Mechanical behaviors of double-cracked limestone under hydro-mechanical coupling: Experimental, theoretical, and numerical investigation

In this study, a series of laboratory experiments including triaxial compression tests, acoustic emission (AE) monitoring and discrete element numerical simulations, combined with a self-developed high-performance copper sheet-blocking hydraulic sealing method, are carried out to investigate the mechanical behaviors, fracture characteristics and hydro-mechanical (HM) coupling of double-cracked limestone. Effects of pore pressure (P), confining pressure (σ3), and crack inclination angle (α) on the stress–strain curves exhibiting multi-peak patterns, crack initiation stress, damage stress, peak strength, deformation modulus, Poisson's ratio, and AE signal characteristics of the double-cracked limestone specimens during the HM coupling progressive failure process are analyzed. The AE signal features include stronger signals under lower pore pressure and sparser AE ringing counts at larger inclination angles. Subsequently, a compression-shear fracture criterion incorporating crack inclination angle parameters is established based on the experimental results, and numerical simulations further clarify the failure modes of the specimens: tensile failure for those with a 15° crack inclination angle, tensile-shear failure for those with 45°, and shear failure for those with 75°, thereby revealing the HM coupling failure mechanism. These experimental results, numerical simulation findings and HM coupling failure mechanism provide a deep understanding to researchers and engineering technicians for monitoring and controlling rock stability in geological engineering projects under HM coupling environments.