Design of Shallow and Deep Foundations

Roger Frank, Fahd Cuira, Sébastien Burlon

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000423433
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

Design of Shallow and Deep Foundations introduces the concept of limit state calculations, before focusing on shallow and deep foundations. The limit state combinations of actions are examined, and practical calculation models of the bearing capacity and of the settlement are presented, particularly from the results of Ménard pressuremeter tests and cone penetration tests. Attention is also given to the use of numerical methods, which has been developed over the past twenty years. It provides an overview of various elements of ground-structure interaction that are pertinent for a refined design of both shallow and deep foundations, such as allowable displacements of structures, and ground-structure couplings.

This guide will be useful to practising engineers and experts in design offices, contracting companies and administrations, as well as students and researchers in civil engineering. Though its focus is generally on the French practice, it is more widely applicable to design based on, or generally in line with, Eurocode 7, with references to BS ENs.

Roger Frank is an Honorary Professor at Ecole Nationale des Ponts et Chaussées (ENPC). From 1998 to 2004, he chaired the committee on Eurocode 7 on Geotechnical design.

Fahd Cuira is the Scientific Director of Terrasol (Setec group), France. Since 2018, he has been in charge of the course on the design of geotechnical structures at ENPC.

Sébastien Burlon is a Project Director at Terrasol (Setec group), France. He is involved in the evolution of Eurocode 7 and teaches several geotechnical courses, especially at ENPC.

Chapter 1

Actions for Limit State Design

1.1 Definition of actions

Serviceability limit states (SLSs) and ultimate limit states (ULSs) need to be distinguished. Generally speaking, we will remember that for each of these limit states, we must firstly form combinations of actions in order to determine the load on the foundation F_d and secondly determine the ground resistance R_d, which itself depends on the limit state under consideration (see §2.5 for shallow foundations and §3.6 for deep foundations). We must also, if it is required by the supported structure, determine displacement (or their order of magnitude) under various combinations of actions (§2.5.2.2 and §3.6.4).

According to Eurocode: “Basis of structural design” (EN 1990, BSI, 2002), SLSs are “states that correspond to conditions beyond which the specified performance requirements for a structure or a structural element are no longer satisfied”. These states include the following:

• “Deformations that affect the appearance, the comfort of users, the functioning of the structure (including the functioning of machines or services), or that cause damage to finishes or non-structural members;
• Vibrations that cause discomfort to people or that limit the functional effectiveness of the structure;
• Damage that is likely to adversely affect the appearance, the durability or the functioning of the structure”.

ULSs are the ones “associated with a collapse or other forms of structural failure” as well as, by convention, with some states that precede them. They “concern the safety of people and/or the safety of the structure”. These states include the following:

• “Loss of equilibrium of the structure or any part of it, considered as a rigid body;
• Failure by excessive deformation, transformation of the structure or any part of it into a mechanism, rupture, and loss of stability of the structure or any part of it, including supports and foundations;
• Failure caused by fatigue or other time-dependent effects”.

Regarding the design of bearing capacity (calculation in terms of forces), the “limit state” approach consists in guaranteeing that

${\text{F}}_{\text{d}}\le {\text{R}}_{\text{d}}$

with

F_d being the design load applied to the foundation, taking into account possible load factors (usually greater than 1), which are partial factors on actions (see below);

R_d being the corresponding design bearing capacity (or design resistance), taking into account the partial safety factors on the ground resistance (§2.5 et §3.6).

We shall provide here merely a few general principles, without going into the details of the limit state design. The situations, the various types of actions and their values to be taken into account within the design are defined in normative or regulatory documents. In particular, they vary depending on the type of structure being considered.

For foundations of bridges and buildings, the following actions are commonly distinguished according to the French standards for the application of Eurocode 7 (AFNOR, 2012 and 2013).

1.1.1 Permanent actions G

These are permanent actions of any nature. Their characteristic values are noted G. As examples, we may mention the following:

• The self-weight of the foundation;
• The self-weight of the support (pier, abutment, pile cap, etc.);
• The fraction of the self-weight of the building or of the considered structure and of its equipment carried by the foundation;
• Forces due to shrinkage, creep, etc.;
• Forces due to ground weight and ground pressure;
• Groundwater pressure applied on a retaining wall.
  ...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Additional Preface for the English Version
• Authors
• 1 Actions for Limit State Design
• 2 Shallow Foundations
• 3 Deep Foundations
• 4 Interactions with the Supported Structure
• Bibliography