INVESTIGATION TO THE TECTONITE ROOF OF THE COAL SEAM FOR THE STABILITY

The roof of the 2₁ coal seam in Gaocheng area of Dengfeng Coal Field is a tectonite formed by gliding. It is broken,incompact in texture and difficult to control. According to the results of the field work, the microscopic examination and the fabric analysis, this tectOnote roof can be divided from the lower to the upper into four zones,they are the gouge, the fault breccia,the tectonoclastic and the crack zones. The fault breccia includes two kinds of tension and shear, they are formed under the deepseated plastic deformation, with addition of the late shallowseated brittle deformation. After the engineering properties tests, it is found that the clay grouting of the tectonite is obvious. In order to control the roof of the 2₁ coal seam following measures are taken. First the underground lanes are dug and built rapidly and short range by short range so as to shorten the time for the lane walls to open. Then the pressure relieve troughs are dug in the side walls of the lanes to save the swell of the wall rocks. The slurry is preinjected into the working faces to make them firm and to keep the wall rocks from collapsing. Last the roof is supported with dense woody props or made collapsed forcibly.