Geotechnical risks on large infrastructure projects can have significant impacts if not properly understood and managed. A lack of understanding of geotechnical engineering among project managers can lead to insufficient site investigation and underestimation of risks. Poor contractual risk allocation and a lack of appreciation for geotechnical risks can also increase impacts. Mistakes in design, unforeseen ground conditions, and inadequate monitoring have led to costly delays and failures on some projects. Proper management of geotechnical risks requires engaging experienced professionals, independent review, clear communication, and attention to limitations of data and methods used.

1. Geotechnical risk on large scale
infrastructure projects
Dr Chris Bridges CEng FICE
(chris.bridges@smec.com)
19 November 20201

2. • https://australiangeomechanics.org/chapter/queensland/
2

3. Contents
• Introduction
• Understanding
• Impacts
• Recommendations
3

4. Introduction
4

5. Geotechnical engineering
Introduction
5

6. Geotechnical engineering
Introduction
6

7. What is risk?
“Risk is like love: we all know what it is, but we don’t know how to define it”
(Joseph Stiglitz quoted in (Nguyen, 2007))
“……the fear of an evil ought to be proportionate, not only to its magnitude,
but also to its probability…”.
(from 1662 by Arnaud (Arnaud, 1850))
Introduction
risco - danger
rischiare – run into danger risquer
risque
ITALIAN
FRENCH
RISK = LIKELIHOOD x CONSEQUENCE
7

8. Lower Risk Lower Risk
Higher Risk
8
Introduction

9. Understanding
9

10. Civil engineers do not understand
geotechnical engineering
“The major part of the college training of civil engineers consists in the
absorption of the laws and rules which apply to relatively simple and
well-defined materials, such as steel or concrete. This type of education
breeds the illusion that everything connected with engineering should
and can be computed on the basis of a priori assumptions.
Unfortunately, soils are made by nature and not by man, and the
products of nature are always complex.”
(Terzaghi, 1936)
10
Understanding

11. This lack of understanding continues today
(Kajastie, 2020)
“… lack of investment in earlier site investigation, … lack
of technical understanding among project managers and
a trend towards reduced quality across the industry.”
11
Understanding

12. A lack of appreciation of geotechnical risks
Project Management
(General Geotechnical Risks)
Line Management of Different Project Risks
Specific Geotechnical Risks
Contractural Technical
Geological Engineering
Material
Properties
Team
Leadership and
Experience
(Baynes, 2010)
High level risks –
General lack of
appreciation of
geotechnical risks – i.e
restrict geotechnical
budget
Specific risks
12
Understanding

13. Poor investment in investigation can have
impacts
0
20
40
60
80
100
120
140
160
180
0 2 4 6 8 10 12
As-builtconstructioncostas%ofengineers
estimate
Investigation cost as % of construction cost (excludes variations)
Engineers estimate = 100%
13
(National Research Council, 1984)
Understanding

14. Geotechnical risks
Project Management
(General Geotechnical Risks)
Line Management of Different Project Risks
Specific Geotechnical Risks
Contractural Technical
Geological Engineering
Material
Properties
Team
Leadership and
Experience
(Baynes, 2010)
High level risks –
General lack of
appreciation of
geotechnical risks – i.e
restrict geotechnical
budget
Specific risks
14
Understanding

15. Contractual risks are the foundations
for poor project performance
Contractual
• Risk transfer
• GBR - Crossrail
0 10 20 30 40 50 60 70 80 90 100
Cl
PM
Cons
PC
SC
Sup
Man
Percentage Risk Allocation
Organization
Cl PM Cons PC SC Sup Man
Cl = client; PM = project manager; Cons = consultants; PC = primary contractor;
SC = subcontractor; Sup = supplier; and Man = manufacturer
(Loosemore & McCarthy, 2008)
15
Understanding
Client: 35% PM 45% PC 10% Client
PC: 25% PM 35% PC 20% Client
Consult: 35% PM 25% PC 30% Client

16. Different parties to a contract view risks
differently
(Smith, 2019, Smith, 2018)
16
Understanding

17. Different parties to a contract view risks
differently
(Castro-Nova, Gad, Touran, Cetin, & Gransberg, 2018)
17
Understanding

