Abstract:The completely weathered granite is easy to disintegrate and destroy when it meets water, and often induces geological disasters such as water inrush and mud inrush under the engineering disturbance. To realize effective design of grouting reinforcement parameters for completely weathered granite, this paper investigated the law of three factors, namely, grouting pressure, initial water content and clay content, to the anti-disintegration characteristics and compressive strength of completely weathered granite after grouting by response surface method, and the fitting equations were obtained. The results show that the order of grouting pressure, initial water content and clay content on anti-disintegration characteristics and compressive strength is grouting pressure < initial water content < clay content and grouting pressure < clay content < initial water content. There is a positive correlation between grouting pressure and reinforcement effect, but when the grouting pressure reached 1.5 MPa, the increment of compressive strength and anti-disintegration characteristics decreased. The effect of grouting reinforcement increased first and then decreased with the increase of initial water content and clay content, the optimal value of initial water content and clay content is 16% and 24%, respectively. The interaction among grouting pressure, initial water content and clay content was analyzed, and a design criterion for grouting parameters was proposed. According to the initial water content and clay content, completely weathered granite can be divided into the low pressure grouting zone (0.5～1.0 MPa), medium pressure grouting zone (1.0～2.0 MPa) and high pressure grouting zone (2.0～3.0 MPa). The research results can be used to guide the design of grouting reinforcement parameters in this stratum through engineering field verification, and the criterion can be applied to evaluate the effect of grouting reinforcement in this stratum.