Abstract
Profiles of matric suction are critical for assessing the stability of unsaturated soil slopes, and the strength of unsaturated soils is affected by the intermediate principal stress. This study presents a theoretical formulation of safety factor for infinite unsaturated soil slopes under four different profiles of matric suction using the limit equilibrium method. The unified shear strength equation under plane strain conditions is adopted to capture the effect of intermediate principal stress on the strength of unsaturated soils. The proposed formulation of safety factor is found to have good comparability and broad applicability. The validity of the proposed formulation is demonstrated by comparing its predictions with the results of the extended shear strength method and the finite element method available in the literature. Parametric studies show that the effect of intermediate principal stress on the stability of unsaturated soil slopes is significant; the difference of safety factor among four suction profiles is pronounced, and the safety factor is highest for a linear suction profile. In addition, the safety factor changes with the infiltration depth in two stages, decreases with the slope angle, and increases with effective strength parameters. The results of this study are capable of providing beneficial guidance for optimization designs and disaster preventions of unsaturated soil slopes.
Highlights
Profiles of matric suction are critical for assessing the stability of unsaturated soil slopes, and the strength of unsaturated soils is affected by the intermediate principal stress. is study presents a theoretical formulation of safety factor for infinite unsaturated soil slopes under four different profiles of matric suction using the limit equilibrium method. e unified shear strength equation under plane strain conditions is adopted to capture the effect of intermediate principal stress on the strength of unsaturated soils
Parametric studies show that the effect of intermediate principal stress on the stability of unsaturated soil slopes is significant; the difference of safety factor among four suction profiles is pronounced, and the safety factor is highest for a linear suction profile
Introduction e safety factor of an infinite slope is commonly defined as the ratio of shear strength of the soil to the shear stress developed along a sliding surface, and it is a critical indicator for evaluating slope stability situations. e slope is in a stable state if the safety factor is greater than one, whereas the slope is unstable when the safety factor is less than one
Summary
Received 27 November 2020; Revised 26 January 2021; Accepted 23 March 2021; Published 5 April 2021. Is study presents a theoretical formulation of safety factor for infinite unsaturated soil slopes under four different profiles of matric suction using the limit equilibrium method. The slope stability of unsaturated soils is underestimated along with a smaller safety factor based on the MC failure criterion attributed to not achieving strength contributions from the intermediate principal stress effect. E objective of this study is to present theoretical formulations of safety factor for an infinite unsaturated soil slope under four different profiles of matric suction based on the limit equilibrium method. A parametric study is performed to explore the effect of typical parameters (e.g., the intermediate principal stress, the infiltration depth, the slope angle, and effective strength parameters) involved in the proposed formulation on the stability of unsaturated soil slopes under four suction profiles.
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