Abstract: Based on twostage method， a new theoretical method which was used to analyze the impact of adjacent piles when the tunnels were excavated with metro shield was proposed. In this method Winkler model was used to divide the pile into same pieces of micro units， and the effect of end bearing pile was taken into consideration according to the transfer of vertical load. The calculation results showed that the vertical settlement of the pile changed slowly with the depth of the pile， and the additional axial force increased first and then decreased with depth of the pile. The maximum additional axial force occurred in the depth close to the tunnel axis. In order to verify the accuracy of this method， the calculation results were compared with those analyzed by Klar using deformation differential equations. In addition， the additional axial force and pile settlement decreased rapidly with increasing horizontal distance. When the horizontal distance exceeded 4R， the impact of tunnel excavation on the pile can be ignored.

Key words: shield, twostage method, Winkler model, pile, impact analysis