Calibration and validation of DEM-FEM model parameters using upscaled particles based on physical experiments and simulations

Study on the Microscopic Mechanism of Grouting in Saturated Water-Bearing Sand Stratum Based on VOF-DEM Method

During the construction of tunnels in saturated water-bearing sand stratum, water and mud inrush disasters often occur. Grouting is the most convenient and effective method to improve the mechanical properties of the soil and prevent groundwater seepage. The reasonableness of the Discrete Element Method (DEM) contact parameters is verified by comparing the repose angle test with that obtained by simulations. The grouting model of saturated water-bearing sand stratum was established based on the Volume Of Fluid-Discrete Element Method (VOF-DEM). Then, the effects of sand stratum porosity and grouting pressure on grouting were discussed. The results show that (1) in dense sands, the permeation diffusion of the slurry dominates, whereas in loose sands, the compaction zone is well developed. (2) Loose sand has a wider propagation of stress and dense sand has a larger increase in the stress state. (3) In loose sand the slurry diffusion is significantly affected by gravity, whereas in dense sand the slurry diffusion along the dominant path of the grouting pipe wall boundary is obvious. (4) The range of slurry diffusion and compaction zone is positively related to the porosity and grouting pressure. (5) In loose sand with grouting pressure below 200 kPa, no compaction diffusion occurs during the grouting process, whereas in dense sand, when the grouting pressure is below 500 kPa no compaction diffusion occurs during the grouting process.