Inadequate site investigation
A report by the Ground Board of the Institution of Civil
Engineers on inadequate site and groundinvestigations leading
to construction delays and additional costs
I Thomas Telford, London
‘1-
Published for the Institution of Civil Engineersby Thomas Telford Ltd, Thomas
Telford House, 1Heron Quay, London E14 4JD
First published 1991
A CIP cataloguing record for this report is available from the British Library
ISBN 0 7277 1645X
0 The Institution of Civil Engineers, 1991
All rights, including translation, reserved. Except forfair copying no part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by
any means electronic, mechanical, photocopying, recording or otherwise, without the
prior written permisson of the publisher. Requests should be directed to the Publications
Manager, Thomas Telford Ltd, Thomas Telford House, 1 Heron Quay, London
E14 4JD.
Printed in Englandby Faygate Printing Services,
Faygate, Horsham, West Sussex.
Foreword
Continuing national disquiet concerning the late completion of construction
projects and high-cost overruns which have been attributed to inadequate site
investigations cannot be ignored. Something positivemust be done quickly to
improve thesituation.
Factors influencing the outcome of site investigation include the initial
pressures of time and money, and also the interrelationships and working
climate between politicians, clients, land-owners, designers,
site investigation
specialists and main contractors, as well as the technical aspects of design,
execution and interpretation of the results.
First there must be an awareness programme to alert clients to the inherent
risks associated with site investigation. Now, and in the future, it is vital that
financial decision-makers appreciate that you pay for a site investigation
whether you have one or not.
Ground isa vital elementof most structures and as
much care and attention
should be given to itas isroutinely given to the other aspects of the engineered
structure.In this respect ground investigationisaninterdisciplinary subject and
professionals with special training and experience in geotechnical
engineering
should be involved.
It is essential to maintain a continuous thread of responsibility for the
geotechnical input of a project, starting with the feasibility studies andextending through to project completion.
In this report a series of national guidelines are proposed to encourage
improved uniform practices in site and groundinvestigations in the UK .
G. S. Littlejohn
Chairman of the Ground Board
February 1991
Acknowledgements
The Ground Board wishes to thank all the local associationsand the secretariat
of the Institution of Civil Engineers who devoted much time and effort to
deliberations on which this report is based. The Boardis also deeply indebted
to many organizations and individuals who provided helpful comments.
Contents
Principal findings, conclusions and recommendations
1. Introduction
2. Scale and nature of the problem
2.1. Industrial buildings
2.2. Commercial buildings
2.3. Low-rise buildings
2.4. Roads and bridges
2.5. General remarks
3. Expenditure on site and ground investigations
4. Site and groundinvestigation practice
4.1. General
4.2. Procurement
4.3. Definition of contract work
4.4. Methods of obtaining tenders
4.5. Placing and defining responsibilities
4.6. Conditions of contract
4.7. Technical specifications
4.8. Planning and design
4.9. Execution and supervision
4.10. Interpretation and utilization of data
5. Contractual claims related to unforeseen ground conditions
6. Conclusions
7. Recommendations
References
Appendix 1.Guidelines on ground investigation practice
Appendix 2. Criteria for the preselection of specialist contractors
Appendix 3. Members of the Ground Board, ICE
1
2
2
2
3
4
5
5
6
8
8
9
10
10
11
12
12
13
16
17
18
19
19
22
24
25
26
Principal findings
Based on various reports over the past 25 years it has been shown that in civil
engineering and building projects the largest element of technical and financial risk lies normally
in the ground
(sections 2 and 5).
A statistical review of 5000 industrial building projects by the National
Economic Development Office (NEDO) has shown that about half of the
projects overran by one month ormore. 37%of a representative group of 56
case study projects suffereddelays due to ground problems. Without exception on second-hand sites unforeseen ground conditions were met during
construction (section 2.1.1).
In an analysis of 8000 commercial building projects, NEDO found that one
third of the projects overran by more than a month; a further third overran
by up to one month. 50%of a representative group of 60 on-site casestudies
suffered delays due to unforeseen ground conditions (section 2.2.1).
Following a review ofover 200 roads and bridges where early remedial costs
exceeded €100OOO (1988 prices), the National Audit Office has expressed
concern at the high costs associated
with geotechnical problems. Geotechnical problems on eight road and six bridge projects resulted in extra work
costing €18 million (section2.4.1).
On ten large highway construction projects, the Transport and Road Research Laboratory has observed that the final cost wasaverage
on
35%greater
than the tendered sum. Half of this increase was dueto inadequate planning
of ground investigation or poorinterpretation of the results (section 2.4.1).
Principal conclusions
0
0
Clients are concerned about delays and escalating costs of construction
frequently attributed to inadequprojects throughout theUK. The delays are
ate site and groundinvestigations (section 2).
It is not clear which factorsof the construction processcontribute to inadequate site investigation. In addition to the technical aspects of planning,
execution and reporting, it is necessary to consider also the contractual
environment between all parties (section 4.8).
Most construction activitiesinvolving the groundare sufficiently close the
to
critical path for any delay to those activities to affect the whole project
(section 5).
The consequences of inadequate investigations are not only severe for the
design and construction phases of a project but areeven moreserious when
continued into full-lifecosting (section2.5).
Inadequate site investigations can arise from a lack of client awareness,
inadequate finance, insufficient time and a lack of geotechnical expertise
(section 4).
Positive actionmust be taken now by
the construction industry and clients
its
to improve this intolerable situation.
Principal recommendations
A geotechnical awareness programme should be organized for clients and
engineers to highlight the significance of ground oncivil engineering and
building projects and the benefits of executing site investigations, particularly with the involvement of a geotechnical specialist (sections 4.2, 4.9 and
7.1.1).
A national specification and method of measurement for site and ground
investigation should be introduced (sections 4.3,4.7 and 7.1.2).
1
A national procurement guide should be produced for clients,highlighting
the essential aims and benefits of site investigation, and how these can be
achieved by following appropriate procurement routes (sections 4.2 and
7.1.3).
National guidelines on the extent and intensity of investigations should be
published to indicate the minimum requirements for a complete range of
construction projects (sections4.8 and 7.1.4 and Appendix 1).
As a contractual requirement all investigations should be carried out under
a formal quality assurance system (sections 4.9,7.1.5and 7.6).
All factual geotechnical reports which are relevant to a project should be
made available to all the parties involved in the planning, design, tendering
and construction of the project (sections4.10 and 7.2).
1. Introduction
This report establishes the scale and nature of the problems of inadequate site
and ground investigations * which lead to construction delays and additional
costs. Current investigation practicesare described with particular reference to
procurement, design, execution and interpretation, from which conclusions
have been drawn. Recommendations are made to improve practice for the
benefit of the construction industry and itsclients.
2. Scale and natureof the problem
2.1. Industrial
According to a report issued by NEDO,' industrial construction in the early
1980scomprised factories where most of the buildings were steel-framedsingle
storey units, often with a two-storey office block.
Of the 8000-9000 projects started each year, 66% cost less
than €50 000 each,
but these accounted for only 10%of the total output. Few projects were valued
at more than €2 million. Thetotal output for industrial building was valued at
€2943 millionin 1980, which represents 20% of all new construction,
and €3020
million for 1987.
Based on a statistical review of 5000 projects and a detailed analysis of 56
industrial projects completedduring 1980-81,theNEDO report showed that the
average duration of construction for industrial projects ranged from 5 months
(for projects costing €100 000) to 12 months (for projects costing€1.5 million),
and that about half of the projects overran their planned times byone month or
more. Moreover, '37% of the case studies suffered delays due to ground
problems -water, rock etc.
-although such problems occurred on both fast
and slow projects.'
The report also noted that much industrial construction took placeon second-hand sites, and that 'Without exception these projects met unexpected
ground conditionsduring construction.'In general, projectson greenfield sites
were constructed up to 2 months faster than those on reused land.
buildings
2.2.1. Financzal
considerations
2.1.2. Physical
The sites in the cases reviewed often contained man-made obstructionssuch as
foundations and services. Information about their nature and location was
missing or inaccurate or had not been pursued with sufficient determination.
Ground problems included soft spots in recycled ground and industrial waste
which required piling, waterloggedground, rock in ground, methane pollution,
and ex-colliery waste which required deep compaction.
dificulfies
*
2
Site and ground investigations are defined
in section 4.1 where a ground investigationis part of the
used frequently by non-specialists
broader processof site investigation.In practice, both terms are
to mean the same type
of investigation.
Comment
Many of these incidents can
be detected by deskstudy; nevertheless the client shouldbe
madeawarethatitissfillpossibleforanunforeseenrisktooccurandthismustbejudged
against its financial implications.
