Numerical Modeling of Rock Damage during Indentation Process with Reference to Hard Rock Drilling

Abstract

Drill bits, such as roller cones and hammers, are equipped with inserts; once in contact with the rock, each of them applies mainly a compressive action called indentation. In this paper, a numerical modeling-based analysis of single and double rock-indentation processes using the finite-element method is presented. Based on damage mechanics, Mazars’ model, initially developed for concrete, has been used to simulate the extent of the damaged zone within a rock in the vicinity of a spherical drill insert during single- and double-indentation processes. The effects of loading and insert spacing on the damaged-zone extent and the interaction between two neighboring inserts were investigated numerically and compared with the results of a recent experimental study. The latter used an image analysis–based technique applied on thick sections prepared from three types of rocks (granite, limestone, and sandstone) subjected to indentation tests. This procedure enabled quantification of the extent of the damaged zone within the rock samples under different indentation test conditions. Results of the proposed numerical analysis reveal that Mazars’ damage model is relevant to simulating rock response under indentation loading and that indentation-induced rock damage is caused mainly by extension strain development.