Abstract:
In urban areas, excavations for cut-and-cover tunnels and basement construction cause detrimental
effects on adjacent existing piles. Hence quantifying the excavation induced lateral deformations and
bending moments on piles are important to ensure the stability of structures. In this paper, behaviour
of a single pile subjected to excavation induced ground movements is analysed using the finite element
method, which has the ability to simulate the construction sequence comprising soil excavation, defor mations due to dewatering within the excavation and installation of struts. A fully coupled analysis is car ried out based on the effective stress principle. The numerical model was verified using the centrifuge
test data found in the literature. A parametric study was carried out to establish the excavation induced
pile behaviour varying the depth of the excavation, soil properties, wall support system, pile fixity con ditions and pile location with respect to the excavation. Increasing axial load does not have a significant
influence on the pile behaviour. However, pile head fixity condition, and stiffness and spacing of the wall
support system have a significant influence on the pile behaviour adjacent to the excavation. Finally,
based on the parametric study, a set of design charts are developed to predict the pile behaviour by taking
into account the depth of excavation, undrained shear strength, width of the pile, spring stiffness, spacing
of vertical supports, and unsupported depth of the excavation. The capability of the proposed design
charts are demonstrated using a three-dimensional finite element analysis, a case study from the litera ture and a previously published simplified analysis procedure.