2.1.3. Conclusions Although the NED0 report observed that constructiondelays, caused by inadequate site investigations, were considerable, itconcluded that: 'variations due
to unexpected site or soil conditions may be unavoidable' and as a COquence, argued that in any particular case a balance
should be struck between
the substantial cost of an exhaustive site investigation and therisk of extra cost
and delay arising from an inadequate one. In this regard, the report found that
'practice tends to err the
in direction of paying too little attentionto investigatory work.'
As a result of the survey, the NEDO report recommended that as much
information as possible should be obtained before asite is purchased. Furthermore, the design team should take full responsibility for advising on the need
for and natureof site investigation.It was also suggested that separate contracts
for site preparation could be helpful in ensuringthat any problems are dealt
with at the appropriate
stage.
2.2. Commercial
In the fast-growing commercial market-placeof multi-storey highly serviced
buildings such as office and shopping developments, hotels, private hospitals
and leisure centres, the total output in 1986 was valued at €4226 million.
Of the lo00 such projects started each year, at that time 400 schemes represented over half of the total output andcost individually more than €lmillion.
Over half of all works were offices and another quarter were shopping developments. Demand was heavily concentratedin the South East and one third of
the total work was in Greater London.
Drawing on 60 on-site casestudies, detailed informationon 260 other rojects
and a statisticalanalysis of 8000 commercial building projects, NED$ found
that 'unexpected ground conditions delayed one in two projects.'
2.2.2. Physical
dificulties
Besides unforeseen ground being encountered, other recorded problems included a site over an Underground station which produced piling difficulties,
differential settlement which led to foundation problems, old underground
chambers, tunnels and shafts, an unknown spring, site flooding which required
groundwater lowering, the underpinning of an adjacentbuilding,rocky
ground, a sloping site which proved difficult, undetected ground/groundwater
conditions which led to change
a
in concrete design, existing massive
foundations which could not be removed and wells.
buildings
2.2 .l.Financial
considerations
Comment
Many of these incidents canbe detected by desk study.
2.2.3. Conclusions
The NEDOreport considered that although building sites were often difficult
in terms of legal and planning requirements, as well as having demands and
constraints imposed on the building operation by conditions on the ground, the
most frequent explanation of overruns andlong delays (more than 10 weeks)
was unforeseen obstacles in the ground.
It was also noted that ground works and foundations for newbuildings can
be time-consuming and absorb up to one third of the construction time (although only 10%of the contract value).
According toNEDO, owners and developers take risks with conditions on
their sites, and often investigations are inadequate. For example, mostground
problems were unforeseen, either because a site investigation had failed to
detect the problems or, more frequently, becausethe close follow-on
of redevelopment after demolition did not leave room for thorough investigation of the
site.
3
Comment
Clients should be persuaded that siteinvestigation should be undertaken for every site.
Without a properlyprocured, supervisedand
interpreted ground investigation, dangers
which lie beneath the site cannot be known.
2.3. Low-rise
buildings
2.3.1. Financd
considerations
According to the Building Research Establishment (BRE)3 little attention has
been paid to ground conditions associated with low-rise buildings, such as
domestic houses. Problems which are costly to solvehave arisen because these
buildings are normally founded on relatively simple foundations at shallow
depths where the soil tends to be more variable and compressible than it is at
depth. Furthermore, brick structures are particularly sensitive to differential
foundation movements.
The National House Building Council4pays out on claims having a total
value of €5-11 million each year, over
half of which are related to geotechnical
problems.
Traditionally, expenditure on ground investigations has amounted to 0.10.2% of construction costs? Mostof this small investment has been spent on a
limited number of trial pits and boreholes.
2.3.2. Physical
dificulties
The BRE has described a variety of ground problems related to low-rise buildings (see Table 1) which were associated with particular combinations of site
conditions, ground conditions and the design of the buildings.
Table 1. Groundproblems and low-n'se buildin2
Differential settlement or heave of foundations or floor slabs
Soft spots under spreadfootings on clays
Growth orremoval of vegetation on shrinkable clays
Collapse settlements on preexisting made ground
Mining subsidence
Self-settlement of poorly compacted fill
Floor slab heave onunsuitable fill material
Soil failure
Failure of foundations on very
soft subsoil
Instability of temporary or permanent slopes
Chemical processes
Groundwater attack on foundation concrete
Reactions due to chemical waste or household refuse
Variations during construction
Removal of soft spots to increase depth of footings
Dewatering problems
Piling problems
Comment
A significant number of ground problems for low-rise buildings arise due to lateral
movements which are often ignored (see ref. 6).
2.3.3. Conchsions
The BRE concluded that thorough ground investigationswere most important
for low-risedevelopment, and that with limited finance available for
trial pits
and boreholes more effort should be concentrated on desk studies, including
air photographic interpretation, during the initial site investigation. For
example, air photographs could be used to detect slope instability and old
Ordnance Survey maps might highlight contaminated or infilled ground.
Some form of desk study wasconsidered by the BRE to be a prerequisite for
any competent foundation design for any structure, however small.
Comment
Desk studies and routine ground investigations should be planned and interpreted by,
or with theassistance of,ageotechnical specialist, i.e. aprofessional with special training
and experience in geotechnical engineering.
4
The interpretation ofaerial photographs is not a routine practice and training will
be requiredto protide thenecessay skills.
2.4. Roads and
bridges
2.4.1. Financial
considerations
The Department of Transport, the Scottish Development Department and the
Welsh Office(the transport departments) together spent well over€1000million
in 1988-89 on the construction and maintenance of the national road system
which covers 9500 miles ofmotorways and trunkroads and 14 500 bridges and
other structures.
Within their design lives all roads and bridges require maintenance, but in a
number of cases the transport departments have incurred substantial expenditure onmaintenance and repair earlier than was expected at the time of construction.
Following a review of 210 roads and bridges with remedial costs which
exceeded €100OOO,the National Audit Office (NAO)in 198g7noted eight road
and six bridge projects where geotechnical problems resulted in extra work
costing in total €18 million.
The NAO examined the procedures for identifying and analysing the causes
of expenditure on premature maintenance, and expressed 'concern at the high
remedial costs associated with geotechnical problems.'
Comment
Geotechnical problems can arise from several factors such as poor design, bad comtruction implementation and poor routine maintenance, as well as inadequate ground
investigation.
The problem of inadequate ground investigation has also been highlighted
by Tyrrell et a18 Based on an analysis of ten large highway constructionprojects,
they found that 'the final cost was on average 35% greater than the tendered
sum, and half of this increase was directly attributable to inadequate planning or interpretationof ground investigation.'
Comment
This inadequate planning is considered to be ground investigation planning.
High remedial costs can be misleading, as they frequently ignore additional costs
which would have been incurred in any event to deal with theadverse condifions.The
report by Tyrrell etal. was based on projects carried out in the 2970s and early 2980s.
I f is understood that the2990 final cost was on average 28% greater than the tendered
sum.
2.4.2. Physical
difficulties
2.4.3. Conclusions
The NAO report stated that inadequate ground investigationsled, for example,
to the use of unsuitable materials, or poor drainage causing embankment
failures and, while designs were altered, delays in construction.
As a result of its survey, the NAO recommended that the Department of
Transport and theWelsh Officeshould carry out cost-benefit analyses to review
whether or not spending more on site investigations would save money in the
long run.
comment
Bearing in mind that earthworks and pavement foundations represent major cost
elements of highway schemes, there have been suggestions that the transport departments should ernploygeofechnicalspecialistsinall their regional offices. In this way the
departments can ensurea geotechnical presence throughout the planning,design and
construction of each project.
2.5. General
remarks
None of the national reports referred to report what site or ground investigations, if any, were carried out. It is therefore not possible to diagnose any
inadequacies associated with the site investigation or ground assessment or
their extent.
5
Another unknown in relation to constructiondelays is the amount of experience that the planning/site management teams had andthereforethe likelihood
of their being able to carry out the work in theproposed time-scale.
Many clients express dissatisfaction with the quality of site and ground
investigation work and value for money.9
It may be readily argued that inadequate investigations lead to delay and
increased engineering costs but, more important, such inadequacies can seriously affect the full-life financial performance of a structure. Their effect on
internal rate of return, cash flow and other economic parameters should be
determined to demonstrate the overall risks involved.
Despite the uncertainties involved, the amount of material sampled from the
ground influencing, or influenced by, the structure is invariably low compared
with the testing, considered routine and rarely questioned, for the quality
control of concrete and steel. This inconsistency
is not logicalwhen the ground
forms part of the engineered structure.
