Mesh-free methods, such as the Smooth Particle Hydrodynamics (SPH) method, have recently been successfully developed to model the entire wetting-induced slope collapse process, such as rainfall-induced landslides, from the onset to complete failure. However, the latest SPH developments still lack an advanced unsaturated constitutive model capable of capturing complex soil behaviour responses to wetting. This limitation reduces their ability to provide detailed insights into the failure processes and to correctly capture the complex behaviours of unsaturated soils. This paper addresses this research gap by incorporating an advanced unsaturated constitutive model for clay and sand (CASM-X) into a recently proposed fully coupled seepage flow-deformation SPH framework to simulate a field-scale wetting-induced slope collapse test. The CASM-X model is based on the unified critical state constitutive model for clay and sand (CASM) and incorporates a void-dependent water retention curve and a modified suction-dependent compression index law, enabling the accurate prediction various unsaturated soil behaviours. The integration of the proposed CASM-X model in the fully coupled flow deformation SPH framework enables the successful prediction of a field-scale wetting-induced slope collapse test, providing insights into slope failure mechanisms from initiation to post-failure responses.

The soil moisture content (SMC) of moist clay directly affects the traction performance of off-road tire. This study set up a high-fidelity interaction model between off-road tire and moist clay with various moisture content, developed by coupling the finite element method (FEM) and smoothed particle hydrodynamics (SPH) algorithm. The interaction behavior between pneumatic tire and moist clay is studied. Firstly, a finite element model of tire which can characterize the complex structure and nonlinear mechanical properties is established. The Drucker-Prager (D-P) constitutive model parameters of clay with various moisture levels are calibrated by soil mechanical test. The moist clay with various moisture content is modeled through the SPH algorithm. The hybrid FEM-SPH interaction model is used to define the tire-moist clay interaction. Moreover, a traction performance test device suitable for tire-moist clay is developed to verify the accuracy of the interaction model. The influence of soil moisture content and tire operating conditions include vertical load and inflation pressure on the longitudinal traction coefficient, rolling resistance coefficient and instantaneous sinkage of tire center are quantitatively analyzed. The purpose of this study is to provide accurate tire force information under moist clay for unmanned ground vehicle (UGV), which can improve the problem of wheel instantaneous sinkage of tire center and slip under moist clay, and effectively reduce the yaw phenomenon in the path tracking process.

Accurate modeling of soil behavior under seismic conditions is critical for understanding and mitigating earthquake-induced hazards. In this study, the Dyna-Simhypo model, an enhanced hypoplastic framework incorporating the intergranular strain tensor, is integrated with smoothed particle hydrodynamics (SPH) method for the first time to simulate co-seismic large deformation processes of slopes. The model's performance is validated through cyclic triaxial tests, seismic wave propagation analysis, and large-scale seismic slope simulations. Compared to the original Simhypo model, it eliminates ratcheting and reliably captures shear modulus reduction, damping buildup, and progressive soil degradation under cyclic loading. These advancements enable precise site response evaluations and accurate slope instability predictions, offering a robust tool for seismic hazard assessment.

This study introduces a coupled peridynamics (PD) and smoothed particle hydrodynamics (SPH) model to handle the complex physical processes in concrete dam structures subjected to near-field underwater explosions. A robust coupling algorithm is applied to ensure accurate data exchange between PD and SPH domains, enabling the simulation of fluid-structure interactions. To account for the material behavior under high strain rates, a rate- dependent concrete model is integrated into the PD-SPH framework. The developed PD-SPH model is validated through simulations of centrifugal model tests, with results benchmarked against experimental findings and finite element method (FEM) predictions. The simulation captures key damage features, including horizontal tensile cracking at the dam head and an oblique penetrating crack in the dam body, forming an angle of approximately 17 degrees relative to the horizontal. Velocity and strain responses at critical monitoring points demonstrate strong agreement with FEM results, showcasing the model's capability in accurately predicting the structural responses and failure of concrete dams caused by underwater explosions. To the best of the authors' knowledge, research applying a coupled PD-SPH model to concrete structures under blast loading is still rare, particularly when considering the entire physical process, from explosive detonation to structural failure, accounting for fluid-structure interactions.

This paper experimentally investigates the wave pressure and pore pressure within a sandy seabed around two pipelines under the action of random waves (currents). The experiments revealed that when the random wave plus current cases are compared with the random wave-only case, the forward current promotes wave propagation, whereas the reversed backward current inhibits wave propagation. Furthermore, the wave pressure on the downstream pipeline decreases as the relative spacing ratio increases and increases as the diameter increases. However, alterations in the relative spacing ratio or dimensions of the downstream pipeline exert a negligible influence on the wave pressure of the upstream pipeline. Moreover, the relative spacing ratio between the pipelines and the dimensions of the pipelines considerably influence the pore pressure in the sand bed. When the relative spacing ratio remains constant, increasing the downstream pipeline diameter will increase the pore-water pressure of the soil below the downstream pipeline.

