Numerical Simulation of Borehole Slotter Layout Optimization

Abstract

Abstract This paper briefs the basic principle, current methods and test process for measuring in-situ stress by the borehole slotter method. Studies are carried out to optimize the slot’s cutting depth and layout by means of 3D numerical simulation. Such simulation results show that when the original stress field is parallel to the slot, the required cutting depth to fully release the stress on both sides of the slot reaches its peak (16 mm). In order to avoid interaction between slots and enhance reliability, only one slot is arranged at a given drilling depth and the space between slots should generally be greater than 200 mm. Based on such results, the in-situ stress measurement was conducted by means of the borehole slotter method in an underground laboratory in Jinping. The tested rock mass is in stress concentration area in a tunnel face, and the acquired vertical component of the stress is found greater than the self-weight of the overlying rock mass. This field test shows that such test rock mass is under extremely high stress condition, which is in compliance with disked rock cores discovered during tunneling.