It is not realisticto expect asite or ground investigation to revealconditions
in their entirety, but provided the data areanalysed and interpreted correctly
such investigationswill reduce the level of residual risk associated with
unfore
seen conditions to one which is recognized as tolerable within the project in
terms of the consequences of such events.
Risk analysis, as a management tool, should be considered byengineers to
demonstrate in financial terms the benefits of comprehensive site and ground
investigations. Programs could be generated to quantify the effects of ground
investigations on the cost and time uncertainties of geotechnical activities.
Ground conditions may be divided into two categories: natural and manmade. Unforeseen natural conditions include strata or substances not discovered byinvestigatory work, whereas unforeseen man-made conditionsmay
also result from the way engineers interpret ground investigation data or model
the groundfor design or construction purposes.
In either category it should be appreciated that geotechnical engineering
knowledge of the ground conditions depends on the extent and quality of the
ground investigations. Such knowledge and the control of workmanship are
more significant to fulfillingthe fundamental requirements than is the precision
used in calculation models and the choice of safety factors."
Given the scale of the perceived ground-related problems which have been
highlighted in reports on buildings and highways, there is clearly a need the
for
profession toexamine ways in which more clients mayobtain better long-term
value for money.
3. Expenditure onsite and groundinvestigations
The Economic Development Committee for Civil Engineering (EDCCE) observed in 1968" that there was little scope for reducing prices in ground
investigation without seriously impairing the quality of the work. Since that
date, Uff and ClaytonI2have reported that, in real terms,prices havebeen forced
down further, so that investigation today is often basedon minimum cost and
maximum speed. This inevitably increases the risk of poor quality work.
Based on the results (54% returns) of a questionnaire survey conducted in
1987 by
the University of Manchester Institute of Scienceand Technology, many
organizations have estimated their expenditure on site investigation as a percentage of total project costs.I3
Other r e p ~ r t s ' ~ ' ~site
o n investigationcosts have
been used to calculatethe amountsactually spent by clients. Theseestimates
are shown in Table 2 together with the average percentages reported by clients.
There is a wide variation in financial allocation tosite investigation among
the different types of client and consultant. This should not be so if the basic
requirement is to produce satisfactory guidance to the project designer. The
6
investment parameters should relate to the project, notthe views or callingof
the professionals involved.
All consumer groups perceive the costs of site investigation to exceed real
costs bya considerable margin. this
In regard, consumers were alsoasked if they
thought that sufficient money was spent on site investigation. Of those who
replied nearly 50% thought that on average the amount spentshould be more
than doubled.
Table 2. Funding of site investigation projects aas
percentage of total project costsz3
Consumer
clients
Government authorities
Manufacturing/commerce
Civil engineering contractors
Developers/builders
Consultants
Architects
Multidiscipline consultants
Civil engineers
Structural engineers
Average
Questionnaire
replies:
mean % spent
Calculated:
% spent
2.21
0.76
0.29
0.22
0.23
0.11
0.85
0.72
0.29
0.14
0.92
1.94
0.23
0.23
0.W
0.29
0.16
0.21
In judging routinely what cost should be allocated tosite investigation it has
been suggested that a funding range (expressed as a percentage of the total
project costwhere known) should be recommended.As an example,the BRE5
recommends a minimum figure of 0.2% for small projects such as low-rise
buildings. Such recommendations on minimum spending could give practical
backing tothe professionals when they propose a scale of investment.
The solution to the problem, however, is not justto spend more moneyon
more groundinvestigation. Inmany cases, greater benefits forthe client can be
obtained at little or no extra cost simply by better
planning of the investigation
using a geotechnical specialist(see also section4.8).
Much money can be wasted by covering
sites with regular grids of boreholes
and extensive programmes of routine tests, rather than targeting investigations
towards areaswhere information is required and by using more appropriate
methods of investigation.
The clientor theproject managementteam often does not employ a geotechnical specialist (see section 4.2) and may therefore not always appreciate the
significance of appropriate and adequate groundinvestigations. As a consequence, insufficient time and/or money are allocated for a realistic ground
investigation.
On occasions clients
without a geotechnicalawareness present ground investigation reports of one investigation for a different development on the same
site. In such circumstances the client is often unwilling to pay for further
investigation.
Comment
Given the additional expense often associated with inadequate investigations, it is
apparent that initial payment is usually achieved via insurance claims. The costs of
insurance provision are borne directly by the industry and ultimately by the client.The
have one or not'.
adage is 'you pay for a site investigation whether you
7
4. Site and ground investigation practice
4.1. General
A site investigation is an essential preliminary to construction, by which geotechnical and other relevant information which might affect the construction or
performanceof a civil engineeringor building project is acquired. In accordance
with current UK guides to good practice (e.g.BS 593018), the primary aims of a
site investigation include
(a) to advise on the relative suitability of different sitesor distinct areas of
one site for the positioning of structures or services
(b) to allow adequate and economic design of both temporary and permanent works
(c) to discover and evaluate possible problems in the construction of both
temporary and permanent works
( d ) to reduce the risk of unforeseen ground conditions, thereby decreasing
the likelihood of changesin design and constructionmethods, delaysand
consequent claims
(e) to appraise likely changes in the environmentalconditionsof the site and
adjacent areas due to the construction and operation of the project.
A site investigation will normally proceedthrough the following stages
(a)desk study (examinationof existing information about the site including
the engineering geology)
(b>site reconnaissance (visual examination of the site and its environment)
(c)preliminary ground investigation, if judged appropriate, to facilitatethe
design of the detailed ground investigation
( d ) detailed ground examinationfor design and construction (ground investigation, topographic and hydrographic survey and special studies)
(e)supplementary investigations during construction.
The ground investigation is the physical examination of a site and provides
geotechnical data which are representative of the subsurface conditions and
relevant to the
Ground investigation usually involves
drilling,
boring and digging trial pits, together with in situ sampling and testing, and
laboratory testing. Geophysical exploration may alsobe used.
With the increasing use of marginal and derelict land, geochemical explorations may be included to determine the level of contamination?'
Guidelines on groundinvestigation practice are listed in Appendix 1.
Cornme@
BS 5930, published in 1981, is not sufficiently specific to ensure consistent good
practice. For example, under sampling procedure (clause 19.4.2) the drop weight or
sliding hammeris not defined in terms of location, weight or stroke andyet these details
are important to ensure thatthere is no pull-back during driving.
Although important, theshortcomings
of BS 5930 are not considered to beasserious
as a lack of competent supervisionand reporting of site investigationdata (see sections
4.9 and 4.10).
Although thereisacaseforfheupdatingofBS5930,theBritishSfandardsInstitution
(BSI) is concentrating its support on Eurocode 7.l' As a member bodyof the Comite'
nao or updated British standEuropien de Normalisation, the BSI will encourage
not
ards if thesame subject is to be covered by European standards. Given this strategy,
the
construction industryshould encourageits geotechnical specialists to participate in the
work of the European drafting groups
of Eurocode 7. The topic and scopefor each group
is expected to be agreed Ey the Eurocode 7 Panel in 1991. All such work should be
organized through the BSI International Geotechnics Co-ordinating Committee.
If the draft directive on civil liability fordamage caused by wastt? is implemented,
there will be an increased need for ground investigations to include chemical and
8
biological information. In this regard, ground monitoring techniques should be developed which are capableof measuring low concentrationsof contaminants.
Research in collaboration with environmental scientistsshould also be encouraged
for theevaluation of contaminant concentrationlevels which areconsidered safe.
The EDCCE report" identified methods of competition and conditions of
contract as causesof poor ground investigation,and it ofisconsiderableconcern
to note that nearly 20 years later, Uff and Clayton12highlighted the following
primary causes for shortcomingsin ground investigation
(a)unfair or unsuitable methods of competition
(b)inappropriate conditions of contract
(c)inefficient and inadequate supervision
( d ) inadequate and unenforceable specificationsof work.
These aspects of ground investigation practice are now reviewed.
4.2.
Procurement
Table 3 shows the frequency with which different categories of client instigate
site investigation services in the UK. It is shown that private consultants and
government authorities are responsible for 60% of the market.
Once a site investigation has been commissioned, the client's appointed
manager, whether an in-house member of staff, an independent consultant or
a specialist contractor,has overall responsibility for the suitability of the site
investigation procedure. Table 4 lists the types of site investigation manager
used in the UK and by government authorities.
