Studies on pile bearing characteristics in saturated clay under excavation by model tests and a simplified method

Based on a centrifuge pre-consolidation loading device, a model of pile vertical loading system can effectively control over consolidation ratio is developed out. The laboratory model tests of a single pile in saturated clay under excavation are carried out. Based on the results of model test, considering the change of undrained shear strength and K₀ coefficient of soil caused by excavation, a simplified nonlinear approach for analysis of a single pile under excavation is proposed. Calculated results are compared with the test results of laboratory model tests of pile. Good agreement is achieved. In addition, responses of a single pile after excavation under vertical load are studied by the simplified method. Computational results show that after excavation, the ultimate bearing capacity of pile and pile head stiffness will reduce. A rational prediction method for estimating the loss of bearing capacity should consider not only the decease of the overburden pressure of the surrounding soil, but also the increase of the K₀ coefficient and undrained shear strength.