Rainfall is one of the most significant triggering factors for slope failures in many regions around the world. Numerous research studies have been conducted to investigate infiltration of rainwater into a slope, and the effect of water infiltration on slope stability. In this paper, a review of existing research on infiltration analysis and slope stability analysis under rainfall infiltration is presented. Studies on infiltration analysis with conceptual models, analytical analysis and numerical modelling are first reviewed. The typical pore water pressure profiles in the slope are then discussed. Subsequently, recent developments in analyses of slope instabilities under rainfall conditions using the limit equilibrium method and coupled hydro-mechanical modelling are summarised, and major findings on critical hydrological factors related to rainfall-induced landslides are summarised and discussed. Finally, several research topics are suggested for further study.

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Stability analysis of rainfall-induced slope failure: a review

Internal erosion involves selective loss of fine particles within the matrix of coarse soil particles under seepage flow, which affects the hydraulic and mechanical behavior of the soil. In this research, extensive laboratory internal erosion tests were conducted under complex stress states following three stress paths: isotropic, drained triaxial compression, and triaxial extension stress paths. These tests were designed to investigate the initiation and development of internal erosion and the effect of stress state on critical hydraulic gradients. The entire erosion process can be divided into four phases: stable, initiation, development, and failure. Accordingly, three critical gradients termed as initiation, skeleton-deformation, and failure hydraulic gradients, can be defined. These critical gradients correspond to the onset of erosion of the fine particles filling the large pores of the skeleton, the buckling of the strong force chains formed by the coarse particles, and the soil failure, re...

Critical Hydraulic Gradients of Internal Erosion under Complex Stress States

An interesting risk analysis of clay slopes for short-term and long-term analysis, including pore water pressures in sensitive clays, is presented. Application of the analysis to typical clay slopes indicates the contribution of different soil parameters and model uncertainty to the total variance and probability of stability failure. Current design factors give a relatively high risk of failures in practice and are justified on economic grounds except for embankment dams. /Author/

Risk analysis of slopes and its application to slopes in canadian sensitive clays

Extended internal stability criteria for soils under seepage

Suffusion in soil involves selective erosion of fine particles within the matrix of coarse soil particles under seepage flow. Such loss of fine particles affects the hydraulic and mechanical behavior of the soil. In this study, a stress-controlled erosion apparatus was developed to investigate the initiation and development of suffusion under complex stress states and to study the effect of suffusion on soil stress-strain behavior. The apparatus allows independent control of hydraulic gradient and stress state. The hydraulic gradient is controlled using a water-head control method. The eroded soil and the outflow rate are measured using a soil collection system and a water collection system, respectively. The measurements can be used to study the erosion rate and variations in soil permeability during the erosion process. A series of erosion tests was conducted on a gap-graded soil under the same confining stress but different deviatoric stresses. The results show that the maximum erosion rate, the variations in soil permeability, and the total deformation of the soil specimen increase with the increase of deviatoric stress. After the loss of a significant amount of fine particles in the soil, the stress-strain behavior of the test soil changes from dilative behavior to contractive behavior.

A Stress-controlled Erosion Apparatus for Studying Internal Erosion in Soils

The stepped spillway has increasingly become and effective energy dissipator. When the hydraulic performance of the overflow is clearly known, the energy dissipation could be increased. However, the study of stepped spillway overflow has been based only on model tests until now. In this paper, the \ik-ϵ turbulence model is used to simulate the complex turbulence overflow. The unstructured grid is used to fit the irregular boundaries and the volume of fluid method is introduced to solve the complex free-surface problem. The free surface, velocities, and pressures on the stepped spillway are obtained by the turbulence numerical simulation. Furthermore, the simulation results compare well with measured data. The study indicates that the turbulence numerical simulation is an efficient and useful method for the complex stepped spillway overflow.

Volume of Fluid Model for Turbulence Numerical Simulation of Stepped Spillway Overflow

Failure of colluvial soil deposits induced by rainfall is a common geohazard in the natural terrain. Many colluvial soils are widely and gap graded with a minimal sand fraction. In order to study the pore water pressures in such gap-graded, unsaturated soil deposits through a seepage analysis and to evaluate the stability of these soil deposits, the soil-water characteristic curves for gap-graded soils must be known. Usually, gap-graded soils exhibit bimodal grain-size and pore-size distributions. This technical note presents a theoretical continuum method for the determination of soil-water characteristic curves for soils with a bimodal or multimodal pore-size distribution. Based on the capillary law, the water content in a multimodal soil is equal to the sum of water stored in each pore series in the soil. Therefore, the bimodal or multimodal soil-water characteristic curves can be obtained by combining the unimodal soil-water characteristic curves for all components of the soil corresponding to the pore series weighted by the respective volumetric percentages. The proposed method is verified using experimental soil-water characteristics data of sand-diatomaceous earth mixtures with dual porosity.

Predicting Bimodal Soil-Water Characteristic Curves

https://www.jstage.jst.go.jp/article/sandf/46/5/46_5_557/_pdf

Seepage failure mechanism of the gouhou rockfill dam during reservoir water infiltration

Discrete numerical modeling of particle transport in granular filters

The Gouhou Dam was a concrete-faced rockfill dam built in a steep canyon that collapsed in 1993 due to internal erosion during the initial reservoir filling. In this paper, the process of water inf...

Qun Chen

Papers

Volume of Fluid Model for Turbulence Numerical Simulation of Stepped Spillway Overflow

Predicting Bimodal Soil-Water Characteristic Curves

Seepage failure mechanism of the gouhou rockfill dam during reservoir water infiltration

Discrete numerical modeling of particle transport in granular filters

Three-dimensional analysis of water infiltration into the Gouhou rockfill dam using saturated-unsaturated seepage theory