Study On Stope Stability Control Based On Prestressed Expandable Pillar Group

In order to reduce the ore loss rate and improve the economic benefit,it is necessary to replace the original rock pillar left in the stope with artificial pillar and other supporting bodies in the later stage of mining.In view of the shortcomings and disadvantages of several common support system,the research group developed a new type of prestressed expandable pillar with the advantages of active supporting roof and strain hardening bearing,and achieved certain results in laboratory and field applications.Therefore,it is of far-reaching significance to study the stope stability under the action of prestressed expanable pillar group.In this paper,based on the stope roof stability of prestressed expandable pillar,the stability of the stope roof was studied.By combining the methods of formula calculation,theoretical analysis,numerical simulation optimization and field industrial test,the analytical solution of the complex variable function of the surrounding rock stress and deformation under the stope support in three-dimensional space was obtained.The division method of different area of stope roof characteristic curve is determined.Based on the ore-body stoping in the No.2836 test stope of prestressed expandable pillar in Sandaogou Gold Mine,Fengcheng,Dandong,the optimization design of the stope support parameters of prestressed expandable pillar group was carried out,and the field industrial test was conducted.The main research contents of this paper are as follows:(1)Based on the theory of conformal transformation of complex function,the analytical solution of the plane complex function for the stress and deformation of surrounding rock surrounding a rectangular excavation under the support action is studied.Then,based on the two-dimensional plane problem,the solution of the plane complex variable function is extended and extended,and the three-dimensional three-dimensional semi-analytical formula of stope roof deformation is obtained,and the accuracy of the formula is verified by numerical simulation method,which can meet the calculation requirements.(2)By means of the semi-analytical formula of stope roof deformation in three-dimensional space,the roof characteristic curves of three rock masses with good stability,average stability and poor stability are obtained.By solving the critical support pressure picr,the loose dislocation displacement u0 and the loose ground pressure ps,the elastic deformation zone,plastic fracture zone and failure instability zone of the stope roof characteristic curve are divided.Based on the principle that the surrounding rock in the plastic fracture zone can be kept stable,the roof load range of the prestressed expansive support group is determined.(3)Taking No.2836 prestressed expandable pillar test stope in Sandaogou Gold Mine,Fengcheng,Dandong as engineering background,the evolution law of deformation and plastic zone of stope roof under different arrangement modes,different quantities(support spacing)and different bearing capacities is analyzed,and the optimal support scheme of prestressed expansion support group is determined:The rectangular layout is applied,the support spacing is 5 m,the bearing capacity of the pillars is 2.5 MPa-3 MPa,and a total of 9 prestressed expandable pillars need to be evenly arranged in the stope.Based on the optimization results of supporting parameters,the plastic fracture zone of roof characteristic curve was further divided into plastic fracture zone and plastic fracture zone,and the plastic fracture zone was determined to be the optimal support zone,and the boundary point of plastic fracture zone and plastic fracture zone was the optimal support point.(4)Based on the optimized support parameters of the prestressed expansive strut by numerical simulation,field industrial tests were carried out to monitor the deformation of the roof and the change of the bearing capacity of the prestressed expansive strut during the tests.The test results show that the maximum deformation of the roof is 22.7 mm,less than about 1 mm from the numerical simulation results.The bearing capacity of the prestressed expandable pillar is larger in the center and smaller near the wall,and the average bearing capacity is 2.67 MPa when the pillar is stable,which is within the range of support parameters optimized by numerical simulation.The stability of the test stope is good in the process of ore stoping and 60 days after stoping.