Stress–strain and acoustic emission characteristics of cement-based materials used to simulate soft rock with fractures

Instability failure in rock mass engineering is closely related to the expansion of joint fissures. In this study, uniaxial compression tests and acoustic emission (AE) measurements were simultaneously carried out on soft rock-like material with different angle and connectivity of fractures to better understand their influence on soft rock-like deformation and failure. The stress– strain curve and AE signal of fractured soft rock-like material exhibit similar stages as intact soft rock; namely a compaction stage, elastic deformation stage, stable fracture development stage, and unstable fracture development stage. The main differences occur within the post-peak failure stage. Under the combined influence of fracture angle and connectivity, the uniaxial compressive strength of fractured soft rock-like material (f'cu) is lower than that of the intact soft rock-like material (fcu) to varying degrees and can be described as f'cu =fcu• α , where α is the strength reduction coefficient, fitted as α = 0.8228 + 0.00411x―0.00789y. In this equation, x is the fracture angle (°) and y is the fracture connectivity rate (%). Under uniaxial compression, secondary cracks caused by the deformation and failure of the fractured soft rock-like specimens mainly included wing cracks and secondary coplanar cracks. The specimen with a fracture angle of 30° mainly underwent tensile failure under loading, whereas the specimens with 45° and 60° fracture angle mainly underwent shear failure under high-connectivity conditions (45%).