Table 3. Site investigation commi~sionin$~
Category of client
Frequency of instigation:%
Private consultants
Government authorities
Manufacturingindustry
35
25
4
7
11
15
3
Commerce
Civil engineeringcontractors
Developers/builders
Others
Table 4. Managers of site investigationprojects13
Site investigation manager
Architect
Project manager
Site investigationfirm
Civil engineer
Structural engineer
Geotechnical personnel
Other
Government: %
5
0.5
18
38.5
20
9
9
National:%
9
7
12
33
30
4
5
The national figures show that only 16% of projects are managed by
geotechnicalspecialists, i.e. the use of qualified and experienced geotechnical
managers is the exception rather than the rule.
Uff and ClaytonI2 state that the fundamental cause of shortcomings in the
ground investigationindustry liesin the
methodsof procurement used,because
they inhibit the proper use of expertise and allow those involved to take on
duties which they are unable to perform. They recommend
that there should be
an identified,experienced, well-qualified geotechnical
engineer associated with
every project from conception to completion.
Two suitable systems of procurement are also identified
9
(a)system 1:the use of a geotechnicaladviser with the separate employment
of a contractor for physical work,
testing and reporting as required
(b) system 2: the use of a single contract for geotechnical
expertise together
with physical work,testing and reporting.
Whichever system is adopted, the design professional and any geotechnical
adviser should pay particular regard to the need for careful preselection of
tenderers, and to the limits on the number of tenders which are invited. The
preselection of tenderers should be based on the same criteria for all (see
Appendix 2).
Clients should be advised that when procuring a ground investigation it is
contrary to theirlong-term financial interest to attempt to obtain work at prices
lower than those which would result from selectivetendering.
Comment
For site investigation projects which involve consultants withgeotechnical expertise,
system 1 has been used successfully formany years. Thereis no evidenceto suggest that
system 2 has been widely implemented for routine site investigation work across the
UK.
A national procurement guideshould be produced for clients which highlights the
essential aims and benefits of site investigation, and how these can be achieved by
following appropriate procurement routes.
The majorelements which makeup a system of procurement are
(a)the way in which the contract workis defined
(b)the method by which an acceptable tender is obtained
(c)the placing and definition of responsibility
These elements are now described.
4.3. Definition
of contract work
The form of contract is usually a choice between method and end result; most
contracts are based on the former. Incurrent practice, undue emphasis appears
to be placed on physical workand its quantity and it is not adequately appreciated that the quality or reliability of the data produced is dependent on the
degree of supervision and control.
Where the work is defined by method and quantity one of two pricing
mechanisms is normally encountered: a bill of quantities coupled with a specified method of measurement, or a schedule of rates for the provision of plant
and personnel. The first method is the more common, but Uff and Clayton12
state that the technical specifications covering
working methods and test procedures are usually insufficiently detailed, so that they permit rejection of only
the most obviously deficient work.
Comment
Without a basis of common standards of work, specialist contractors complain of unfair
competition,
I n the absence ofproperly defined specifications and standards, and without adequate
enforcement through supervision, fhe sfandard of investigation work produced is
unpredictable (seealso section 4.7).
4.4. Methods of
obtaining
tenders
10
Both the EDCCE"and Uff and Clayton12have recommended the discontinuation of open competitive tendering based on price alone.To illustrate how the
industry responded during 1983-87,Table 5 shows that there has been a significant increasein the use of selective competitivetendering by most consumers.
The trend is encouraging, and selective tendering on the basis of some form
of specification and bill of quantities is the most frequent method of procurement in the UK?2
Often used:%
Private consultant
Open tendering 1987
Sometimes
used:%
Rarely used:%
Never used:%
7
0
80
59
19
45
16
4
14
15
48
22
16
0
2
7
10
7
61
96
4
19
23
26
Selectivetendering 1987
Selective tendering 1983
Negotiation 1987
Negotiation 1983
4
18
54
18
6
9
2
18
25
55
25
46
17
0
2
0
17
18
77
64
19
27
52
27
Manufacturinglcommere
Open tendering 1987
Open tendering 1983
Selective tendering 1987
Selective tendering 1983
Negotiation 1987
Negotiation 1983
0
0
22
14
22
29
11
14
33
43
33
43
22
0
0
33
14
67
86
34
43
12
14
Contractors
Open tendering 1987
Open tendering 1983
Selective tendering 1987
Selective tendering 1983
Negotiation 1987
Negotiation 1983
15
22
35
28
6
9
6
0
20
20
25
46
15
9
17
6
17
18
64
69
28
48
52
27
Open tendering 1983
Selective tendering 1987
Selective tendering 1983
Negotiation 1987
Negotiation 1983
Government
Open tendering 1987
Open tendering 1983
Table 5. Comparison
of procurement
methods 1983-8?3
11
Six or more tenders are usually invited from contractorschosen bythe engineer
or client, on the basis of their reputation, ability to carry out the work or past
performance. The client
is then virtually bound to acceptthe lowest tender.
Comment
In spite of the encouraging trend,preselection is not applied systematically and some
clients still ask for
local companies to be placed on lists of tenderers. These contractors
may be relatively inexperienced, and their inclusion leads to long tender lists, and
inhibits serious biddingby specialist contractors. Longunbalanced lists lead to wildly
fluctuating prices and quality.
Preselection doesnot work unless
all the tenderers are selectedby the samesearching
criteria (see Appendix 2).
4.5. Placinand
de lning
responsibilities
P
The contractual arrangements commonly used in ground investigation make it
difficult to
determine theextent of the responsibilitiesundertakenby eachparty:
the investigation contractor, the engineer and the client. In addition, the variability of ground and groundwater, which influences procedures, makes it
difficult toidentify the source of any error or omission. These factors, coupled
with the practice of defining contractual obligations by reference toactivities
rather than the quality of results, often make
it practically impossibleto apportion blame.
11
In terms of responsibility, Uff and Clayton12conclude that the client is best
served by dealing with only one contracting party, so that there is no doubt
about responsibilities.
Comment
Irrespective of the fom of contract, a prerequisite is a clearidentification and definition
of the responsibilities of each party to the
contract. For example, if the contractis based
on a performance specificationfor field instrumentation the investigation
contractor is
clearly responsible. A method statement, however, tends place
to the responsibilitywith
the engineer.
4.6. Conditions
of
contract
Ground investigations are frequently carried out under the ICE Conditions of
~ontract.2~
The results of the survey reported by Peacockand Whyte13showed that 30%
of consumers used no formal conditions of contract, and fewer than 14% of
replies mentioned the ICE Conditionsof contract for ground in~estigafion?~
Both ICE forms of contract require the designation of an engineer who is
assumed to provide a full design for the investigation and the necessary supervision for the work. Under these conditions the contractor's duties in relation
to the implementation and management of the site investigationoperations do
not extend to ensuring suitability of the work.
In other cases, the client may not appoint an independent engineer or the
consulting engineer may have limited geotechnical knowledge. such
In circumstances the control and direction of the investigation work may be left to the
contractor. On small contracts, for example,the client may invite quotations
directly from specialist site investigation contractors. In practice, the form of
contract varies; there is often no standard specification,although the contractor
may offer hisown specification,and supervision of the work is usually carried
out by the contractor.These circumstances
are not reflectedin the standard form
of contract (ICE Conditionsof Contract, 5th edn).
Comment
The ICE Conditions of contract for ground investigation indicate that
in the absence of
an independent engineer, the client
should nominate an appropriate individual toact as
the engineer who may,for instance,be employed by the contractor. It is further
assumed
that geotechnical specialists wilf be involved in the work.
When used, the ICE ground investigation contract works satisfactorily
and there is
little justification in repfacin this o m of contract by the flexible model contract
f
proposed by Barnes and Perry.3 5 Providing
theseruices of a geotechnical specialist are
part of the contract management, the wordingof the various conditionsof contract is
not a significant contributoryfactor to theadequacy of site investigation.
4.7. Technical
specifications
12
Government departmentsand rofessional bodies have published specifications for ground investigation19,q627 which provide excellent guidelines. However, engineers do not follow them as a routine procedure.
In current practice the technical requirements of the quality of work are often
covered by reference to the procedures recommended in BS 593018for site work
and BS 137728for laboratory testing. Alternatively,a specification maybe put
together using abstracts from several specifications; this often leads to ambiguities, errors andomissions.
It is clear that there is no commonly accepted
standard specification, and on
small projects the contract documentation may not include a specification.
In reviewing the Department of Transport (DTp)and the Institution of Civil
Engineers (ICE) specifications for
ground i n ~ e s t i g a t i o n ' a~ working
#~~
party of
the Association of Geotechnical Specialists29concludedthat a new national
specification should be produced, to be acceptable tothe full range of professionals in the civil engineering and building industries.
