Three measurement relationship and control principle of overburden movement in cemented filling

In order to study the characteristics of overburden deformation in the filled goaf，based on the spatial and time effects of the deformation of the surrounding rock in the filled goaf，the pre⁃filling displacement，the un⁃ der⁃connection and the compression of the filling body are taken as the main sources of the overburden deformation. The “ three⁃measurement relationship ” of the overburden movement is revealed， and the influencing factors of the three⁃measurement deformation are analyzed. Based on the pressure balance arch theory，the equilibrium relation⁃ ship between the pressure of surrounding rock and the bearing capacity of filling body is established，and the synergis⁃ tic effect of “three measurement relationship” is studied，and the “three degree principle” of overburden deformation control is proposed. The overburden deformation is reduced by controlling the filling velocity，filling compactness and filling intensity. The research results show that the pre⁃filling displacement is proportional to the overhanging roof time and the filling step，and its deformation is significantly smaller in the first stage of recovery than in the last stage，and the filling efficiency decreases，leading to an increase in the overhanging roof time and its deformation in⁃ creases. The under⁃connection amount increases with the increase of bleeding rate，and its under⁃connection area is tri⁃ angularly distributed，and the under⁃connection range decreases with the increase of coal seam inclination，while the under⁃connection height increases at the upper entrance of the filling branch lane. The compression of the filling body is inversely proportional to its elastic stiffness.Increasing the filling speed and compaction significantly reduces the overburden deformation in the early stage of filling，while increasing the filling body strength is the key factor to con⁃ trol the overburden deformation in the late stage of filling. The numerical simulation results show that in the two⁃ stage mining mode，the filling body produces only partial roof contact in the first stage，complete roof contact and inter⁃ mittent roof contact in the second stage，and finally forms complete roof contact. Based on the “three degrees princi⁃ ple” of overburden deformation control，Haoyuan Coal Mine adopts the continuous mining and continuous filling ce⁃ mented coal mining technology to achieve the parallel operation of continuous coal mining and continuous filling，which significantly improves the filling efficiency and reduces the pre⁃filling deformation of the overburden. The results show that the overburden only produces small separation layer，which greatly maintains the stability of the surrounding rock and realizes the deformation control of the overburden，which verifies the effectiveness of the “three degrees prin⁃ ciple” on deformation control and provides a reference for the study of overburden deformation control under simi⁃ lar conditions.