Modelling the shearing behaviour of joints using an improved shear box genesis approach in particle flow code (2D) and its validation

Abstract

The smooth joint contact model has been used extensively to simulate the shear behaviour of joints in the numerical simulations with particle flow code. Results from existing studies have revealed that this model suffers from the particle interlocking problem taking place at the shear displacement greater than the minimum particle diameter. To solve this problem, the shear box genesis approach was proposed, by which particles in the upper and lower halves of a joint are generated separately, and the intended joint plane will be added as a common boundary. However, the shear box genesis approach is not a satisfactory solution to the interlocking problem yet. Three problems are usually encountered in practice: first, particles are still likely to move across the intended joint plane and cause the interlocking; second, the shear box genesis approach inevitably causes the periodic change in the contact number along the intended joint plane; third, it is difficult to incorporate the nonlinear closure behaviour of joints. Therefore, this paper aims to solve the shortcomings, and to apply the improvements to the simulation of joint shear behaviour. The interlocking problem was successfully solved by introducing the joint side checking method, and specifying the value of maximum allowed closure. The periodic stress fluctuation during shearing was eliminated by the non-unified ball generation method. The nonlinear closure behaviour of joints was captured by embedding the Barton–Bandis model. To verify the applicability of the improvements to rough joints, a series of numerical and experimental direct shear tests of rough joints were conducted. In general, good agreements were achieved between the numerical modelling results and laboratory measurements. This improved shear box genesis approach enhances the ability of the smooth joint contact model to simulate the shear behaviour of joints, and also has the ability to track the damage evolution during the joint shearing process.