The pile-anchor structure is widely used in slope/landslide reinforcement, and is also applicable to debris flow and rockfall barriers in mountainous areas. However, the impact behavior of this structure has not been studied. To promote the use of this retaining structure in the prevention of slope geological disasters, this study investigated the dynamic responses and impact behavior of pile-anchor structures through a set of impact experiments, wherein dry granular materials with different particle size and sliding blocks with different masses were adopted to simulate different impact loading scenarios of granular flow and rockfall. The impact pressure on the pile-anchor structure, the seismic signals induced inside the slope during the sliding and impact processes, and the deformation characteristics and failure modes of the piles and anchors were systematically investigated. The results indicate that the peak impact force and intensity of the seismic signal are affected by the particle size of the impact granular materials. As the impact loading of sliding blocks increased, the tensile force of the anchor increased nonlinearly, the distribution pattern of the pile's impact dynamic moment changed, and anchor prestress loss was observed. The preliminary results obtained by this study are expected to provide the theoretical basis for designing relevant barriers in areas prone to debris flow and rockfall, and promote the inclusivity of the impact behavior of slope retaining structures in existing design codes pertaining to retaining structures.

Understanding the motion of particles in very dense granular flows is crucial for comprehending the dynamics of many geological phenomena, and advancing our knowledge of granular material physics. We conduct transparent ring shear experiments to directly observe the granular motion under relatively high-pressure conditions, and find that the granular velocity non-linearly decays, forming an approximately 7-particle-diameter-thick localized shear band. A fitting curve underlying non-local physics can be used to well predict velocity profile geometries that are almost independent of normal stress and shear velocity. Moreover, experimental results show monotonically decreasing granular kinetic temperature, which may be caused by energy dissipation due to more inelastic contacts under high confining pressures. The variation of granular temperature will significantly influence the local yield stress and rheological properties, which may lead to inhomogeneous fluidity of the material and thus to shear localization in very dense granular flows. Understanding how particles move under high pressure is essential for studying various geological phenomena and advancing our understanding of granular material physics. In this study, transparent ring shear experiments are conducted to observe the motion of granular particles in very dense granular flows under high normal stress. It is found that the velocity distribution progressively decays and forms a shear band with a width of approximately 7 particle diameters. We suggest an equation that can well predict the velocity profile both of the quasi-linear velocity in the fast-moving shear zone and the exponential velocity curve in the slow-motion region. Furthermore, we analyze the distribution of particle velocity fluctuation and particle density across the sample. Near the moving plate, the particle velocity fluctuation is more intense and the particle density is lower, gradually decreasing far from the moving plate. This phenomenon may be caused by energy dissipation due to inelastic contact between particles. The mechanical properties of the granular material are influenced by these variations in velocity fluctuation and particle density. Thus, this leads to an inhomogeneous shear strain rate and promotes the formation of shear zones under relatively high-pressure conditions. A nonlinearly decayed velocity profile and spontaneous shear localization are observed in plane shear granular flows under high normal stressThe monotonically decayed granular temperature may lead to inhomogeneities in very dense granular flows and thus to shear localizationThe length scale of the non-local model in very dense granular flows is estimated based on experimental observation

In this study, we develop a Smoothed Particle Hydrodynamics (SPH) 2D-model for simulating fully submerged granular flows and their arising water waves. The granular particles are characterised by a non-Newtonian flow pattern, following a Casson constitutive law, generalised by applying the infinitesimal strain theory to avoid numerical singularities inherited from the original law. The implementation of this rheological model on the weakly compressible viscous Navier-Stokes equations enables the simultaneous modelling of the motion of granular flows and their resulting water waves, establishing a monolithic representation of fluid-structure coupling. The novelty of this model lies in the numerical continuity of the generalised rheological model based mainly on the yield stress criterion, which is computed purely from the mechanical properties of granular materials, including internal friction, cohesion, and viscosity coefficients. The proposed SPH model is validated through two benchmarks available in the literature, representing a submarine landslide along an inclined plane and an immersed granular column collapse. The outcomes of our study illustrate the effectiveness of the proposed model in accurately predicting the motions of submerged granular masses and their resulting water waves, which is crucial for accurately predicting the behaviour of underwater landslides and other natural hazards.

In this study, landslide potential is investigated, using a new constitutive relationship for granular flow in a numerical model. Unique to this study is an original relationship between soil moisture and the inertial number for soil particles. This numerical model can be applied to arbitrary soil slab profile configurations and to the analysis of natural disasters, such as mudslides, glacier creeping, avalanches, landslips, and other pyroclastic flows. Here the focus is on mudslides. The authors examine the effects of bed slope and soil slab thickness, soil layered profile configuration, soil moisture content, basal sliding, and the growth of vegetation, and show that increased soil moisture enhances instability primarily by decreasing soil strength, together with increasing loading. Moreover, clay soils generally require a smaller relative saturation than sandy soils for sliding to commence. For a stable configuration, such as a small slope and/or dry soil, the basal sliding is absorbed if the perturbation magnitude is small. However, large perturbations can trigger significant-scale mudslides by liquefying the soil slab. The role of vegetation depends on the wet soil thickness and the spacing between vegetation roots. The thinner the saturated soil layer, the slower the flow, giving the vegetation additional time to extract soil moisture and slow down the flow. By analyzing the effect of the root system on the stress distribution, it is shown that closer tree spacing increases the drag effects on the velocity field, provided that the root system is deeper than the shearing zone. Finally, the authors investigated a two-layer soil profile, namely, sand above clay. A significant stress jump occurs at the interface of the two media.