Numerical Simulation for Wave Propagation in Pile Integrity Test

During the construction of deep foundations there are different circumstances that are likely to affect the final shape of piles that tend to affect the designed depth, cross section and material quality. For quality control assurance of these elements pile integrity test (PIT) is often used. PIT as a method that involves the impact of a hammer on the head of the pile generating a low strain compression wave that propagates along the pile and afterwards is reflected at the bottom of the pile, or where there are changes of impedance related with variations in cross section or density of the material. In this paper a numerical solution is presented for the problem of one dimension wave propagation along a concrete pile. The problem consider a longitudinal element with a piece wise varying section, friction forces along the element and a reaction force at the tip, with a transient stress pulse applied at the top. This problem is representative of low strain pile integrity tests. Different alternatives for the solution of the problem were considered, and the spectral analysis method was chosen and implemented using Matlab. The test was modeled for several cases, comparing the results with actual PIT measurements. The parameters for the analytical model were obtained from numerical models of soil-pile interaction.