Why Geotechnical Investigations?

It is imperative that the ground conditions are understood before any recommendations are made to found a structure or support an excavation.  There have been numerous civil engineering and mining failures in the past, some spectacular, some with tragic outcomes, some with no greater consequence than a bruised ego. Some of these events were avoidable if a good geotechnical model had been developed at the outset.

In this light then, GeoZone GeoServices subscribes to the new Site Investigation Code of Practice (2010) published by the Geotechnical Division of SAICE.  The new code is a welcome summation of the current status of site investigations (SI) and as its name indicates, a Code for conducting investigations for various types of infrastructure.  It is alarming to see that there has been a steady decrease in the spend on geotechnical investigations over the decades since the 1940’s.  What is also of interest in the code is a Figure which shows that the cost of the investigation varies according to the complexity of the project, the nature of the ground conditions and the level of acceptable risk, and that there is little doubt that the risk to the project is increased by inadequate provision being made for site investigation.

Geotechnical Tender CostsFigure 1

Quoting liberally from the code:

“The cost of the investigation varies according to the complexity of the project, the nature of the ground conditions and the level of acceptable risk. There can be little doubt that the risk to the project is increased by inadequate provision being made for site investigation. Kingdom highway projects (Mott MacDonald and Soil Mechanics Ltd, 1994.) Over the years, the provision made for site investigation costs in the project budget has tended to decrease. This is partly the result of failure on the part of clients and project managers to recognise the value to the project of adequate geotechnical data and the risks posed by inadequate site investigation. It is compounded by the mistaken belief that responsibility for unforeseen ground conditions can be passed on to the designer or the contractor simply by including the necessary clauses or disclaimers in the contract documents.

At the end of the day, the site belongs to the client and the client must bear the costs of executing the project in a manner compatible with the conditions present on the site. The most cost-effective way of doing this is to ensure that adequate geotechnical information is available to facilitate the selection, design, pricing, programming and execution of the works in the most appropriate way from the outset.
Failure to do so leads either to the adoption of conservative assumptions regarding the soil conditions or the adoption of inappropriate or unsafe solutions, both of which have severe cost implications. Clayton (1995) reports that in the 1940’s the cost of site investigations “for fair sized works” was typically about 1% to 2% of the cost of the main work. ……. It is a sad reflection on the profession that the amount of money spent on investigation, testing and professional fees after problems have occurred on a project frequently eclipse the amount spent on the original investigation.”

For a copy of the Code (425 KB) please click here.

In short, it is worthwhile spending what is generally a very small part of the contract costs to characterise the geotechnical and geological conditions that underlie a site.  This will save costs in terms of the correct foundation solution and prevent any unwanted surprises further down the line when construction starts, or during the lifespan of the structure.