Gently Inclined Heavy Ore Body Is A Two-step Extraction Pressure Control Technology

Exploitation of mineral resources, one of foundation properties of national economy, is classified into two basic mining methods, open pit and underground mining. Safety and rock mechanics will become a serious problem along with increasing mining depth. On the other hand, unforeseen structural weak planes such as joint, fissure and fault may result in disasters in a mine. It is crucial for preventation of such problems to control ground pressure. It is very important to increase safely recovery rate thinking of a fact that safety is greatly emphasized and national economy increasingly depends on non-renewable mineral resources. It has been proven by practice that canceling of permanent pillar is a good way to reach above task for a large thick orebody.No.1 orebody of Xinqiao Mineral Corporation Limited (XMCL) is slightly inclined (12 °) and thick. It is mined by two steps. Several years' exploitation left a large mined-out area of 1500,000 to 200,000m2 at -230m level. Permanent pillar is not designed in order to reduce loss of mineral resources, and mined-out area is supported only by cemented and uncemented filling materials, which is a rare case both in China and in the world. The major task of this study is to develop controlling theory and technique of ground pressure within large mined-out area.This study is classified into two categories: theoretical research and field test. The former includes (1) rock mechanics survey within mining area, (2) stability classification and evaluation of roof rock, (3) analysis of filling mechanism, (4) measurement of physical and mechanical characteristics of rock, ore and such structural plane as joint, fissure and fault, and (5) numerical simulation of roof rock's stability and ground pressure's dynamic distribution. (6) Discussed the effect of backfilling on the control of ground pressure, which assures the safety of mining.The research points out a new method to study and to monitor the ground pressure under the large mining spaces.The ground pressure could be controlled well when the backfilling rate passed over 50%.The result obtained played an important role in controlling the ground pressure, preventing from the ground pressure disasters, which can be the main principles for the deep mining as well.