Abstract: Predicting the internal forces and deformation of the adjacent pile is significantly important for the impacts of tunnel excavation. The traditional elastic foundation beam method ignores the plastic deformation of pile-soil interface and its interaction, resulting error between actual results and predicted values. Based on Mindlin solution, we assume the interface is perfectly elastic-plastic for the pile-soil interactions, and derive the maximum shear stress and lateral soil pressure according to Mohr Coulomb criterion. From the constitutive equations, we derive the plastic solutions considering internal force and deformation of the pile due to tunneling. The validity of this new method can be verified by comparing the plastic solutions and the centrifugal test results. By accounting the plastic deformation in pile-soil interface, additional deformation by proposed procedure is greater than that by traditional foundation beam methods. Finally, the effects on the internal forces and deformation of adjacent pile are analyzed. Results show that large deviation of internal force and deformation in pile occurs in case where plastic deformation of pile-soil interface being ignored, and this deviation increases with the increase of ground loss rate.

Key words: tunnel, pile, Mindlin solution, pile-soil interface