Quarterly Journal of Engineering Geology and Hydrogeology-2010-Baynes-321-31

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Quarterly Journal of Engineering Geology and Hydrogeology

doi: 10.1144/1470-9236/08-0032010, v.43; p321-331.Quarterly Journal of Engineering Geology and Hydrogeology

F.J. BaynesSources of geotechnical risk

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Sources of geotechnical risk

F.J. BaynesBaynes Geologic Pty. Ltd., 9 Chester Street, Subiaco, WA 6008, Australia

(e-mail: [email protected])

Abstract: The geotechnical risks that can affect projects result from a range of hazards associated

with geological conditions and geological processes, but also from hazards associated with the

geo-engineering process. For example, active faults identified during pre-feasibility studies will pose

one type of hazard, whereas a management decision to limit the extent of a site investigation to save

money will pose another type of hazard. A systematic assessment of the nature and the source of the

various hazards may be used to differentiate the types of geotechnical risk. Examples from projects are

provided and some statistics are presented, to indicate the rates of occurrence of the various types of

geotechnical risks in projects. Some established approaches to managing geotechnical risks in projects

are noted.

Effective management of geotechnical risks is supremely

important in many projects. In an authoritative publica-

tion, geotechnical risk has been described as the risk tobuilding and construction work created by the site

ground conditions (Clayton 2001). At first reading, this

might suggest that the ground conditions are the only

source of geotechnical risk. However, the publication

went on to describe how geotechnical risk is created by

both the ground conditions and the geo-engineering

process. This is an important distinction, because the

management of geotechnical risks created by the site

ground conditions (essentially the geological conditions)

may require a very different approach compared with the

management of geotechnical risks created by the geo-

engineering process (essentially a human endeavour).

The terms geotechnical risk and geotechnical hazard

are used in different ways by different researchers and it

is difficult to find an unequivocal definition. In this

paper the terms are used with the following meanings. A

geotechnical risk is something associated with the

ground that might happen and that would have adverse

consequences for the project. The something . . . that

might happen may also be called a geotechnical hazard.

The geotechnical risk may be measured as the product of

the likelihood of the geotechnical hazard occurring and

the consequences to the project. The sources of geotech-

nical risks are thus geotechnical hazards, in the broader

sense of the word. It should be noted that an identifiedgeotechnical risk, like all risks, is not an inherent prop-

erty of the ground or of an engineering process, rather it

represents a subjective belief of the probability of a

hazard with given consequences occurring, on the part

of those charged with assessing the risks (Harr 1987).

The premise of this paper is that to effectively manage

geotechnical risks, those involved in geo-engineering

must both appreciate the subtleties of the various types

of geotechnical risks and understand how, where and

why these types of geotechnical risks occur within

projects; that is, they must understand the sources of

geotechnical risks. This knowledge is particularlyimportant to practitioners of engineering geology, as

they are responsible for developing the geological model

(Fookes 1997) and they are increasingly charged with a

responsibility for using the geological model as a funda-mental tool to assist in geotechnical risk management

(Morgenstern 2000; Knill 2003).

Types of geotechnical risk

Various types of geotechnical risk have been described in

the prolific and ever-increasing literature on the subject.

The matter has been discussed for many years by many

experts and the intent of this paper is not to attempt to

review these studies but instead to provide a brief

glimpse of three of the more incisive contributions.

McMahon (1985) identified three main types of geo-technical uncertainty associated with geotechnical

design, which he described as the risk of encountering

an unknown geological condition, the risk of using the

wrong geotechnical design criteria, and the risk of bias

and/or variation in the design parameters being greater

than estimated. He also identified other uncertainties

that can affect projects, including human error, design

changes and over-conservatism.

Clayton (2001) noted that geotechnical risks have

three components or impacts, which he divided into

technical, contractual and project management. Techni-

cal risks arise from the particular problems on the site

such as soft ground or contaminated land, contract riskis associated with the type of contract that the developer

adopts, and project management risks are determined by

the way the project manager or his advisors elect to

manage the project.

