Research On Safety Control Techniques For Recovery Of Residual Ore Under The Open Pit

The lower residual ore inⅠ# orebody of tonglvshan mine was small scale and deep buried under the south open pit. A great fault separated the orebody from surrounding rock on the hanging wall. The footwall was marble, whose cave and fissure were well developed and strong permeability and mine was impacted by the private mining for a long term. After the south open pit was closed, the infrastructure stripping waste rock of the north pit backfilled into the south pit, and backfill has reached the present height of 80m by now, the direct catchment area of open pit was about 45.8×104m2 so that the seeper might penetrate into the underground. The mining enterprise would stope the lower residual ore inⅠ# orebody with the ordinary upward flat-cut-and-fill stoping method. To ensure the safety of mining operations process, the following aspects were studied in depth and presented the corresponding technical measures for safety control:(1) Studying to determine the rock mass mechanical parameters of residual ore area. By the indoor rock mechanics testing and engineering treatment method of rock mass mechanical parameters, mechanical parameters of rock mass was obtained which was accordance with the engineering practice.(2) When the lower residual ore turned open pit into underground, studying to determine the reasonable parameter of boundary pillar on the open pit bottom. Making use of FLAC3D to simulate excavation for different boundary pillar parameters, then contrasting simulation results and considering all factors, finally obtaining the best boundary pillar thickness was 15m and the best pillar width was 7m.(3) Studying to determine the width of separation jamb between the fractured fault zone in the mining process. Obtaining the reasonable width of separation jamb was 5m by numerical calculation of FLAC3D.(4) To evaluate the risk of water inrush and present control measures in the process of recovery of residual ore, the analytical hierarchy process and fuzzy comprehensive evaluation were combined to evaluate the safety of stope water inrush. In order to reduce the occurrence of water inrush, presenting the advanced detect of water and other measures in the preparation tunnel.