Tensile cracks play a pivotal role in the formation and evolution of reservoir landslides. To investigate how tensile cracks affect the deformation and failure mechanism of reservoir landslides, a novel artificial tension cracking device based on magnetic suction was designed to establish a physical model of landslides and record the process of landslide deformation and damage by multifield monitoring. Two scenarios were analyzed: crack closure and crack development. The results indicate that under crack closure, secondary cracks still form, leading to retrogressive damage. In contrast, under crack development conditions, the failure mode changes to composite failure with overall displacement. The release of tensile stresses and compression of the rear soil are the main driving forces for this movement. Hydraulic erosion also plays a secondary role in changing landslide morphology. The results of multifield monitoring reveal the effects of tensile cracking on reservoir landslides from multiple perspectives and provide new insights into the mechanism of landslide tensile-shear coupled damage.

In this paper, the Huangtupo Riverside Slump 1#, a reservoir landslide with double sliding zones in the Three Gorges Reservoir Area of China, is selected as the prototype for a scaled physical model test subjected to water level fluctuation and rainfall. The spatial-temporal characteristics of the multi-physical monitoring data are thus obtained, including the pore water pressure, earth pressure, surface deformation, and deep deformation. Subsequently, the failure mechanism and evolution process of the landslide model are discussed. The results indicate that the rise and fall of reservoir water correspondingly increase and decrease the pore water pressure and earth pressure at the front edge of the model, while having almost no effect on the trailing edge. The rainfall increases the pore water pressure and soil pressure of the entire model, and the increase is proportional to its duration and intensity but limited by the height of overlying soil. Both the surface deformation and deep deformation increase with the fall of reservoir water and rainfall. Except for the weakening effect of the soil caused by the first rise of reservoir water, which results in a certain surface deformation and deep deformation, the surface deformation has almost no response with the subsequent rises, while the deep deformation decreases with the rises. The Riverside Slump 1-1# exhibits the characteristics of retrogressive failure with whole evolution phases, while the Riverside Slump 1-2# exhibits a composite evolution, in which its middle front belongs to the retrogressive failure within the initial deformation, and the trailing edge belongs to the progressive failure within the accelerated deformation.

Rainfall-induced landslide mitigation remains a critical research focus in geotechnical engineering, particularly for safeguarding buildings and infrastructure in unstable terrain. This study investigates the stabilizing performance of slopes reinforced with negative Poisson's ratio (NPR) anchor cables under rainfall conditions through physical model tests. A scaled geological model of a heavily weathered rock slope is constructed using similarity-based materials, building a comprehensive experimental setup that integrates an artificial rainfall simulation system, a model-scale NPR anchor cable reinforcement system, and a multi-parameter data monitoring system. Real-time measurements of NPR anchor cable axial forces and slope internal stresses were obtained during simulated rainfall events. The experimental results reveal distinct response times and force distributions between upper and lower NPR anchor cables in reaction to rainfall-induced slope deformation, reflecting the temporal and spatial evolution of the slope's internal sliding surface-including its generation, expansion, and full penetration. Monitoring data on volumetric water content, earth pressure, and pore water pressure within the slope further elucidate the evolution of effective stress in the rock-soil mass under saturation. Comparative analysis of NPR cable forces and effective stress trends demonstrates that NPR anchor cables provide adaptive stress compensation, dynamically counteracting internal stress redistribution in the slope. In addition, the structural characteristics of NPR anchor cables can effectively absorb the energy released by landslides, mitigating large deformations that could endanger adjacent buildings. These findings highlight the potential of NPR anchor cables as an innovative reinforcement strategy for rainfall-triggered landslide prevention, offering practical solutions for slope stabilization near buildings and enhancing the resilience of building-related infrastructure.

