Porosity-Tensile Fracture-Strength Characteristics of MICP-Repaired Rock Fractures

Microbial induced carbonate precipitation (MICP) technique, as a low-carbon and environmentally friendly reinforcement method, has demonstrated potential for application in rock fracture repair. However, related studies have primarily focused on the distribution characteristics of calcium carbonate and changes in permeability within rock fractures, with relatively few investigations on the mechanical properties. In particular, the compressive failure mechanism when the principal stress direction is parallel to the fracture plane remains unclear. Using computed tomography (CT) scanning, shear wave velocity measurements, and uniaxial compression tests, this study investigates the uniformity and uniaxial compression failure mechanism of MICP-repaired limestone fractures with varying apertures under a two-phase continuous grouting strategy. The results indicate that MICP significantly reduces the porosity of limestone fractures and increases shear wave velocity. During the uniaxial compression process, the specimens primarily experience splitting failure dominated by tensile cracks. This failure process can be divided into three stages: the tensile failure stage of the MICP-repaired fracture, the compressive failure stage of the rock on both sides of the fracture, and the multi-peak failure stage of the residual rock. As the fracture aperture increases, the shear wave velocity and the fracture tensile failure strength of the MICP-repaired specimens exhibit a trend of first increasing, then decreasing, and subsequently increasing again, whereas the porosity shows an opposite trend. Based on the experimental results, an empirical equation relating shear wave velocity to fracture tensile failure strength is further proposed.