A discontinuous smoothed particle hydrodynamics (DSPH) method considering block contacts is originally developed to model the cracking, frictional slip and large deformation in rock masses, and is verified by theoretical, numerical and/or experimental results. In the DSPH method, cracking is realized by breaking the virtual bonds via a pseudo-spring method based on Mohr-Coulomb failure criteria. The damaged particles are instantaneously replaced by discontinuous particles and the contact bond between the original and discontinuous particles is formed to simulate the frictional slip and separation/ contraction between fracture surfaces based on the block contact algorithm. The motion of rock blocks and the contact force of discontinuous particles are determined following Newton's second law. The results indicate that the DSPH method precisely captures the cracking, contact formation and complete failure across six numerical benchmark tests. This single smoothed particle hydrodynamics (SPH) framework could significantly improve computational efficiency and is potentially applicable to broad multi-physical rock engineering problems of different scales. (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/).

Earthquake-induced soil liquefaction poses significant risks to the stability of geotechnical structures worldwide. An understanding of the liquefaction triggering, and the post-failure large deformation behaviour is essential for designing resilient infrastructure. The present study develops a Smoothed Particle Hydrodynamics (SPH) framework for earthquake-induced liquefaction hazard assessment of geotechnical structures. The coupled flowdeformation behaviour of soils subjected to cyclic loading is described using the PM4Sand model implemented in a three-phase, single-layer SPH framework. A staggered discretisation scheme based on the stress particle SPH approach is adopted to minimise numerical inaccuracies caused by zero-energy modes and tensile instability. Further, non-reflecting boundary conditions for seismic analysis of semi-infinite soil domains using the SPH method are proposed. The numerical framework is employed for the analysis of cyclic direct simple shear test, seismic analysis of a level ground site, and liquefaction-induced failure of the Lower San Fernando Dam. Satisfactory agreement for liquefaction triggering and post-failure behaviour demonstrates that the SPH framework can be utilised to assess the effect of seismic loading on field-scale geotechnical structures. The present study also serves as the basis for future advancements of the SPH method for applications related to earthquake geotechnical engineering.

With the increasing number of projects in cold regions and the widespread use of artificial freezing methods, conducting research on the dynamic properties of frozen soil has become a considerable issue that cannot be avoided in permafrost engineering. Currently, the numerical simulation research on the dynamic mechanical behavior of frozen soil is less concerned with the changes in stress, strain, and particle damage inside the material. The necessary conditions for conducting this study are compatible with the core idea of smooth particle hydrodynamics (SPH). In this study, the Eulerian SPH method was modified to address numerical oscillations and errors in solid mechanics, particularly impact dynamics problems. A numerical scheme for simulating the split Hopkinson pressure bar test was developed within the modified Eulerian SPH framework and implemented using self-programming. The frozen soil dynamic mechanical behavior was simulated under three strain rates. The accuracy and superiority of the SPH method were verified through calculations and experiments. The simulation captures the stress and strain responses within the sample at different moments during the impact process, indicating that the frozen soil strain rate-strengthening effect resulted from microcrack expansion and inertial effects.

Permanent deformation and uplift caused by fault rupture is one of the most significant hazards posed by earthquakes on the built environment. In this paper, we use smoothed particle hydrodynamics (SPH) to explore the effects of soil layering or stratification on the trajectories and deformation patterns caused by rupturing reverse faults in bedrock, as well as in the foundations of engineered earth structures. SPH is a continuum meshfree numerical method highly adept at modeling large deformation problems in geotechnics. Through the use of constitutive models involving softening behavior as well as critical state type models, we isolate the effects of rigid body rotation from critical state behavior of soil in helping explain the frequently observed rotation of shear bands emanating from the bedrock fault. This analysis is facilitated by the fact that the SPH method allows us to track the propagation of shear bands over substantial amounts of vertical uplift (more than 50% of the total height of the soil deposit), far beyond many previous computational studies employing the finite element method (FEM). We observe and characterize various emergent features including fault bifurcations, stunted faults, and tension cracking, while providing insights into practical guidelines regarding the potential surface distortion width, and the critical amount of fault displacement required for surface rupture depending on the multilayered constitution of the soil deposit. Finally, we predict the expected amount of surface distortion and internal damage to earthen embankments depending on varying fault location and soil makeup.

Seepage-induced backward erosion is a complex and significant issue in geotechnical engineering that threatens the stability of infrastructure. Numerical prediction of the full development of backward erosion, pipe formation and induced failure remains challenging. For the first time, this study addresses this issue by modifying a recently developed five-phase smoothed particle hydrodynamics (SPH) erosion framework. Full development of backward erosion was subsequently analysed in a rigid flume test and a field-scale backward erosion-induced levee failure test. The seepage and erosion analysis provided results consistent with experimental data, including pore water pressure evolution, pipe length and water flux at the exit, demonstrating the good performance of the proposed numerical approach. Key factors influencing backward erosion, such as anisotropic flow and critical hydraulic gradient, are also investigated through a parametric study conducted with the rigid flume test. The results provide a better understanding of the mechanism of backward erosion, pipe formation and the induced post-failure process.