In the project of underground excavation beneath existing building supported by piles

there is a need to evaluate the vertical bearing capacity of the in-service piles under the condition of soil excavation. The influence of variation of soil stress and soil rebound on the bearing characteristics of soil around pile and at pile base was determined. Considering the effect of soil excavation

a hyperbolic model of load transfer along pile shaft and a bilinear model of load transfer at pile end were established. In view of the over-consolidation state of soil induced by the unloading effect of excavation

the calculation method was established to evaluate the ultimate unit skin friction of pile shaft under the condition of excavation. On the basis of the finite difference method and the load transfer method

the calculation method was proposed for predicting the vertical bearing characteristics of in-service pile under the condition of underground excavation beneath existing building. The validity of the proposed method was verified by comparing with the experimental results. Results show that the influence of soil rebound and the over-consolidation state of soil due to excavation on the pile shaft resistance and pile base resistance should be taken into account for the analysis of the pile behavior subject to underground excavation. If the calculated normalized soil rebound is relatively small (e.g.less than 1)

the soil rebound can be neglected in the settlement analysis.