ENGINEERING TRIPOS PART IIB - 2012/2013

Module 4D5 - Foundation Engineering

AIMS

All civil engineering structures from houses to tethered oil platforms require foundations. This module aims to introduce the challenges of foundation design and examine possible solutions; from simple pad footings, through piles and caissons, to drop-and drag-anchors.

The module begins by examining the requirements of a foundation; the applied loading, the acceptable deformations and the derivation of appropriate soil properties for each aspect of design.

The module then builds on material from 3D2 (geotechnical engineering) to examine theoretical solutions for the capacity (strength) and settlement (stiffness) of shallow and deep foundations under simple loading conditions in idealised soils. Strength is dealt with using plasticity. Stiffness is dealt with using elasticity. These theoretical solutions are then extended to more complex loading conditions and less idealised soils. The course is widely illustrated with case studies from the offshore industry.

LECTURE SYLLABUS

Foundations Design (2L)

• Foundation types;
• Loading conditions;
• Allowable deformations;
• Relevant soil behaviour and soil models;
• Selection of design soil properties

Shallow Foundations (6L)

• Strength: Undrained failure of strip footings: Vertical (V), Horizontal (H) and Moment (M) capacity;
• Strength: Drained failure of strip footings: V-H-M capacity, superposition of surcharge and self-weight effects;
• Effects of footing shape and embedment, and soil heterogeneity;
• Stiffness: Elastic settlement of shallow foundations: drained and undrained;
• Stiffness: Settlement of shallow foundations on non-linear soil.

Deep Foundations (6L)

• Deep foundation types and construction methods; piles, caissons, drop-anchors;
• Pile strength: Axial and lateral capacity;
• Pile stiffness: Axial and lateral deformations;
• Piles: load testing, influence of installation method on performance;
• Pile groups: mutual influence, block behaviour, differential settlement;
• Offshore solutions: caissons, anchors: installation methods and capacity.

COURSEWORK

The preliminary evaluation of three design solutions for an offshore wind turbine foundation.

OBJECTIVES

On completion of the module students should:

• Be able to assess the design requirements of a foundation;
• Be able to deduce appropriate soil properties for foundation design from site investigation data;
• Be able to decide whether to use a shallow or deep foundation
• Be able to design shallow and deep foundations against collapse;
• Be able to design shallow and deep foundations against excessive settlement;
• Be able to explain the difference between drained and undrained response;
• Recognise mechanisms which contribute to generating deformations and load capacity;
• Be able to back-analyse observed foundation performance;
• Appreciate lessons learnt from field data obtained from case histories.

REFERENCES

Please see the Booklist for Group D Courses for references for this module.

Last updated: June 2012