Time-dependent ultimate bearing capacity of jacked pile based on total stress method

Considering the stress history and the initial stress anisotropy of natural clay, the stress variation of the soil around the pile during the pile installation process and the reconsolidation phase is derived. Then, according to the relationship among the stress states of the soil near the pile during pile loading and the stress variation of the soil in the simple shear and triaxial tests, an analytical solution to the time-dependent ultimate bearing capacity of the jacked pile is derived based on the total stress method. A theoretical method for calculating the bearing capacity factor of pile shaft and tip is proposed. The theoretical solution is verified by the centrifuge tests, and the variation of the bearing capacity with reconsolidation time is studied. The relationship between the bearing capacity factor and the in-situ mechanical properties of the natural clay is also analyzed based on the theoretical solution. The results show that the increase of the bearing capacity of the jacked pile after installation mainly stems from the increase of the bearing capacity of pile shaft. The bearing capacity increases rapidly in short time after the pile installation. Then, the change of bearing capacity is insignificant and tends to a stable value. The larger the overconsolidated ratio and the lateral pressure coefficient, the faster the increase of bearing capacity. However, the bearing capacity factors of pile shaft and tip decrease with the increase of the overconsolidated ratio and the lateral pressure coefficient.