How To Undertake Finite Element Based Geotechnical Analysis


The aim of this book is to guide both new and experienced analysts on the use of finite element techniques to solve geotechnical problems.

Finite element analysis has been used within the realm of geotechnical engineering for some time. Universities and various specialist organisations now have experts in this field. More recently, however, there have been significant increases in the availability and affordability of computer power, and a proliferation of finite element packages that are relatively easy to use thus drastically reducing the learning curve for a novice user. This combined with the increased pressure for ever more efficient structures is leading to the use of finite element analysis becoming far more widespread.

This book is intended to be an introductory text for new users of the software, many of whom will fall into one of two groups. Those who have a wealth of geotechnical engineering experience, but are relative novices in the art of numerical analysis and “young engineers” who have recently graduated from University and have typically spent a short time since graduation performing linear static finite element analysis. Some basic geotechnical aspects have been described and a glossary summarising the geotechnical terms (shown in bold italics) used in this booklet has been included. However, non-geotechnical engineers are advised to refer to other texts for a more detailed description.

Potentially there is a dangerous consequence of software becoming too easy to use in that such packages may be used completely as a “black box” without some knowledge of the underlying mechanics. As such, it is recognised that a need to understand the principles of the finite element method is required to help analysts in converting a real world problem into a representative finite element model. The aim of this booklet is to fulfill that need. It is assumed that the reader understands a little Finite Element jargon, including the terms such as node, element etc. If this is not the case, the reader is strongly advised to refer to other booklets such as ‘How to get started with Finite Elements’, ‘How to model with Finite Elements’ and ‘How to understand Finite Element Jargon’.

Contents

1. Introduction3
2. Background5
3. Approaches For Geotechnical Analysis9
3.1 Traditional Methods9
3.2 Numerical Methods12
4. Geotechnical Concepts15
4.1 Spring-Dashpot Model for Soil15
4.2 Effective Stress Analysis16
4.3 Total Stress Analysis16
4.4 Dry and Wet Unit Weights17
4.5 Pore Fluid Pressures17
4.6 Drained Analysis19
4.7 Undrained Analysis19
4.8 Groundwater Flow Analysis19
4.9 Consolidation Analysis20
4.10 Sign Convention20
5. Modelling Concepts21
5.1 Plane Strain Analysis21
5.2 Axisymmetric Analysis21
5.3 Three-Dimensional Analysis21
5.4 Non-Soil Structural Components21
5.5 Interfaces22
5.6 Modelling Construction and Excavation22
5.7 Undrained or Consolidation Analysis23
5.8 Failure Mechanism and Factor of Safety25
5.9 Geometric non-linearity26
6. Soil Modelling27
6.1 Mohr-Coulomb29
6.2 Drucker-Prager30
6.3 Cam-Clay and Modified Cam Clay31
6.4 Choice of Material Model32
7. Worked Examples33
7.1 Smooth Rigid Strip Footing on an Elastic Soil33
7.2 Smooth Rigid Strip Footing on an Elastoplastic Soil35
7.3 Drained Excavation of a Building Pit in Sand39
Glossary47
Bibliography55
Appendix 1: Effective Stress and Pore Pressure Calculation57

Document Details

Reference

HT27

Authors

Mar. A

Language

English

Type

Publication

Date

2002-01-01

Organisations

Region

Global

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