Geotechnical risk on large scale infrastructure projects
- 1. Geotechnical risk on large scale infrastructure projects Dr Chris Bridges CEng FICE (chris.bridges@smec.com) 19 November 20201
- 3. Contents • Introduction • Understanding • Impacts • Recommendations 3
- 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
- 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
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- 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)
- 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
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- 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
- 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