Abstract:During the process of coring in deep highstress strata, the core exhibits significant diskshaped damage characteristics due to disturbance and stress release effects. In this paper, taking the drilling samples from Triassic strata in Sichuan Basin at a depth of 1800 m as the research object, through a combination of macroscopic observation and microscopic analysis, the differences in the diskshaped damage of shallow and deep surrounding rock cores and their formation mechanisms have been systematically revealled. It is found that the nonuniform diskshaped damage characteristics of shallow cores are dominated by the random damage effect caused by drilling and blasting disturbance, while the uniform thin diskshaped damage of deep cores reflects the intrinsic effect of insitu stress release. In addition, the diameter of the borehole and the grain characteristics of the core have a significant impact on the diskshaped damage behavior, with larger diameter boreholes and coarsergrained cores more likely to form thicker diskshaped damaged cores. Through quantitative analysis of cross experiments of numerical simulation, different effects of horizontal and vertical stresses on crack propagation and energy evolution have been revealled, and close relationship between the diskshaped damage phenomenon and insitu stress conditions have been verified. The study clarifies that the horizontal stress significantly promotes crack propagation, while the vertical stress has a certain inhibitory effect on the diskshaped damage phenomenon. The core diskshaped damage phenomenon and its stress characteristics from macroscopic damage morphology to microscopic mechanism have been explained. It will provide insights and technical optimization suggestions for deep geological drilling and resource development engineering.
