Study on surrounding rock deformation failure law and soft rock roadway support with thick composite roof

With exploitation of coal resources, mining activities in China have gotten increasingly deeper. Risk coefficient increases continuously, and the supporting difficulty has become more prominent in deep soft rock roadway because of the increasing complexity of geological conditions. Although existing roadway support technique is applicable to shallow surrounding rocks, it is not well suited for deep complicated fractured soft rock roadways. In order to solve the problem that the conventional support technique cannot provide stable support to prevent serious surrounding rock deformation failure in deep soft rock roadway with thick composite roof, in this study, the mechanical parameters of soft rocks in the air return roadway of A3 coal seam in Xieyi Mine of Anhui China were tested through the rock mechanics experiment. The failure area of soft rock roadway with thick composite roof was analyzed by drilling site test. A 3D numerical model of the soft rock roadway was constructed to explore the roadway deformation and failure range under different support schemes. Results demonstrate that in a thick composite roof, the roof that surrounds the rocks are loose and weak, accompanied with crack development in the separation line. The loose failure range is approximately 2.4 m, and the maximum failure range is approximately 4.2 m, indicating that the conventional support technique cannot offer stable support for similar roadway. The support scheme that integrates super-long strong pre-stressed anchor cable + bolt + boltgrouting was proposed on the basis of the characteristics of the surrounding rocks. Results indicate that this combined support scheme has acceptable application effects and can effectively control great deformation failures in deep soft rock roadway with thick composite roof. Related study conclusions can provide reference for soft rock roadway support under similar geological conditions. © 2017 Eastern Macedonia and Thrace Institute of Technology.