Simulating fracture and friction of Aue granite under confined asymmetric compressive test using clumped particle model

Abstract

Fracture and friction behaviors of Aue granite (Erzgebirge, Germany) under confined asymmetric load are simulated using a clumped particle model. In contrast to conventional circular bonded particle assemblies, clumped particle models consist of groups of neighboring individual particles tied together to mimic unbreakable larger grains of irregular shape (clumps). An optimized clumped model is used for all calculations, which is calibrated by the strength and deformation data from laboratory data of uniaxial and triaxial compression. At a first order approximation, the simulated fracture paths obtained from the clumped particle model match the observed fracture paths from laboratory experiments at various confinements. Under low confinement (<5 MPa), the fracture initiates in mode I from the edge of the asymmetric loading platen and propagates toward the unloaded portion of the granite. In this scenario, tensile cracks dominate in the fracture process zone. Under higher confining pressures (10 and 40 MPa), after nucleus of mode I fracture an inclined rupture path develops and propagates towards the loaded portion of model. Temporal change of the numerically computed Gutenberg–Richter b-values shows low b-values in the fracturing regime and higher b-values during stick–slip and frictional sliding post-failure regime, which are in accordance with the laboratory findings.