Mechanical mechanism and support technology of deep-buried roadwaytensile-shear failure of rib spalling

In view of the phenomenon of rib spalling in tensile-shear form in the initial stage of deep-buried roadway excavation, and according to Mohr-Coulomb yield criterion and the limit equilibrium equation of coal body in rib spalling, the mechanical model of rib spalling body under the interaction of the abutment pressure, the self-weight stress, the tensile stress at the back edge and the slip force on the shear plane were established. On the basis of the ultimate equilibrium condition of rib spalling body, the theory of key parameters such as the front edge height, tensile fracture depth at the trailing edge, and horizontal collapse width of the rib spalling mass were derived. The effects of cohesion, internal friction angle, tensile strength and horizontal collapse width of the rock mass on the depth of the trailing edge of the rib were discussed. The results show that there are positive correlation between trailing edge cracking depth and cohesion or internal friction angle of coal and negative correlation between tensile strength of the coal and trailing edge cracking depth when the tensile-shear failure of rib spalling happens. The tensile-shear failure of rib spalling will develop into a single-inclined rib spalling when the cohesion, internal friction angle and tensile strength of the roadway side wall reach a certain value. Based on the determination of the failure parameters of the rib spalling mass, a combined support method of bolts and cables for the coal body in the slab area was proposed. When the optimal installation angle of the anchor rod is controlled between 30° and 90°, it can form an effective support structure with the anchor cable, and the optimized support method can effectively prevent the roadway side wall from the tensile-shear failure of rib spalling. Finally,taking the 130-225 m section of the 401 working face transportation roadway of Tingnan Coal Mine as an engineering example, the key parameters such as the front edge height, horizontal collapse width and trailing edge crack height of the rib spalling mass were analyzed theoretically. Furthermore, the initial bolt support scheme and its parameters of this section of the roadway rib were optimized, and a good support effect was achieved.