Abstract: The essential researches on pile foundations are on bearing capacity of piles and interaction between the pile and subsoil, including deformation of soil and pore pressure change of saturated silty clay around the pile. Centrifuge model testing is used to study vertical bearing capacity of single pile both in saturated and unsaturated silty clay. The pile is pressed into the soil by vertical loading device, and deformation of soil around the pile and pore pressure change during the loading of pile are measured and then analysed. When saturated, the soil around pile results in pile’s softening of bearing characteristics, and the bearing capacity of pile gets smaller than in unsaturated soil. However, an obvious ultimate bearing capacity in the experiment of unsaturated silty clay does not exist. Deformation of subsoil has a significant relevance to the loading of piles. The impact of loading of the pile on the deformation of soil around the pile has a certain limit of distance, out of which the displacement of soil is negligible. The results show that the limit of distance is about 7 times the length of pile section, and a certain limit of distance exists in the impact of loading of the pile on the water pressure changes in saturated silty clay around the pile, which reflects the same rule as the displacement of soil around the pile. Displacement of soil is greater in the places closer to the pile. As the distance from the pile increases, the impact of piles on soil deformation decreases.

Key words: pile foundation, vertical bearing capacity, silty clay, centrifuge model test