Small-strain behavior-based method for eflect of excavations on adjacent pile foundations

Estimating the damage potential on buildings induced by excavations is required because more and more foundation pits are excavated near the existing buildings. Thus, displacement control becomes a critical index of excavation design. Unfortunately, there is nearly no simplified method that can estimate the influence of excavation on the existing buildings and easy to be used. Small-strain behavior of soils should be considered when establishing method to estimate influence of excavation on the adjacent buildings for the strain of the soils is very small under displacement control design. In order to fit the requirement for the simplified method to estimate the influence on excavation on the existing buildings supported by pile foundation, a two-stage method is proposed herein to estimate the responses of piles adjacent to the excavation. Firstly, the empirical method based on small-strain behavior of soils proposed by Mu and Huang is employed to calculate the three-dimensional soil displacement induced by excavation. Then, a two-stage method is proposed to calculate the vertical and horizontal pile responses in layered soils. The method is verified through comparison with the results from FEM. And the influences of excavation depth and the distance between pile and retaining on pile responses are analyzed. The study shows that the additional force and deformation of piles increase with the increase of excavation depth, and the excavation base should avoid the base of the pile. It is most dangerous when the pile is 0.5H from the retaining wall.