Study on dynamic deformation of overlying strata and pressure behavior law for extraction of multiple coal seams

According to the mining condition of multiple coal seams with deep overburden strata and large panel in Datong Mining Area, dynamic deformation of ov erlying strata and pressure behavior were studied. Based on the mining practice of No.8105 working face of Tongxin Coal Mine, a dynamic load calculation method for t he unextracted area, coal pillar area and mining collapse area of the upper coal seams was established. The strata caving interval under the influence of dynamic load was modified. The results showed that under the influence of extraction of the upper Jurassic No.14 coal seam of Tongxin Coal Mine, the main key strata caving interval was determined from 38.23 m to62.32 m. With the wide influence range of roof strata from the working face, synchronous instability of key stratum was the cause that「 esulted in intense mining pressure occurrence. Dynamic changes of the main key stratum caving interval which increased the potential of synchronous instability were t he cause of the frequent occurrence of intense mining pressure. Moreover, under the mining condition of deep overburden strata and broad mining area, strong pressur e influence from the upper coal pllars to the working face appeared with a lag.