Numerical Modelling of Frictional Sliding Induced Damage and Heating Effects on Rock With an Application to Sievers’ J-Miniature Drilling on Granite

Abstract

The present study develops a finite element-based numerical method for simulation of frictional rotational sliding induced damage and heating effects on rock. The method is applied to the Sievers’ J- miniature drill test, which is widely used for estimating the rock drillability and predicting the cutter life. A continuum approach based on a damage-viscoplastic model for rock failure is adopted. The viscoplasticity part, based on the Drucker–Prager yield surface with a rounded Rankine criterion as the tensile cut-off, defines the stress states leading to rock failure. This failure is captured by the damage model, which uses separate damage variables for tension and compression (shear). A special workflow for generating granite mineral mesostructures based on Neper, DREAM3D, and Matlab software is developed. Moreover, nanoindentation tests are performed for determination of the elastic material constants for the Kuru granite constituent minerals. The global coupled thermo-mechanical problem with frictional contact is solved with a staggered globally iterative approach. The FE discretized balance of linear momentum is time discretized with the Newmark scheme, and the FE discretized heat equation is time discretized with the Backward Euler scheme. The tangent stiffness operator required by the Newton–Raphson iteration is derived for the isothermal case using the penalty method for contact modelling. Preliminary numerical simulations of the Sievers’ J-miniature drill test on granite demonstrate that the approach holds some promise and thereby provides a platform to be extended to simulate frictional rotational sliding induced damage and heating effects on rocks in other applications as well.