Research On Strata Behavior And Failure Of Overlying Strata Of Gently Inclined Thin And Medium-Thickness Phosphate Ore Body By Underground Mining

Based on the experimental study of gently inclined thin to medium-thicknessphosphate ore body from open pit to underground mining which is at fourth mining areaof Kunyang Phosphate of Yunnan Phosphorus Group, by conventional mechanical testof rock samples collected at the scene then processed into the standard test pieces,mechanical parameters of the key strata are measured. Considering the seam occurrenceconditions and geological profile of the exploration line, three mining methods arechosen primarily, which are room and pillar mining method, cemented filling methodand long wall caving mining method. Analysis and comparison on stope stress behavior,the stability of pillars, the failure law of overlying strata and the slope stability ofground surface with the numerical simulation of FLAC3D, it can provide the basis andreferences for mining of analogous gently inclined thin to medium-thickness orebody.The main work and conclusions are as follows:①With the indoor mechanical test of the ore body, roof and floor of the fourthmining area of Kunyang Phosphate, physical and mechanical parameters of key strataare measured;②According to the geological conditions of orebody and the properties ofsurround rock mass, choose three mining methods as the objects of study, which areroom and pillar mining method, cemented filling method and long wall caving miningmethod;③With different mining methods, the roof pressure relief varies degrees, pillars(walls) bear stress of different concentration factor. The vertical stress decreases andStress concentration factor increases from filling mining method, room and pillarmining method to caving mining method, and the stability of pillars is influenced by themining of adjacent room much more than the other rooms, then keep in a certain state;④With different mining methods, the subsidence displacement and influenceextent is different, so is the disturbance degree. The subsidence displacement, influenceextent and disturbance degree decrease from filling mining method, room and pillarmining method to caving mining method, when mined with room and pillar miningmethod and filling mining method, open pit and slope keep stable basically, while slopehas a great disturbance mined with caving mining method, and monitoring systemshould strengthen as recommends; ⑤Stope stress behavior keeps more consistent in the process of room and pillarmining and filling mining; the stope stress, subsidence displacement and influenceextent of overlying strata is smaller with filling mining method; but considering the highproduction cost and complex mining technique of filling method mining, it is properwise to have an economically rational analysis and further optimize the structuralparameters of the filling mining method.