The new specification should be prepared using the ICE specificationas the
base document, and comprehensive notes for guidance should be included.
DTp features such as accredited drillers, access and reinstatement responsibilities, and comprehensive data on sampling, in situ testing and laboratory
testing should be added. Furthermore, the specification should be extended to
cover topics such as contaminated ground, geophysics, work over water, traffic
management, computerized data andquality assurance requirements.
Comment
A single national specificationwith appropriate notesfor guidance would greatly
reduce
by tenderers in becoming familiar with different documents.It
the time currently spent
would also reduce the potential for inappropriate tendzrs due to misinterpretation
of the
various documents.
There is a need for a nationally
accepted specificationwhich canbe easily understood
by site operatives andis enforceable by supervisoy staff.
The specification should bemodular. I t should define thelimits of accuracy, quality
of materials, equipment tobe used and detailed operational procedures.
In the absence of clearly and properly defined contract specifications, and without
their adequate enforcement through supervision, the
standard of ground investigation
work willbe unpredictable.
4.8. Planning
and design
Site investigations oftensufferfrom the rush and tumble associated with
planning pressures, provision of access, last-minute changes in scheme layout
and construction deadlines. There appears to be an inadequate appreciation by
clients, planners and administrators of the importance of site investigation and
the need toallow adequate time forits planning, design and execution. Itis also
vital that the site investigation should be directly relevant to' the final linesand
levels of the project.
Schemes change as a result of political and environmental influences, such
as those produced at public inquiries,and geotechnical design may depend on
the extrapolation of site investigation data derived for other locations. Where
sea outfall tunnels or roads are constructed along changed routes or buildings
are repositioned, the original site investigations may have been fit for their
intended purposes but may not be relevant for the projects in their new positions.
There is a failure to realize that ground is complex and even when strata
inconsistencies becomeapparent further investigation is often omitted. There
is frequently a lack of flexibility in the design approach to site and ground
investigations.
Only small investigations can be controlled adequately by one person. Normally site and ground investigations, and subsequent geotechnical design,
require input from geotechnical specialistswith different skills and expertise,
e.g. a geotechnical engineer, an engineering geologist, a geophysicist and a
groundwater hydrologist. Ground investigation is aninterdisciplinarysubject,
and the differences in the experience of such specialists must be appreciated if
the design of investigations is to beimproved.
In current practice, ground investigations are carried out primarily to provide data for use in the design of permanent works. Thedesign requirements
for temporary works are generally different from those for permanent works
and thesampling and laboratory testing carried out may be insufficient forthe
former.
The separation of the site exploration team from those responsible for the
design and constructionof the project canlead to poor communicationbetween
the various disciplines, which may in turn lead to a lack of awareness or
appreciation of the requirements of others. It is vitally important to recognize
the links between site investigation, planning, design and construction.
13
Comment
It is a prerequisiteof all successful projects that adequate
time and funding be devoted
to site investigation.At the planningstage, extreme care must be taken to establish the
correct contractual environment to ensure an effectiveinterrelationship between the
client, site investigation specialist, engineering designer and main contractor. I t is
thought by some that thisis not always thecase.
Site and ground investigations should be conducted as operations of discovery.
Investigations shouldproceed in logical stages and planning should be flexible so that
work canbe varied as necessa y in the light of new information.'8 In other words, after
each stage of a site investigation it should
be possible to assess the degree of uncertainty
that remains in relation to vital aspects of the ground. This observational approach
should allow thebest engineering strategyto be developed.
The important phasingof investigations will be easier to implement if the client is
advised at the outsetthat phasing may be a contingency requirement.
Designers of site and ground investigationsshould attempt to answer the following
questions.
(a) What is knownabout the site?
(b) What is not known about the site?
(c) Whatneeds to be known?
A person who cannot adequately answer all these points probably has insufficient
expertise to design the investigation.
A provisional bill of quantities and associated specification forfurther investigation
works should be provided in the maincontract documents,so that clients and enginens
can instigate in an orderly way investigations which mayin the long run prove to be
beneficial economically to both the client and the contractor,and also the project as a
whole.
If designers of investigations were to assess the cost of each week's delay during
construction caused by unforeseenground conditions,it would enable them to influence
the level of site investigation activity. Those with the wholeof the
view
project available
to them would be less likely to follow a predetermined patternof investigation which
takes little account of the consequences of non-discovery of obstructivefeatures.
An important trend is the increasing sensitivity of construction methods to
ground conditions. For example, different tunnelling methods have different
sensitivities to variations of the ground. Major costs may be incurred when a
tunnel-boring machine encounters ground with properties for which it not was
designed, but hand methods of tunnelling can often be varied without excessive
cost. Certain piling and ground improvement methods can present the same
problems.
In order to establish minimum requirements for the extent and quality of
ground investigations, Eurocode''7 recommends that the difficulty and complexity of each geotechnicaldesign should be clearly identified.To facilitate this,
three geotechnical categoriesare defined. Eurocode 7 further states that ground
investigations should be planned to take into account the construction and
performance requirementsof the proposed structure. However, designenmust
be aware that complex ground conditions associated with relatively simple
structures may still lead to construction or performance inadequacies, and so a
flexible approach is necessary in all situations.
Comment
National guidelineson the extent,intendyand quality ofground investigationsshould
be produced for theben+ of clients, plannersand engineers. These guidelines should
follow the philosophyof Eurocode 7 on geotechnical categories.
Thepracticeof havingonlyonepersonororganization co-ordinatingall thedecisions
with respect toground investigationonanyoneproject is recommended (seealsosection
4.5).The decisions shouldbe relatedto theproject design, and takeaccount of construction methods where theseare known.
14
Valuable information can be obtained from desk studies at low cost, but
insufficient attention is given tothis preliminary phase of a routine site investigation. A guide to the information required in desk studies is provided in BS
593018and a list of sources is given by Dumbleton and West?' As an example,
the routine check-list recommended by the B E 3 for desk studies associated
with low-rise building is shown in Table 6.
Table 6. Desk study checklist for low-rise building3
Topography, vegetationand drainage
Does the site lie on sloping ground, and
if so what is the maximum slope angle ?
Are there springs, ponds or watercourses on or
near the site ?
Are there or were there trees or hedges in the area of proposed construction ?
Is there evidence of changes in ground level, e.g. by placement of fill or by the
demolition of old structures ?
Ground conditions
What geologicalstrata lie belowthe site and how thick are they ?
What problems areknown to be associatedwith this geological context?
Is the site covered by alluvium,glacial till(boulder clay) or any possible soft deposits?
Is there available information onthe strength and compressibility of the ground ?
Is the subsoil a shrinkable clay ?
Does experiencesuggest that groundwater in these soil conditions may attack concrete ?
Is there evidence of landslipping either on or adjacent to thesite or on similar ground
nearby ?
Is there, or has there ever been, mining or quarrying
activity in this area ?
Are there coal seams under the site ?
The proposed structure
What area will the buildingsoccupy ?
What foundation loadingis specified
How sensitive is the structure likely to be to differential foundation movements?
What soilsinformation is required for the design of every likely type of foundation ?
Is specialist geotechnical skillrequired ?
~
~
~~
~~
Comment
Invaluable informationcan often be obtainedfrom aninvestigation of geology, geomorphology, aerial photographs and archival research.
Theseshould be essentialsteps in any
deskstudy.
Additional ground types (e.g. limestones which are subject to dissolution, peat or
contaminated ground) could be included in the check-list to provide early warning of
potentially difficult ground conditions.
With reference detailed
to
ground investigation, monitoring of groundwater
is often totally inadequate and greater use of piezometers is recommended in
order to identify water levels and monitor their movements. Since there is a
general tendency to underestimate the importance of piezometric data in d e
sign, piezometers in sealed response zones should be installed as a matter of
course in most boreholes. An understanding of hydrogeology is also needed.
In thepast little attention has been paid on a routine basis to the chemical
compositionand physical microstructureof the ground. Problems canarise due
to inadequate consideration of mineralogy because the potential effects of
chemical and physical changes (e.g. moisture variations) may not be identified
by traditional laboratory tests. Examples of such ground problems include
softening of lime stabilization, expansion of bentonitic fractions of volcanic
rocks, alkali silica reactionsand different forms of sulphate attack.
Increased use of ground probing (e.g. piezoconesounding andgeophysical
techniques) should be encouraged to help with the interpolation of ground
strata between boreholes, and to try to locate anomalies.
15
Sampling and delineation of soft materials often require sophisticated methods, but a great deal of useful information could be gained by greater use of
simple hand tools such as probe penetrometers and vane testers.
