The applicability of the common surrounding rock mass classification methods in the deep buried tunnels

• 1、Institute of Engineering Geology, Chengdu University of Technology
• 2、East China Investigation and Design Institute

Abstract： deep buried tunnel in China has characteristics of high field stress and high external water pressure. It has reached 42 MPa field stress and 10 MPa external water pressure in some areas. In general, if the major principal stress is greater than 20 MPa, then the field stress is called high field stress. And the high external water pressure is pointed to the external water pressure which is much greater than 1 MPa.The four common surrounding rock mass classification methods ,i.e. Q-system, RMR method ,HC method, and BQ method are used in the surrounding rock mass classification. The classification results show that the Q-system has a good applicability and the other three methods have a bad applicability in the conditions of high field stress. The four common methods have a bad applicability in the conditions of high external water pressure. The main reason which caused the above results is as followed. The Q-system considers the high field stress by introducing σθ/σc ,σθ is the maxim

Keywords： rock mechanics surrounding rock mass classification high field stress high external water pressure applicability Q-system RMR method HC method BQ method normalization method