Study On Weakening Technology Of Top-coal And Parameter Optimization Of Caving In HouAn Mine

Thick seam reserves are abundant in our country, accounts for about44%of total reserves of coal seam, and it’s Production also accounts for some45%of the total coal production, but the top-coal recovery rate is generally low, result in thick coal seam mining can’t get rid of the extensive mode of production. So thick seam bed mining to reduce the cost of production, to achieve safe and efficient production, is of great significance.This paper use the study method of field investigation, theoretical analyses, FLAC3D and PFC2D numerical simulation, and field test to analysis the mining ratio of top-coal in the fully mechanized top coal caving face of Hou An mine; analysis and study of the restricting factors of top-coal caving, and caving property in exploitation is analogue simulated with FLAC3D; loose blasting technology to improving the mining ratio of top-coal is designed, and blasting effect is analogue simulated with FLAC3D; caving process is analogue simulated with PFC2D, and new caving parameter is put forward; field tests is carried out at last. Research suggests that:(1) Depth of coal seam hosting top Seam, coal strength, top-coal thickness, top-coal jointed fissure distribution, coal seam parting, coal caving step distance, caving mode are the main factor of coal caving;(2) In the mining process, supports pressure is relatively small, its peak appear ahead of mining face5~7m, take value12~16MPa, compared with the strength of coal, supports pressure cannot broken top coal to the caving degree; in FLAC3D model use top coal damage coefficient to characterization top coal broken effect, top coal damage coefficient of0.26~0.51is get through simulation, which state that poor crushing represent the poor caving.(3) Poor roof coal caving, and big caving block means deep hole loose blasting technology should be used. two rows of blast hole should be layout along with working face, each in80°,75°elevation bias the goaf and the diameter is42mm; rear blast hole far from goaf1965mm, inter-row spacion is3100mm×3100mm; the length of blast hole is8~9m; no charging in Positive focus axial, each blast hole charge1.8~2.55kg, cartridge diameter32mm and packing length1002mm.(4) Under the current production conditions, the blasting of weakening top-coal technique should be increased, and caving technology should be adopted: apheresis is4m, caving step is0.6m (Two Wining and One Caving), two-times interval caving.After the scene using the above research results, r blasting the coal is relatively uniform, granularity is smaller blocky structure compared with not blasting. long hole loosen blasting technology of presplitting top-coal is good. Top-coal can be successfully put down and cavibility been greatly improved, and it’s caving extraction rate increased to90.8%.