on the acceleration. Stress concentration caused by hollowed-out overhangs and stress discontinuity caused by the transverse through crack is the internal factor of the wall failure, the plastic yield of soil caused by the AE of slope and wall height on displacement is the external factor of large-scale collapse of wall. The research results can provide theoretical guidance for the restoration and reinforcement of ancient sites.

Understanding the mechanical response of Q2 loess subjected to dry-wet cycles (DWCs) is the premise for the rational design of a hydraulic tunnel. Taking the Hanjiang-to-Weihe south line project in China as the research background, the microstructure evolution, strength degradation and compression characteristics of Q2 loess under different DWCs were investigated, and the fluid-solid coupling analysis of the hydraulic tunnel was carried out using the FLAC3D software. The amplification effect of tunnel surrounding soil pressure (SSP) and its influence on the long-term stability of the tunnel under different DWCs were obtained. The results showed that the pore microstructure parameters of the undisturbed and remolded loess basically tend to be stable after the number of DWCs exceeds 3. The porosity of Q2 loess is increased by 26%. The internal friction angle and cohesion of Q2 loess are decreased by 35% and 31%, respectively. The vertical strain of Q2 loess is increased by 55% after considering the DWCs. After the DWCs stabilized, the SSP ratio is increased between 10% and 25%. With the increase in buried depth of the tunnel, the SSP ratio is increased by 8%-10%. The SSP is reduced from 8% to 16% by the rise in groundwater level. As the number of DWCs increases and the burial depth of the tunnel decreases, the distribution of SSP becomes progressively more non-uniform. Based on the amplification factor and the modified compressive arch theory, the SSP distribution model of loess tunnel was proposed, which can be preliminarily applied to the design of supporting structures considering DWCs. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

In this study, the one-dimensional nonlinear Matasovic model was extended to the two- and three- dimensional stress space by replacing the shear strain with the generalized shear strain. The extended Matasovic model was subsequently combined with Dobry's excess pore water pressure generation model, and the reliability of the proposed loosely coupled effective stress analysis model was verified through undrained cyclic triaxial tests and a one-dimensional site response analysis. Finally, this method was applied to an engineering site in China to evaluate the nonlinear seismic response of liquefiable sites. The results show that the proposed effective stress analysis method can capture the dynamic behavior of the soil and the generation of pore water pressure during strong shaking. Moreover, there are differences between the proposed effective stress analysis method and the total stress analysis method for liquefiable sites, which indicates the need for careful selection in practical applications.

This study proposes a rapid seismic resilience assessment framework of tunnels in mountain regions considering the topography amplification effect and tunnel-soil dynamic interaction based on the indirect boundary element method (IBEM) coupled with the finite element method (FEM). The high efficiency is achieved by using a surrogate model to determine the tunnel fragility curves. This model reflects the relationship between the geometric and material variables of mountains and tunnels, as well as the tunnel damage index. To obtain the surrogate model, the identification of model variables is first explored quantitatively based on the random forest algorithm due to the high variable quantity. The dataset for training and testing the random forest is constructed from 600 numerical simulations. The IBEM-FEM coupling scheme is employed to describe the large-scale site response for tunnel damage analysis and significantly reduce the number of finite element grids for each sample. This scheme solves the nonlinear dynamic response of mountain tunnels under near-fault earthquakes. The surrogate model is then used to obtain the tunnel functionality and resilience. Based on the proposed framework, the influence of the mountain material, mountain height-span ratio, and tunnel position on the seismic fragility, functionality, and resilience are investigated. The results reveal that a surrogate model can be employed to replace a series of nonlinear time-history analyses of tunnels, with a high accuracy and efficiency. The shear modulus of the surrounding rock, the height-to-span ratio of the mountain, and tunnel position have a significant impact on tunnel fragility and resilience. This impact is correlated with the tunnel height. The mountain topography can cause a difference of approximately 20 % in the tunnel resilience.

The spatial variability of soil properties is pervasive, and can affect the propagation of seismic waves and the dynamic responses of soil-structure interaction (SSI) systems. This uncertainty is likely to increase the damage state of a structure and its risk of collapse. Additionally, conducting multiscale simulations efficiently in the presence of uncertainties is a pressing concern that must be addressed. In this work, a 3D probabilistic analysis framework for an SSI system considering site effects and spatial variability of soil property (i.e., elastic modulus, E) has been proposed. This framework is based on the random finite element method (RFEM) and domain reduction method (DRM). A multiscale model of a five-story reinforced concrete (RC) frame structure was developed on an ideal 3D slope to verify the effectiveness of the proposed framework. The dynamic responses of the structure were analyzed, and the peak floor acceleration (PFA) and peak interstory drift ratio (PSDR) were selected to estimate the damage state of structures. It was found that the proposed method significantly improves computational efficiency approximately 20 times compared with the direct method. In the regional models, with the increase of the coefficient of variation (COV) of E, the energy of seismic waves becomes more concentrated at the crest and the response spectrum value of medium and long periods increases. In the local SSI model, the soil variability increases the mean value of PSDR, resulting in a more severe damage state compared to the results from the deterministic analysis. Consequently, this study provides some suggestions for engineering practice, and the importance of probabilistic analysis considering spatially variable soils in the SSI problem is highlighted.