Axially Loaded Pile Numerical Models vs. Experimental Data
In the paper the performances of two numerical models are compared through the backanalysis on experimental data. The first numerical model has been implemented by the authors and, under many aspects, can be regarded as a simplified algorithm; the second
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E. Cabella and R. Passalacqua University of Genoa, Genoa, Italy
ABSTRACT: In the paper the performances of two numerical models are compared through the backanalysis on experimental data. The first numerical model has been implemented by the authors and, under many aspects, can be regarded as a simplified algorithm; the second one is an "open code", commercially available. The experimental data come from medium size models performed in a laboratory facility. 1. INTRODUCTION
In the present work two numerical models have been used to backanalyze a set of directly observed data, these being some of the results of an experimental program devoted to study the behaviour of axially loaded, medium-size pile models. The main objective is to assess the performances of two programs by using as a benchmark a set of experimental data, these gained from a series of tests conducted within a laboratory facility where the relevant parameters are strictly under control.
2. THE NUMERICAL MODELS, GENERAL DESCRIPTION. The two programs used in the present work are substantially different: the first one is a
A. Cividini (ed.), Application of Numerical Methods to Geotechnical Problems © Springer-Verlag Wien 1998
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E. Cabella and R. Passalacqua
multi-purpose, commercially available code (FLAC®) which allows the user's definition of constitutive laws and the computed data manipulation in a wide variety of ways; the second one, named PILE, has been implemented directly by the authors and can simulate exclusively a pile-granular soil interaction. 2.1 THE COMMERCIAL CODE. The commercial code is a two-dimensional, explicit difference based, program (Cundall 1976) originally developed for geotechnical and mining engineering problems. The explicit Lagrangian calculation scheme and a mixed discretization zoning technique (Marti & Cundall 1982) are used to ensure that plastic collapse and flow are modelled very accurately. Each element of the discretization grid could behave according to either a linear or a non-linear stress-strain prescribed law. The code also contains a powerful built-in programming language which offers a way to manipulate the introduced and calculated data and also the opportunity to implement a user's defined constitutive model. The drawbacks of using this approach instead of the classic Finite Element Method (Zienkiewicz 1977) lies in the need to perform the analysis through small timesteps and in the necessity to take into account of a damping effect (Cundall 1982). Other advantages allowed by this program are, for instance, the opportunity of selecting the most appropriate among numerous built-in constitutive models, the possibility to create interface elements in order to simulate planes along which slip and/or separation can occur and plane strain, plane stress or axisymmetric geometry modes. The program offers a wide range of capabilities especially suited to solve geotechnical problems and complex geometry in mechanics. Particularly, it permits the modelling of steady and flowing groundwater (with fully couple
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