Development of a Laboratory Test Apparatus for Simulating Core Drilling under High In Situ Stress

Rock cores drilled under high in situ stress environments are inevitably permanently damaged due to the stress relief, which significantly affects the evaluation of the physical and mechanical properties of deep rocks. Quantitatively correlating this sampling damage with in situ stress distribution is challenging because of the complexity of the geological environment and the diversity of rock materials. To address this challenge, a laboratory test apparatus has been developed that can apply specific pressure to shallow rock materials to simulate high in situ stress environments and drilling-coring to simulate the sampling process of deep rock masses. The results of verification tests demonstrate that the integrity of cores gradually deteriorated as the sampling confining pressure increased. Moreover, simultaneous increases in the density and size of microcracks were observed within the cores, where these microcracks propagate through grain boundaries, generate intragrain and transgranular microcracks, extend outwardly to form macroscopic cracks, and enhance porosity. These findings confirm the applicability of the apparatus for conducting quantitative sampling damage studies. In the future, further investigations using the apparatus will be conducted to explore the mechanical attenuation patterns of rock cores, thereby providing a reference to evaluate rock mechanics parameters for engineering practices.