Layered fractures induced by principal stress axes rotation in hard rock during tunnelling

Abstract

During tunnelling, layered fractures occurred in the deep tunnels at the Jinping II Hydropower Station. Using numerical simulation methods and the basic theories of fracture mechanics, the mechanism of rock crack propagation influenced by the intermediate principal stress, the stress path and the principal stress axes rotation was studied. In addition, based on the analysis of the stress path and principal stress rotation of the surrounding rock mass in the test branch tunnel F during the excavation process, the mechanism of formation of layered fractures is discussed.

Keywords:

• Layered fractures
• Principal stress axes rotation
• Stress path
• Crack propagation
• True triaxial test

The authors gratefully acknowledge the financial support of the National Science Foundation of China under Grant Nos. 2010CB732006, 50709037, 50979104 and 50909007 and the research funding support of Ertan Hydropower Development Company, Ltd. We are also grateful for the support and assistance of the engineers of East China Investigation and Design Institute in the test tunnel design and construction.