This is the second in the series of the subject geotechnical engineering. In the previous series I mentioned five areas of its applications. Right! The areas of application continue. This series will discuss, among others, the development and use of geotechnical engineering in Ghana.
- Dams, Embankment, dykes & levees – the relevance of geotechnical engineering is to provide detailed assessment of subject sites. Assessment normally targets the surface and sub-surface at areas covering all structures to provide relevant information that aid the understanding of deformation and erosion characteristics among others. The subject goes the extra mile to assess the availability of construction materials including quality control works for such projects.
- Landfills – this area of application is referred to as environmental geotechnics. The geotechnical aspect considers geosynthetics application for barriers, filter, and reinforcement for vertical walls serving as retaining structure. In addition, geotechnical engineering will perform site investigation to provide information about the surface and subsurface prevailing conditions, and on borrowed construction materials including quality control services.
- Offshore engineering – offshore structures such as those used in the oil and gas exploration including production, and other facility – subsea pipelines, need input from geotechnical knowledge to design their foundations. In addition, offshore renewable energy structure – wind turbines – needs geotechnical input for their design and construction.
- Ground improvement – ground improvement involves adding construction inclusions to soils or alteration of soil properties to achieve a desired performance. The geotechnical involvement includes construction methods and quality control, specification and designing with inclusions (e.g. geogrid, geotextile etc.). Ground improvement may be relevant in foundation, pavement and embankment design and construction including areas with expansive soil behaviours.
- Deep excavation – deep excavation normally involves construction with basement. The geotechnical involvement is to provide information about prevailing subsurface conditions that will impact on design and construction. Geotechnical engineering will provide information to design retaining walls, any shoring system and challenges associated with groundwater. In addition, for example, in a well urbanized setting the subject will consider soil-structure interactions with other existing structures, which may affect performance.
Other areas of application include land reclamation, Scour and Erosion control, Preservation of Historic Sites, Flood control, Megacities development, Energy and Frost geotechnics.
Geotech in Ghana
Largely the development of geotechnical interest in Ghana started with Ing. Professor Nicholas Kumapley (of blessed memory). As an authority for the subject, he made significant impact in its teaching and practice. In fact, most practitioners today with more than 17yrs of professional experience were under his tutelage and am glad to be one of them! The geotechnical industry is very grateful to him. We cannot forget late Ing. Dr. Gidigasu and Ing. Prof. Gogo (all formerly of BRRI) for their immense contributions to the subject especially in the area of construction material research. Ing. Prof. Samuel I.K. Ampadu (the immediate Provost of College of Engineering, KNUST) continued, from where late Kumapley left, with the academic impartation and great contributions to research and practice. Ing. Prof Ampadu re-organized the Geotechnical Society, which is affiliated to the International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE).
In Ghana the geotechnical industry is divided into three groups. These are consultants, contractors and laboratory providers. The consultants mainly handle the development of geotechnical issues for projects. These issues includes development of, scope depending on the type of project, specifications, supervision of fieldwork, preparing laboratory schedules and general reporting (investigative report – preliminary, factual, interpretative; design and validation report). It is important that consultants are included in the project’s development phase by the client or project leader as this helps in the definition of clear scope of works.
The contractors act as “supporting staff” by providing services on the field. In fact they support geotechnical fieldworks. Some the services are drilling and sampling, geophysical probing, in situ testing, instrumentation monitoring among others. The laboratory providers also support the industry by testing samples retrieved from the field. Test results augment field data to formalize a comprehensive report.
The use of geotechnical engineering in Ghana spans from building, pavement, bridges, dams, railways, and in fact most construction projects. However, in my view, clients and other stakeholders have still not noticed its importance in project delivery. One challenge, for example in building projects, is with the National Building Regulation/Code (currently under review). The regulations for geotechnical inclusion require that there should be geotechnical investigation for buildings going up at least 3-storeys. This is a serious limitation because it appears geotechnical involvement is only about structural loading. This is a big No and I hope the review will address this flaw. It is important to note that geotechnical outlook for building projects goes beyond structural loadings. Always bear in mind that it is site investigation and should be key for all types of buildings. I argue this point because a client may develop just a single storey along a slope, river bank, and seismic zone or within an expansive soil locations, which loading may not be an issue. It is important that the site is assessed, documented and appropriate risk made known to influence decision making in terms of land-use, design; cost and construction technology. Another area of concern is the use of prescriptive approach to dealing with geotechnical design issues as recommended in the regulations. This may not be scientific enough especially for large building projects. The geotechnical engineer should validate the design for the final foundation layout to check on serviceability and its construction. In Ghana, this critical component is not done and may have negative influence during forensic investigation and structural integrity assessment.
To be continued……
About the writer:
The writer is , a Fellow of the Ghana Institution of Engineering and Chairman for the Civil Technical Division. He is the Secretary of the Ghana Geotechnical Society and deeply involved in geosynthetic issues. He holds a BSc (Hon) degree in Geological Engineering and an MPhil in Geotechnical Engineering from KNUST with over 17-yrs of professional practice.