Dongguashan Mine is Located at about 1000m depth underground and also the first metal mine in which systematical rock burst study has been done in China, and its development project has been completed. During the development, several rock bursts occurred in the development works. Analyses of the properties to the rock bursts of Dongguashan Mine on the basis of the result of in-situ investigation of rock burst and experiments with rock samples taken from the site of these rock bursts are introduced is this paper.
Dongguashan copper ore deposit is the deep ore body in Shizhishan copper mining area, which includes mainly copper skarn, coprcous brazil, copreous magnetic pyrite, copreous serpentine and magnetic pyrite. The main ore body, No 1 ore body, is located in the Jinshan anticlinal axis, and controlled strictly by strata in the shape of a saddle and occurs as laminarization. It is at an elevation of -680m--1000m and 1820m in length and 204m-882m in width of horizontal projection and 30m-85m in thickness. Its occurrence is basically identical to adjacent rock, tallying with the shape of the anticline. The thickness of the ore body is large in the middle part, pinching along its strike and two fold limbs. The strike is 35° and the dip angle is about 20°. The dip is in the direction of the west-north and east-south respectively along with the occurrence of adjacent rock. There are quartz sandstone, siltstone, diorite and skarns in footwall, and marble, skarns and dioritic porphyrite in hanging wall. There are few joints and no karst cave in the ore body and snrreunding rock, which strength is great.
The mine is in the course of capital construction and has completed basically development opening. Since the first rock burst occurred in the rock mass at the bottom of -790m haulage drift in cross with Dongguashan service shaft at the end of 1996, rock bursts have been noted ten times in development openings. From the beginning of 1997, we started investigating the rock bursts of the mine in situ. Several common properties have been found in the investigation from these rock bursts. First, rock pieces were ejected about 30cm from the origin. Second, there was burst sound when rock was fractured, then was clear and melodious sound while rock was being ejected. Third, the place where rock pieces was thrown was the working front where blasting had just been conducted, and the lime when burst occurred was within one shift period after blasting. Forth, rock pieces thrown out were laminary. Fifth, drilling and blasting were easier. These properties of the kind of rock failure are different from that of general rock failure, but is the properties of rock burst. These rock bursts occurred in two areas
adjacency to cross of excavations;
the harder rock mass, adjacent to the contact zone of different rock strata. In March, 1999, a rock burst occurred at the cross.
