Hydromechanical behaviour and stability of reservoir landslides in the Danjiangkou Reservoir area under rainfall and water level fluctuation

Effects of rainfall intensity and slope gradient on shallow loess landslides: flume model test and numerical simulation

Rainfall-Induced Slope Stability and Deformation around Rajui Dam Infrastructure Using Finite Element Analysis

Rainfall-induced slope instability poses a significant risk to dam infrastructure in tropical regions, where intense and prolonged precipitation frequently alters subsurface stress conditions. This study aims to evaluate the effects of rainfall infiltration on slope stability in the Rajui Dam area, Aceh, Indonesia, by quantifying changes in safety factor and deformation behavior under existing and high-rainfall conditions. A finite element–based numerical approach was employed using two-dimensional slope models representing critical slopes near the dam access road and spillway. Soil mechanical and hydraulic properties were derived from field and laboratory data, while rainfall was modeled as surface infiltration corresponding to a high-intensity scenario of 150 millimeters over ten days. Slope stability was evaluated using the strength reduction method, with safety factor and total displacement adopted as primary indicators of stability. The results indicate that rainfall infiltration consistently reduces the safety factor and increases slope displacement at both locations. One slope exhibited lower safety factor values, indicating higher susceptibility to instability, while the other showed greater deformation despite maintaining a marginally higher safety factor. Displacement patterns concentrated near slope toes and propagated along potential shear zones, suggesting progressive instability driven by increased pore water pressure and reduced effective stress. These findings demonstrate that identical rainfall conditions can produce different stability responses depending on slope geometry and material characteristics, highlighting the importance of site-specific evaluation.

Characteristics and triggering mechanism of buoyancy-driven and seepage-driven landslides: insights from physical model tests

Geosynthetic reinforcement and drainage in fine-grained embankments under rainfall

The increasing use of locally sourced fine-grained soils in embankment construction increases susceptibility to rainfall-induced instability due to low permeability, high water retention and limited shear strength. This study investigates the coupled reinforcement–drainage behaviour of geosynthetics in fine-grained embankments subjected to controlled rainfall infiltration. Laboratory-scale physical model tests were conducted to examine moisture migration, pore water pressure, earth pressure and deformation. Unreinforced slopes exhibited rapid infiltration with moisture contents increasing to 27.6–29.5% within the first hour. Reinforced slopes showed capillary barrier effects, causing transient moisture accumulation above reinforcement layers, while geocomposites provided effective lateral drainage, producing a pore pressure differential of 2.56 kPa, nearly three times that of geotextiles. Geocomposites reduced pore pressure rise by approximately 37% relative to unreinforced conditions and induced negative pressures beneath the reinforcement, indicating enhanced suction recovery and stress redistribution. Soil fines content strongly governed the hydraulic response where a 20% fines embankment showed rapid infiltration and low retention, whereas a ≥40% fines embankment retained over 50% moisture. The 20% fines embankment exhibited the largest crest settlement and localised toe failure. Numerical simulations reproduced the observed hydro-mechanical responses with minor deviations during post-rainfall dissipation, demonstrating that geocomposites significantly enhance the rainfall resilience and stability of fine-grained embankments.

An Unsaturated Soil Material Point Method for Simulating Rainfall-Induced Landslides

Rainfall infiltration frequently triggers slope failures by elevating pore water pressure and compromising the shear strength of unsaturated soil layers. Modeling these severe geological events remains computationally challenging. Standard grid-based techniques, such as the Finite Element Method (FEM), typically fail due to severe mesh distortion under large deformations, whereas the Discrete Element Method (DEM) demands excessive computational resources. Addressing this gap, we develop an advanced theoretical framework utilizing the Material Point Method (MPM) integrated with a liquid-solid-gas three-phase mechanics model. We first verify the algorithmic accuracy using a 1D unsaturated soil column test. Subsequently, the framework is deployed to capture the dynamic displacement and mechanical responses of a 2D rainfall-induced landslide. Benchmarking against FEM data confirms that our multiphase MPM accurately models the infiltration process and subsequent structural collapse. Ultimately, this approach offers a highly robust computational strategy for analyzing large-scale landslide deformations and improving predictive assessments.

Deformation behaviour of over-consolidated soil in a deep confined aquifer under multi-stage pore pressure changes in Shanghai, China.

Shanghai, a typical coastal soft-soil area, is characterised by thick soft layers with high compressibility and low permeability. Together with five confined aquifers, these layers form a complex multi-aquifer system. Historically, excessive deep groundwater extraction caused severe land subsidence. However, after years of extraction restrictions and artificial recharge, subsidence has been controlled and groundwater levels have risen, creating possibilities for groundwater extraction in emergency situations. Focusing on Shanghai's third confined aquifer (Layer ⑪) and the adjacent aquitard (Layer ⑫), this study first employed high-pressure consolidation tests to verify the over-consolidated state of the deep soils, followed by high-pressure triaxial tests and numerical simulations to investigate their deformation behaviour under staged pore pressure changes. The triaxial tests indicated that during staged dewatering, the deformation modulus (E) dropped sharply once the effective stress exceeded the preconsolidation stress, falling to 1/2 to 1/4 of its initial value and marking the elastic-elastoplastic transition. Moreover, the void ratio change was strongly negatively correlated with the over-consolidation ratio (OCR), and a higher OCR significantly suppressed compression during pore pressure changes. Numerical simulations based on the Modified Cam-Clay model agreed well with the experiments. These findings provide a scientific basis for predicting safe drawdown thresholds in emergency groundwater extraction.