Brittle behavior and brittleness indicators around hard rock mass excavations

Abstract

In deep underground mining operations, field stresses are increasing and may lead to brittle failure in excavations in hard rock masses. Brittle failure indicators include crack initiation and propagation in intact rock, the extent of failure or spalling limit and damage thresholds for high and low damage conditions. To predict damage around excavations and degraded properties within the rock mass are important to ensure production and may impact in ground support performance. For modeling purposes, brittle behavior has been successfully reproduced with strength parameters variation like Cohesive-Weakening-Friction-Strengthening. In this research, this model was applied using an equivalent plastic strain parameter for typical tunneling conditions in hard rock masses under high stresses using literature available data. Then, an analysis of brittleness behavior parameters like Damage index and Brittleness Index were obtained, to recreate conditions and behavior of the rock mass near excavations. Criteria for parameters evolution and damage magnitude depending on principal stress for directions within the rock mass can be obtained.