Study On The Law Of Surface Movement Under The Influence Of Extremely Thick Key Strata

The mining of coal resources has a significant impact on the destruction of the surface environment,and the research on the mechanism of surface destruction is crucial to surface environmental protection.In the actual geological survey of Jianzhuang mining area,it is found that there is a huge layer of rock in the overlying coal layer.The subsidence law of the surface is closely related to the movement of this layer.Through the analysis of the hardness of the formation,it is found that the lithological structure characteristics of the coal cover rock in Jianxin Coal Mine are generally soft-hard-medium-hard structure,which is beneficial to the control of surface movement and deformation,and the subsidence coefficient and subsidence are expected to be relatively high.small.The key layer theory is used to discriminate the key layer position of the overlying coal layer.The calculation results show that the overlying coal layer belongs to the multi-layer key layer structure model,and the middle sandstone at 142.49 m from the coal layer is determined as the main key layer;through two different calculations The formula calculates the height of the water-conducting fissure zone of multiple boreholes and compares and analyzes it with the measured results of the surrounding mining area.The results show that the main key layer is located in the water-conducting fissure zone and no large-scale fracture occurs;the elastic foundation beam theory is used to derive the surface subsidence and bending Curve,and analyzes the relationship between the key layer thickness and the surface subsidence coefficient and subsidence.The UDEC numerical simulation software was used to simulate the dynamic curve between the main key layer and the surface subsidence during mining in the strike direction.It was found that the surface subsidence and the main key layer subsidence form remained the same and the surface subsidence had a subsidence relative to the main key layer subsidence.Obvious hysteresis;Simulated the surface subsidence process when mining in multiple working faces in the inclined direction.The results show that due to the influence of the huge thick main key layer,the surface subsidence in the inclined direction is not obvious and the mining is inadequate.The field subsidence characteristics on the strike and trend of the working face were analyzed using field measurement methods.The surface subsidence in the direction of the trend was jump-type subsidence consistent with the numerical simulation results,and the amount of surface subsidence in the direction of the tendency was less,compared with the simulation results Agree.And the characteristics of surface subsidence speed are analyzed,and the applicable formula for calculating subsidence speed is given.The paper has 39 pictures,8 tables,and 61 references.