Pile driving models within the framework of a non-dimensional analysis
(2019)
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- Authors
- Supervisors
- Holeyman, Alain
- Abstract
- Hammer driving is the oldest and most popular way of installing piles. The need to estimate rapidly and precisely the bearing capacity from driving data is essential. This thesis focuses on the elaboration of pile-driving models with the aims of providing new ways of assessing pile resistance. The models are developed within the framework of dimensional analysis — a tool which we have made an extensive use throughout this thesis. This framework thus provided allows to simplify the models while extending their applicability to wider cases, since the analysis does not depend upon physical units. In a first instance, we focus our attention to the mechanisms of energy-transfer between the hammer and the pile. To this end, various analytical impact models were explored. Within the framework of those analyses, we examine the issue related to the parameters to feed those models. This analysis has shown that the uncertainties inherent to the determination of those input parameters can make the most complex models useless, as the latter require more parameters. To address this issue, we suggest a method to derive the stiffness of the cushion and the ram’s impact velocity, based upon the measure of the maximum force, or the maximum velocity, measured at the pile’s head. The second step of the research was to understand how the stress-wave generated by the impact travels along the pile, while interacting with the surrounding soil. Thus, based upon a traveling wave approach, we devise a strategy to solve various boundary-value problems related to the wave equation. The next step leads us to tackle the problem of bearing mechanisms. In this respect, we adopted a two-fold approach in order to understand the behavior of the ideal rigid pile model, and that of the more realistic elastic pile. This analysis has shed some light upon the shortcomings inherent to a rigid-pile modeling, which are precisely adopted in the implementation of classical driving formulae. Based on the static and dynamic analyses of the soil-pile interaction, we suggested an equivalent single degree-of-freedom lumped-parameter model. A simplified procedure for the determination of the characteristics of this model was also suggested. This model proves to be particularly suitable to the study of piles with low end-bearing capacity with respect to the shaft resistance. The case of an end-bearing pile was tackled using a continuous 1D modeling based upon the solution proposed before. The soil around the base is assumed to behave in a viscoelastoplastic manner. The various analytical solutions obtained — namely, when the soil is in elastic or plastic stage — were implemented into a Matlab® script in order to simulate the dynamic behavior of a pile during driving. Based on those calculation codes we were able to perform parametric analysis on drivability analysis. The validity of the proposed model was tested, first numerically, by comparison against data from the wave equation analysis program GRLWEAP™. Later, the model was tested with data from small-scale testing conducted at UCLouvain, which aims to understand the dynamic behavior of offshore piles driven into indurated formations. The results demonstrated the ability of the model to accurately reproduce the bearing graph. In addition, the reliability is extended even in the area of small penetration, which precisely in practice corresponds to a pile near its seating depth. This key characteristic of the developped model overcomes one of the main stumbling blocks of presently available driving-formulae.
- Affiliations
UCLouvain SST/IMMC - Institute of Mechanics, Materials and Civil Engineering
Citations
Victor, K. H. (2019). Pile driving models within the framework of a non-dimensional analysis. https://hdl.handle.net/2078.5/61458