Law of pile in expansive soils with introduction of water

A group of model tests for single piles are performed to study the interaction between single pile and expansive soils with continuous introduction of water. Theoretical analyses on the interaction are made in terms of relative deformation and interactive forces. The study shows as follows: with the increase of the pile depth that was embedded into the zone of expansive influence zone, the pile displacement will dramatically decrease; the distribution of axial stress along the pile is like the shape of "wave crest" with the maximum value occurring below the middle of the pile; the position of the maximum value will move downwards to lower parts along the pile length with time lapse; the relative difference in movement between the soils and the pile are the reason that results in an upward shear force above the middle of the pile and downward withholding force below that level; the neutral point is, actually, just the maximum value position; total uplifting force is always a little bit greater than total withholding force for the pile that was wholly embedded within the influence zone, which causes the pile to continue moving upwards; pile length for design would be controlled by force equilibrium: total uplifting force is equal to total withholding force; the time related swelling curve of the soil around the pile is fitted well by exponential functions, which provides basis of studying the time related characteristics of pile behavior in expansive soil. This study achieves a lot of experimental and theoretical basis of numerically stimulating the pile-expansive soils interaction.