Deformation failure and countermeasures of deep tertiary extremely soft rock roadway in Liuhai coal mine

In view of failure phenomena with nonlinear large deformation including extensive damage, whole section destruction in short time, high rate of repair, most destruction forms occurred in the tertiary roadway of soft rocks engineering in Liuhai mine, according to the methods of geological survey, theoretical analysis, numerical calculation and in-situ test, the composite failure mechanism of molecular expansion, tectonic stress, gravity stress and engineering deviatoric stress, faults and random joint in this area is analyzed deeply, then an coupling support of double-layer-truss is proposed. The research results show that the first wave of deformation energy was released by bolt-mesh-cable fixed into the roof, floor and two sides of the roadway. While the second wave of deformation energy was released through the interface function between double-layer-truss and the surrounding rock. The double-layer-truss that characterized by high strength, good integrity can absorb high deformation energy of surrounding rocks, which led to the uniform distribution of the stress. Engineering practice shows this technology has been successfully applied to control the deformation failure of the tertiary extremely soft rock roadway.