Extent of Failure Zone in Soil at the Cutting Edge of Open Caisson: FE Evaluation and Regression Analysis-Paper

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The study uses finite element analysis to examine the extent of the soil failure zone beneath the cutting edge of an open caisson during sinking. The failure zone’s radial and vertical dimensions are normalized by the cutting-edge width. An axisymmetric model in PLAXIS-2D represents the soil using the Mohr–Coulomb model and the cutting edge as linear elastic.<br /><br />The analysis investigates the effects of caisson radius ratio and cutting-edge taper angle, soil unit weight, cohesion and friction angle, and surcharge representing sinking depth. Results show that the failure zone expands as the radius ratio, soil cohesion, friction angle, and surcharge increase. It contracts as the taper angle and soil unit weight increase.<br /><br />Using the finite element results, the authors develop multivariate linear and second-order polynomial regression equations to estimate the normalized failure-zone dimensions. The nonlinear equations generally provide better overall fit, with coefficients of determination of 0.94 and 0.97, compared with 0.82 and 0.80 for the linear equations. The equations are intended for preliminary estimates to help engineers assess the influence zone and plan excavation strategies for controlled caisson sinking.

Keywords

finite element analysis

open caisson

soil failure zone

cutting edge

sinking analysis

PLAXIS-2D

Mohr-Coulomb model

axisymmetric model

regression equations

excavation strategy