Trenter (2003) also divided geotechnical risk into

three interrelated categories, which are equivalent to

Claytons three components:

(1) design risk (equivalent to Claytons technical risk),

which was further divided into three areas of

uncertainty (which are somewhat equivalent to

McMahons three main types of geotechnical

uncertainty): uncertainty associated with the geo-logical framework (taken to be equivalent to the

Quarterly Journal of Engineering Geology and Hydrogeology, 43, 321331 1470-9236/10 $15.00 2010 Geological Society of LondonDOI 10.1144/1470-9236/08-003

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geological model); the appropriateness of the engi-

neering analysis; the reliability and representabilityof the engineering properties used in design;

(2) the below-ground contract risk, because contracts

fundamentally involve transfer of risk.

(3) project management risk, because project managers

are ultimately responsible for the successful man-

agement of all of the geotechnical risks in a project.

The basic types of geotechnical risk outlined by these

researchers are clearly a well-accepted and useful frame-

work and have been adopted in this paper. This frame-

work is used to consider the relationships between the

various types of geotechnical risk and the most likely

sources of these types of geotechnical risk. By under-standing the sources of geotechnical risks it is possible to

appreciate the reasons why these geotechnical risks arise.

Discussion of types of geotechnicalrisk

A suggested schematic relationship between the basic

types of geotechnical risk that form the accepted frame-

work identified in the literature is portrayed in Figure 1,

which could be thought of as a project organizational

structure that indicates responsibility for the manage-

ment of the various types of geotechnical risk.In Figure 1 specific geotechnical risks form one

obvious category of project risks and may be divided

into technical and contractual. The term technical is

preferred to design because some of the geotechnical

risks in this category are associated with activities other

than design. Technical risks can be subdivided into those

associated with the geological model, those associated

with the engineering analysis and those associated with

the engineering properties used in the analysis. Each of

these subcategories could be the responsibility of some-

one within an organization. There are usually many

other project risks and line management usually carriesthe responsibility for them. However, some types of

more general geotechnical risks that relate to overall

project implementation are the sole responsibility of

project management, and have been indicated as such in

Figure 1. The types of geotechnical risk portrayed in

Figure 1 and the geotechnical hazards that are the

sources of the risks are discussed in more detail below.

Project management

Identifying and managing geotechnical risks, in a general-

ized way, is a fundamental project management activity in

any project with a geo-engineering content. Project staff

are responsible during both the pre-project planning phase

and the main works construction stage for managing

specific types of geotechnical risks, but also for managing

the broader aspects of the project that can incur or

mitigate geotechnical risk (e.g. overall project planning,

construction planning, the choice of project procurement

model, information acquisition for decision making, the

preparation of a risk register and the responses to any

risks that happen). Potent geotechnical risks often develop

at a very early stage if appropriate project-wide geotech-

nical risk mitigation measures are not implemented.

When these risks develop it is usually because high-level

decisions have been made by people who are over-

worked and under-resourced and/or who do not appre-

ciate the importance of geotechnical risks, through a

lack of experience, education or training; those people,

unwittingly, become the source of the geotechnical risk.

Contractual

Geotechnical risks are associated with contracts that

relate to the ground conditions. Contracts involve the

transfer of risk and, in many projects, geotechnical risks

are transferred against some form of site investigation

report on the basis of the information presented therein.

Thus the quality of the site investigation report, and how

it is communicated, plays a pivotal role in the way

contractual geotechnical risks can develop in projects,

particularly in respect of claims based on unforeseen

ground conditions. Contracts usually refer to designs,

quantities and specifications, and can also include

measures to allocate risk and resolve disputes, so the

quality of these aspects of the geo-engineering, and howthey are communicated, is often equally important. The

contract will also reflect the risk allocation model for

project procurement that has been chosen by project

management (Eddlestonet al. 1995) (e.g. lump sum, bill

of quantities, cost plus, etc.). When the contract and

accompanying documentation is inadequate, the source

of the risk must be the project staff responsible for

managing the procurement and production of the docu-

mentation. The reason that this occurs is usually an

inadequate understanding of the importance of the

geo-engineering aspects of the contract on the part of the

project staff, or a limitation placed on those staffby ahigher-level project management decision.

Fig 1. The relationship between the types of geotechnical riskidentified in the literature.

