In this paper the physical process of the rockbursting is described on the basis of the observations of projects in China, and the principles and support design for the prevention and control of the rockbursting are discussed also.
The rock-bursts create probably the most typical hazard associated with hard intact rock around the underground openings in the highly geostressed areas. In China the rock-bursts have often accured in ~any underground engineerings, including hydrostation, coal pits and metal mines. n this paper the experiences from the construction and support design of tunnels subjected to rockbursting are described.
The physical process is described on the basis of the observation of projects in China as follows: ---- The rockbursting have a development process, in general, there are three stages, i.e. the first stage is the initiation of the cracks, the second stage is adjustment of the geostresses in nature rock and the third stage is that the rock-block is shot out (rockbursting). This developemnt process is the physical fundament for the prevention and control o the rockbursting. ----- The occurence of the rockbursting phenomenon is mainly due to excavation of the underground opening which formed a new Surface and stress concentration, and, the initiation of cracks near the surface in the rock mass is induced. The initiation on cracks have quite clear direction, in general, it is parallel to the new surface of the underground opening and to major pricipal geostress direction, and accompanies with occurence of acoustic emission phenomenon. Therefore, using the acoustic emission may be monitoring the rockbursting because it is in need of time to complete the second stage of the rockbursting i.e. adjustment stress stage. ＿＿＿＿ Owing to different magnitude and degree of stress concentrations and different characteristics of rock, the different rockbursting phenomenon appears also. In some conditions this is only dilatation and stripping or collapse, and in another conditions the rock-block is shot off from rock surface. Therefore, the classification can be given on the basis of the different conditions of rockbursting. In general, the slight and medium-sized rockburstings are not great hazard for construction. It is necessary to take note of the heavy rockbursting for which the appropriate prevention technology is carried out according to concrete engineering condition. ＿＿＿＿ Precisely because of rock-bursts associated with the stress concentration, it is related to the shape of underground openings. In fact, the special rockbursting phenomenon is often observed at the sharp-pointed corner in the highly geo~ stressed areas such as the rock powder continued to shoot out (hight reached 20 - 30 em) at the exploring tunnel No.2 of Ertan hydro station in China.
3.1 Lithological factor The nature rock in which the rock bursting
