Abstract：The mechanical properties of the sedimentary rock mass structures depend on the lithological characteristics of rock and different types of structure planes. The percent content K of stiff rock is select to represent lithologic characteristics in the layered rock mass，and the rock mass is classified as stiff，middle stiff and soft rock masses. Based on developing degree of structure planes and scale of project，rock mass structures of coal roof are divided into intact，blocky and heavily fractured structures. Through simulation test of similar materials，the underground pressures of the working faces with different rock mass structures are analyzed. The test results indicate that the abutment stress ahead of working face reduces from intact structure to blocky and heavily fractured one，and the position of peak abutment stress migrates inside to roof rock mass.