F.J. BAYNES322



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Analytical

The engineering analysis that is adopted may not reflect

the actual failure mechanisms that occur or may be

based on unreasonable assumptions about the system

being analysed. If the engineering analysis is not appro-

priate, then the source of this risk is usually the projectstaff, who are responsible for electing to use the par-

ticular analytical method. It may be that they have

an inadequate understanding of what would constitute

an appropriate engineering analysis for the particu-

lar project and ground conditions. Of course, it is

also possible that the project staff are acting under

instructions from project management.

Properties

The engineering properties used in design may not be

reliable and may not be representative. For example,

they may be chosen from test results which may beaffected by sample disturbance, a limited sampling pro-

gramme, sampling or testing bias, etc. If the engineering

properties chosen for use in design are not reliable or not

representative, then the source of this risk is usually the

project staff, who are responsible for the choice, and

who probably have an inadequate understanding of

what would constitute reliable or representative engi-

neering properties for the particular analytical approach

and ground conditions. Again, it is also possible that the

project staffare acting under instructions from project

management.

Geological

Geotechnical risks associated with the geological and

geomorphological conditions are somewhat different

from those associated with the geo-engineering process,

as the latter is essentially a human endeavour. Uncer-

tainty is part of geological knowledge and is best con-

sidered relative to the concept of the geological model

(Fookes 1997; Fookes et al. 2000; Knill 2003). It is

suggested that within any geological model three sources

of uncertainty can be identified. These create different

types of geotechnical hazard that could lead to adverse

project consequences and hence are the source of differ-ent types of geotechnical risk. The three sources of

geotechnical risk are as follows.

(1) Variability in the 3D distribution of geological

units and variability in the geological characteris-

tics of each of the units, which could be caused by

facies changes, unconformities, folds and faults,

weathering profiles, soil fabric, rock structure, the

groundwater regime, etc. The potential geotechni-

cal hazard to the project results from shortcomings

in knowledge of what each and every part of the

ground consists of; boreholes, test pits, mapping,

etc. can only ever acquire information about a verysmall proportion of the total volume of ground

being investigated. The hazard results from the

presence of geological detail that is unforeseeable

within the practical limits of an investigation, and

differences between the scale of the project, the

scale of the investigation and the scale of the

geological features will have a profound influence

on the extent to which this source of risk is allowed

to develop.

(2) The occurrence of actual hazardous geological

conditions or processes within the ground. There

may be uncertainty about the spatial distribution

of some hazards; for example, a seam of asbesti-

form mineral may be known to exist on a site and

to be a significant health hazard if it is comminuted

and the dust inhaled, but the exact location of that

seam may not be known. Alternatively, there may

be uncertainty about the temporal occurrence of

some hazards; for example, a landslide may be

known to exist at a certain location or an activefault might have been identified but the precise

timing of the next movement of the landslide or the

fault will not be known. Of course, there can be

both spatial and temporal uncertainty with some

hazards.

(3) When there is an absence of knowledge of what

might be in the ground in which the project is

being built (and this happens regularly on major

projects around the world), a hazard to the project

is created because of the possibility of encounter-

ing an unforeseen ground condition that might

adversely aff

ect the project.

Unforeseen versus unforeseeable

An important distinction exists between unforeseen

conditions and unforeseeable ground conditions.

Fookes (1997) and Fookes et al. (2000) have argued as

follows.

(1) There is very little geology or geomorphology that

will be unforeseen on a site if the investigation is

carried out properly. This means that if a project is

managed in a way that implements all of the

established techniques developed to mitigate geo-

technical risk, and the work that is carried out is ofhigh quality, then the probability of an unforeseen

condition being encountered during construction

should be reduced to negligible proportions.

(2) Nevertheless, there are some geological conditions

that are unforeseeable, and when those con-

ditions are encountered (they will have been antici-

pated) there will inevitably be some undetectable

variations in the geology that can never be com-

pletely investigated within practical limits; for

example, cavernous ground as a result of karst

may be recognized but it may be impractical to

attempt to investigate the details of every singlecavity; the details are unforeseeable.

SOURCES OF GEOTECHNICAL RISK 323



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Types of unforeseen ground conditions

The concept of unforeseen ground conditions is associ-

ated with two types of geotechnical risk, as follows.

