Analysis of ultimate bearing capacity of X-section cast-in-place concrete pile composite foundation under rigid load

Based on the principle of enlarging perimeter with the same section area, X-section cast-in-place concrete pile (abridged XCC pile) is developed by changing the convex of circular-section to concave. As a new special section pile, the ultimate bearing capacity is calculated by empirical formulas in standard. The in-situ static load tests are carried out based on the foundation treatment project in Qiaobei sewage treatment plant in Nanjing. Besides, a finite element model is established to simulate the XCC pile composite foundation under the rigid base by software ABAQUS. The ultimate bearing capacities are discussed considering some factors including elastic modulus of pile, modulus of surrounding soil, pile length, cushion thickness and cushion modulus. The results indicate that XCC single-pile composite foundation can increase the bearing capacity by 20% more than that of traditional pile. The ultimate bearing capacity of XCC four-pile composite foundation can increase the bearing capacity by 12.35% more than that of traditional pile. The ultimate bearing capacity increases with the increase of pile modulus, cushion modulus surrounding soil modulus and pile length. From the factors, the effect of modulus of surrounding soil is most obviously.