The raw-material mix ratio and preparation of similar materials are crucial for the success of physical model tests and for accurately reflecting prototype properties. In this study, an optimum similar material for plateau alluvial and lacustrine (PAL) round gravel was developed based on similarity theory. The similar materials were subjected to sensitivity factor analysis and microscopic analysis. Subsequently, the optimum similar material was applied to a three-dimensional (3D) physical model test of an ultradeep foundation pit (FP). The findings show that the similar material prepared with gypsum, LD, bentonite, water, barite powder, and DS at a ratio of 1:1:1.4:3.5:8.8:13.2 was the best for a 3D physical model test of the ultradeep FP in PAL round gravel strata. The sensitivity-factor analysis revealed that barite powder had the greatest impact on gamma, that c and phi were primarily affected by bentonite, and that the LD-gypsum ratio controlled E. A nonuniform particle-size distribution as well as the presence of edge-to-face contacts and small pores between particles constituted the microphysical factors affecting the mechanical properties of the optimum similar material. Using dolomite with a Mohs hardness of 3.5-4 instead of traditional quartz sand with a Mohs hardness of 7 as the raw material can produce a similar material for the target soil with mechanical parameters closer to those of the ideal similar material. The application of the optimum similar material in physical model tests has revealed the stress field response law of ultra deep foundation pit excavation. This study could provide reference and inspiration for the development of similar materials in gravel formations with weaker mechanical properties.

The weak mechanical properties of weak interlayers are crucial for controlling landslide deformation and failure under water level fluctuation. The instability and failure of landslides in reservoirs can lead to unpredictable consequences. In this study, the reservoir bank landslide with a weak interlayer was selected as the research subject. The material composition, structural characteristics, mechanical properties, and permeability of the landslide were determined through field investigations and tests. Additionally, a physical model test was conducted to explore the groundwater variation rules and deformation failure modes of landslides with weak interlayers under different water level fluctuation rates. The results indicate that due to the low permeability of the interlayer, there was a significant lag in monitoring data such as pore water pressure within the interlayer under the same water level fluctuation rate. At the same point, the faster the water level fluctuation rate, the greater the degree of lag. The deformation and failure mode of landslide with weak interlayer under reservoir water level fluctuation can be summarized as the following five stages: slope toe erosion stage, cracks on slope surface and interlayer stage, micro-collapse of slope toes and crack expansion of slope surface and interlayer stage, local micro-collapse of slope toe and crack penetration of slope body stage, crack development leads to landslide of slope body stage. This study provides theoretical support for prevention and control of landslides with weak interlayers in the gravel soils of reservoirs.

Geosynthetic-reinforced pile-supported (GRPS) embankments are a primary method for mitigating subgrade settlement. However, the load transfer mechanism between piles and soil remains incompletely understood, with the load sharing ratio (LSR) between piles and soil serving as a critical indicator for this mechanism. This study conducted a model test at a similarity ratio of 1:10 to investigate the effects of load amplitude, load frequency, number of geogrid layers, and pile types on the LSRs of piles and soil in GRPS embankments. The test results show that the pile's LSR increases with rising values of these parameters, while the corresponding LSR of the soil decreases. Among these parameters, the number of geogrid layers has the least effect on the LSRs of both piles and soil. Furthermore, the rigid long pile demonstrates a higher LSR than the flexible short pile, attributed to its greater stiffness. The influence of load frequency on the LSRs of the rigid long pile is also less significant compared to the flexible short pile. Variations of LSR increment can be predicted using a formula that incorporates the number of loading cycles. These findings provide deeper insights into the load transfer mechanism in the pile-soil system, contribute to the optimization of GRPS embankments design practice, and ultimately enhance performance and reliability of the GRPS embankments in geotechnical engineering applications.

