Research On The Movement Law Of Floor And Roof In No.3 Coal Mining Face Of Changping Coal Mine

During working face mining, roof and floor will be destroyed, which has an important impact on bottom water. So it is necessary to study the movement law of roof and floor of No. 3 coal 2308 mining face of Changping coal mine by the means of field measurement, theoretical analysis and numerical simulation.Using the field observation data of support working resistance in the coal face, the law of strata behaviors and were summarized. Then, combined with the physical and mechanical parameters of surrounding rock tested in the laboratory, classification on stability of the surrounding rocks was performed. The overburden movement was studied and calculated theoretically by “key strata theory”; combined with formula and the working face strata structure, and the overlying strata were divided into the "three zones" at coal face. According to different movement of roof in the coal mining Process, floor stress field and floor failure features were analyzed and studied. The elastic theory of arbitrary Point stress distribution in half-Plane infinite body with distributed force function was applied. After that, we judged the elastic zone and the plastic zone with the Mohr-Coulomb criterion. The maximum depth and failure scope of the floor Strata was calculated with the plastic theory and empirical expression. Using UDEC software studied different mining height of roof and floor failure law.Using FLAC3 D constructed the numeric model to study the movement law of roof and floor with different depth, different length and different mining working face.The result shows that, the periodic weighting step distance is between 9.16 m and 32.81 m, average periodic weighting step distance is 18.15 m. Work face top class belongs to 1b unstable roof. The basic roof belongs to roof pressure obviously. The height of caving is 24.95m; the height of the fractured zone is 61.47 m.The roof of working face three development zones and high positive correlation. The buried depth and working face length have little effect on the three zones. Abutment pressure peak value and mining height has a negative correlation. Breakage depth of floor of 2308 working face is 12 m, mining width and floor failure height is not a single linear relationship. Floor damage has a critical face slant length.