18. Different parties to a contract view risks
differently
(Lo, Fung, & Tung, 2006 - Construction Delays in Hong Kong Civil Engineering Projects)
18
Understanding

19. Team risks are often forgotten
Team
• Leadership
• Availability
• Role separation
19
Geotechnical
Manager
Hydraulics/
Hydrology -
parameters for
scour
assessment,
climate change,
flooding
Environmental -
acid sulfate soils,
contaminated
land, cultural
heritage,
sensitive areas,
sustainability
Contractor -
constructability,
cost, temporary
works
Independent
Verifier /
Independent
Checking
Engineer -
design
verification &
compliance
Client - design
life,
maintenance,
compliance,
whole-of-life
cost,
stakeholders
Pavement -
subgrade
properties,
expansive soils
Structures -
earth pressures /
foundation
parameters,
retaining wall
and foundation
design
Alignment -
Shallow in cuts
to avoid blasting,
low
embankments on
soft soil, batter
slope angles,
cut/fill balance
Site
Investigation
Contractor -
ground
investigation
data

20. Geological risks are often considered as
the main geotechnical risks
• groundwater
• geological features
• compressible soils
• unstable slopes
• strength and stiffness
• anthropogenic materials
• geomorphology and landform
• problem soils
20
Understanding

21. Material properties are critical to design
(Bond & Harris, 2008)
-40
-35
-30
-25
-20
-15
-10
-5
0
0 20 40 60 80
Depthbelowgroundlevel(m)
Undrained shear strength (kPa)
21
Understanding

22. Material properties are critical to design
(Bond & Harris, 2008)
-40
-35
-30
-25
-20
-15
-10
-5
0
0 20 40 60 80
Depthbelowgroundlevel(m)
Undrained shear strength (kPa)
Range of interpretations
22
Understanding

23. Material properties are critical to design
23
Lower bound: c=0, f’=25
Upper bound: c=0, f’=39
Understanding

24. Can we be sure of the data we receive
24
Understanding
Laboratory testing: Revealing consistency concerns
31 January, 2018 By GE Editorial
c. 9% variation c. 15% variation

25. Understand where your data comes from
25
50mm (ID) x 500mm – 0.00098m3
Understanding

26. Understand its reliability
“Every experienced contractor knows that ground investigations can
only be 100% accurate in the precise locations in which they are carried
out. It is for an experienced contractor to fill in the gaps and take an
informed decision as to what the likely conditions would be overall”.
(Mr Justice Coulson (Van Oord UK Ltd & Anor v Allseas UK Ltd, 2015))
26
Understanding

27. Don’t believe all you see
27
Understanding

28. 28

29. Understand the scale of your
information
29
Understanding

30. INB drilling accounted
for only about 10m3 of
soil/rock from
70,000m3 excavated
(0.015%)
Understand the scale of your
information
30

31. Sieffert & Bay-Gress (2000) Comparison of European bearing capacity calculation methods for shallow
foundations Proc. Instn Civ. Engrs Geotech. Engng, 143, 65-74
734kN
1297kN
31
Understand the limits of your analysis
Understanding

32. Understand the limits of your analysis
(Morgenstern, 2000)
Shallow foundation on sand
0 2 4 6 8 10 12 14
Bad (<50)
Poor (50-75)
Fair (75-85)
Good (85-95)
Excellent (95-105)
Good (105-115)
Fair (115-125)
Poor (125-150)
Bad (>150)
Bearing Capacity Settlement
Bearing - 66% Poor / Bad
Settlement - 90% Poor / BadWithin 25%
of the answer
Over-estimate
Under-estimate
32
Understanding

