geotechnical projects in in Ir Ireland Paul Quigley Principal - - PowerPoint PPT Presentation

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geotechnical projects in in Ir Ireland Paul Quigley Principal - - PowerPoint PPT Presentation

Feb 16, 2024 165 likes •407 views

Some trends fr from recent ground in investigation contracts and geotechnical projects in in Ir Ireland Paul Quigley Principal Engineer pquigley@gdgeo.com This talk will discuss Risk and the role of geotechnical engineering

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Some trends fr from recent ground in investigation contracts and geotechnical projects in in Ir Ireland

Paul Quigley Principal Engineer pquigley@gdgeo.com

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This talk will discuss…

  • Risk and the role of geotechnical engineering
  • Ground investigation in Ireland
  • Commercial out-turn from GI contracts
  • Trends from the data
  • Some comments and discussion
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Previous papers and presentations

  • Internal paper at Arup (2011)
  • Quigley, P. (2012) The value of ground

investigation in Ireland, BCRI, Dublin.

  • Quigley et al. (2015) Some trends from

recent ground investigation contracts in Ireland, Proc. XVI ECSMGE 2015, Edinburgh.

  • Quigley et al. (2016) Some trends from

recent geotechnical projects in Ireland,

  • Proc. ICE Forensic Engineering, Vol. 169

Issue 3, August 2016, pp. 83-93

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Ground related risks

BCRI 2012

From Tim Chapman (2008), ‘The relevance of developer costs in Geotechnical risk management’. IEI (2003)

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Road construction

BCRI 2012

Clayton, C.I. (2011), ‘Managing Geotechnical Risk – 10 years on’.

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Risk management

BCRI 2012

Lazarus & Clifton (2001) Managing project change – a best practice guide, C556, CIRIA, London

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Percentage fee scales

  • Some clients link fees to percentage of the capital costs
  • This incentivises reducing effort spent on geotechnical engineering in competitive tenders.

Some clients do not include geotechnical engineering in quality assessments.

  • This can result in excessively conservative design to account for the lack of geotechnical

engineering input. The works usually take longer to implement which has significant costs. Worse case is that the structure fails to meet performance criteria.

Scheme Civil Fee scale – detailed design Geotech proportion of

  • verall design fee

Buildings 2 – 4% 2 – 10% Roads 3 – 5% 10 – 20% Flood defence 3 – 5% 25 – 70% Ports and harbours 3 – 6% 25 – 70%

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Ir Irish ground conditions

Glacial landscape

Unsorted nature of glacial till

Image taken from University of Sheffield

  • Peat covers 17% of country
  • Very soft silts adjacent to rivers,

estuaries, inter-drumlin areas, etc.

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Ground investigations

Motorway development 2000 - 2010 Basement and deep excavations

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Techniques

Plus trial pits, geophysics, CPT (infrastructure / civil), dynamic probes…. Numerous contracts: Remeasureable, Lump sum, Public Works Contract, etc.

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Authors and assistance fr from:

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Before we have a look at the data…….

Each project is different and requires an individual assessment. But…………………..

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How much of f the tender sum is is paid id out?

  • 1. This is an investigation
  • 2. Rotary core boreholes more expensive

than cable percussive

  • 3. Conservative estimates of quantities of RC

follow on in glacial till?

  • 4. Conservative estimates of number of tests

required

  • 5. Occasionally addition ground investigation

is required or delays/overruns occur

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When the data is is presented in in a histogram….

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Is Is there a trend with project value?

€10K - €20K, N = 219 €20K - €50K, N = 77 >€50K, N = 89

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Does it it matter who designs the GI? I?

  • Contrib. N = 106

Non contrib. N = 119

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How much of f the contract is is based on fi fieldwork?

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What proportion of f the construction budget is is spent on GI? I?

Building projects Road and Bridge projects

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How many explorations on a typical sit ite?

Building area Construction cost

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Tender award based on price only…..

BCRI 2012

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AGS BDA taskforce in UK The two lines are speculative, subjective, unquantified and unsubstantiated but useful for stimulating debate

Start of CPT use in Ireland Geophysics & Geobor S Restricted budgets and site supervision

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Conclusions and Recommendations

  • Poor ground investigation and geotechnical design

is frequently an issue in project cost and programme overruns.

  • Early intervention produces greater opportunity to

provide developers with certainty and guidance.

  • Ground investigations frequently cost less than the

tender cost. This suggests the presence of a conservative bias when competent geotechnical engineers design ground investigations.

  • A remeasurable contract is ideally suited for most

ground investigations. Please use the Engineers Ireland Specification and Related Documents for Ground Investigation 2nd Edition 2016 (Green Book)

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Conclusions and Recommendations

  • The proportion of the construction budget spent on

ground investigations tends to decrease with increasing project value.

  • There is a need to record data and improve

decision making. The cause of failures or losses on projects would be worthwhile sharing.

  • Is there a need to introduce quality requirements

for Ground Investigation Contractors by the State to promote best practice?

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Thanks to: