22 August 2001
The Geotechnical Adviser explained
Jim Cook of Buro Happold Ground Engineering takes a look at why a Geotechnical Adviser should be brought on board during the early design stage of any project.
Value Engineering and Risk Management are the latest construction industry buzzwords, phrases well used to promote cost efficient design opportunities and minimise liabilities by controlling perceived risks. These issues are well understood in consideration of a building or structure, but are not usually associated with the ground below.
Failing to identify and manage hazards within the ground can lead to severe financial and programming consequences. Hazards could include old landfill, contaminated land, expansive/shrinkable soils, groundwater and soil chemistry, underground voids, soft spots, high groundwater, vegetation and trees, and underground obstructions such as tunnels and foundations.
It has been pointed out by organisations within the industry such as the Transport Road and Research Laboratory (1983) that minor design modifications can easily add 5% to construction costs and that figures can be as high as 30 to 50. A subsequent Transport Research Laboratory (1994) publication highlighted that additional costs as high as 100% of the total project price may be incurred if unforeseen ground conditions are encountered.
The DETR “Construction Industry Task Force” (1998) provided details of what client needs are in terms of greater value for money and quality. This also noted that clients believed that the integration of design and construction solutions would result in achieving these objectives.
National Economic Development Office reports in 1983 and 1988, National House Building Council reports in 1990, National Audit Office (1989) and Public Accounts Committee (1993) have all reported concerns with regard to ground conditions, and increased project costs and overruns.
The Site Investigation Steering Group documents produced by the Institution of Civil Engineers (ICE) in 1993 highlight the scale of the problems associated with construction and civil engineering projects and ground conditions. They also advocate the appointment of geotechnical expertise within the team advising the client, and define the Geotechnical Adviser.
Clearly the Geotechnical Adviser should come into play at the initial engineering assessment stage of a project as member of the principal technical team.
It is a sad fact that frequently, the above ground structure of a building can be developed to almost a final design stage, but the ground upon which it will stand is not considered until very late in the day, when a lot of creative time has already been devoted to the building. However, unless the developer really intends a lop sided long-term tourist attraction like the Leaning Tower of Pisa, the ground conditions on any proposed site should not be taken for granted.
An understanding of the ground conditions should be of paramount importance to any project team, as well as to the client. Additionally, geoenvironmental issues concerning brownfield sites – urban areas where there has been a previous building or industrial use - can have a major financial impact on the viability of a project.
Clients rely on projects being promoted and carried out under the direction of lead professionals such as architects, structural engineers and construction managers. At some stage in the development of a project, the design team will have to focus upon the suitability and viability of ground conditions, and a geotechnical engineer is usually called in.
The geotechnical engineering requirements of any structure need to be addressed so that appropriate foundation solutions can be developed. When undertaking a geotechnical design, the geotechnical engineer has to deal with materials that have no 'guaranteed' stiffness or strength, quite unlike the steel, concrete and other materials that will be used to construct the building. Contamination and pollution may also have to be dealt with.
The Geotechnical Adviser establishes appropriate geotechnical requirements for the project, going beyond the site investigation stage and taking into account temporary and permanent works requirements, and can usually provide or procure any other specialist services needed. Thus the role is one of developing the whole geotechnical strategy for a project and ensuring the objectives are achieved.
The recent ICE-DETR publication “Managing Geotechnical Risk” (2001) highlights the need for geotechnical risk management as a fundamental activity in the development of a project, and emphasises the importance of the appointment of a Geotechnical Adviser at the conception stage.
The Association of Geotechnical and Geoenvironmental Specialists (AGS), whose membership comprises over 100 companies involved in ground engineering, can provide a Code of Conduct for Site Investigation which encourages clients to appoint a Geotechnical Adviser. In addition to this the AGS Guidelines for Good Practice advises members to encourage clients to utilise the services of the Geotechnical Adviser.
Background information for Editors:
Press Office and Practice information
Buro Happold is a multi-disciplinary international practice of consulting engineers established in 1976 offering civil and structural engineering, mechanical and electrical engineering, quantity surveying, building services and environmental engineering, infrastructure and traffic engineering, geotechnical engineering, façade engineering, fire engineering, Computational Fluid Dynamics analysis, access consultancy, project management, urban design and a range of specialist CAD services.
