The influence of the drilling rate of the raise boring machine on the stability of the surrounding rock of a inclined shaft with large dip angle

The drilling method of counter-well drilling rig has become an important construction method for the construction of large inclination Angle pressure pipeline in pumped storage power station. In order to study the effect of the drilling rate on the stability of the surrounding rock of the inclined well. The method of numerical analysis is used to simulate the drilling rate of backwell drilling machine by changing the drilling depth of certain calculation step, and the drilling depth is along the inclined shaft line. The selection of drilling parameters is optimized and the drilling rate of the reverse well rig is determined. The results show that the tunneling rate has a significant influence on the deformation rate of surrounding rock and the change rate of stress gradient in the process of drilling with reverse-well drill. With the increase of drilling rate, the deformation rate and the change rate of stress gradient increase. The variation amplitude of the surrounding rock deformation and stress value at the monitoring point increases first and then decreases, and finally tends to be stable. Under this formation condition and drilling scheme, the deformation of surrounding rocks in wellbore after drilling at the same depth is small, and the effect of stress disturbance is not significant. The maximum deformation of surrounding rocks in inclined Wells is only 0.27mm, and the strong disturbance zone is about 2.0m. Combined with field drilling test results, the optimal drilling rate of reverse well reaming is determined to be 1.2m/h.