Influence of the Geometric Characteristics of Fractures Induced by the Sandstones With Different Strength on the Hydro‐Mechanical Behaviors Within a Single Rock Fracture

ABSTRACT The correlation between rock compressive strength and fracture roughness represents a significant area of research within the disciplines of rock mechanics and geological engineering. In this study, laboratory flow experiments were performed on sandstone (with different compressive strengths) single‐fractures created by the Brazilian splitting to investigate the hydro‐mechanical behaviors. The effects of geometric characteristics of fractures with different compressive strengths were examined. For the tested specimens, the results indicate that the fracture surface roughness coefficients ( JRC , R p , and Z 2 ) and mean aperture of fracture with high compressive strength are relatively smaller, indicating that the fracture surface is smoother. For a given constant loading level, a larger contact ratio and a more uniform contact distribution are observed, leading to fewer connected flow channels. The nonlinear flow behaviors of the water can be satisfactorily described by Forchheimer's law. The transmissivity of fracture with high compressive strength is lower than those with low compressive strength, which is attributed to the combined effects of smaller initial aperture, smoother surfaces, larger contact‐area growth under loading, and the resulting shrinkage of effective flow channels. Under the tested conditions and at equivalent pressure gradients, fractures in high‐compressive‐strength sandstone exhibit smaller Reynolds numbers. They also exhibit higher critical Reynolds number and critical pressure gradient. Although based on one specimen per strength level, the obtained results provide an indicative reference for understanding the nonlinear seepage mechanism in single‐fracture sandstone.