Theoretical bases of joint strength in rock masses with non-associated flow laws
Keywords:Shear strength of rock joints, Theoretical model, Non-associated flow law
This article presents the theoretical bases to evaluate the shear strength in rock joints and derive an equation that governs the relationship between tangential and normal stresses acting on the joint. The theoretical equation is applied to two non-linear failure criteria: Modified Hoek and Brown and Modified Mohr-Coulomb, on which non-associated flow laws are applied. The theoretical model considers as dependent variables the geometric dilatation, the instantaneous friction angle and a parameter that incorporates the roughness of the joint surface. This model mathematically deduces a similar equation structure as the empirical law proposed by Barton in 1973. However, a good correlation is only achieved with the empirical values and, therefore, with Barton's equation, by incorporating a law of unassociated flow governing the failure processes. This flow law becomes more significant in highly fractured media, which can be induced in a rock joint.
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