Back-Analysis Scheme of Shear Strength Parameters of Soil Slope Based on Strength Asynchronous Reduction Mode

Shear strength parameters of soil (i.e., cohesion c and internal friction angle φ) are inevitably involved in slope stability analysis. Back-analysis scheme of c and φ is becoming increasingly important for more accurate evaluation of slope stability, while few reports consider the inconsistent attenuation of c and tanφ to determine c and φ. This paper presents a back-analysis scheme of c and φ based on strength asynchronous reduction mode (SARM). In the scheme, SARM was employed to characterize the inconsistent attenuation of c and tanφ by the reduction coefficient of c and tanφ (i.e., SRCc,i and SRCφ,i) and the calculation model of safety factor (SF). Mechanism and theoretical derivation for back-analysis scheme with SARM were then investigated to establish a relationship between c, tanφ, SRCc,i and SRCφ,i. The shear strength parameters ratio (SSPR) consisting of c and φ as well as the dimensionless shear strength parameter (λcφ) with SSPR, slope height (H) and unit weight (γ) was further derived to control the position of the critical slip surface. This back-analysis scheme provides the basis for obtaining the initial cohesion (cis) and initial internal friction angle (φis) through the linkage of λcφ (or SSPR) with the position of the critical slip surface. A case example is used to validate the reasonability of the proposed back-analysis scheme by taking the central coordinate of circle of the critical slip surface (O (x, y)), arc radius (R) and relative ratio of safety factor (RRSF) as the evaluation standard.