Testing method of rock structural plane using digital drilling

The rock mass consists of rock blocks and structural planes, which can reduce its integrity and strength. Therefore, accurately obtaining the characteristics of the rock mass structural plane is a prerequisite for evaluating stability and designing supports in underground engineering. Currently, there are no effective testing methods for the characteristic parameters of the rock mass structural plane in underground engineering. The paper presents the digital drilling technology as a new testing method of rock mass structural planes. Flawed rock specimens with cracks of varying widths and angles were used to simulate the rock mass structural planes, and the multifunctional rock mass digital drilling test system was employed to carry out the digital drilling tests. The analysis focuses on the variation laws of drilling parameters, such as drilling pressure and drilling torque, affected by the characteristics of prefabricated cracks, and clarifies the degradation mechanism of rock equivalent compressive strength. Additionally, an identification model for the characteristic parameters of rock mass structural planes during drilling is established. The test results indicate that the average difference of the characteristics of prefabricated cracks identified by the equivalent compressive strength is 2.45° and 0.82 mm, respectively. The identification model while drilling is verified to be correct due to the high identification accuracy. Based on this, a method for testing the characteristic parameters of the surrounding rock structural plane while drilling is proposed. The research offers a theoretical and methodological foundation for precise in situ identification of structural planes of the surrounding rock in underground engineering.