Comment
Recent@ developed in situ testing techniques using self-boring pressuremeters and
dilafometers should be exploifed more in ground invesfigafionpractice. In order f o be
cost-effective, such testsshould be specified andsupervised by geotechnical specialists.
4.9. Execution
and supervision
Although no distinction is drawn inthe ICE forms of c ~ n t r a c ? ~ #in~the
~ oACE
r
Conditions of Engagement?' the type and degree of supervision required in
ground investigation is different from that required during a construction
project. Inthe latter case, it is generally sufficient for
supervision to detect any
defect in the finished work before itis covered up.
In ground investigation, supervision should ideally be continuous if inadequacy is to be detected. For example, a good quality standard penetration test
requires attention not only to the test equipment and method of test, but also to
the method of boring to reachthe test location,the position of the casing relative
to the bottom of the boring, and the water levels within the boring, beforeand
during the test. The end product is a number, the accuracy of which can be
known only if all thesematters have been observed,reported on and considered.
For supervision to be effective, the person towhom it is entrusted should
(a) be fullyaware of the aims of the investigation and the expected ground
conditions
(b)be experienced and competent in the field and laboratory techniques in
Use
(c)have delegated powers to alter the size and scope of the investigation as
it proceeds.'2
Comment
Supervision of ground investigation can becarried out only when the work is in
progress. In this way the detailed procedures can be monitored continuously and the
supervisor can amend, if necessary, the scope of the investigation as it proceeds. The
supervisor should have geotechnical expertise and experience, us well as practical
knowledge of different exploration techniques.
The trainingneeds of site investigationsuperoisors and the current training pm'sion by the investigation industry should beassessed by the Associationof Geotechnical
Specialists, the British Drilling Association or other appropriate bodies.
Efforts have been made to publicizeUK geotechnical expertise including the
personnel employed in ground investigation, e.g. ref. 32. Through the British
Drilling Association's accreditation scheme for
drillers and theNational Measurement Accreditation Service for laboratories,
the quality of personnel, equipment and procedures should improve.
One way to testthat procedures are adequate is
to subjectthem to a quality
assurance system. Quality assurance, as defined by BS 5750p3 is gradually
gaining acceptancein the UK constructionindustry and the Government, which
funds a substantial proportion of site investigation in the UK, is actively
promoting the use of Britishstandards andquality systems.
The quality assurance systemfor the site investigationmust includeeveryone
involved, fromdriller to client, and should be part of a quality assurance system
for the whole project, so that site investigation is not divorced from the design
and construction phases of the project.
Quality assurance has been an integral part of offshore site investigation for
many years and was greatly refined through experience in the North Sea.
A BSI quality assessment schedule relating to ground investigations and
foundations sets out common quality practices forthe site investigationindustry?3
16
Comment
Since all new constructionhas to consider ground conditions, for
the purposes of both
design and construction, it is likely that there are too few professional gwtechnical
engineers and engineering geologists working in the UK construction industy. To
assess the situation it would be useful if an organization such as the Associationof
GeotechnicalSpecialists could establish how manygeotechnical specialistsare currently
working and potentially available to theindusty, compared with market needs(e.g. the
number of projects startedeach year).
If a shortfall is confirmed more courseson site investigation technology shouldbe
introduced into undergraduate and continuing professional development programmes
for civil engineers, architects, builders and planners.
4.10.
Boreholes provide only a microview of the ground at their specific locations.
Interpretation Interpretation of the ground conditions between boreholes is a matter of judgeand utilisation ment by the engineer and/or geologist basedon his knowledge and experience.
of data
Ground investigation data should be interpreted by experienced people and
the results should be assessed during the period of the site work, thereby
enabling any necessary additional work to be carried out.
Adequate time needs to be given to tenderers for main works if they are to
assess thoroughly the data provided.
A large amount of factual data can begenerated by aground investigation,
which a tenderer has to assimilatedurirlg the tender period. The time-scalemay
show that the tenderer does not have adequate resources to assess thoroughly
all the data.
There is evidence of inadequate communication of ground datato the contractor which has led to incorrectassumptions by the contractor as to the best
methods for carrying out the ground andfoundation work.
With the implementation of Eurocode 7, the geotechnical engineer may in
future be required to produce a geotechnical report which will vary greatly
depending onthe type of design. For simple designs, a single sheet may suffice.
The report will normally include
(a)a description of the site, its past history, usage and surroundings
(b) a description of the ground conditions
(c)a description of the proposed construction, including actions
( d ) design valuesof soil androck properties, including justification
(e)statements on safety requirements
(p list of items to be checked during constructionor requiring maintenance.
Comment
Although a controversial proposal,it is the view of the Ground Board that all factual
geotechnical data, and wheneuer available a separate interpretative report relevant to
the project, should be made available to all tenderers whoplace relianceon ground data.
This would give tenderers theopportunity toform apictureof thesiteconditions without
having to wade throughjust thefactual data.
Such an interpretativereport, prepared by a geotechnical engineer, should
describe
only theground conditions and the groundwater regime,and give a summa y of the
enginem’ngproperties relatingto thernaterialspresent. Theinterpretativereportshould
notincludedesignrecommendationsconcemingparameterssuchasearthpressuresand
bearing capacities rehted to earthworks, foundationsand retaining walls.
A nationally accepted methodof digitizing factual ground data
on to floppy disks for
computer processing and transfer from one organization to another would facilitate
assessment by geotechnical specialists both for the designerof the worksand tenderers.
I t would enable easy and rapid datasearching and subsequent plottingof ground strata
and laboratory test results. As an example, the computer could be instructed via a
processingprogram tosearch thedatabaseforandplot undrainedshearstrengthagainst
depth for a particular stratum.
17
Given considerations of copyright the transfer of such information should be made
only tothose organizations involved in the project. Other groups might negotiate with
the owner for the factual resultsof an investigation.
5. Contractual claims related to unforeseen
ground conditions
When unforeseenground conditionsoccur during construction, they may result
in a change in the permanent works, the temporary works or the method of
construction.
If the permanent works are affected, the engineer will be obliged toissue a
variation to the contract and award anextension of time if the contract is likely
to be delayed beyond the contract completion date. Some risk of unforeseen
ground conditions is therefore borne by the client.
If the contractor’s temporary works or methods of construction are affected,
the contractor may have to makea claim for additional money and extension of
time. The claim will
usually be decided on in relation tothe ground conditions
23,
that could reasonably have been foreseenby an experienced contractor (ref.
5th edn, clause 12).
Clause 11 of the ICE Conditions of Contract, 5th
states that the
contractor,before submitting his tender, must satisfy himselfas to the nature of
the ground so far as is practicable. In realityit is not normally practicable for
contractors to carry out their own pre-contractground investigationswithin the
time-scale of the tender period. They invariably have to rely on the ground
investigation data supplied to them at the time of tender. Some riskof unforeseen ground conditions is therefore borne by the contractor.
Any delay due to unforeseen ground conditions may lead to the disruption
of other construction activities and delay the whole of the works. An example
would be where an excavation is delayed by unforeseen groundwater. The
contractor has to install a dewatering system and this delays the completion of
the excavation. However,
this delay pushes concreting work into winter months
and this work is further delayed because of cold weather. While the excavation
is delayed the contractor has to do other work out of sequence. The consequential cost of the overall delay and disruption can far exceed the direct cost
associated with dealing with the unforeseen conditions.
It maynot be possible toevaluate fully the realized financial risk associated
with unforeseen ground conditionsuntil after constructionhas been completed.
The resultant delays often lead to contractual disputes.
Comment
The largest element of technical and financial risk is normally in theground.
As the risk of unforeseen ground conditions is borne by the client and the contractor,
it is obviously to the benefit of both parties that they understand the extent and
consequences of the risks they accept.
Better siteand ground information, included in the contract,is an important part of
a better quality of service to the client. The engineer and the ground investigation
contractor should be encouraged to provide more skill in pursuit of the best product.
The client should be apprised by the engineer of thefinancial risks at all stages,from
project conception to completion. Otherwise, an uninformed client is unlikely to be
sympathetic to a speedy resolution of a realized risk for which he has to pay.
As claims for unforeseen ground conditionsform the largest proportion of contractual
claims, geotechnical specialists should be more closely involved in the supervision of
construction. It is essential that geotechnical specialists are involved at the earliest
opportunity wheregroundproblems and potential claims are envisaged to ensure that
(a) apprupriate remedial measures or design changes are carried out
(b) accurate records are obtained of the ground actually encountered
(c) anysupplementary investigation thatmay mitigate the problems is implemented.
