Centrifuge modelling of working performance of foundation pile embedded in expansive clay with high liquid limit

The centrifuge tests are carried out to study the change of displacements of pile head and axial forces of four single piles embedded in strong expansive black cotton soil with high liquid limit after being submerged considering the influences of pile length, pile head load and expansion isolation measures. The self-developed rainfall facility in the centrifuge and the artificial seepage path in the model stratum control the submerging condition of the black cotton soil foundation. It is found that the effects of rainfall condition on the axial forces of piles can be divided into two phases. In the first softening phase, the wetted expansive soil provides less friction resistance, which increases the axial forces of piles. And in the second expansion draft phase, the swelling uplift of expansive soil produces more friction resistance and the axial forces of piles decrease. In addition, the displacement of pile head caused by the submerging is closely related to its load. Under rainfall conditions, the pile without load is uplifted, while the pile with load of 625 kN settles. Taking expansion isolation measures around the pile body will decrease or even eliminate the negative effects of expansive soil deformation on pile foundations.