Previous earthquakes reveal that the sedimentary V-shaped canyon (SVC) may result in severe damage of canyon-crossing bridges (CCBs). The seismic response of CCB is affected by various parameters, including sedimentary soil characteristics and fault rupture mechanisms. However, these influential parameters of SVC on the seismic response of CCB have not been sufficiently studied in the existing literature. Thus, this study aims to identify the most influential factor on the seismic response of bridges across SVC using parametric analysis. For this purpose, the spectral element method (SEM) is adopted to simulate the wavefield of SVC considering the fault dynamic rupture. The characteristics of ground motions in the Forward region (FR) and the Middle region (MR) are investigated. The sensitivity of ground motions recorded in SVC to four main influential factors (i.e. shear wave velocity of sedimentary soil Vs, the ratio of sedimentary soil depth to canyon depth d/D, layer sequence O, and fault-to-canyon distance Rrup) is numerically evaluated. Furthermore, the parametric analysis is performed to estimate the impact of these influential parameters on the seismic response of a CCB. The results reveal that the amplitudes of pulse-type ground motions in the illuminated side of SVC increase with the decrease of Vs. As the Vs decreases from 2300 m/s to 400 m/s, the residual deformations of four bearings increase by 293 %, 93 %, 451 %, and 292 %, respectively. When the d/D is 0.3, the velocity pulse ground motions in SVC have the largest PGVs. The base shear of the piers in the case of d/D = 0.3 increases by more than 77.3 % compared to that without considering the sedimentary soil (d/D = 0). The inverted sequence may result in larger seismic responses of bearings and piers compared to normal sequence. Rrup has the most significant effect on the seismic response of CCBs. The higher-order effect and additional plastic hinges are more noticeable when Rrup is less than or equal to 7.5 km.

Despite the prevalence and validity of the universal distinct element code (UDEC) in simulations in geotechnics domain, water-weakening process of rock models remains elusive. Prior research has made positive contributions to a presupposed link between modelling parameters and saturation degree, Sr. Nevertheless, this effort presents inaccurate results and limited implications owing to the misleading interpretation, that is, devoid of the basic logic in UDEC that modelling parameters should be calibrated by tested macroscopic properties in contrast to a presupposed relation with Sr. To fill this gap, a new methodology is proposed by coupling a computationally efficient parametric study with the simulation of water-weakening mechanisms. More specifically, tested macroscopic properties with different Sr values are input into parametric relations to acquire initial modelling parameters that are sequentially calibrated and modulated until simulations are in line with geomechanical tests. Illustrative example reveals that numerical water-weakening effects on macroscopic properties, mechanical behaviours, and failure configurations are highly consistent with tested ones with noticeable computational expediency, implying the feasibility and simplicity of this methodology. Furthermore, with compatibility across various numerical models, the proposed methodology substantially extends the applicability of UDEC in simulating water-weakening geotechnical problems. (c) 2025 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 recent years, the escalation in accidental explosions has emerged as a formidable threat to tunnel infrastructures. Therefore, it is of great significance to conduct a dynamic performance analysis of the tunnels, to improve the safety and maintain the functionality of underground transport hubs. To this end, this study proposes a dynamic performance assessment framework to assess the extent of damage of shallow buried circular tunnels under explosion hazards. First, the nonlinear dynamic finite element numerical model of soil-tunnel interaction system under explosion hazard was established and validated. Then, based on the validated numerical model, an explosion intensity (EI) considering both explosion equivalent and relative distance was used to further analyze the dynamic response characteristics under typical explosion conditions. Finally, this study further explored the influence of the integrity and strength of the surrounding soil, concrete strength, lining thickness, rebar strength, and rebar rate on the tunnel dynamic performance. Our results show that the dynamic performance assessment framework proposed for shallow circular tunnels fully integrates the coupling effects of explosion equivalent and distance, and is able to accurately measure the degree of damage sustained by these structures under different EI. This work contributes to designing and managing tunnels and underground transport networks based on dynamic performance, thereby facilitating decision-making and efficient allocation of resources by consultants, operators, and stakeholders.

Granular piles, either ordinary or encased with geosynthetic materials are being extensively used as one of the ground improvement techniques, depending on the strength of the adjoining soil. The optimum granular pile (GP) length is still a matter of research, even though the approach is widely established in the literature. In the present study, a thorough and detailed parametric analysis has been carried out to ascertain the optimum length for ordinary and encased granular piles using a 2D axisymmetric finite element model. The soil behaviour has been modelled with the linearly elastic perfectly plastic Mohr-Coulomb failure criterion constitutive model. The parameters considered in this study are area replacement ratio, encasement stiffness, soil properties, infill material properties, and crust layer thickness. The findings revealed that the parameters with the greatest influence on the optimum length are the area replacement ratio, encasement stiffness, surrounding soil strength properties, and friction angle of the infill material. For encased granular piles, the optimum length was often found to be longer than ordinary granular piles. It was found that the optimum length for ordinary and encased GP ranges between 0.8-2.12 and 1-2.75 times of footing diameter (D), respectively. Through this study, an effort has also been made to investigate how the aforementioned parameters affect the radial bulging of the end-bearing GP. The upper of 0.5-1.5D showed excessive bulging in each case. Additionally, the optimum encasement length was determined, and it was found that increasing the encasement length beyond 1.5D results in minimal improvement. Furthermore, a multiple regression analysis was employed to establish the correlation between the optimum length of GP and potential influencing factors.

Landslide-generated debris flow is one of the severe outcomes of slope failure in hilly areas that have the potential to severely affect the physical and biological environment. The precise identification of the vulnerable areas depends on a broad understanding of the flow morphology and deposition process of the flowing debris. However, owing to varying compositions of the flowing debris coupled with inherent complex field topography, makes the flow prediction more complex. In this study, numerical analysis was performed using a distinct element-based numerical modelling technique. The numerical model was calibrated using a physical scale-down model of the residual soil slope. Calibration of the numerical model was performed under both dry and wet debris flow induced in the scale-down laboratory model. The final calibrated model was used to validate a case study. Following the successful validation of the developed numerical model, parametric analysis (various slope profiles, heights, inclinations, and particle size distributions of debris) was performed to study the rheology of the debris under both dry and wet conditions generated post-landslide event. This study gives a reliable idea about the possible flow behaviour in a simple residual soil slope and can be used as a guide to performing debris flow analysis for any natural slope. It also emphasises the need for the adoption of more robust debris runoff preventive measures in case of failures observed after precipitation owing to the very high energy and momentum of flowing wet debris in comparison with dry debris.

In this study, a single-layer SPH approach that takes into account full soil-water interactions is proposed. The approach updates the propagation of pore pressure through combination of volumetric strain and Darcy's law, accounting for the momentum equation, soil constitutive behavior, and the development of pore pressure at each timestep of the simulation. The proposed method is validated by analytical solutions of consolidation problems. To showcase its capability in simulating large-deformation problems with hydro-mechanical interactions, a physical test of a seepage-induced sinkhole was simulated using the proposed SPH method. The good agreements suggest that the proposed method can capture the key features of sinkhole developments and serve as a promising tool to explore the associated failure mechanism. A series of parametric studies are then conducted to reveal the influences of material properties and hydraulic conditions on the failure behavior of sinkholes, including failure patterns, influence zone, and surface settlement.