Abstract: During tunnel construction, the superstructure and pile foundation of buildings, stratum, tunnel construction are in an interaction system. Functional mode of each section results in cooperating and interaction. So, they should be considered comprehensively. Firstly, soil is interaction medium of the tunnel and pile foundation. Constructing tunnel at shallow depth damages stratum. And stratum deformation is delivered to adjacent piles, which result in the reduction of pile foundation bearing capacity. Load fluctuation is transferred to the superstructure by pile foundation. Then sedimentation and deformation of adjacent structures is generated. Therefore, the crux in tunnel construction is to make the superstructure safety by analyzing and controlling for the existing pile foundation. Based on detailed discussion about the interaction of the superstructure and pile foundation of buildings, stratum, tunnel construction, pile deformation mechanism and grouting reinforced mechanism, the 2D－Sigma code is applied to simulate effect of existing pile foundation induced by shallow tunnel construction from Yonghegong Station to Hepingli North Street Station interval of line No.5 in Beijing. The universal law of pile foundation deformation is obtained; and necessity of grouting reinforced stratum and related processing parameters in construction are suggested by analyzing front-to-back response of pile foundation. Finally, based on analysis of comparison between numerical results and field measurement results for pile foundation deformation, their law is quite similar. Research shows that grouting reinforced stratum is effective for reducing deformation of pile foundation and making superstructure safety. The achievement will guide subway construction later.

Key words: shallow tunnel construction method, pile foundation, numerical modeling, grouting reinforcement, field measurement