The most critical parameter for determining equivalent values for the Mohr-Coulomb friction angle and cohesion from the nonlinear Hoek-Brown criterion is the upper limit of confining stress. For rock slopes, this value is the maximum value of the minimum principal stress ([Formula: see text]) on the potential failure surface. The existing problems in the existing research are analyzed and summarized. Using the finite element method (FEM), the location of potential failure surfaces for a wide range of slope geometries and rock mass properties are calculated using the strength reduction method, and a corresponding finite element elastic stress analysis was carried in order to determine [Formula: see text] of the failure surface. Through a systematic analysis of 425 different slopes, it is found that slope angle (β) and geological strength index (GSI) have the most significant influence on [Formula: see text] while the influence of intact rock strength and the material constant [Formula: see text] are relatively small. According to the variation of [Formula: see text] with different factors, two new formulas for estimating [Formula: see text] are proposed. Finally, the proposed two equations were applied to 31 real case studies to illustrate the applicability and validity.
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