Study and application of paste-like filling mining parameters of shallow buried coal seam in Northern Shaanxi

The ecological environment is fragile and water resources are scarce in northern Shaanxi,and abundant shallow coal seam resources exist in this area. In order to solve the problem of water resources loss caused by coal mining,the paper proposes to apply the technology of replacement of eolian sand paste-like filling strip in the "water-retaining area" of Northern Shaanxi. Based on the theory of elastic foundation,the mechanical model of coal pillar roof in strip mining is established,and the deflection formula of the roof after mining is deduced. Combined with Winkler foundation theory and ultimate strength criterion,the reasonable mining width and reserved width of strip working face are calculated. The study results show at the backfill formed by the mixture of aeolian sand as aggregate,fly ash,cement,as binder and water. Based on the laboratory cross matching experiment,the optimal filling material ratio and strength index are obtained,and at the micro level,the mechanism that the strength of backfill at different age is determined by the degree of crystal interpenetrating into mesh is revealed. Taking Shanghe coal mine in Yulin City as an example,through the numerical simulation of the movement law of the aquiclude in the mining process of the experimental No.3216 working face,it shows that the maximum value of the settlement of the aquiclude after mining is 27.9 mm,which indicates that the aquiclude keeps stable in the mining process and the overiying rock structure of the stope is well controlled. The industrial experiments show that the filling effect of the strip gobs is good,and the displacement of overburden rock is not obvious. In general,lower strata displacement＞middle strata displacement＞upper strata displacement. Through successful practice of strip filling replacement mining technology,the good stability of overburden rock was ensured in Shanghe Coal Mine,the development height of water-conducting fracture zone in overburden is greatly reduced,the problem of water gushing after filling of No.3216 working face is fundamentally solved,and the recovery rate of Coal in Shanghe Coal Mine is greatly improved in Northern Shaanxi.