Research on deformation control of long and short anchor cable combined support in "three soft" roadway

In response to the challenges of severe deformation, difficult control, low excavation efficiency, and challenging mining replacement in the surrounding rock of "three soft" ultra-thick coal seam roadways, a control technology utilizing anchor net cable support is proposed. Through on-site ultrasonic detection and borehole observation, the plastic range of the loose zone in the surrounding rock is determined to be from 2.4 m to 3.0 m. By using numerical simulation, the supporting effect under different spacing of long and short anchor cable is obtained. The supporting scheme of using anchor net cable for roof and using rock bolt for two ribs is determined. The reasonable supporting distance is designed and successfully applied in practice. The results show that the combined support can effectively control the deformation of composite soft rock roadway. The convergence of the two ribs and the roof and floor is not more than 30 mm; during roadway excavation, the stress of roof anchor cable is in the range of 60 kN to 170 kN, which is relatively stable.It can be seen that the combined control techniques of long and short anchor cables can effectively improve the control effect of roadway surrounding rock. Moreover, the production practice has proved that the average monthly footage of the long and short anchor cable combined control technology has exceeded 143 m (compared to an average monthly advancement of 60 m with shed support), the excavating efficiency has increased exponentially, and the difficulty of mining replacement has been effectively solved. The economic and social benefits are significant.