Analysis of stratum deformation and pile foundation response during subway station built by pile-beam-arch construction method

Based on the construction of Beijing subway line 10 of Guomao station, the influence law of surrounding stratum and adjacent pile foundation is analyzed as the large span separation-formula subway station is built by Pile-Beam-Arch construction method. The field measurement indicates that: (1) the longitudinal stratum settlement caused by the hole-pile construction can be described in three areas, named as: initial settlement, sudden settlement, and convergent area of the settlement. And the sudden depressed section can be defined in three stages: the lead-hole's construction, the buckle arch, the lower part's excavation; (2) The horizontal deformation conforms to the Peck curve and the affected area is 3-4 times of hole-diameter. Using three dimensions dynamic numerical simulation during construction process, the distortion of neighboring pile foundation as well as the surface settlement caused by station construction are analyzed. The result matches well with field monitoring data. It shows that the neighboring pile foundation's settlement and the deformation are consist of three steps: lead-hole's excavation, the buckle arch, the lower part's soil excavation, which is corresponded to the construction process. Some useful conclusion is drawn in this paper. Firstly, it is indicated that the key factor of settlement influence of construction to adjacent pile foundation is space position between the pile and station, such as the minimum distance between the pile foundation and the station structure etc.. Secondly, it is obtained that the stratum condition which near the pile end also contributes certain influences on this settlement; Further more, it is introduced that the disturbing influence of construction to adjacent pile foundation in the horizontal direction is extremely remarkable, the buckle arch construction has the biggest influence to the lateral deformation of neighboring pile foundation. At last, the deformation of the side pile, middle side pile, low side pile and the other neighboring pile foundations are summarized in the article.