Study on instability mechanism of tunnel face in clay-gravel strata under confined water conditions based on DEM-CFD coupling method

• Published in: Computers and geotechnics Vol. 164; p. 105769
• Main Authors: Duan, Zhibo, Yang, Jun, Ma, Shaokun, Huang, Zhen
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2023
• Subjects: Composite strata; Confined water; DEM-CFD coupling; Shield tunnel; Tunnel face stability; Shield tunnel; Tunnel face stability; Confined water; DEM-CFD coupling; Composite strata
• ISSN: 0266-352X; 1873-7633
• DOI: 10.1016/j.compgeo.2023.105769

A coupled discrete element methods (DEM)-computational fluid dynamics (CFD) method was adopted to study the tunnel face instability mechanism in clay-gravel composite strata with confined water. This method was verified by the results of the transparent soil model tests previously conducted by the authors. On this basis, The DEM microscopic change trends and the variation in the composite strata and soil stresses were systematically analyzed. The results show that under confined water conditions, the failure zone of the lower gravel strata is wider, with a decrease of about 30° with the horizontal direction. The width of the ground settlement trough has widened by about 43.8%, while the maximum surface subsidence has reduced by about 46.2%. Further, the effect of confined water on the vertical stress of the soil is significant; nevertheless, it has almost no effect on the average horizontal stress. Moreover, the horizontal displacement of the lower gravel stratum is larger than the upper clay stratum, while this rule is not observed under no confined water conditions. To avoid tunnel face instability in clay-gravel composite strata, the horizontal displacement and the variation of vertical stress in front of the tunnel face should be carefully monitored during shield tunnel construction.