Finite element evaluation of bearing capacity factors for cutting face of open caissons

ABSTRACT Open caissons are massive foundations sunk to the required depth by excavating the soil in contact with the cutting edge of the caisson through the annular space of the shaft. The sinking of caisson initiates when the soil in contact with the cutting edge fails in bearing. The evaluation of bearing capacity of the cutting edge helps in proper planning of the excavation strategy, analysis and design of caissons. In the present study, the bearing capacity factors for the cutting face of open caisson are evaluated using finite element method for different configurations of the cutting edge, properties of the soil and depth of sinking. The cutting edge with varying radii ratio (ri /ro = 0.35 to 0.95) and different cutting angles (β = 30° and 45°) is considered. The Mohr–Coulomb model with non-associated flow rule is used in the two-dimensional finite element (FE) analysis. The bearing capacity factors for the cutting face of the open caisson are evaluated for different friction angles of the soil (ϕ = 5° to 35°). The depth of sinking is accounted for in the FE analysis by considering the soil present above the base of the cutting edge as surcharge. The present FE results are compared with the results available in the literature and presented in the form of ready-to-use charts and tables for design purposes.