Research On Movement And Stress Evolution Law Of Super Thick Key Strata In Gaojiapu

In recent years,with the increasing depth of coal resource exploitation,it has been found that some of the deep coal seams are covered with huge thick hard rock formations.There will be significant differences in the characteristics of fractured motion of rock formations under the condition of upper hard and thick rock formations,and the characteristics of crack development and stress distribution of rock formations.Gaojiabao coal mine in its main mining above the coal seam has a typical layer of huge thick hard rock layer,in a large area of mining after the surface subsidence is small,lead to the mining process there are impact ground pressure disaster,surface subsidence and other problems.In this paper,the motion and stress evolution of the giant thick key layers of the Gaojiabao coal mine are studied by means of field observation,physical simulation and numerical simulation.The main research work and conclusions are as follows:(1)The distribution characteristics of the giant thick key layers of Gaojiabao coal mine were studied.Based on the analysis of surface subsidence data,it is determined that the surface of Gaojiabao coal mine does not reflect the characteristics of the sinking basin,the distribution status of the key layers of the Gaojiabao coal mine is judged according to the drilling column chart,the typical huge thick key layer is determined,and the thickness of the main key layer is shown to be non-homopholy distributed and the thickness of the key layer of the first and second plate intervals is more severe according to the plot of the main key layer contours drawn.(2)The breaking motion characteristics of the huge and thick key layer of Gaojiabao coal mine are analyzed.According to the geological data of Gaojiabao coal mine laying similar material model,a comparative analysis of displacement and stress monitoring results can be seen: in the case of different main key layer thickness and high recovery,there is a difference in the position of the bottom fissure of the main key layer,in the mining process,the main key layer fissure gradually developed and did not break after mining,analysis of the mining area and coal column pressure can know the main key layer and the pressure above it to the two sides of the coal column transfer,not fully transferred to the working surface.(3)It reveals the gradual destruction process from bottom to top in the huge thick key layer crack of Gaojiabao coal mine.In view of the fissure evolution law of the huge thick key layer of Gaojiabao coal mine under the influence of different mining height and mining size,the simulation results show that only the lower key layer appears micro-crack in the initial stage of surface mining,and the fissures produced in the early stage of mining continue to develop upward and new A crack appears above the working surface of the mining,and when the upper fissure of the main key layer develops close to the working surface at a height of 12 m after mining,it indicates that the fissure of the main key layer develops continuously with the exploitation of the work surface,and the height of the fissure development increases with the increase of the height of the extraction.(4)Based on the different thicknesses and mining heights of the giant thick key layers of the Gaojiabao coal mine,a numerical model of UDEC discrete meta was established to analyze the motion and stress evolution laws of the giant thick and hard key layers under different conditions.It can be seen from the simulation that the change of the thickness of the main key layer will significantly affect the maximum amount of sinking,and the change of mining height will have less influence on the amount of sinking.With the increase of the thickness of the main key layer,the stress of the coal column will change from "U" shape to the trapezoidal distribution,the maximum stress in the middle of the coal column will increase during mining,and the average stress and central area stress will increase and then stabilize with the thickness of the main key layer.There are 57 charts,4 tables and 109 references in this paper.