33. DESIGN ELEMENT UNDER DESIGN
(NO./%)
OVER DESIGN
(NO./%)
ACCEPTABLE
(NO./%)
REFERENCE
STEEL DRIVEN PILE CAPACITY: BASE
SHAFT
TOTAL
4 / 25
13 / 18.25
11 / 68.75
6 / 37.5
1 / 6.25
3 / 18.75
6 / 37.5
2 / 12.5
2 / 12.5
(Anon, 1999)
BASE GROUTED STEEL DRIVEN PILE
CAPACITY: BASE
SHAFT
TOTAL
3 / 18.75
4 / 25
2 / 12.5
10 / 62.75
7 / 43.75
11 / 68.75
3 / 18.75
5 / 31.25
3 / 18.75
(Anon, 1999)
SHALLOW FOUNDATION ON SOFT CLAY:
ULTIMATE CAPACITY
SETTLEMENT AT FAILURE
39 / 78
4 / 8
3 / 6
43 / 86
8 / 16
3 / 6
(Doherty et al.,
2018)
SHALLOW FOUNDATION ON SAND:
BEARING CAPACITY
SETTLEMENT
10 / 34
18 / 58
9 / 31
10 / 32.3
10 / 34
3 / 9.7
(Morgenstern,
2000)
EMBANKMENT COLLAPSE HEIGHT 21 / 48.8 4 / 9.3 18 / 41.9 (Morgenstern,
2000)
EMBANKMENT ON SOFT GROUND,
SETTLEMENT WITH TIME: 106 DAYS
1095 DAYS
15 / 44
17 / 55
4 / 12
1 / 3
15 / 44
13 / 42
(Kelly et al., 2018)
33

34. Impacts
34

35. Geotechnical risks cause project impacts
35
GEOTECHNICAL CAUSE RANK
(COST IMPACTS)
RANK
(DELAY IMPACTS)
Lack of sufficient boring locations 1 1
Misclassified / mischaracterized
soils
2 2
Higher groundwater table than
expected
3 3
Dewatering due to seepage 4 3
Design changes to
superstructure
4 2
Prescribed soil treatment not
suitable
5 4
Variation of piling quantities due
to wrong pile type
5 3
Mismatch in pile quantities 6 5
Erosion and sediment control 7 6
60.5
38.3
1.2
Negative No impact Positive
60.8
36.7
2.5
Negative No impact Positive
Cost overrun (%)
Schedule overrun (%)
Impacts
(Shrestha & Neupane, 2010)

36. How good is engineering judgement?
36
CAUSE
CLAIM
Failure of flood protection system >$60 bn
Construction claim on volume losses in dredge-fill >$400 m
Concerns over future failures of MSW systems >$100 m
Excessive settlement of high-rise building >$200 m
Settlement of homes >$100 m
Property damage from failure of dam over 10 m high >$100 m
Delays and damages from excavation support system >$100 m
Heave of pavement subgrade >$100 m
Failure of tailings dams – 2008, 2015, 2019 >$1 bn each
Impacts
(Marr, 2019)

37. Case study literature
Impacts
37

38. Mistakes can be expensive
Impacts
(Peracha & Pengelly, 2020)
38

39. The role of geotechnical sub-consultant
(temporary tunnel support)
• Geotechnical sub-consultant put forward 3 staff – only 1 accepted
(24/7 Operation)
• Provided with 3 juniors by the contractor who were not NATM
experienced
• Did not certify construction of the works they designed
• Inadequate computer software system for processing the monitoring
data
39
Impacts

40. Settlement at Camborne House
exceeded predicted settlement
(9mm) after only concourse
tunnel completed by about
20mm.
40

41. 41

42. 42

43. The findings
• lack of on-site NATM authority at Heathrow
• lack of experience among the field engineers, the tunnelling foremen
and the crews – design did not take this into account – poor
workmanship an issue
• lack of full-time geologists within an NATM supervision team
• Contractors geotechnical sub-contractor not kept in the loop
• Instrumentation - limited data available, poor quality, serious
omissions, "inadequate" computer software
• there was still enough data available to see what was happening
43
Impacts

44. Mistakes can be expensive
• Contractor fined £1.2M + £100k costs (contract value £60M)
• Recovery took nearly two years and cost around £150M - nearly
three times the cost of the original contract
44
Impacts

45. ……and embarrassing
Impacts
(Anon, 2020)
45

46. Recommendations
46

47. 47
Safetyindesignandprojectriskregisters
detailingriskprocess.Processtobeupdated
throughoutthedesignandconstruction
Establishing
the Context
• Project details - scope, alignment etc
• Desk study, historical records etc.
• Site investigation data
Risk
Identification
• Ground model development, parameter selection
• Developing concept design
• Identifying geotechnical risks
Risk
Analyses
• Combining identified risks with their likely consequences
Risk
Evaluation
• Evaluating which risks require treatment
Risk
Treatment
• Detailed design to eliminate or manage risks
• Instrumentation and ongoing monitoring to manage risks
Establishing
the Context
• Reviewing site data as construction proceeds and update models
/ design as necessary
• Review risk process and update as necessary

