Effect of Borehole Positions and Depth on Pressure Relief of Cavern Surrounding Rock Mass: Fid-Bau Portal

Effect of Borehole Positions and Depth on Pressure Relief of Cavern Surrounding Rock Mass

Chen, Zhaofeng / Xu, Tao / Dai, Xu / Song, Jiacheng

Abstract As the development scale and depth increasing, the frequency and intensity of rock burst and other surrounding rock dynamic disasters are also increasing, which seriously affects the safety construction and operation of cavern engineering. At present, one of the most commonly used methods to control rock burst risk is use borehole pressure relief technology. In this paper, the pressure relief effect of surrounding rock drilling with different borehole positions and borehole depth. Firstly, the stress evolution process of surrounding rock after excavation is analyzed. Then, the influence of drilling position and drilling depth on the stress evolution process of surrounding rock is explored. The research results show that drilling in the surrounding rock will reduce the stress near the borehole, while the stress of surrounding rock in the depth direction of the borehole will increase. With the increase of drilling position H, the stress in the drilling area of surrounding rock decreases gradually. On the contrary, the stress concentration in other areas near the borehole gradually increases. With the increase of drilling depth, the stress of surrounding rock of the cavern continuously transfers to the interior, and when the drilling depth is greater than 1500 mm, the pressure relief effect does not continue to improve. After drilling, the damage of surrounding rock transfers to the interior of surrounding rock, and the damage degree near the tunnel wall is less than that without drilling. Different borehole location will lead to different failure characteristics of borehole. With the increase of drilling depth, the failure depth of surrounding rock will transfer to the interior.