Surrounding Rock Deformation Failure Mechanismand Stability Study For Guanshan Tunnel

In this paper, it is based on the science projects of Guan Shan tunnel of Tian Ping railway and in the study area the surrounding rock of the tunnel is the hard brittle rock mass diorite. The largest depth of the tunnel is 831 m.The science problem belongs to the typical large buried depth, high ground stress of tunnel surrounding rock deformation and failure problems. Nowadays, there is little research data about this science problem. So, this paper aimed at the large buried depth and high geostress special engineering geological conditions of surrounding rock deformation failure mechanism and stability study, which is very important to the practical engineering and scientific research.In this paper, on the basis of previous studies, based on the site engineering geological data, the data of rock mass structural plane and the data of borehole TV experiment, to study the hard brittle rock mass deformation failure mechanism and stability of surrounding rock. Discussing the deformation and failure mode of the high depth and high geostress surrounding rock, establishing a set of suitable classification method for high geostress surrounding rock and analyzing the stability of tunnel is very important to the science study. The main researches are as follow:1)We should analysis engineering geological conditions of the tunnel surrounding rock mass in the study area and understanding the tunnel surrounding rock occurrence conditions sufficiently, which provides enough relevant information for the following study.2)With the data of the joints of excavation face, we can get the space RQD of the tunnel. By calculating the space RQD and modulus ratio vary with the load angle, which reflect the strong anisotropy of rock mass. It is the strong anisotropy of rock mass that makes the deformation failure modes different when the field stress was released.3)Block theory could analysis the failure mode of surrounding rock and the potentially unstable block which caused by the joints.4)We could observe the same borehole fissure on different time and analysis the deformation failure mechanism of the surrounding rock mass.5)We could analysis the deformation failure mechanism of the surrounding rock mass by the rock mechanics experiments.6)We could simulate the different supporting conditions of tunnel excavation effect by Phase2 which is a finite element program and calculate SRF by the method of strength reduction.By the above several aspects of research, we conclude that the surrounding rock mass of the tunnel with large buried depth, high ground stress become loose. And the locked structure interface opened when the field stress had released. The rock block had slid along the opened structure interface, which cause concrete cracking and steel deformation of the support of tunnel. By the strong primary support, the stability of surrounding rock mass is suited.