48. In developing solutions and presenting
these to our clients we must be aware of
the limitations
• Investigations sample a very small amount of the site
• Laboratory and insitu testing is subject to errors and inconsistencies
• Engineers can derive a range of interpretations for a single set of test data
• Design methods can give significantly different answers
• Software outputs are only as good as the information we put in and need to be checked against what
we consider to be reasonable
• Team leadership and inexperience can seriously affect project outcomes and magnify the likely risks
48
Recommendations

49. Geotechnical engineers should be
• Engaging senior professionals early as possible in the project
• Using independent reviewers or verifiers
• Communicating and building relationships with the various parties and stakeholders (establishing
trust) as early as possible
• Adopting procedures based on precedence so that methods of analysis etc. are the same for each
project i.e. Department of Transport and Main Roads (2015) and United States Army Corps of
Engineers (2003)
• Expressing results with likely variability
• Explaining the design and design intent to the relevant site engineers prior to construction,
including likely risks and uncertainty
• Supporting and mentoring Team Leaders throughout the project
49
Recommendations

50. Questions
• Introduction
• Understanding
• Impacts
• Recommendations
50
chris.bridges@smec.com
RecommendationsBridges, C.A. (2019) Geotechnical risk: it’s not only the ground. Australian Geomechanics
54(1) 27-38

51. References
• Anon. (2020). Piling design error leads to Sheffield building demolition. Ground Engineering(October), 6.
• Arnaud, A. (1850). Logic, or the Art of Thinking being the Port-Royal Logic (Translated from the French by Baynes) (T. S. Baynes, Trans.).
Edinburgh, UK: Sutherland and Knox.
• Baynes, F. J. (2010). Sources of geotechnical risk. Quarterly Journal of Engineering Geology and Hydrogeology, 43, 321-331.
• Bond, A., & Harris, A. (2008). Decoding Eurocode 7. Abingdon, UK: Taylor & Francis.
• Bridges, C. (2019). Geotechnical risk: it's not only the ground. Australian Geomechanics, 54(1), 27-38.
• Buxton, J. A., Henry, B., Crabtree, A., Waheed, A., & Coulthart, M. (2011). Using qualitative methods to investigate risk perception of
Canadian medical laboratory workers in relation to current prion disease infection control policies. Journal of Toxicology and Environmental
Health, Part A, 74, 241-247.
• Castro-Nova, I., Gad, G. M., Touran, A., Cetin, B., & Gransberg, D. D. (2018). Evaluating the Influence of Differing Geotechnical Risk
Perceptions on Design-Build Highway Projects. ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering,
4(4). doi:10.1061/AJRUA6.0000993
• Committee of Inquiry. (2005). Report of the Committee of Inquiry into the Incident at the MRT Circle Line workste that led to the collapse of
the Nicoll Highway on 20 April 2004 (Volume 1 (Part I)).
• Douglas, M. (1970). Natural symbols: explorations in cosmology. London, UK: Barrie & Rockliff.
51

