Study On The Regulation Of Strata Movement And The Predication Of Surface Movement Caused By Shallow Seam Mining

The shallow coal seam mining often use longwall mining,and the roof control use caving method.This makes the strata movement is violent and the surface subsidence is large.In this paper,the theoretical model analysis,surface subsidence observation and numerical simulation method are used to study the strata movement and surface subsidence after the shallow coal seam mining.After the shallow coal seam mining,there is no bending subsidence zone in the overlying strata,and the overlying strata show the distribution of "three zones"(caving zone,fracture zone and loose layer).The caving zone is adjacent to the goaf.The fragmentation of caving zone is small,and it breaks down immediately after coal mining.Fracture zone is located in the upper of caving zone,rock breaking larger pieces,and can keep the layered distribution in fractured.The granular media in the loose layer of the ground surface are dispersed,and the movement has the characteristics of random medium moving,and the subsidence basin is formed on the surface.The gob area is simplified into an elliptical cavity before the caving zone break,and the stress of the caving zone is analyzed.With the exploitation of the coal seam,the caving rock stratum is simplified as a cantilever beam,and the stress of the caving zone is calculated.The breaking mechanism of the caving zone is obtained by the combination of rock breaking condition.The coefficient of bulk increase of rock is summarized,and the experience of subsidence is obtained.The key stratum plays an important role in the strata movement.Based on the simplified model,the elastic foundation beam model is established,and the analytic solution of the bending moment,shear force,deflection and rotation angle is obtained.Based on the broken condition of the rock beam,the first break distance and the periodical break distance of the key stratum are obtained.The model is applied to practical engineering.The results show that the elastic foundation model can estimate the breaking distance of the key stratum.By using the theory of random medium,the surface subsidence curve of cell mining is obtained.The surface subsidence formula of semi infinite mining is obtained by integral.The finite mining is regarded as the 1/2 of the sum of two infinite mining,and the formula of surface subsidence is obtained.The relationship between lithology and subsidence parameters is obtained by regression analysis.The surface subsidence caused by coal seam mining is measured and the measured value of surface subsidence is obtained.The results show that the correlation between the theoretical predictions and the observed results is high,and the theoretical model can be applied to the prediction of surface subsidence in shallow coal seam.The UDEC shallow coal seam mining model is established,and the strata movement rule is obtained by distributing the excavation.Compared with the numerical simulation and monitoring results,the relative error is small.This shows that the numerical simulation can be applied to the prediction of surface subsidence in shallow coal seam.