Testing and Numerical Simulations on Fracture Behavior of Fresh Quartzite Rock Using the Discrete Element Method

Abstract

Discontinuities play a significant role in the analysis and design of rock structures, e.g., tunnels, stability of slopes, blocky rock masses, etc. Therefore, the following study is conducted using a discrete element method (DEM) model in Universal Distinct Element Code (UDEC) software which takes into consideration the discontinuities present in the material medium, both load-induced as well as inherent discontinuities. The DEM model in UDEC is used for the study to simulate the Uniaxial Compressive test response of Fresh Quartzite Rock. The Quartzite Rock is taken for this study because the same rock was encountered at a project site Saundatti, Karnataka, which has been identified as an amenable place to develop an integrated project by Greenko Group. In this study, all the laboratory experiments are performed on the Quartzite rock, and its behaviour is understood with those experimental results. Out of all the experiments, Uniaxial Compressive Strength (UCS) Test is chosen for the simulation purpose. The specimen model used for simulation of UCS is 110 mm in height and 54 mm in width. The specimen is further subdivided into around 900 smaller deformable blocks to simulate the field condition accurately. The model is bounded at the top and bottom by steel platens to ascertain relatively uniform load transfer across the specimen cross-section. The contact points between the deformable blocks are characterized with the normal and shear stiffness, with their nonlinear behaviour modelled from Mohr–Coulomb failure envelope (shear regime) and Rankine tension cutoff (tension regime). These micro-mechanical parameters to the DEM model are characterized by the obtained macro-level parameters from laboratory experiments. The simulation of UCS using UDEC is carried out to quantify the deformability characteristics, fracture patterns, and the stress–strain curve of the rock specimen. The deformability characteristics obtained from the numerical model are quite consistent with that of experimental observations and is mainly due to the precisely chosen micro-mechanical parameters. Moreover, the cracks initiation and propagation, stress profiles and deformation patterns obtained in the simulation are studied intricately.