Geotechnical engineering involves the assessment of the soil and rock conditions at a particular site, and their implications for the development of that site. As most structures rely on the ground for support, it is without surprise that a detailed understanding of the ground conditions, and the suitability of foundation systems, are vital to the long-term stability and performance of the building or structure.
This is where the critical work of a geotechnical engineer is needed. Specialising in the investigation of geological formations and ground behaviour, geotechnical engineers perform scientific investigations and testing to understand the impact these geological formations may have on the design and construction of building, civil and infrastructure projects.
This expertise is crucial for the design and construction of buildings, roads, tunnels, dams, bridges, and water supply and sewage systems. Therefore, geotechnical engineers are often required to solve problems and devise practical solutions for complex engineering projects.
The geotechnical team at Douglas Partners routinely consult with architects, design engineers, developers, and builders to make recommendations on design and development proposals to ensure that the built structures are suitably designed for the ground conditions. For example, the design of footing systems needs to consider the weight of the structure, the ability of the ground to support that weight together with movement tolerances and efficient construction.
A typical geotechnical investigation will follow these steps:
This is an initial, remote, assessment of the site and may include a review of the site using detailed geological maps, past project data and collecting historical information of the area to understand previous developments and issues which may affect future development.
This task is greatly simplified by the use of our Douglas Map geospatial platform which makes this information readily accessible in an easy to use web browser interface.
A geotechnical engineer will direct the drilling of boreholes and test pits to collect soil and other samples, and also assess surface features and ground exposures to form a geotechnical model of the subsurface conditions. Selected samples are usually submitted for laboratory testing to assist in the assessment of pertinent geotechnical parameters for use in design.
Depending on the project type and ground conditions encountered, laboratory testing may among other things assess strength, compressibility, reactivity and/or permeability of soil and rock samples.
After this data is collected and collated, the results are used for a geotechnical model of the site, which is typically presented as sections across the site. Geotechnical properties can then be assigned to the various soil and rock layers encountered at the site. A geotechnical engineer is then able to use their expertise to assess a range of engineering parameters to assist design and identify risks and opportunities for each phase of the project.
The geotechnical engineer has a wide range of analytical tools at their disposal, which may include calculations, design charts, spreadsheets, or specialist numerical modelling software, depending on the complexity of the issue.
A formal report is always prepared for the client, documenting the geotechnical findings, potential risks, opportunities, recommendations, and any other necessary details to ensure that construction can proceed safely and efficiently in accordance with good engineering practice.
A geotechnical investigation by nature can only assess the ground conditions at the locations drilled or excavated.
Natural variations in soil and rock conditions can occur across a site and between test locations. It is therefore good practice that the geotechnical engineer be retained throughout construction of the project to provide on-site verification that the ground conditions encountered are consistent with the expectations and advice provided in the geotechnical investigation report.
