A continuum method of pile driving analysis: Comparison with the wave equation method

What may be called a ‘Continuum’ method of finite element analysis is used in this paper to predict the behaviour of a pile during driving. In this both the pile and the soil are treated as two distinct parts of the same solid continuum, but with different properties. The behaviour of the soil medium, assumed to be semi-infinite and nonlinear, is represented by the hyperbolic stress-strain relationship. Discretizing the pile-soil system in turn by conventional axi-symmetric and mapped finite elements, the problem is solved in the time-domain using the central difference scheme.

The example considered is that of a fully embedded steel pipe pile for which both field test data and Wave Equation solution are available. Results show that: the Continuum Method is capable of a greater degree of accuracy than the conventional Wave Equation Method, but it is far more expensive than the latter in terms of computational effort needed; the effects of radiation damping and wave dispersion in the soil are found to be small; and the mapped finite elements give significantly better results than conventional elements.