It would be useful if completed projects, both successful and those which have
incurred significant claims related to unforeseen site conditions, could be analysed to
ascertain their technical and contractual elements. The technical problems could be
categorized to establish particular areas of site investigationdeficiency,and study of the
contractual aspects might highlight the conditions and procedures which are unhelpful
to successful construction.
6. Conclusions
Clients are concerned about the delays and escalating costs of construction
projects throughout the UK. Based on a review of technical reports on
practice over the past 25 years, the delays are frequently attributed to inadequate site and groundinvestigations.
It is not clear whichfactors of the construction process contribute to inadequate site investigation. One has to consider not only the purely technical
aspects of planning, execution and reporting, but also the contractual environment between all parties - the client, site investigation specialist, d e
signer and main contractor.
Most major construction activities involving the ground lie on or are sufficiently close to the critical path for any delay to that activity to affect the
whole of the project.
The consequences of inadequate investigations are shown to be severe for
both the engineering and construction phases of a project but are probably
even more serious when continued into full-life costing.
Inadequate site investigations can arise from a lack of client awareness,
inadequate finance, insufficient time
and a lack of geotechnical expertise.
Positive action has to be taken now by the construction industry and its
clients to improve this intolerable situation.
Siteand groundinvestigationsand their planning, design and appraisal must
be fully integrated into the project design and construction process.
Experienced geotechnical engineers and/or engineering geologists should
be responsible for siteand ground investigations.Where this expertise is not
held within the project design group, geotechnical specialists should be
added to the team.
Of the technical shortcomings in the design of ground investigations a
recurring theme is the inadequate attention given to obtaining reliable piezometric level data in order to gauge groundwater levels and their movements with time, coupled with inadequate interpretation of the data resulting
from a limited understanding of hydrogeology.
7. Recommendations
The ICE should establish a broadly based steering group to carry out the
following tasks. Its membership should comprise representatives from organizations such as the ICE, the Institution of Structural Engineers, the Royal
Institute of British Architects,the Departments of Transport and the Environment, the British Geotechnical Society,
the Association of Geotechnical Specialists, the BritishDrillingAssociation,
the GeologicalSociety, the British
Tunnelling Society, the Building Engineering Confederation, the National
House-Building Council, the Association of Consulting Engineers and the
Federation of Civil EngineeringContractors.
0
A programme of awareness should be implemented with other professions
(clients, planners, architects, engineers, builders and quantity surveyors)
and organizations such as insurance and property development companies,
19
with the aim of highlighting the significanceof site and ground investigation
on civil engineering and building projects.
The awareness programme could include
(a) stage 1
(i) publication of this ICE Ground Board report and press releases, and
associated meetings
(ii) circulation of findings, recommendations and available guidelines to
all organizations involved in education and training courses related to the
construction industry
( b ) stage 2
(iii) publication of a series of national site investigation guides over the
next two years covering the topics of procurement, planning and design,
quality assurance, specificationand methods of measurement
(iv) a publicity campaign for (iii), coupled with a conferenceon site and
ground investigations.
A national specification and method of measurement for site and ground
.investigationsshould be created, based on the current ICE specification?’
but augmented to accommodate the philosophy of Eurocode 7 and new
topics such as contaminated land. This single reference should provide a
uniform standard for improved site investigation practice and its supervision.
Clients should be advised by their professional consultants of the need for
careful preselection of tenderers and rigorous acceptance criteriawhen seeking ground investigation services. To support this approach, a national
procurement guide should be produced for clients,
highlighting the essential
aims and benefits of site investigation, and how these can be achieved by
following appropriate procurement routes.
To assist the preliminary planning of site and ground investigations, the
value of desk studies should be highlighted and more detailed guidelines
should be published on the extent and intensity of investigationsrelated to
type and uniformity of the ground and the size and type of development.
These national guidelines (including check-lists where appropriate) should
be written in a formthat enables developers and planners to appreciate the
basic requirements of adequate site investigations.
Quality management systems (quality assurance) (e.g. BS 575d3) should be
developed for site and ground investigations whereby auditing and assessment concentrate on demonstrating that a reliablemanagement system is in
operation and that responsibility canbe traced throughout.
All factual geotechnical data, and whenever available a separate relevant
interpretative report, should be made available to all tenderers who place
reliance on ground data.
Risk analysis,as a management tool, should be considered byengineers to
demonstrate in financial terms the benefits of comprehensive ground investigations.
A reviewof completed contracts, both successful and unsuccessful, should
be undertaken by the ICE or others to study the nature of claims related to
ground conditions. A key objectiveis to determine the extent of these claims
and delays which are caused byinadequate site investigationsand conditions
of contract.A thorough assessmentof theeffectsof thecontractual environment
between the client, site investigation specialist, designer and main contractor
should be made.
Factual ground investigation data should be digitized by geotechnical specialists to nationally
a
accepted standard for ease of processing and transfer by
computer. This should reduce significantly the time required to sortand assess
the large amount of data generated by comprehensive ground investigations.
20
Quality assurance should be considered as a contractual requirement to
ensure that the client's specificationis met. The management system should
define who is qualified to take ground investigation decisionsand ensure that
that person is properly trained. The aimshould be to create chains of communication and working procedures for instruction which help to do routine things
well.
You pay for a site investigation
whether you have oneor not
21
References
1. NATIONALECONOMICDEVELOPMENTOFFICE.
Faster buildingfor
industry. NEDO, London, 1983.
2. NATIONALECONOMICDEVELOPMENTOFFICE. Faster building for
commerce. NEDO, London,1988.
3. BUILDING RESEARCH ESTABLISHMENT. Site investigationfor low-rise
building: desk studies. Bldg Res. Dig.,1987, No. 318.
4. JOHNSON R. Symposium report on quality management in geotechnical
engineering. Ground Engng, 1990,23, Oct., 23.
5. BUILDING RESEARCH ESTABLISHMENT. Site investigation for low-rise
building: procurement. Bldg Res. Dig.,1987, No. 322.
6. BRITISH STANDARDS INSTITUTION.Code of practice for foundations.BSI,
London, 1986, BS 8004.
7. NATIONAL AUDIT OFFICE.Qualify control of road and bridge construction.
HMSO, London, 1989.
8. TYRRELL A. P. et al. An investigation of the extra costs arising on highway
contracts. Transport and Road Research Laboratory,Crowthorne, 1983, SR
814.
9. THOMAS TELFORD.Investigation of value. New Civ. Engr,1987,5 Mar., 14.
10. EUROCODE 7 DRAFTING PANEL. Common unified rules for geotechnics,
design. British Standards Institution, London, 1989, Eurocode 7,lst draft.
11. ECONOMIC DEVELOPMENT COMMITTEE FOR CIVIL ENGINEERING.
Contracting in civil engineering since Banwell.
HMSO, London, 1968.
12. UFF J. F. and CLAYTONC.R. I. Recommendationsfor the procurement ofground
investigation. ConstructionIndustry Research and Information Association,
London, 1986, SP 45.
13. PEACOCK W. S. and WHYTE I. L. Site investigation practice. Mun. Engr,
1988, S, Oct., 235-245.
14. ROWE P. W. The relevance of soil fabric to site investigation practice.
Ghtechnique, 1972,12, June, 193-301.
15. GREEN P.A. Ground and materials investigations for road schemes, needs
and methods. Proc. Instn Civ.Engrs, 1968,41,635-638.
16. MATHESON G. D.and KEIR W. G. Site investigationin Scotland. Transport
and Road Research Laboratory,Crowthorne, 1978, LR 82.
17. GROUND ENGINEERING. The investigation business - a matter for
concern. Ground Engng, 1974, May, 26-34.
18. BRITISH STANDARDS INSTITUTION.
Code of practicefor site investigations.
BSI, London, 1981, BS 5930.
19. DEPARTMENT OF TRANSPORT.
Specification and methodof meusurmentfor
ground investigation.HMSO, London, 1987.
20. BRITISH STANDARDS INSTITUTION.Code of practice for the identification
of potentially contaminated land and its investigation.BSI, London, 1988, DD
175.
21. EUROPEAN COMMUNITY.Framework directiveon civil liubilify fordamage
caused by waste. EC, Brussels, l989,75442/EEC.
22. RYS L. G. and WOOD I. R. A question of priority - product before
procurement in site investigation practice: assessing
BS 5930. Site investigation practice, edited by A. B. Hawkins. Geological Society, London, 1986,
Engineering GeologySP 2,349-355.
23. INSTITUTION OF CIVIL ENGINEERSet al. Conditionsof contract and forms
of fender, agreemenf and
bond for use in connection with works of civil engineering
construction. ICE et al., London, 5th edn, 1973; 6th edn, 1991.