(1) Technical risk. A truly technically unforeseen

ground condition would be a ground condition

encountered during construction that was not rec-ognized or anticipated at all during site investi-

gation. An example might be if the presence of

faulting was not anticipated and then an adversely

oriented fault that was not identified during the

site investigation was unexpectedly encountered in

an excavation and caused instability, which in turn

gave rise to cost and time over-runs. It should be

noted that this is not the same as an unforeseeable

condition, where the condition is anticipated but

the detail can never be investigated.

(2) Contractual risk. Unforeseen ground conditions

can be those ground conditions that one party to a

contractual dispute claim to have encountered

when contractual geotechnical risks happen; for

example, an adversely oriented fault may be

encountered in an excavation and lead to instabil-

ity, which in turn gives rise to cost and time

over-runs, which are then the subject of a contrac-

tual dispute. Typically in such a dispute one party

will argue that the instability was caused by a

ground condition that could not have been fore-

seen and the other party will argue that it could

have been foreseen. It would be naive to think that

such disputes are settled solely on the basis of

scientific facts, as a range of commercial, legal andpersonal factors will come into play. Thus, where

unforeseen ground conditions are claimed within a

contractual setting, they should be thought of as a

special case of unforeseen ground conditions that

may or may not have a basis in scientific facts.

They can be distinguished by referring to them as

contractually unforeseen ground conditions and

represent a link between technical geotechnical

risks and contractual geotechnical risks.

Sources of geotechnical riskLike all risks, the various types of geotechnical risks are

the product of hazard and consequence. The consequences

to projects are similar for each type of geotechnical risk

and consist of significant cost or time over-runs and/or

physical failure of the facility. The hazards are any con-

dition or process that is associated with the geology and

geomorphology that may have adverse consequences for

the project, and are different for each type of geotechnical

risk. Each hazard has a primary source, which may relate

to the geological conditions and geological processes, or

to various aspects of the geo-engineering process.

The types of geotechnical risks that have been dis-cussed above, the hazards that they are associated with,

and the primary source of these hazards, are summa-

rized in Table 1. It should be noted that because the

various risks are interrelated, the sources are also inter-

related. Table 1 suggests that within the three types of

geotechnical risk identified by Clayton (2001) and

Trenter (2003) there are only two ultimate sources of

geotechnical risk, as follows.

(1) Project staff responsible for the geo-engineering

process who have an inadequate understanding of

the ground conditions and/or who do not appreci-

ate the importance of ground conditions. Often

this deficit of knowledge is compounded by that of

high-level decision makers: politicians, financiers

and promoters who determine funding and timing

and who probably have never even heard of geo-

technical risk.

(2) Geological conditions or geological processes

that are difficult to investigate or inherently

hazardous.

Examples of geotechnical risks inprojects

Examples are presented below of projects from the last

two decades that the author has been involved in and

that have been affected by many of the types of geotech-

nical risks that are identified in Table 1. The authors

role varied from project to project and the examples are

presented anonymously, and have been modified to

make them difficult to identify, for reasons that are fairly

obvious.

Project management

A major industrial facility was being designed and built

by a contractor. The site had been investigated by over

300 boreholes but the work had been carried out with a

tick the box when the geotechnical work is done

mentality; there was no geological map or sections, no

understanding of the geology, no awareness of the active

geological processes and no appreciation of the geotech-

nical risks that the project faced. Consequently, despite

the huge amounts of information available, the follow-

ing problems developed during construction.(1) Granular construction materials that could have

been used in wet weather were neither identified

nor preserved, and consequently construction

ground to a halt during the rainy season as the

haul roads had no pavement; construction plan-

ning did not take into account the ground con-

ditions.

(2) Although noted in early investigations, the pres-

ence of acid sulphate generating soils was not

anticipated during design and late-stage changes

had to be made, including protecting footings and

treating runoff; an unreasonable analytical modelwas chosen for footing design.

F.J. BAYNES324



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(3) Landslides were present in many parts of the site,

reducing soil strengths to residual values and lead-

ing to unstable cuts and fills; optimistic strength

values were initially chosen for slope design.

(4) Faulting affected parts of the site, resulting in deep

weathering and low strengths requiring over-

excavation and replacement of foundation soils;

optimistic strength values were initially chosen for

foundation design.

(5) Coastal erosion occurring at rates that would

affect facilities within their design life required

changes to the design of port facilities; inherently

hazardous ground conditions existed and were notrecognized.

