Experimental and numerical characterization of hydro-mechanical properties of rock fractures: The effect of the sample size on roughness and hydraulic aperture

This paper investigated fluid flow in low-stress conditions through rock fractures in Kuru granite measuring 25 cm × 25 cm. Physical aperture and roughness were measured using high-precision photogrammetry. Anisotropy in roughness was observed in two perpendicular directions. Physical aperture under normal stresses was measured, and fracture closure was compared with linear variable displacement transducer (LVDT) measurements, showing good agreement. Hydromechanical tests exhibited nonlinear behavior between fluid pressure gradient and flow rate, following the Forchheimer equation. Applying normal stress resulted in decreased hydraulic aperture and increased nonlinearity of fluid flow. Experimental hydromechanical tests also revealed anisotropy in perpendicular directions, aligning with fracture roughness measurements. Photogrammetric models, aided COMSOL simulations, closely …