Research On Strip Filling Mining Technology Of Middle And Small Coal Mines In Northern Shaanxi

Yushenfu mining area in Northern Shaanxi is located at the junction of Maowusu Desert in Western China and Loess Plateau in Northern Shaanxi.The original ecological environment is fragile,soil erosion and land desertification are serious.A large number of local small and medium-sized coal mines in the mining area basically adopt the old house pillar mining method in the early stage of mining,resulting in frequent occurrence of mining earthquakes in recent years.Filling mining is one of the effective methods to alleviate the damage of surface subsidence,soil erosion and mining earthquake caused by mining in the ecologically fragile area of Northern Shaanxi.Based on Shanghe coal mine in Yuyang District,Yulin City,this paper studies the technology of strip filling and replacement mining in Shanghe coal mine by theoretical analysis,laboratory experiment,numerical simulation and field test.Based on the beam theory and the ultimate strength theory,the paper determined the mining benchmark parameters of "mining 7,reserving 8" by theoretical analysis.The design mining process is divided into two stages:the first stage is the stage of mining working face and filling strip goaf,and the second stage is the stage of replacing strip coal pillar and filling strip coal pillar goaf.Based on the design concept of staged filling mining,the numerical simulation test is carried out.The results show that,in the process of replacement mining,the load borne by the strip coal pillar,which is the main body of the overburden load,first transfers to the adjacent strip coal pillar,which results in the expansion of the plastic area of the adjacent strip coal pillar and the significant reduction of the stability,so that the overburden load transfers to the strip filling body.If the filling body and roof are well connected and meet certain strength requirements,they can jointly bear the load of overburden,so as to ensure the stable transition from the overburden load to the strip filling body in the process of filling replacement mining.According to the laboratory research,the No.I ratio which meets the demand of filling mining in Shanghe coal mine is determined.After 28 days of curing,the uniaxial compressive strength of the test block can reach 6.845MPa,which meets the theoretical design strength requirements.The field industrial test shows that the uniaxial compressive strength of the filling block is up to 8.222MPa,and the strength index is better than the theoretical design strength,which can meet the loading requirements of the filling body in the field.The prediction of surface movement and deformation in filling mining shows that the surface movement and deformation after filling mining in 3216 working face are less than grade I damage index.The study provides theoretical guidance for the reform and practice of Shanghe coal mining method,and is of great significance to the reform of coal mining method and ecological environment protection under similar conditions in this area.