A GSI-softening model for characterizing strength behavior of thermally-damaged rock: Fid-Bau Portal

A GSI-softening model for characterizing strength behavior of thermally-damaged rock

Peng, Jun / Tang, Zhi Cheng / Hou, Di

Abstract Strength behavior of thermally-damaged rock is quite different from that of undamaged or intact rock. In this study, a concept of degradation of geological strength index (GSI) is used and a GSI-softening model in the framework of generalized Hoek-Brown (HB) failure criterion is proposed to characterize the strength behavior of thermally-damaged rock. The proposed GSI-softening model is then verified using several sets of test data collected from previous publications. It is found that the fast increase of strength with increasing confining pressure for thermally-damaged rock can be well captured using the proposed GSI-softening model. The results also show that the GSI value degrades from 100 of undamaged rock to a value ranging from 72 to 88 for the thermally-damaged rocks examined in this study. The material parameter for the thermally-damaged rock is about 1.5 to 3 times higher than the original value of undamaged rock, which indicates that the frictional strength of thermally-damaged rock is much more prominent than that of undamaged rock. The degraded GSI value generally decreases linearly as the temperature in the treatment increases for the examined rocks in this study, while the material parameter linearly increases with the increase in the treatment temperature.

Highlights • A new model is proposed to capture strength behavior of thermally-damaged rock. • The model uses a concept of degradation of geological strength index in HB model. • Fast increase of rock strength with increasing confinement is reproduced using the model. • The parameters in the proposed model are comprehensively studied and discussed.