Accurately modeling soil-fluid coupling under large deformations is critical for understanding and predicting phenomena such as slope failures, embankment collapses, and other geotechnical hazards. This topic has been studied for decades and remains challenging due to the nonlinear responses of geotechnical structures, which typically result from plastic yielding and finite deformation of the soil skeleton. In this work, we comprehensively summarize the theory involved in the soil-fluid coupling problem. Within a finite strain framework, we employ an elasto-plastic constitutive model with linear hardening to represent the solid skeleton and a nearly incompressible model for water. The water content influences the behavior of the solid skeleton by affecting its cohesion. The governing equations are discretized by material point method and two sets of material points are employed to independently represent solid skeleton and fluid, respectively. The proposed method is validated by comparing simulation results with experimental results for the impact of water on dry soil and wet soil. The capability of the method is further demonstrated through two cases: (1) the impact of a rigid body on saturated soil, causing water seepage, and (2) the filling of a ditch, which considers the erosion of the foundation. This work may provide a versatile tool for analyzing the dynamic responses of fluid and solid interactions, considering both mixing and separation phenomena.

The practice of widening levees to mitigate frequent river flooding is globally prevalent. This paper addresses the pressing issue of sand-filled widened levee failures under the combined effect of heavy rainfall and high riverine water levels, as commonly observed in practice. The primary objective is to illuminate the triggering mechanism and characteristics of such levee failures using the well-designed physical model experiment and Material Point Method (MPM), thus guiding practical implementations. Experimentally, the macro-instability of the levee, manifested as slope failure within the sand-filled widened section, is primarily triggered by changes in the stress regime near the levee toe and continuous creep deformation. Upon failure initiation, the levee slope experiences a progressive failure mode, starting with local sliding, followed by global sliding, and ultimately transitioning into a flow-like behaviour, which characterises the slide-to-flow failure pattern. The slope failure along the interface between the original and new levees is the result of shear deformation rather than the cause. Parametric studies conducted using the calibrated MPM model reveal a critical threshold for the widening width, beyond which the volume of sliding mass and travel angle exhibit no further variation. Increasing the cohesion of the river sand used for levee widening demonstrates the most pronounced improvement in levee stability in the face of the combined effect of intense rainfall and elevated river levels. The MPM-based evaluation of common slope protection measures demonstrates the superior protective benefits of grouting reinforcement and impervious armour layer protection, providing valuable insights for reinforcement strategies in levee engineering applications.

Landslides, which are a type of process-based geological hazard, exhibit stagewise characteristics that serve as important guidance for the prevention and mitigation of slope engineering disasters. The cross-correlation and randomness of soil parameters can influence the evolution of landslide characteristics. This paper, based on the spatial variability of slope soil parameters, combines copula theory and the material point method (MPM) to establish a Monte Carlo-random material point method considering the cross-correlation of soil parameters. This resulting method is called copula-RMPM. It investigates the probability distributions of slope instability and landslide large deformation characteristics, such as sliding distance, landslide thickness, collapse range, and volume of sliding mass. The results indicated that in the study of soil parameter characteristics, failure probability increases with increased correlation coefficient. Also, failure probability showed a positive correlation with the variability coefficient of cohesion and internal friction angle, with failure probability being more sensitive to the variability coefficient of the internal friction angle. The landslide large deformation characteristics generally follow the normal distribution; they exhibit significant fluctuations in sliding distance and sliding mass area despite the relatively small variability coefficient. Compared with the results of random field simulation of soil parameters, the probability of landslide large deformation characteristics obtained by deterministic soil parameters is often lower. Therefore, the probability distribution of landslide large deformation characteristics obtained by the Monte Carlo-random material point method considering the cross-correlation of soil parameters is more meaningful for engineering guidance.

The frequent occurrence of extreme rainfall events often triggers levee slope failure (LSF), which, due to the levee effect, significantly damages the roads behind the levee. This paper presents a novel framework for the quantitative risk assessment of roads posed by LSF. Within the framework, the innovative integration of Monte Carlo simulation (MCS) and Material point method (MPM) provides a unique solution for simulating the complicated dynamic relationship between LSF and road destruction. MCS generates precise failure scenarios for MPM simulations, overcoming the limitations of traditional approaches in addressing uncertainty in complex scenario systems. With its technical superiority in capturing post-failure deformations, MPM offers critical insights for assessing road exposure and vulnerability. The framework also accounts for indirect losses from road disruptions, which have long been overlooked. The application of the framework to the risk assessment of the road behind the Shijiao Levee in the Pearl River Basin fully demonstrates its practicality and robustness. Compared to traditional risk assessment methods, the proposed framework provides a more refined dynamic evaluation, facilitating the formulation of more effective disaster mitigation strategies.

