Abstract
When a tunnel or an underground structure is excavated in a highly stressed rock mass, rock damaged zone is formed around the tunnel due to the stress concentration resulting from stress redistribution. Recent studies on the rock damaged zone revealed its importance to structural stability around deep underground openings. In order to evaluate the characteristics of the rock damaged zone by brittle failure, physical model test and numerical model tests have been conducted. For this study, a new true triaxial chamber has been designed and fabricated. It is possible to load highly in all three orthogonal directions. All three independent stresses applied to rectangular prismatic specimens, 30x30x30cm in size, are servo-controlled. The test models, made with cement mortar, have an opening of 6cm in diameter and 15cm in length. The experiments were conducted under true triaxial test using new testing system. The experimental results indicate that the shape of the failure zone around the opening is V-shape and the extent is affected by the magnitude of applied stress. However, the numerical predictions using general failure criteria, Mohr-Coulomb criteria, are found to be different from the experiments results. These differences call for further investigation on understanding the brittle failure and developing new criteria for predicting the brittle failure. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.
Published Version
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