Study on Influence of Lower Protective Seam Mining on Stability of Roadway Surrounding Rock

In order to study the stability influence of upper protective seam mining on overlying roadway surrounding rock, taking 1331 transportation roadway located above 11^# coal seam of Dingji Mine as research object, we carry out numerical simulation research for the surrounding rock stress, deformation and changes of bolt axial force. The results showed that the 1331 transportation roadway has a dynamic effect with mining 11^# coal seam, according to the dynamic impact, roadway can be divided into three regions: mining influence region, intense mining influence region, and postharvest unloading region; change rule of roadway surrounding rock deformation and bolt axial force is almost the same, the largest growth region is located in the range at the front of working face 10 m to the rear of 40 m, belongs to the range of intense mining influence region. Surrounding rock stress shows a trend of decrease negative exponential function, the vertical stress and shear stress respectively decreased 20.917 MPa and 6.96 MPa, decreasing amplitude is 44.24% and 38.03%. The scope of surrounding rock region affected by upper protective seam mining is about 50 m, the degree of surrounding rock roof influence region is bigger, accumulative settlement is 165 mm to 248 mm.