Analysis of the Bearing Capacity of a Single Pile Based on an Analytical Solution of Pile–Soil Interaction in Expansive Soil

The pile–soil interaction in expansive foundation is complicated. The expansive action affects the performance of the pile foundation. To explore impact of the expansive action on the bearing capacity of a single pile, an analytical solution to the elastic theory of the load-transfer of a single pile is put forward by using the shear displacement method and considering the law of soil shear modulus changing with depth. On this basis, via combination with the load transfer matrix, a nonlinear analysis method for calculating the bearing capacity of a single pile in expansive soil after immersion is put forward. The validities of the suggested methods are confirmed through comparisons with the test results. Then, the influence of various parameters on the performance of a single pile are analyzed. It is determined that an increase in the pile length can effectively reduce the uplift of the pile top and improve the bearing capacity of the pile when part of the pile is under expansive action. However, the effect is not obvious when the pile length is approximately 3 times that of the affected depth. Compared to the pile length, the pile diameter exerts less of an effect on the performance of single pile, and when the entire pile is under expansive action, the increase in the pile length will augment the uplift of the pile top. Additionally, the bearing capacity first increases and then decreases with an increase in the pile length.