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Money can't buy risk-freeground

A new study on managing geotechnical risk isprompting the ground investigation industry to re-evaluate its role

It is a well-worn argument that risk in the ground is the greatest uncertainty in civil engineering. The statistical evidence collected over the years is over-whelming. Yet despite there being so much at stake, the message is still not getting through and the geotechnical community is left feeling misunderstood and undervalued.

Ground investigation costs are usually between 0.1% to 1% of project costs. The ground investigation industry will tell you that at this level of spending clients can rarely secure peace of mind - cost overruns may still be as high as 80%. But spend 5% of project costs on investigation and this uncertainty is statistically reduced to a maximum overrun of about 20%. This has always been used as justification for spending more on site investigation.

But Southampton University's Professor Chris Clayton - the practising site investigation engineer's guru - says it is time to rethink.

For the past two years Clayton has been working as research contractor for the ICE and DETR joint funded initiative 'Managing geotechnical risk.' The project is being managed by Neil Trenter, who took it on following his retirement as head of geotechnics with Halcrow.

When the project was launched, it was met with little enthusiasm from the geotechnical community as there was a perception that it would be going over well-trodground.

True, the project as first conceived was focused on familiar issues such as the effect of preplanning on project costs and the impact that conditions of contract have on project out-turn. The work was principally trying to assess the benefits of various risk management tools within a conventional project set-up.

But the project's steering group, which has a strong representation among clients, felt this was not the most productive direction, pointing out that it was broadly repeating what had already been done.

Two years down the line, preliminary findings are beginning to come out and some interesting ideas have emerged, though they may not be to the liking of everyone within the geotechnical sector. Last month Clayton used the ICE's prestigious Unwin Memorial Lecture to update the civils community on the progress of the project, and he has some fairly brutal points to make about the traditional ground investigation process.

'The traditional view is that ground is a hazard and therefore one should do a large, expensive and detailed ground investigation to identify all the risks and quantify them, ' he says.

'The assumption is that if the client has enough money, if the designer has the knowledge and the contractor has the right people, plant and skill, then there will be no problems. The view we have always believed is that when things go wrong it is because one of the parties has not fulfilled its role properly, ' says Clayton.

He believes this view is out-dated and wrong -'we need to reinterpret the facts in a different way'.' He says there are well-recorded cases where a lot of skill and care was taken, but where there were still time and cost overruns resulting from un-expected ground conditions.

For example there have been some very high cost overruns on previous highways projects, even though the Highways Agency is a discerning client and has very demanding qualification requirements for its consultants and contractors - it could hardly be accused of employing cowboys. The old assumptions about quality and reliability do not stack up.

'However much you spend on ground investigation, you are never going to absolutely know what is in the ground. The idea that you can discover all the hazards is naive, ' Clayton says.

Good ground investigation takes time and with the move towards rapid design and construction, there is insufficient time to carry out the process properly.

Clayton says that if there is not enough time for proper site investigation - and in any case, the rationale behind 'proper site investigation' is flawed - we should accept that simply putting the case for more and more site investigation is not going to achieve much or result in better use of geotechnical expertise.

'Geotechnical risk can be managed better than it is at present and at relatively low cost.'What is needed, he believes, is a shift in emphasis from full detailed design to risk management and design using a systematic approach.

Systematic design, despite the rigidness implied by its name, is about identifying needs and problem solving, albeit within a structured framework. It is a more creative process, which emphasises conceptual design rather than detailed design, he says, and should result in solutions that reduce geotechnical risk by avoiding the hazards.

Taking this idea forward could see a shift from the current focus on deterministic analyses. After all there is increasing acknowledgement among geotechnical engineers that analytical methods of foundation design do not work as well as most would like to think. Look, for example, at Imperial College's recent pile predictions symposium (Ground Engineering November 1999).

This would mean a fundamental change to the way geotechnical expertise is used. The often neglected desk study takes on even more importance, as does the early use of specialists, who may find themselves brainstorming within multidisciplinary teams to identify hazards to the project.

If the 'Managing geotechnical risk' project increases awareness of the power of desk study, and nothing else, then it will have been worthwhile, says Clayton. In the future, he foresees projects in which a geotechnical specialist, on the basis of a decent desk study, might decide there is little to begained from carrying out boring, trial pitting or testing - radical stuff indeed.

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