Lower bound limit analysis using nonlinear optimization for solving axisymmetric problems using Hoek-Brown yield criterion

Abstract

ABSTRACT This study presents a computational methodology for solving axisymmetric stability problems in rock mechanics by using the finite element lower bound limit analysis. The generalized Hoek and Brown (GHB) yield criterion, which is often recommended to define failure in the intact and jointed rock mass, has been employed. No assumption(s) are required to make either on the value of circumferential stress (σ θ) or the exponent (α) in the GHB yield expression. It is understood that the assumption of choosing α = 0.5 provides an unsafe solution for the values of GSI ≪ 30. For the purpose of illustration, the bearing capacity factor N σ has been evaluated for a circular footing. The results obtained from the analysis were compared with that reported in the literature and it is concluded that the present formulation by incorporating the true variation of α with GSI significantly improves the existing solution(s) for GSI < 30.