Bearing capacity of single pile in some sites with shallow thin layer of collapsible loess

To understand the impact of loading force on the performance of piles in a shallow thin layer of collapsible loess, the authors carried out non-flooded test and immersion test using a filling pile. The results reveal that when the soil is submerged, the collapse of the soil results in a negative friction along the pile. In addition, the pile settlement, axial force of pile and lateral friction on the pile changed significantly. Compared with the performance of the pile in soil under natural water content, when the pile was installed in submerged loess, the pile settlement increased significantly. When the ultimate designed load was applied, the increase rate of pile settlement changed resulting in an increase of residual settlement. The location of maximum axial force was observed at the base of the pile located in the collapsed loess, rather than at the top of the pile in the soil under natural water content. In addition, the observed maximum axial force was larger than the loading force. Also, the axial force above the middle section of the pile in the submerged soil was overall larger than that in the soil under natural water content. The location of the maximum axial force coincides with the location of the neutral point of the pile. The authors also observed two peak values of the lateral friction along the pile in the submerged soil. It can be concluded that the deformation and settlement of a pile in submerged loess soil varies a lot compared with that in the soil under natural water content. Therefore, it was suggested that these differences resulting from the collapse of the loess should be taken into account in the pile design.