Modelling the dynamic pile-soil-pile interaction in a multi-layered half-space

Regular paper

Waleed Hamad

University of Cambridge

Tuesday 2 june, 2015, 13:40 - 14:00

0.1 London (90)

Within the context of railway ground-borne vibration, the dynamic pile-soil-pile interaction remains an area that has not been sufficiently investigated. Whilst, in recent years, a number of researchers have scrutinised the vibration response of piled-foundations, their approaches exhibit a compromise between computation time and solution accuracy. The few existing computationally efficient piled-foundation models either adopt simplifying assumptions or neglect the influence of neighbouring piles on the vibration response; both may lead to unreliable results. In this paper, two approaches of modelling piled-foundations in a multi-layered half-space are presented. The first is an efficient semi-analytical model that calculates the Greenís functions of a multi-layered half-space soil using the thin layer and the flexibility matrix methods. The second is a fully-coupled model that utilises the boundary element (BE) method to simulate the soil, where the Greenís functions are calculated using the ElastoDynamics Toolbox (EDT). The pile is simulated, in both modelling approaches, by an elastic bar for axial loading and an Euler-Bernoulli beam for transverse loading. In the semi-analytical model, the coupling at the soil-pile interface is achieved by relating the discretized reaction forces to the corresponding displacements at the nodal points. In the BE model, the transfer function matrix of the pile nodes around the circumference is coupled to that of the soil cavity adopting compatibility and equilibrium at the interface. The paper performs a set of comparisons between the two methods. First, the response of a single pile in a multi-layered half-space subject to a harmonic loading is simulated. This is then extended to simulate the response of a pile-group subject to harmonic loading. In both cases, the vibration response at different points in the free-surface and internal points in the soil is examined. The comparisons highlight the efficiency and accuracy of the semi-analytical model and illustrate its practical application.

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