Numerical study on Slurry-induced Fracturing Pressure of Cohesive Soil

The stability of the tunnel face during the slurry shield tunnelling is controlled by the slurry pressure in the slurry chamber, and excessive slurry pressure will cause fracturing on excavation face. In order to prevent the occurrence of slurry fracturing, it is necessary to conduct a detailed study on the slurry support pressure when the slurry fracturing occurs. In this study, the hydraulic fracturing experiment of cohesive soil samples was carried out by the self-developed hydraulic fracturing device, and the improved XFEM was used to simulate the experiment process. The influence of various factors on the fracturing pressure was analyzed, and the accuracy of the numerical simulation method was also verified. In addition, the calculation method of fracturing pressure of soft cohesive soil is obtained by fitting the influence of each factor. The results show that the improved XFEM can accurately simulate the shear failure of soft cohesive soil. The fracturing pressure increases linearly with the increase in the circumferential pressure, indicating that a higher overburden of the tunnel can help resist the initial fracturing induced by shield tunneling. The fracturing pressure increases with an increase in the unconfined compressive strength as well as the slurry viscosity. Based on the regression analysis of the numerical results, an empirical approach was proposed for estimating the slurry-induced fracturing of soil.