Non-axial analysis and coupled modelling in dynamic pile testing

Pile foundations are the most known and used deep foundation technique in civil engineering to support structures. This research treats the problem of dynamic pile loading in both steady state and transient conditions, when a non-axial load is applied at the pile head. The objective of the present research is to investigate the effects of non-axial loading on the dynamic axial pile response. A horizontally coupled axial soil reaction (so-called impedance) is first developed in harmonic loading for a soil disk based on analytical and semi-analytical solutions. Then, coupled soil impedances are introduced into the pile equation of motion to solve the pile-soil vibration problem. It is concluded that the soil disk impedance as well as the axial pile-soil response in coupled analysis are affected by the lateral load depending on the loading intensity, soil parameters, frequency, etc. Transient pile loading as imposed by high strain dynamic loading tests (a pile driving test) are addressed in the second part of the thesis. Full-scale pile tests from three sites are considered: Limelette (Belgium), Tessenderlo (Belgium), and Loon-Plage (France), where measurements of axial and flexural pile resistance are presented. An analytical solution and a numerical program to take into account the non-axial pile behaviour are proposed. The analytical solution provides a first indication of the transient pile bending in pile driving. The numerical model (called LPDM for Lateral Pile Driving Model) is more advanced than the proposed analytical solution and gives an insight of the whole problem including non-axial pile head impact, axial and lateral pile and soil vibrations. Finally, the hypoplastic soil model for sandy soils is integrated into LPDM to account for large deformations and non-linear behaviour of the soil. Hypoplastic parameters for Brusselian sand, located in the Limelette site, are calibrated based on advanced laboratory tests. The axial pile response recorded from in-situ pile tests is better fitted by LPDM simulations where both low and high strain behaviour of the soil are well captured. A parametric analysis is also performed to generate axial-lateral interaction diagrams of a soil disk subjected to a pile translation.