All of these problems affected the construction pro-

gramme, leading to significant cost and time over-runs,

although the facility was eventually successfully con-

structed. Many specific geotechnical risks were encoun-

tered on this project, but the fundamental source of the

risk was poor project management: the significance of

the specific geotechnical risks was not appreciated until

too late.

Contractual

A contractor tendered for work that involved road cuts,a tunnel and embankment construction using clean,

strong, durable angular rockfill won from the excava-

tion. The total amount of rockfill available from exca-

vation was enough to build the embankments but

because of the complex sequencing of the construction

and restricted access, the rockfill required double han-

dling and longer than anticipated haul distances, and a

claim resulted. Upon independent review of the tender

documents, the following conclusion was drawn. The

limited availability of rockfill from excavations could

have been anticipated from consideration of the docu-

mentation, site inspection and the viewing of the cores.

However, the precise extent to which rockfill availability

would be limited was difficult to evaluate as thedocumentation did not include geological sections or

maps relating the proposed structure to the observed

and interpreted geology on a chainage basis. The

as-encountered limitations on the availability of rockfill

could have been anticipated only with great difficulty by

the contractor during the tender period. The claim was

partially successful and the contractor obtained some

financial relief.

This is an example of contractual geotechnical risk

caused by a well-planned and well-executed site investi-

gation that was poorly documented and poorly pre-

sented, and this deficiency led to difficulties in thecommunication of the ground conditions. It also

Table 1. Sources of geotechnical risk

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reflected poor project management, as the documenta-

tion could have been better prepared if the project

manager had appreciated the importance of getting it

right and had allocated sufficient resources to the task.

Analytical

A tunnel was to be built by a design and construct

contractor that involved excavation through rock

beneath a palaeochannel containing permeable gravels.

During bid preparation, the tunnel was designed to be

drained; that is, flow of water into the tunnel was

considered to be of no great consequence. However, softcompressible sediments occurred in the palaeochannel

overlying the permeable gravels downstream of the

tunnel (Fig. 2), and to prevent settlement damage occur-

ring during construction the tunnel lining had to be

redesigned to be less permeable and the dewatering

effects of the tunnel had to be compensated for by

injection wells, and large delays and costs were incurred.

In this case an unreasonable engineering analysis was

initially adopted that did not allow for the potential

settlement problems associated with the geological con-

ditions along the palaeochannel. The other type of

geotechnical risk that occurred was associated with

project management: the significance of the geotechnical

risk to the project was not recognized and was not

allowed for in the bid, and consequently the construction

cost was underestimated. The matter ended in litigation.

Properties

A road involving a large amount of earthworks was

being designed and built by a contractor. Very stiff,

low-plasticity clays and silts had been identified and

characterized by laboratory testing along the route, and

earthworks with cut batters at 2h:1v were designed,

based on average measured properties. When construc-tion started it was realized that the clays and silts were

deeply weathered, more plastic and had softened over

the top several metres, and that the lower shear strengths

exhibited by only a small proportion of the tested

samples would have to be adopted for cut batter design.

The cut batters were flattened to 4h:1v, resulting in a

larger volume of excavation, increased spoil requiring

disposal and increased construction time.

Prior to construction all of the information was avail-

able to make the correct choice of parameters but the

significance of the range of measured strengths was not

appreciated and unreasonable design values were chosen.

The unreasonable design values were chosen because the

understanding of the ground conditions contained in the

simple geological model illustrated by Figure 3 was not

communicated amongst the project staff.

Unforeseeable geological details

A dam was being built by a government utility with

well-developed in-house design and construction capa-

bility. The dam was to be founded on karstic limestone

and extensive investigations were carried out in four

phases that involved regional mapping, aerial photo-

graph interpretation, detailed geological mapping, hun-

dreds of boreholes and test pits, seismic refraction

survey, an extensive laboratory testing programme,

grouting trials, and external review. The last phase of the

investigation was carried out after construction was

temporarily halted, to relocate the dam to a less hazard-

ous position.

Despite the amount of investigation, and the late-

stage relocation, the utility was of the view that thereremained too many unforeseeable details of the ground

conditions, and that this presented a significant geotech-

nical risk (Fig. 4). A very conservative belt and braces

design was adopted, the observational method was used

when construction recommenced, and an extensive pro-

gramme of monitoring and maintenance was put in

place and continues to this day. The dam functions

acceptably. However, there were significant cost and

time over-runs when compared with the original cost

estimate and schedule.

