Research On Rules Of Surface Movement And Deformation Under Mining In The Second Panel Of Tingnan Coal Mine

The surface geomorphology of Binchang mining area belongs to remained loess and ravines cut severely. 100-300 m thick-hard Luohe formation sandstone generally occurs in the upper part of overburden above the coal seam. It plays a controlling role in the surface subsidence. The thickness of topsoil and topography also has great impact on surface movement and deformation. Surface movement character results from coupling motion between topsoil and Luohe formation sandstone. To master the rules of surface movement under this special condition is of great significance to the safety of coal mining under construction of the entire Binchang mining area.In this paper, taking coal mining in the second panel of Tingnan coal mine in Binchang mining area as research background, on the basis of analyzing the geological conditions of the second panel, surface movement observation was carried out in No.204 face and No.205 face. Observation results show that Luohe formation sandstone controls the surface movement and deformation. Under the condition of super-subcritical extraction, surface movement is small, subsidence ratio is only 0.046, surface deformation is weak and it will not cause damage to surface buildings and facilities. Under the condition close to critical extraction, surface movement increase largely, surface deformation is significant and subsidence ratio reaches 0.22 but far from the maximum subsidence. Subcritical subsidence range is consistent with critical subsidence. Loess layer critical angle depends on its thickness and slope.Applying UDEC 2D numerical simulation software to simulate the surface movement after multi working face mining, the simulation results show that the surface movement rules of mining No.204 and No.205 face is basically consistent with the observation results. After mining No.204 face, the subsidence ratio is 0.392 and it still belongs to subcritical extraction. After mining No.205 face, the subsidence ratio reaches 0.528 and it reaches critical extraction. Under the control of thick-hard Luohe formation sandstone, critical extraction area is much larger than under conventional mining condition. When the ratio of minimum(tendency) mining width to mining depth is less than 1.5, it is subcritical extraction. When the ratio of minimum(tendency) mining width to mining depth is greater than or equal to 1.5, it reaches critical extraction.Based on the results of surface movement observation and numerical simulation, the mechanism of surface movement and deformation of thick Cretaceous sandstone is analyzed. It comes to the conclusion the high-thick-hard rock strata in Luohe formation is the main key stratum. By key stratum control, the surface movement and deformation is consistent with the deformation of the main key stratum. Under these conditions, critical extraction condition should be determined according to whether the maximum subsidence is fit to the maximum deflection of the main key stratum in Luohe formation sandstone.The results of this study lay a foundation for the rules of the surface movement and deformation of thick sandstone layer of Binchang mining area and provide reference basis for the safe coal mining under the building(structure) in Binchang mining area.