52. References
• Kahan, D. M., Braman, D., Slovic, P., Gastil, J., & Cohen, G. (2007). The Second National Risk and Culture Study: Making Sense of - and
Making Progress In - the American Culture War of Fact. Retrieved from New Haven, Connecticut, USA:
• Kajastie, N. (2020). Covid issues mask other concerns. Ground Engineering(October ), 3.
• Kasperson, R. E. (2012). A Perspective on the Social Amplification of Risk. The Bridge, 42(3), 23-27.
• Lo, D. O. K., & Cheung, W. M. (2005). Assessment of landslide risk of man-made slopes in Hong Kong (GEO Report No. 177). Retrieved from
Hong Kong Special Administrative Region, PRC:
• Lo, T. Y., Fung, I. W. H., & Tung, K. C. F. (2006). Construction Delays in Hong Kong Civil Engineering Projects. Journal of Construction
Engineering and Management, 132(6), 636-649. doi:10.1061/ASCE0733-93642006132:6636
• Loosemore, M., & McCarthy, C. S. (2008). Perceptions of Contractual Risk Allocation in Construction Supply Chains. Journal of Professional
Issues in Engineering Education and Practice, 134(1), 95-105.
• Marsden, E. (2017, 31 July 2017). Risk perception. Retrieved from https://risk-engineering.org/static/PDF/slides-risk-perception.pdf
• Morgenstern, N. R. (2000). Performance in Geotechnical Practice. Paper presented at the The Inaugural Lumb Lecture, Hong Kong.
• National Research Council. (1984). Geotechnical Site Investigations for Underground Projects: Volume 1: Overview of Practice and Legal
Issues, Evaluation of Cases, Conclusions and Recommendations. Retrieved from Washington, DC, USA:
• Nguyen, N. C. (2007). Risk management strategies and decision support tools for dry land farmers in southwest Queensland. Australia.
(PhD), University of Queensland, Gatton. Queensland. Australia.
52

53. References
• Peracha, Q., & Pengelly, E. (2020, 27 Jan 2020). The day tunnels below Heathrow collapsed and created giant crater between runways.
Retrieved from https://www.getsurrey.co.uk/news/surrey-news/day-tunnels-below-heathrow-collapsed-17601515
• Sbaraini, A., Carter, S. M., Evans, R. W., & Blinkhorn, A. (2011). How to do a grounded theory study: a worked example of a study of dental
practices. BMC Medical Research Methodology, 11(128). doi:https://doi.org/10.1186/1471-2288-11-128
• Slovic, P., Fischhoff, B., & Lichtenstein, S. (1979). Rating the Risks. Environment, 21(3), 14-39.
• Smith, C. (2018, 13 June 2018). HS2 £1bn over target costs following geotechnical risk warning. Retrieved from
https://www.geplus.co.uk/news/hs2-1bn-over-target-costs-following-geotechnical-risk-warning-13-06-2018/
• Smith, C. (2019). HS2 plans to reduce ground risk cost described as “carnage”. Retrieved from https://www.geplus.co.uk/news/hs2-plans-to-
reduce-ground-risk-cost-described-as-carnage-28-01-2019
• Willingham, R. (2019, 9 December 2019). Melbourne Metro Tunnel project grinds to a halt amid dispute over deadlines and costs. Retrieved
from https://www.abc.net.au/news/2019-12-09/melbourne-metro-tunnel-project-grinds-to-halt-amid-dispute/11779986
53

54. Appendices
54

55. 0 2 4 6 8 10 12
Bad (<50)
Poor (50-75)
Fair (75-85)
Good (85-95)
Excellent (95-105)
Good (105-115)
Fair (115-125)
Poor (125-150)
Bad (>150)
Number of Predictions
AccuracyofPrediction(%)
Driven Steel Pile
Total Capacity (kN)
Base Capacity (kN)
Shaft Capacity (kN)
Under estimate
Over estimate
Shaft - 88% Poor / Bad
Base - 63% Poor / Bad
Total - 88% Poor / Bad
55

56. 0 1 2 3 4 5 6 7 8 9 10
Bad (<50)
Poor (50-75)
Fair (75-85)
Good (85-95)
Excellent (95-105)
Good (105-115)
Fair (115-125)
Poor (125-150)
Bad (>150)
Number of Predictions
AccuracyofPrediction(%)
Jet Grouted Pile
Total Pile Capacity (kN)
Base Capacity (kN)
Shaft Capacity (kN)
Over estimate
Shaft - 69% Poor / Bad
Base - 81% Poor / Bad
Total - 81% Poor / Bad
Under estimate
56

57. 0 2 4 6 8 10 12 14 16
Bad (<50)
Poor (50-75)
Fair (75-85)
Good (85-95)
Excellent (95-105)
Good (105-115)
Fair (115-125)
Poor (125-150)
Bad (>150)
Number of Predictions
AccuracyofPrediction(%)
Embankment Collapse Height
Muar Embankment
Prediction Competition
MIT Embankment
Prediction Competition
Non-conservative
Conservative
60% Poor / Bad – majority
on the conservative side of
prediction
57