24. INSTITUTION OF CIVIL ENGINEERS. Conditions of contract for ground
investigation. Thomas Telford, London,1983.
22
25. BARNES N. M. L. and PERRY J. G. A naosfylecontractforengineeringprojects.
Institution of Civil Engineers, London,1987.
26. ASSOCIATION OF GROUND INVESTIGATION SPECIALISTS. Specification for groundinvestigations. Ground Engng, 1979,12, No. 5,56-67.
27. INSTITUTION OF CIVIL ENGINEERS.Specificationfor ground investigufion
with bill of quantities. Thomas Telford, London,1989.
28. BRITISH STANDARDS INSTITUTION.
Methods of test for soil for civil enginem'ngput.poses. BSI, London, 1975, BS 1377.
29. ASSOCIATION OFGEOTECHNICAL SPECIALISTS.
A nationalspecification
for ground investigation.AGS, London, 1990, Working Party Report 1.
30. DUMBLETON M. G. and WEST G. Preliminary sourcesof information for site
investigations in Britain. Transport and Road Research Laboratory, Crowthorne, 1976, LR 403.
31. ASSOCIATION OFCONSULTING ENGINEERS.
ACE ConditionsofEngugement. ACE, London, 1981.
32. BRITISH GEOTECHNICAL SOCIETY.
Geotechnicul directoryof the W K 298788. Institution of Civil Engineers, London,1988.
33. BRITISH STANDARDS INSTITUTION.
Quality systems. BSI, London, 1987,
BS 5750. (See also Qualify assessment schedule, BS 5750, Part 1: Ground
investigation and foundations.)
23
Appendix 1. Guidelines on ground investigation
practice
Since 1975 various steps have been taken to improve the extent and quality of
ground investigations. Publications or accreditation schemes include the following.
By the BRITISH STANDARDS INSTITUTION.Site investigations. BSI, London, 1981,
BS 5930.
construction
industry asa BRITISH STANDARDS INSTITUTION. Code of practice for the identification of
whole
potentially contaminatedland andits investigation.BSI, London, 1988, DD 175.
BRITISH STANDARDS INSTITUTION.
Methods of test forsoilfor civil engineering
purposes. BSI, London, 1990, BS 1377.
UFF J. F. and CLAYTON C.R. I. Recommendations for the procurementofground
investigation, Construction Industry Research and Information Association,
London, 1986, SP 45.
WELTMAN A. J. and HEAD J. M. Site investigation manual.
ConstructionIndustry Research and Information Association, London,1983, SP 25.
for ground investiBy the INSTITUTIONOF CIVIL ENGINEERS.Conditions of contract
gation. Thomas Telford, London,1983.
Institution of
Civil Engineers INSTITUTION OF CIVIL ENGINEERS.Specificationfor ground investigation
with
bill ofquantities. Thomas Telford, London,1989.
ROBB A. D.Site investigation.Thomas Telford, London,1982.
Also, a wide range of conference proceedings on in situ testing and field
instrumentation.
By the
Government
BUILDING RESEARCH ESTABLISHMENT. A review of routine foundation
design practice. Bldg Res. Dig., 1987, No. 104.
BUILDINGRESEARCHESTABLISHMENT.Site
investigation for low-rise
building: desk studies. Bldg Res. Dig., 1987, No. 318.
BUILDINGRESEARCHESTABLISHMENT.Site
investigation for low-rise
building: procurement. Bldg Res. Dig.,1987, No. 322.
BUILDINGRESEARCHESTABLISHMENT.Site
investigation for low-rise
building: the walk-over survey. Bldg Res. Dig., 1989, No. 348.
DEPARTMENT OF TRANSPORT. Specification and method of measurement for
ground investigation.DTp, London, 1987.
By the BRITISH DRILLING ASSOCIATION. Directory of UK facilities. BDA,Brentwood, 1990.
investigation
industry BRITISH DRILLING ASSOCIATION.Accreditation scheme for drillers.
NATIONALMEASUREMENTACCREDITATIONSERVICE.
Accreditation
scheme for testinglaboratories.
ASSOCIATION OF GROUND INVESTIGATION SPECIALISTS.Specification
for ground investigations.AGIS, Hayes, 1979. (AGIS is no longer active.)
Other efforts BRITISH GEOTECHNICAL SOCIETY.Directory ofgeotechnicalspecialists. BGS,
London, 1988.
CLAYTON C.R. I. et al. Site investigation - a handbook for engineers. Granada,
London, 1982.
HEAD K. H. Manual of soil laboratory testing. Pentech, Plymouth and London,
1986.
NIXON I. K. and CHILD G. H. Site investigation. Civil engineer's reference book,
4th edn, chap. 10. Newnes-Butterworth, London,1989.
Also various conferenceproceedings of the British Geotechnical Society
and the
Engineering Group of the Geological Society.
24
Comment
Specifications and method statementsrelated to the technical issuesof ground investigations are well documented. Less apparent are specific guidelines on the extentand
intensity of investigations related to typeand uniformity of ground and type and size
of structure.
No hard and fast rules exist for the determination of location and frequency of
boreholes. Eachsite should be individually assessed, togetherwith the proposed development.1935
Nevertheless thereis a case for providing more
detailed guidelines to assist planners
and designers of ground investigations,and to highlight thebasic investigation requirements for thebenefit of clients. Theseguidelinesare m substitute forthe employment
of experienced geotechnicalspecialists.
Theaccreditation of drillers or testing laboratories will not eliminatethe need for site
supervision of ground investigationsby geotechnical specialists. The trainingneeds of
site supervisors shouldbe assessedtogether with their necessay provision.
Appendix 2. Criteria for the preselectionof specialist
12
contractors
The followingcriteria should be taken into account in the selection of specialist
contractors for inclusion in a finaltender list
(a) numbers, types and quality of
(i) field equipment
(ii) laboratory equipment and facilities
(b) availability of any special equipment expected to be relevant to the
particular investigation
(c)Numbers, experience, qualificationsand length of service of
(i) professional staff
(ii) drilling personnel and supervisors
(iii) laboratory and field technicians
( d ) whether or not equipment and personnel are permanently retained and,
if they are not, theirstatus and availability
(e)previous performance on
(i) routine investigation work
(ii) projects comparable with that under consideration
(f,the quality of geotechnical reports on other projects
CS> status, ownership and apparent financial standing of the company or
firm.
Proper consideration of these matters requires at least one visit to the company’s premises, and is likely also to involve meeting key personnel and visits
to sites, the plant depot, and the laboratory.
Comment
A pre-tender standard questionnaire could be used, to be completed in part by the
potential tendererand part by the designer.
Care is required to ensure that thepre-selected specialist contractor does not subcontract important elementsof the work to inexperiencedfirms or personnel.
25
Appendix 3. Members of the Ground Board,
Institution of Civil Engineers
*ProfessorG. S. Littlejohn, BSc, PhD, FICE, FIStructE, FGS
(Chairman),University of Bradford
*N. R. Arber, BEng, PhD, MICE,
Travers Morgan Consulting Group
P. A. A. Back, BSc,DPhil, FEng,MICE, Sir AlexanderGibb & Partners
H. M. Bedelian, OBE, MA, FIHT, FEng, FICE,
Balfour BeattyConstruction Ltd
I. F. Christie, BSc, PhD, FICE,Consultant
*C. Craig,MSc, FICE, FIStructE, Soil Mechanics Ltd
J. D. Findlay, MSc, MICE, FGS, Stent Foundations Ltd
*ProfessorM. C. Forde, BEng, MSc, PhD, MICE,
University of Edinburgh
University of Wales
Professor J. D. Geddes, BSc, PhD, FICE, FASCE, FIHT, FGS,
College of Cardiff
P. M. Guthrie, ACGI, BSc, MSc, DIC, FGS, MICE, Scott Wilson Kirkpatrick&
Partners
T. S. Ingold, MSc, PhD, FICE, FIHT, FASCE,Consultant
F.M. Jardine, MSc(Eng), Construction Industry Research and Information
Association
Professor C.J. F. P. Jones,BSc, MSc, PhD, FICE,University of Newcastle-uponTyne
J. A. Lord, MA, PhD, MICE,Ove Arup & Partners
Professor A. McGown, BSc, PhD, MICE, MIHT, FGS,University of Strathclyde
T. W. Mellors, BSc(Eng1, MSc, DIC, PhD, MICE, MIMM, FGS,Consultant
M. J. Sands, BSc, FICE, Hercules Piling Ltd
*Member of drafting and editing team.
26