Bedrock fault dislocation is a crucial structural factor influencing landslide movement. Accurately predicting the location and scale of rupture zones within a slope body is essential for effective slope construction design and risk mitigation. Based on an analysis of seismic damage in slope cross-bedrock faults, this article creatively realizes the physical model test of the slope and its covering layer site with soil rupture zones at the top and toe of the slope caused by the dislocation of the bedrock normal fault. Through the model test, macroscopic phenomena were observed, and microscopic analysis was obtained by deploying sensors. The main results were as follows: (i) The evolutionary process of the instability mechanism could be divided into three stages: crack damage stage (Stage I), crack expansion and penetration stage (Stage II), and slope instability stage (Stage III). (ii) Two rupture modes of the soil body in the slope under bedrock dislocation were identified, with the rupture mode at the slope crest having a greater impact on the soil slope. (iii) Inferring the position of bedrock faults through the location of the main rupture zones on the slope surface represents a feasible supplementary method for identifying seismogenic structures during field surveys. These research results provide a scientific basis for the stability assessment of cross-fault slopes and the reinforcement design of landslide disasters.

The growth of rock structural surfaces makes the deformation and stability analysis of rock pits more complex and challenging than that of soil pits. To investigate the damage mechanism of this foundation and provide ideas for foundation support, the paper constructed a simplified model by approximate plane analysis and dimensionless analysis of the similarity principle. The physical model was constructed from a mixture of materials, and then foundation excavation and loading tests were completed. The strain value of the strain gauges increased in stages in the range of 0-250. Excavation of the structural surface resulted in an increased number of deformation mutations. This type of rocky foundation damage underwent three stages: overburden crack development, cumulative deformation of the S-S, and collapse of the sliding body. Furthermore, numerical simulations corresponding to the physical model tests were set and used to validate and complement the physical tests. When the line loads reached 70.83 kN/m and 127.5 kN/m, the plastic zone of the structural surface was completely penetrated and the sliding body collapsed. The results of the studies can serve as a useful reference and guide for the excavation and support design of real-world rock foundation projects that are similar.

Seepage-initiation-braking-type (SIBT) landslides are the majority of reservoir landslides in the Three Gorges Reservoir Area in China that involve gradual deformation in response to water level (WL) and rainfall rather than experiencing an abrupt failure and sliding directly into the river, highlighting the complex nature of this landslide. Here, a physical model test with the rainfall and the fluctuation of WL was conducted on a representative SIBT landslide, Huangtupo Linjiang No. 1 landslide (HTPLJ1). The changes in pore water pressure, earth pressure, and overall displacement of the landslide model were monitored by a monitoring system. The results revealed distinct stages in the landslide model: impoundment-induced deformation, preliminary sliding, stagnation and stability, re-initiation, short stability, and accelerated sliding to failure. Combined with monitoring system analysis, the rainfall infiltrations destabilized the shallow landslide by reducing the effective stress, while impoundment increased pore water pressure, leading to buoyancy-driven effects. However, the most notable deformations occurred during the WL drawdown stages, when seepage drag force induced by the low permeability of the sliding mass triggered more pronounced deformations. The deformation mechanism of HTPLJ1 with SIBT is attributed to a bulged slope toe induced by the seepage drag force, leading to increased effective stress along the resisting and temporary stabilization. The site geological investigations and monitoring data indicated continuous buoyancy-driven effects and a higher sensitivity to seepage-driven effects in HTPLJ1. It can be inferred that the SIBT landslides undergo repetitive deformation characterized by dragging and compression, which leads to initiation and stagnation.

Weak structural plane deformation is responsible for the non-uniform large deformation disasters in layered rock tunnels, resulting in steel arch distortion and secondary lining cracking. In this study, a servo biaxial testing system was employed to conduct physical modeling tests on layered rock tunnels with bedding planes of varying dip angles. The influence of structural anisotropy in layered rocks on the micro displacement and strain field of surrounding rocks was analyzed using digital image correlation (DIC) technology. The spatiotemporal evolution of non-uniform deformation of surrounding rocks was investigated, and numerical simulation was performed to verify the experimental results. The findings indicate that the displacement and strain field of the surrounding layered rocks are all maximized at the horizontal bedding planes and decrease linearly with the increasing dip angle. The failure of the layered surrounding rock with different dip angles occurs and extends along the bedding planes. Compressive strain failure occurs after excavation under high horizontal stress. This study provides significant theoretical support for the analysis, prediction, and control of non-uniform deformation of tunnel surrounding rocks. (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/).