Numerical analysis of displacements in concrete pile foundationsinduced by adjacent tunnel excavation in sandy soils

ABSTRACT

Tunneling over a field leads to surface, subsurface settlement, and lateral deformation. Tunnels built to nearby foundations of building, produces a ground loss, which affects the foundation behavior. This paper aimed to study the displacement behavior of existing pile foundations in the sandy ground during tunnel excavation using the numerical software PLAXIS 3D. The comparison of published results from various numerical analysis software was used to verify the validity of the PLAXIS 3D approach. However, the uncertainties of material properties of soil in satisfying the parameters of the Mohr-Coulomb model were assumed in the analyses. Both single pile and pile group effects due to tunneling are analyzed. A total of 21 FE analyses were involved in predicting the regular plane strain responses of piles such as lateral displacement and vertical displacement identified during the excavation process of tunneling. The parametric research on pile and pile group responses involved the study of the effect of relative density, pile location from tunnel centerline, pile diameter, pile length, and volume loss. Based on the safe limiting value of lateral and vertical displacement as 5 mm and 10 mm respectively, recommendations for the tunnel's location concerning the adjacent existing piles were provided.

Keywords:
Tunnel excavation; Volume loss; Numerical analysis; Pile displacement; Sandy ground