Abstract: Synchronized grouting in shield tunnels is a multistage grouting process involving void filling and soil infiltration. To investigate this process, the authors developed a filling-permeation multistage grouting test device to conduct a one-dimensional slurry filling-permeation-diffusion test. Using the volume averaging method, the pore boundary effect of the microscopic porous medium is simplified as a resistance term, and a macroscopically coupled slurry diffusion model for the grout filling-permeation-diffusion process is constructed. In addition, the COMSOL finite element platform is employed for equation computation and slurry diffusion visualization, with the model′s applicability validated through indoor tests and case analyses. Finally, a synchronous grouting model is established to analyze the influence of different working conditions on final slurry diffusion by controlling variables. The research findings are as follows: (1) The error between the test results and the model is within 5%, demonstrating that the proposed model effectively represents the slurry′s filling-permeation process. (2) Increasing the number of grouting holes reduces grouting time but raises the maximum pressure in the void at the shield tail and the pressure difference between the upper and lower parts of the void. (3) The properties of slurry materials significantly influence the grouting process.

Key words: shield tunnel, synchronized grouting, saturated sandy soil strata, filling-permeation process, COMSOL