Numerical modeling and damage evolution research on the effect of joint geometrical parameters in nonpersistent jointed rock masses

The strength and deformation of rock masses containing nonpersistent joints are controlled by the complex interactions of joints and intact rock bridges; exploring the relationship between them is the basis of understanding the failure process in the model. In this work, discrete fracture network (DFN) technology was used to construct the fracture system, and synthetic rock mass (SRM) technology was utilized to represent rock masses containing a set of nonpersistent joints. The effect of geometrical parameters (joint dip angle, joint length, and joint density) on the mechanical properties and failure mechanism of the models was studied. The stress redistribution method was used to investigate the failure process of the nonpersistent jointed rock mass under uniaxial compression, and the mechanisms are successfully explained according to their different cracking process. Six failure modes are predicted: through a plane, stepped, rotation of new blocks, mixed, multiplane stepped, and shearing through intact rock. Damage mechanics were suitable for analysis of the nonpersistent joint model, and the initial damage variable was determined by geometrical parameters. Overall, the damage constitutive model fits the stress–strain curve of numerical simulation well and is more suitable for brittle failure of a jointed rock mass than ductile and plastic failure.