Gaining insights into landslide deposits form can help achieve a better understanding of the overall landslide dynamics. Previous studies have focused on understanding global characteristics of the runout process and final deposit, without attempting to comprehend the deposition process and the underlying mechanisms. Here, we employed a combination of flume experiments and numerical simulations based on the material point method (MPM) to investigate the influence of friction on the characteristics of rock avalanche deposits and gain a deeper understanding of the mechanisms involved. MPM simulations have generally relied on simple soil constitutive models, which cannot capture the rate-, pressure-, and size-dependent characteristics of geomaterials. Thus, we adopted a viscoplastic non-local mu(I) rheology model, which has been proven to be able to reproduce depositional characteristics with high accuracy. We identified two stages during deposition, namely a translational stage, primarily influenced by the basal frictional resistance, and a subsequent impact shear stage, governed by the internal frictional resistance.

The paper presents a refined implicit two-phase coupled Material Point Method (MPM) designed to model poromechanics problems under static and dynamic conditions with stability and robustness. The key variables considered are the displacement and pore water pressure. To improve computational efficiency, we incorporate the Finite Difference Method (FDM) to solve pore pressure, stored at the center of the background grid where the material points reside. The proposed hydromechanical MPM cannot only effectively addresses pore pressure oscillation, particularly evident in nearly incompressible fluids-a common challenge with Galerkin interpolation, but also decreases the degrees of freedom of the system equations during the iteration process. Validation against analytical solutions and various numerical methods, encompassing 1D and 2D plane-strain poromechanical problems involving elastic and elastoplastic mechanical behavior, underscores the method's resilience and precision. The proposed MPM approach proves adept at simulating both quasi-static and dynamic saturated porous media with significant deformation.

Aging and heavy rainfall can cause earth dams to undergo failure, which involves large displacements. Due to mesh distortion, however, the finite element method (FEM) is unsuitable for analyzing such large displacements. As an alternative, the material point method (MPM) ensures accurate simulation of large displacements, without the need for remeshing. This study uses MPM to investigate the post-failure behaviors of earth dams with various geometries and under different rainfall intensities. The MPM results are validated by comparing the MPM-derived pore water pressure with FEM-derived values for the same model, and a close alignment is confirmed. Different failure patterns are observed depending on the geometry and rainfall intensity. Under high water levels and rainfall conditions, the distributions and evolutions of the displacements and deviatoric strain are initially concentrated at the dam toe and gradually propagated from the downstream slope toe to the dam crest. Conversely, the distribution of pore water pressure remains relatively constant under high water levels, while rapid changes are observed under rainfall conditions. The runout distance, crest settlement, and sliding volume increase with increasing dam height, decreasing slope ratio, and increasing rainfall intensity. Therefore, MPM can be used as a promising tool for evaluating the entire failure mechanisms and post-failure behaviors of unsaturated earth dams.

Permeable pipe piles accelerate the bearing capacity of the pile foundation by releasing the excess pore water pressure (EPWP) of the soil around the pile through appropriate openings in the pile body. This study couples the Material Point Method (MPM) and the Finite Element Method (FEM) to establish a full-process model of pile driving and consolidation of permeable piles, and proposes a continuous drainage boundary condition that can reflect the plugging effect of permeable holes. The correctness of the model and boundary conditions are verified by comparison with experiments, and then the effects of soil properties, opening characteristics, and boundary permeability on the accelerated consolidation effect of permeable piles are analyzed. The results show that: the permeable pile with a permeable area ratio greater than 50% and a local opening ratio greater than 5% can save more than 60% of the consolidation time compared to conventional piles; the proposed boundary conditions can accurately describe the permeability of the permeable hole under the influence of plugging; in addition, the calculation formulae for the accelerated consolidation effect of permeable piles and the variation of continuous drainage boundary interface parameters with permeable area ratio are given, which can provide references for engineering design.

Seismic-induced submarine landslides pose significant risks to offshore structures. To enhance our understanding of this phenomenon, we have developed a CFD-MPM capable of simulating complete mechanisms behind earthquake induced submarine landslide. Recent centrifuge tests have demonstrated that the permeability of marine sediment is a critical factor in determining the failure mechanism of submarine landslides. Specifically, a lower permeability increases the likelihood of a slope transitioning from failure to gravity debris flow. Our CFDMPM, validated with centrifuge tests, supports this conclusion. Moreover, we conducted a sensitivity analysis of seismic-induced submarine landslides using the CFD-MPM. In the case of contractive soil, a lower permeability leads to slower dissipation of excess pore water pressure, resulting in longer submarine debris flow runouts. Additionally, in the case of softening soil, a lower permeability increases the chances of spreads as a failure mechanism, while a higher permeability favours retrogressive flow slides. This study sheds light on the diverse effects of sediment permeability on submarine landslide mechanisms, offering crucial insights for hazard assessment and mitigation strategies in offshore engineering and coastal management.

This paper investigates the implementation of a nonlocal regularisation of the material point method to mitigate mesh-dependency issues for the simulation of large deformation problems in brittle soils. The adopted constitutive description corresponds to a simple elastoplastic model with nonlinear strain softening. A number of benchmark simulations, assuming static and dynamic conditions, were performed to show the importance of regularisation, as well as to assess the performance and robustness of the implemented nonlocal approach. The relevance of addressing stress oscillation issues, due to material points crossing element boundaries, is also demonstrated. The obtained results provide relevant insights into brittle materials undergoing large deformations within the MPM framework.