Influences of Pore-Water Pressure on Slope Stability considering Strength Nonlinearity

Di Wu,Yuke Wang,Fei Zhang,Yue Qiu,Xinyu Ye

doi:10.1155/2021/8823899

Abstract

The pore-water pressure is a vital factor in determining the slope stability. To deal with the stability of slopes undergoing pore-water pressures, this paper used the pore-water pressure coefficient to develop the three-dimensional limit analysis method for slope stability evaluation with a nonlinear strength envelope. For numerical slope examples, the critical heights and corresponding critical slip surfaces associated with linear and nonlinear envelopes were derived by using a numerical optimization procedure. The influences of pore-water pressures on the slope stability were addressed by comparing the upper-bound solutions derived by linear and nonlinear strength envelopes (the linear and nonlinear results for short). The obtained two critical inclinations between the linear and nonlinear results both decrease and gradually approach with increasing pore-water pressure coefficient. For most slopes subjected to pore-water pressures, using the linear Mohr–Coulomb envelope will obviously overestimate the slope critical height. The overestimation resulted from the linear criterion will become more distinct for slopes with smaller widths. Besides, the presented results showed that the equivalent internal friction angle tends to have a weaker increasing trend for steeper slopes as pore-water pressure coefficient increases. Hence, when pore-water pressure coefficient increases, the critical slip surfaces of gentle slopes with nonlinear strength criteria become shallower, but the critical slip surfaces of steep slopes seem to have no consistent change law. These results and analyses can illustrate the significance of the application of nonlinear strength envelopes in slope stability evaluation considering pore-water pressures and provide certain reference advice in slope engineering design and landslide prevention.

Highlights

In the common analysis methods and design standards for slope and foundation stability problems, the soil shear strength is generally represented in the type of the linear Mohr–Coulomb (MC) strength envelope (e.g., Chen [1], Michalowski and Drescher [2], Gao et al [3], Rao et al [4], Yang et al [5], and Ye et al [6, 7])
The solid lines related to the critical heights are derived by nonlinear PL criterion, and the dotted lines related to the critical heights are derived by linear MC criterion
The slope critical heights and corresponding slip surfaces associated with linear and nonlinear strength envelopes were derived with respect to different pore-water pressures and slope geometries. e linear and nonlinear results were compared to illustrate significant influences of pore-water pressures on the stability of slopes in 2D and 3D conditions. e main conclusions from presented results and discussions are drawn as follows: (1) As pore-water pressure coefficient ru increases, the positions of two critical inclinations β1 and β2 between the linear and nonlinear results gradually approach with β1 becoming smaller and β2 decreasing or even disappearing

Summary

Introduction

In the common analysis methods and design standards for slope and foundation stability problems, the soil shear strength is generally represented in the type of the linear Mohr–Coulomb (MC) strength envelope (e.g., Chen [1], Michalowski and Drescher [2], Gao et al [3], Rao et al [4], Yang et al [5], and Ye et al [6, 7]). For 3D face-failure mechanism with the nonlinear criterion (Figures 2(a) and 3(a)), the pore-water pressure work rates for curvilinear cone Wcuurve are obtained from this equation: Wcuurve. Given a slope with certain nonlinear parameters, geometric parameters, and pore-water pressure, the upper bound on critical height Hcr (when the slope safety factor is equal to 1.0) could be calculated from above-established energy-balance equation in regard to several independent variables: θ0, θh, r0′/r0, b/H, n H′/H (3D face-failure mechanism) or β′ (3D base-failure mechanism), and equivalent friction angle φe. Derived by the tangential method can be upper bounds of critical loads

Slope Examples

Results and Discussion

Conclusions