Other types of geotechnical risks also affected the

project. The dam was founded on an inherently hazard-ous geological condition consisting of karst limestone,

and project management risks occurred because design

and construction of the dam commenced before the

investigation had been completed and before the opti-

mum dam location had been identified.

Inherently hazardous geological conditions

A pipeline being built under a design and construct

contract was located within a route corridor determined

largely by the availability of land that could be pur-

chased. Route options past a village included some

poorly drained ground to the west and some gravel hillsforming a series of low linear escarpments to the east.

Fig. 2. Block model of geological conditions in thepalaeochannel.

F.J. BAYNES326



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After the pipeline corridor was fixed within the east-

ern option, a site investigation was carried out and

major active regional thrust faults were identified (Fig.

5). Five fault crossings had to be designed and built, and

this caused significant delays to construction.

This geotechnical risk was an inherently hazardousground condition that was ultimately catered for in

design. However, other types of geotechnical risks affected

this part of the project: the lack of timely site investigation

resulted from poor project management and led to an

unforeseen ground condition being encountered.

Unforeseen ground conditions

A hydroelectric project being built using a traditional

ownerengineercontractor approach was designed with

an unlined pressure tunnel that required sufficient in situ

stress to ensure high-pressure water containment(Fig. 6). It was assumed that the in situ stress at depth

would include both a gravity and a compressive tectonic

component. The site investigation included a range of

boreholes and pressure tests that suggested that the

tunnel configuration would achieve the design objective.

However, because of the depth of the tunnel and the

remote location, drilling did not extend down to the levelof the proposed downstream limit of the unlined tunnel

(the upstream limit of the steel liner). During construc-

tion, confirmatory testing in the vicinity of the power

station indicated that the in situstresses were a lot lower

than expected and the power station was moved several

hundred metres further into the hillside, where the

stresses were marginally higher. Even after the move, the

as-constructed tunnel configuration required further

remedial treatment to prevent leakage because the in situ

stresses clearly did not include a sufficient compressive

tectonic component.

This unforeseen ground condition resulted in signifi-cant delays and increased costs to the project. With

Fig. 3. A simple geological model illustrating the distribution of weathered and softened clays.

Fig. 4. Dam on karstic foundations resulting in unforeseeable geological details. MFL, . . .; NMOL, . . .




9/12

hindsight, the geological model for the area should

have placed greater emphasis on the regional faulting

pattern, which included normal faults, suggesting tensile

regional tectonic stresses. Other types of geotechnical

risks associated with project management affected the

project. The design of the underground works was based

on a poor understanding of the geological condition,

and recognition of the criticality of this aspect of thedesign and the significance of the risk at an early stage

might have alerted the project manager to the need to

carry out more thorough investigations, and create a

more flexible contract arrangement that allowed changes

to the power station location.

Rates of occurrence of geotechnicalrisk

It is instructive to consider the rates of occurrence of

geotechnical risks, but there is very little publishedinformation available, presumably because of a natural

disinclination to discuss failures. Projects involving a

significant proportion of geo-engineering can be divided

into those where there were no significant geotechnical

risks involved, those where significant geotechnical haz-

ards were present but where the risks were effectively

managed and consequences such as significant cost and

time over-runs and physical failures did not happen, and

those that were affected by significant cost and time

over-runs and/or physical failures.

Stapledon (1983) quoted studies by the International

Commission on Large Dams that indicated that 1% of

all major dams built between 1900 and 1965 failed

during operation. Stapledon also estimated, based on his

personal experience, that 20% of recently built dams had

significant cost and time over-runs during construction

(Stapledon 1983). Whitman (1984) indicated an annual

probability of failure of about 220% for mine pit

slopes and about 0.11% for foundations; presumably

this meant physical failure, as opposed to cost and timeover-runs. McMahon (1985) collected information on

130 major civil and mining projects developed between

1955 and 1985 in the Australasian region and concluded

that 36% of the projects were affected by significant

geotechnical problems and 5% were affected by failure

during operation. Hoek & Palmieri (1998) presented a

review of 64 thermal and 71 hydroelectric plants and

concluded that actual construction costs were, on aver-

age, 27% above estimated costs and schedules were 28%

longer than estimated. A large proportion, but not all of

these time and cost over-runs, were attributed to geo-

technical factors. Clayton (2001) presented a survey ofroad construction that suggested that of 49 road

projects, 55% had a greater than 20% cost over-run. This

author reviewed 70 geo-engineering projects that he

was involved in and concluded that 31% had involved

some form of significant time or cost over-run and that

about 1% had been affected by physical failure during

operation.

