Experimental and analytical study of X-section cast-in-place concrete pile installation effect

A new type of displacement pile, the X-section cast-in-place concrete (XCC) pile, has been developed recently in China. Extensive field and laboratory experiments are being undertaken in order to evaluate the soil displacements during pile installation. The paper describes laboratory arrangements and results of transparent soil model tests aimed at capturing the non-axisymmetric soil displacement field. Results from model tests using the XCC pile are presented to reveal the complete soil displacement patterns (a) in the horizontal plane, and (b) in vertical planes of symmetry. Based on results from the transparent soil tests, a modified cavity expansion model (MCEM) is proposed to predict the radial displacements in any vertical plane induced by XCC pile installation. The radial displacements predicted by the MCEM are compared with data from the transparent soil test and the field experiment. The results show reasonable agreement for all cases, with the proposed MCEM proving more suitable than the conventional (axisymmetric) CEM for predicting the radial displacements induced by XCC pile installation. It may therefore provide a basis in the future for developing predictions of stress changes and, ultimately, shaft capacity of the XCC pile in comparison to displacement piles of circular cross-section.