Experimental Study on The Influence of Primary Micro‐cracks on The Failure Characteristics of Brittle Rock

Abstract In natural rock masses, small closed micro‐cracks ranging from centimeters to decimeters in length are commonly developed. Under engineering disturbances, the local stress at the tips of these cracks increases sharply, leading to the generation and propagation of new cracks, eventually causing macroscopic rock damage, which significantly affects the stability and safety of engineering projects. Taking the Emeishan basalt in the southwest region as an example, this study utilized CT scanning and 3D reconstruction software to construct a three‐dimensional visualization model of primary micro‐cracks and obtain quantitative geometric information. Subsequently, uni‐axial compression tests were conducted to compare and analyze the differences in the strength, deformation characteristics, and failure modes between intact basalt and basalt containing primary micro‐cracks. The results indicate that the strength of basalt is significantly influenced by the distribution of micro‐cracks. The strength of the rock generally shows a decreasing trend with the increase of the volume rate of micro‐cracks inside the rock, and the strength of samples containing primary micro‐cracks is approximately one‐third of that of intact samples, with a minimum of 117 MPa compared to 331 MPa for intact samples. The compaction stage for samples containing primary micro‐cracks lasted longer than that for intact samples, and intact samples mainly exhibited explosive fracturing at the moment of rock failure, while samples containing hidden micro‐cracks remained relatively stable and maintained better integrity.