Analytical model for evaluating XCC pile shaft capacity in soft soil by incorporating penetration effects

Abstract

The derivation of a new analytical model for predicting the soil displacement of X-section cast-in-place concrete (XCC) piles installed vertically into soft clay as well as for predicting limit shaft resistance during loading phases is presented in this paper. The analytical model is formulated by assuming that the XCC pile penetration process is an X-shaped cylindrical cavity expansion process. Based on the theoretical framework of the Strain Path Method (SPM), the strain, displacement and stress induced by X-shaped cavity expansion can be obtained. The proposed analytical model is validated by comparing the degenerate solution of this study with that of conventional circular (cylindrical) cavity expansion theory. Analytical model-based design methods are then proposed for evaluating soil displacement and XCC pile shaft capacity. Theoretical predictions are compared with field test measurements to verify the suitability of the proposed design method. The proposed new analytical model reveals the fundamental penetration mechanics of XCC piles and gives improved design methods for determining XCC pile shaft capacities.