A Splitting Diffusion Model for Synchronous Grouting during Shield Tunnelling in Fault Fracture Zone

The whole process of splitting diffusion and the response of surrounding rock for synchronous grouting in fault fracture zone is studied in this paper. Based on the Griffith strength criterion, the initial splitting pressure is obtained. Combined with the law of grout diffusion along the radial as semi-elliptical plane, a theoretical model that is suitable for grouting splitting diffusion in fault fracture zone is presented, and analytical solutions of spatial distribution, including grout flow velocity, flow volume, splitting diffusion depth, and splitting channel width, are highlighted. The test results show that it is easy to split at the waists of both sides of the tunnel in fault fracture zone, which confirms that the diffusion model based on Griffith strength criterion is applicable to explain mechanical behaviors of grouting splitting. The parameter analysis shows that the lateral earth pressure coefficient and elastic modulus of rock are the major factors affecting the grouting splitting depth.