Research on treatment technology of soft rock roadway floor heave for “triple-shell” bearing structure

Aiming at the serious problem of the floor heave of 131 transportation tunnel in a mine of Panjiang mining area, this paper reveals the deformation and failure characteristics of the floor heave and the causes of damage through field research, laboratory test, theoretical analysis and numerical simulation.It is believed that the main cause of the floor heave is the occurrence of shear failure and the further deepening of the hydraulic action under the high stress of the broken rock of the bottom plate and the unsupported state.Based on this, the “triple-shell” support theory is proposed.The mechanism of the floor heave support is analyzed, and the “triple-shell” control floor heave technology of “shallow bottom grouting anchor rod+deep grouting anchor cable+grouting 500 mm+U type shrinkable bracket” is constructed and successfully applied.The results of on-site monitoring show that the surrounding rock deformation of the roadway is divided into three stages.The 20 d deformation is severe, and the deformation is more moderate from 20 d to 45 d.After 45 d, the deformation area is stable.The maximum floor heave volume is 95 mm, and the deformation rate is 0.35 mm/d after stabilization.Such a deformation amount is within a controllable range, and the support effect is remarkable.