Similar simulation experiment of water loss and settlement in thick loose aquifer

The in-depth research on the breaking and deformation law of overburden rock under the geological and mining conditions of thick loose aquifer are lacking at present. Taking 11111 working face of Pansidong Coal Mine in Huainan mining area as the engineering background, the similar material model is constructed, and the digital photogrammetry extraction displacement method is used to record the overburden rock breaking process and overburden rock deformation during the model roadway heading. The causes of water loss and settlement of aquifer are analyzed. The overburden rocks form two main longitudinal diversion fissure zones under the action of W-type shear stress arch. The further development of the diversion fissure zone causes water loss and consolidation of the aquifer, and the aquifer is further compacted under the action of gravity of the thick loose layer. With the intensification of the overburden rock breaking movement, О type shear stress arch is formed under the joint extrusion of bending zone and overburden rock, which compresses the thin space and leads to the large amount of surface subsidence. The damage of overburden rock under water loss condition is analyzed. After the roadway heading work of the working face is completed and the overburden rock reaches a steady state, the front caving angle is 57°, the rear caving angle is 62°, and the height of the diversion fissure zone is 63 m. Under the action of stress concentration, the overburden rock above the open-cut hole and the stop-mining line is broken to produce longitudinal fissure, and the overburden rock in the area of the collapse zone above the open-cut hole and the stop-mining line produces lateral separation fissure. The longitudinal fissures and lateral separation fissures intensify the hydraulic connection between overburden rock and the aquifer. The dynamic movement law of overburden rock under water loss state is given. With the advance of mining face, the overburden settlement of each observation line increases gradually, and the overburden settlement of the observation line close to the working face is the largest. The trend of the subsidence curves of the observation lines in the overburden rock above the working face is basically similar, and the jump of the subsidence curves is consistent. The trend of the subsidence curves of the observation lines above the aquifer is basically consistent, and the jump of the subsidence curves is synchronous. The jump of the subsidence curves of observation lines in the overburden rock above the working face and the one of the observation line above the aquifer are asynchronous, indicating that the aquifer plays an important role in the movement and deformation of the overburden rock.