Mechanism and experiment of self-stress grouting reinforcement for fractured rock mass of underground engineering

Grouting has been proposed as a effective reinforcement method for the fractured rock of underground engi-neering. However, ordinary cement-based grouting materials have self-shrinkage due to hydration reaction, resulting in the grouting reinforcement effect of the fractured rock mass being greatly reduced. The paper proposed the new self-stress grouting reinforcement method for fractured rock mass. Its advantages include increasing the compactness of the slurry stone and improving the stress of grouting reinforced rock mass. Based on the self-stress grouting reinforcement model of fractured rock mass, the mechanism and effect of self-stress grouting for reinforcing fractured rock mass were investigated by theoretical analysis, physical experiments, and field experiments with the engineering background of the substation roadway of Pingmei No.10 Mine. The results showed that the compressive stress at the slurry-rock interface was increased due to the swelling stress of the self-stress slurry stone. So, the ultimate shear strength of the slurry-rock interface was improved. The larger the swelling stress of the slurry stone, the more obvious the reinforcement effect on the fractured rock mass. As the distance from the slurry stone increases, the effect of self-stress on the rock mass gradually decreases. The peak strength and elastic modulus of the self-stress grouting reinforced sandstone were 1.11 and 1.043 times those of the ordinary grouting reinforced sandstone. The surrounding rock of the the substation roadway with the multiple support methods failed to control was effectively controlled by the self-stress grouting reinforcement method.