This paper presents a case study of a deep-buried underground tunnel project with the buried depth of 1000 m in south-western China. Both the magnitude and direction of the geo-stress were determined through the field measurement. The stress distribution law of the tunnel with different buried depth from 700m to 1000m was comprehensively analyzed and evaluated. Through the laboratory tests and field monitoring, the mechanical parameters and engineering characteristics of surrounding rock were obtained. On the basis of the Kaiser Effect measurement, the real-time tests were carried out in surrounding rock for monitoring the rock burst. The study detected that the acoustic emission parameters multiply before the occurrence of rock burst. Furthermore, the wave-form was obtained when rock burst occurred though analyzing acoustic emission signal. The results of the analyses provide a scientific basis for tunnel support design and section choice of the deep tunnel projects.
Geo-stress is the fundamental force that leads to all kinds of geological disasters, such as rock-burst, collapse and large deformation in underground engineering. It has important influence on the design and construction of deep-buried tunnels. The research on the geo-stress is to ascertain the initial stress field within the rock mass. Rock-burst as an engineering geological problem is often encountered during excavation in deep-buried and high-stressed underground works. It often occurs in the hard, integrity and brittle rock mass. In such rock mass the high elastic strain energy is liable to be stored, which is the basic condition for inducing rock-burst (Hou 1986 & Ma 2006). Measurement and monitoring of in-situ stress is an important method for study of geodynamics, geological disasters and engineering stability (Wu 1997&Cai 2000). Most parts of the deep-buried underground tunnel project in this paper lie in high stress area.