Research On Formation Mechanism Of Yangshui Mining Area Collapse Of Kaiyang Phosphate In Guizhou

Collapses of Yangshui mining area in Kaiyang phosphate are located onYangshui River, town of Jinzhong, Kaiyang County, Guizhou Province. The totalnumber of collapses there is44. To some extent, collapse hazards threaten peoples’safety living in the mining area and mining machinery and equipment as all thesecollapses are located within the range of goaf. It is significant to study deeply theformation and disaster mechanism of collapse hazards for prevention and mitigationwork under similar geological conditions. This thesis attempts to analyze the basischaracteristics and laws of collapse development and to clarify the instability mode ofcollapse in the study area according to different characteristics of collapsedevelopment on the basis of illustrating the geological environment in the study area.Finally, it analyzes the formation mechanism of collapse with the method of physicalmodeling and numerical simulation. Specific research contents and results are asfollows:(1) Collapses of Kaiyang phosphate all occurred in the abrupt cliffs and slopesconstructed by zbdn dolomite. There are zbd rock phosphates and quartz sandstone inthe toe of the cliffs. Cross-strait slope where collapses occurred is under the corrodedanti-dumping mountain of Yangshui anticline. Attitude of rocks on the left bank slopeis N50~70°W/SW∠20~33°and attitude of rocks on the right bank slope is N13~30°E/SE∠30~47°.(2) Geological structure in the study area is complex as development of Yangshuianticline and several slopes nearly incline to parallel fracture, joints and fissuresinside dolomite rock develops, two nearly vertical preferred structure planes developsand a structure plane in the middle steep slope was developed. The combination ofthese kinds of structure planes is very likely to form potential instability block. (3) The instability mode of collapse in the study area is divided into crush-fallmode, tension crack-leap mode, tension crack-slump mode and tension crack-dumpmode according to structural characteristics, stress characteristics and accumulationcharacteristics of the development of collapse.(4) This thesis completes the simulation of collapse forming process tensioncrack-slump mode and tension crack-dump mode with the method of bottom frictiontest. The simulation results indicate that unfavorable rock structural characteristics areessential for the formation of the collapse and underground mining movement is themain factor for influencing the formation of the collapse.(5) Meanwhile, this thesis completes the stimulation of collapse instability modeprocess of tension crack-slump mode and tension crack-dump mode employingdiscrete element software. The results show that underground mining results incracking on the top of overlying slope and crushing at the bottom of it which are inline with the physical simulation and field investigation results.(6) The formation mechanism of collapses can be summarized as undergroundmining, trailing edge cracking, front extrusion and collapse instability after integratingand analyzing the results of field investigation, physical simulation and numericalsimulation.