Mechanical behavior and failure analysis of fracture-filled gneissic granite

Grouting reinforcement is a common way to strengthen fractured rock mass in rock engineering, which will transform the natural open flaws in rock mass into filled flaws. The existence of fillers will change the stress state of the flaws, thus affecting the mechanical properties and cracking behavior of fractured rock mass. In this paper, uniaxial compression experiments were carried out on granite specimens in four different filling states to study the effects of different filling materials on the strength, fracture behavior and strain state of flawed rock specimen. The experimental results show that compared with the unfilled specimen, the fillers can improve the strength of the specimen, delay the crack initiation and reduce the strain at the flaw tip, but these effects will weaken with the increase of the flaw inclination angle. In addition, the effect of fillers varies with different filling materials, and the effect of resin and gypsum fillers is significantly greater than that of silicone filler. Moreover, the mechanism of the interaction between filler and rock specimen is analyzed. The results reveal that the fillers can reduce the flaw tip stress, which is related to filling material parameters. This reduction of flaw tip stress will be more significant with the increase of the elastic modulus of the filling material, the friction angle and cohesion of the interface between rock and filling material.