Theoretical study on sinking resistance of jacked piles in saturated soft clay

Based on the SMP criterion-based Cam-clay model, which can incorporate the over consolidation ratio and properly describe soil strength in three-dimensional stresses state, the cavity expansion solutions are derived under undrained conditions by using the stress transformed method. Then, according to the pile-sinking mechanism in the saturated layered soft clay and considering the influence range of the pile tip, the stress fields around the pile tip and pile shaft during the pile-sinking process are modeled as spherical cavity and cylindrical cavity expansion respectively, and the methods for calculating the pile-sinking resistance in the layered soft clay are yielded. To verify the validity of predictions using this new expression, the results are compared with the measured data, and the influence factors for pile-sinking resistance are discussed. The results show that the proposed method can predict the pile-sinking resistance accurately because the 3D strength characteristics of soils are sufficiently considered by the constitutive model. Compared with the pile tip resistance, the pile shaft resistance is relatively small, the pile-sinking resistance in saturated soft clay mainly consists of pile tip resistance, and the influence range of the pile tip resistance depends on the pile diameter and the soil properties. Both the pile tip resistance and pile shaft resistance are significantly influenced by the pile diameter and the over consolidation ratio. In addition, the pile-sinking resistance is slightly influenced by the effective internal friction angle.