Key technology of advance pre-grouting of ground directional holes to shield roadway passing fault and broken zone

Stress concentration and large deformation of the surrounding rock are often encountered in the deep roadway passing through the fault fracture zone, which is a major safety hazard for excavation and support. In order to improve the deformation resistance and strength of surrounding rock and reduce the anchoring support pressure of the roadway, taking the large fault of the roadway in the Huaibei mining area as an example, the main reasons for the large mining pressure, the poor surrounding rock stability and the difficulty of supporting in the process of excavation and support were analyzed. After using the ground directional holes to advance pre-grouting to modify the surrounding rock of the roadway, the roadway was successfully excavated and passed through the fault fracture zone. The key technical system of directional hole shielding roadway crossing faults based on the key technology of drilling construction and the key technology of high pressure pre-grouting was summarized and proposed. The fault fracture zone was grouted accurately, and the grouting reinforcement effect was evaluated from the aspects of water pressure test, lithology exploration, grouting amount, grouting diffusion distance, geophysical verification and tunneling support effect analysis. The application results show that surface directional drilling method has remarkable advantages on exploring rock lithology with long distance and pre-grouting with high pressure. The method improves the strength of the soft and weak surrounding rock and decreases rock deformation, The maximum floor heave of roadway decreased by more than 62.6%. It provides safety guarantee for roadway support. Thus, we believe that the method has generalizable value.