This information suggests that geotechnical risks

might occur at the following rates.

(1) Physical failures of geo-engineering projects might

occur in around 0.11% of civil projects and up to

20% of mining projects. Presumably this illustrates

a greater appetite for risk on the part of themanagers of mining projects.

(2) Significant cost and time over-runs might occur in

2050% of all projects.

There is even less information regarding the rates of

occurrence of specific types of geotechnical risk.

McMahon (1985) differentiated the 47 projects that

had been affected by significant geotechnical problems

into his three types of technical risk and another cat-

egory, which is taken to be akin to project management

risk. Stapledon (1983) described 13 failures of water-

works and Duncan (1988) described 13 personal lessons

in what not to do from the perspective of a designengineer. The information provided by Duncan (1988)

Fig. 5. Pipeline route options and fault trace.

F.J. BAYNES328



10/12

mainly concerned engineering design because he was a

geotechnical engineer. Fookes et al. (2000) described 31

case histories of geo-engineering failures that illustrated

how understanding the geological model could have

helped anticipate the cause of the failure. This author

reviewed 70 geo-engineering projects that he was

involved in and attempted to identify the specific type ofgeotechnical risks involved in the 22 that had had some

form of significant time or cost over-run or physical

failure. In the case of Fookes et al. (2000) and this

author, a large proportion of the projects that were

categorized involved inherently hazardous ground con-

ditions, because they are the source of many commis-

sions for consultant engineering geologists.

From this information an interpretation of the rates

of occurrence of the various types of geotechnical risk in

projects is provided in Table 2. The information in Table

2 does not provide a clear picture of the distribution of

the types of geotechnical risk but suggests that both the

ground conditions and the project staff responsible forthe geo-engineering process are a significant source of

geotechnical risk, and that the project staffmay actually

be the largest source. The reason why project staffare a

significant source of geotechnical risk has been explored

by Stapledon (1983), who identified 15 factors that

contributed to failures. Of the 15 factors, it is of interest

to note that most relate to people management such as

a lack of training or knowledge on the part of project

staff, poor project management, communication prob-

lems, not asking the right questions, excessive work

loads and poor quality work, and only a few relate to the

engineering design function. Sowers (1993) reviewedapproximately 500 geotechnical failures and concluded

that 88% reflected human shortcomings, and that this

was a factor that could be reduced by addressing people

management issues.

Management of geotechnical riskwithin projects

The implementation of projects can generally be divided

into the idealized stages illustrated in Figure 7. Depend-

ing upon the method of project procurement, differentparties may be responsible for different stages and the

stages might occur in a different order. For example, if

the project is being implemented through a traditional

ownerengineercontractor relationship, the responsi-

bilities for the stages will be different from if project

implementation is through a design and construct con-

tractor. Probably more importantly, in the case of a

design and construct tender, the contract stage and theall-important agreement of the price of the project often

occurs after only a preliminary investigation and hence

the bid price is fixed when only limited information is

available, a classic way in which a project management

decision can generate geotechnical risk.

The idealized project stages can usually be identified

even when different project procurement methods are

employed, and the literature on geotechnical risk clearly

describes the established techniques that are available to

manage the risks during each of the idealized project

stages. These include the following.

(1) The use of risk registers for overall management of

the geotechnical risks (Clayton 2001; Trenter 2003).

(2) An adequate and comprehensive site investigation

(Stapledon 1983; Fookes 1997).

(3) A multistage approach to the site investigation and

an experienced multidisciplinary team to carry out

the work (Stapledon 1983; Fookes 1997; Fookes

et al. 2000).

(4) The use of different types of reports to systemati-

cally convey the findings of the site investigation to

the contractor (Knill 2003; van Staveren & Knoeff

2004).

