Study on roof movement law of local filling mining under peak cluster landform

Abstract

The strip structure filling mining technology is suggested in response to the environmental issues such as surface subsidence and landslides brought on by the mining of 11,071 working faces in a mine in Guizhou. The mining technology system is studied through indoor testing, numerical simulation, and engineering monitoring. According to theoretical study, the filling strip can be steadily loaded and its value doesn't exceed 10 m when the width of the filling strip and the width of the filling interval are set to be equal. According to laboratory testing, fly ash can replace some of the cement in the cement mixture as a binder to maintain strength while cutting costs. The degree of crystallization gradually distributed into the network in the filling paste of various ages corresponds to its strength when combined with the findings of scanning electron microscopy; The numerical simulation results show that the maximum subsidence of the immediate roof is reduced from 340 to 3 mm from the filling rate of 0 to 100%, the filling effect is remarkable, and the shape of the settlement curve is changed from 'U' to 'basin', then to 'W'; during the local filling mining, the settlement curve of the immediate roof presents a 'wave' shape, and the stress curve of the immediate roof in the middle of the stope is also changed. The peak tension of the coal wall falls synchronously with filling spacing on both sides of the stope. The overall vertical stress below the mountain is larger, and the vertical stress at the top of the filling body eventually shifts from a "saddle" shape to a "inverted U" shape without zero support stress. In conjunction with the plastic zone, it is discovered that the stable bearing of the "filling strip-direct roof" composite structure increases with decreasing tensile and shear damage range of the hollow roof area and both sides of the top of the "filling 3 m interval 3 m" scheme; engineering measurement also reveals that the higher the position of the survey line is, the smaller the displacement is. However, the overall displacement of the strata directly above is negligible, and the greatest displacement is only 10.9 mm, which is consistent with the numerical simulation. At the same time, the displacement beneath the mountain area is too great.