Numerical Analysis of the Effects of Crack Characteristics on the Stress and Deformation of Unsaturated Soil Slopes

Liuxin Yang,Enlong Liu

doi:10.3390/w12010194

Abstract

Cracks induced by evaporation or rainfall have a great influence on the stability of unsaturated soil slopes, which can lead to landslides during the rainfall process. In order to study the effect of crack characteristics on the evolution of stress and deformation of unsaturated soil slopes, a series of numerical analyses under different conditions were performed using a coupled elastoplastic finite element program that we developed for unsaturated soil. When carrying out the numerical analyses, the effective stress for unsaturated soil proposed by Bishop and an elastoplastic double-hardening constitutive model for the soil skeleton were employed. The varying parameters, including the crack location, the discharge speed, evaporation rate, infiltration rate, and tensile strength, were investigated to study the coupling process of pore water pressure and deformation in the process of evaporation and rainfall infiltration. The numerical results showed that the minimum pore water pressure of the soil slope at the end of evaporation/rainfall decreased gradually and the crack width increased gradually as the crack set closer to the slope; the larger the discharge speed of pore air, the greater the crack width. With the increase in the evaporation rate, the pore water pressure of the soil slope reduced and the crack initiated earlier and became wider. As the infiltration rate increased, the pore water pressure of the soil slope and the crack width increased, but the decreasing duration became shorter. The change of tensile strength had little effect on the pore water pressure, but the development of the crack width changed with evaporation and rainfall infiltration.

Highlights

Slope instability is related to many factors, such as geological structure, geotechnical properties, climatic conditions, topography, surface water effects, groundwater activities, human engineering activities, and earthquakes
Where σ0 is the effective stress, σ is the total stress, ua is the pore air pressure, uw is the pore water pressure, the term s = ua − uw is called the matrix suction, and χ is called the coefficient of reduced suction
The main conclusions are as follows: The finite element method considering the effective stress for unsaturated soil proposed by Bishop and an elastoplastic double-hardening constitutive model for the soil skeleton can be used to

Summary

Introduction

Slope instability is related to many factors, such as geological structure, geotechnical properties, climatic conditions, topography, surface water effects, groundwater activities, human engineering activities, and earthquakes. Rainfall infiltration is one of the most important conditions that cause slope instability. The occurrence and development of slope failures, such as collapse, landslide, and debris flow, are mostly controlled by factors such as rainfall infiltration [1]. Due to the complexity of field tests on unsaturated soil slopes, there is scant research in this area. Blatz et al [2] initiated a project including a field investigation program, a laboratory testing program, and advanced numerical modeling to identify the cause of two shallow slope failures. Timpong et al [4]

Methods

Results

Conclusion