(5) Peer review at critical hold points for the project

(Stapledon 1983; Baynes et al. 2005).(6) The adoption of the observational method during

construction (Fookes 1997; Fookes et al. 2000;

Knill 2003).

(7) Contract flexibility that allows the contractor to be

paid for work that needs to be done (Fookes et al.

2000; Clayton 2001).

(8) The use of a contract that fairly allocates geotech-

nical risk between the owner and the contractor

(Eddlestonet al. 1995).

(9) The use of residual risk registers to manage risks

during operation (Clayton 2001; Knill 2003).

(10) The adoption of a total engineering geologyapproach, where a lot of effort is applied to

Fig. 6. Cross-section showing underground arrangement and topography; no vertical exaggeration; elevation in metres.




11/12

understanding the geology and defining and docu-

menting baseline or reference conditions at the

earliest possible opportunity (Knill 2003; van

Staveren & Knoeff, 2004; Baynes et al. 2005).

The relationship in time between when these estab-

lished techniques should be used and the idealized

project stages is illustrated in Figure 7.

Unfortunately, the established techniques are seldom

fully adopted in practice, because of cost and time

pressures and inept or inexperienced management. The

consequence of not fully adopting the established tech-

niques is the manifestation of uncontrolled geotechnical

risk.

Conclusions

(1) If past performance can provide a guide to what

will happen in the future, then the likelihood of

experiencing a significant geotechnical risk in the

form of a cost or time over-run on a major projectis somewhere between 20 and 50%.

(2) Similarly, the likelihood of a physical failure is

much less, maybe less than 1 or 2% for civil

projects and up to 20% for mining projects.

(3) Geotechnical risks can be divided into those

associated with project management and those

that relate to technical and contractual matters.

Technical risks can be subdivided into those

associated with the geological model, those associ-

ated with the engineering analysis and those

associated with the engineering properties used in

analysis. The risks associated with the geologicalmodel can be divided into those associated with

unforeseeable geological details, those associated

with inherently hazardous ground conditions and

those associated with unforeseen ground con-

ditions.

(4) Available information suggests that the ground

conditions and the project staffresponsible for the

geo-engineering process are both significant

sources of geotechnical risk and that the project

staffmay actually be the largest source.

(5) Project staffcan be educated and trained to man-

age and mitigate the geotechnical risks, rather than

generate them.

(6) The ground conditions cannot be changed, but

competent engineering geologists can advise how

projects can be engineered to overcome risks

associated with the geological model.

(7) Effective geotechnical risk management techniques

for different project stages are clearly described in

the literature. The single greatest challenge is to

manage the project in a way that incorporates all

of these established techniques and obtains the

maximum benefit from their use.

Acknowledgements.I am grateful to A. Moon and P. Fookesfor their many thoughtful comments and contributions to thisT

ab

le2.Ratesofoccurrence(givenasperc

entages)oftypesofgeotechnicalriskinprojects

Ultimatesource,andhazard

McMahon(1985);47

projectswith

problems*

Stapledon(1983);13

failuresofwaterworks

Duncan(1988);

13

personallesson

s

Fookesetal.(2000);

31casehistories

illustratinggeological

models*

Autho

rsrecordsof22

p

rojectswith

problems*

Proj

ectstaff

Poormanagementofentiregroundengine

ering

process

25

38

95

Poormanagementofsiteinvestigationand

co

ntract

n.a.

46

73

Unr

easonableanalyticalmodelchosen

22

62

46

64

Unr

easonabledesignvalueschosen

58

15

46

6

32

Groundconditions

Unforeseeabledetailsofgroundconditions

n.a.

59

Inherentlyhazardousgroundconditions

n.a.

7

68

73

Unforeseengroundconditions

33

8

29

73

n.a.,

thiscategorywasnotusedbyMcMahon.

*Th

efrequenciesadduptomorethan100%becausesomeprojectsencounteredmoretha

nonetypeofproblem.

Itshouldbenotedthat18%oftheprojectsin

volvedallofthetypesofrisk.

F.J. BAYNES330



12/12

paper, and also to two anonymous reviewers who took the

time to comment on this paper so constructively. The views

expressed here are my own.

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Received 4 March 2008; accepted 3 March 2010.

Fig. 7.The management of geotechnical risk at the various project stages (indicated at the top of the figure and progressing in timefrom left to right).



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