Written by Shane Teek – GEOSS South Africa (Pty) Ltd (14 December 2022)
There are many fields of Earth Science, and many of these fields overlap with engineering problems. Examples of such scenarios include the geotechnical design of structures, the development of groundwater supply, or the characterisation of contaminants and the development of a remedial action plan, to name a few.
Earth Science: The Dark art
Earth science is often referred to as the ‘dark art’ or ‘geopoetry’ since the margins of error and assumptions associated with what we cannot see are substantial (Figure 1).
Therefore, at a given site, data is collected within the time available, and a model is developed; more data collected allows for a more robust model of a given area to be developed.
In consulting, time is always a limitation, considering that more time spent equates to more money used on a project. Therefore, when the data collection time is reduced often, only rudimentary models can be conceptualised.
The issue with rudimentary models is that they come with plenty of limitations, which, unfortunately, increase uncertainty and the risk of inaccuracy.
Figure 1: Harry Hess delivering a lecture on mantle convection following a paper he published entitled “Essay in Geopoetry”, in which he explained the driving forces behind continental drift. Hess is now regarded as one of the founders of Plate Tectonics, a widely accepted theory in the field of Geoscience (image from Merritt, 1979).
The Multidisciplinary Approach: An Overview
When a phased approach is adopted to solve a problem, often the cumulative spread of resources is greater across those phases; for example, where time is overspent in one phase of the investigation, time might be saved in another because the challenges had been overcome in the previous phase of the investigation. Such a phased approach also allows for a consistent method of data collection, analysis and ultimately, understanding or development of a site model (Figure 2).
The real value of using an Earth Science consultant is realised when such a phased approach is adopted. The consultant can work through the data with a greater deal of caution, leading to more robust site models, owing to the spread of time spent across numerous phases and increased consistent data collected throughout the phases. Better still, when the phased approach to investigation involves several means of data collection.
Depending on the nature of the project, this might include, for example:
Phase 1:
A rigorous desk study to review available literature for an area, including geological maps and consultancy reports (Figure 2).
Phase 2:
A hydrocensus to acquire an understanding of the depth of the water table and quality of groundwater in an area.
Phase 3:
Excavation of trial pits on the site to characterise the engineering properties of soil and determine what materials are on site.
Phase 4:
Collection of geophysical data on a site provides insight into the depth of bedrock (Figure 3).
Phase 5:
Performance of penetration testing or drilling, which allows for an understanding of soils and rock properties at depth to be acquired. This also allows for the calibration of interpretations made during the compilation of the geophysical survey report.
Figure 2: Desk work is critical to completing a successful geoscience project. This includes a preliminary desk study to review and collect all available information about an area, and later during the analysis of information, once data has been collected on-site during fieldwork, e.g. interpretation trial pit, hydrogenous, laboratory, geophysical and drilling data (image from Ashworth, 2021).
Multidisciplinary Approach: Where does the value lie?
With each subsequent data collection phase, new insights into the ground conditions at a site are gained, and the model is refined.
The danger with several sub-consultants working on the same project, each tackling a single phase listed above, is a general lack of communication between the sub-consultant team.
Often, even if there is communication between sub-consultants, there might not be a ‘need’ to share their findings, and even if there is sharing, there might not be time to include the findings in each other’s models.
Not to mention that data collected by another individual is always questionable. When conflicting results arise, each sub-consultant will stick to their interpretation of the data they collected.
When multidisciplinary science is undertaken by a single entity, consistency between models will be greater, yielding a better understanding of the site conditions.
The primary function of a geo-professional is to deliver a solution to a client’s problem, and the primary aim of the geo-professional is to highlight and manage the risks associated with the said solution. The less reliable the model is, the more risk is associated with the project’s outcomes.
Figure 3: Electrical resistivity data (above) and interpretation/geological model (below), one of several geophysical methods that provide insight into the geological and geotechnical conditions (image from Bran et al., 2018). This is useful for several purposes: i) dam foundations; ii) structure foundations; iii) groundwater development, to name a few.
References
Ashworth, A. (2021). How to Start a Geology Consulting Business.
Blog posting on Association of Engineering Geologists webpage, available at:
https://www.aegweb.org/index.phpoption=com_dailyplanetblog&view=entry&year=2021&month=02&day=23&id=16:how-to-start-a-geology-consulting-business
Bran, D., M., Tassone, A., Menichetti, M., Cerredo, M., E., Lozano, J., G., Lodolo, E., and Vilas., J., F. (2018). Shallow architecture of Fuegian Andes lineaments based on Electrical Resistivity Tomography (ERT). Evidences of transverse extensional faulting in the central Beagle Channel area. Andean Geology 45 (1): 1-34, January, 2018.
Merritt, J., I. (1979). Hess’s Geological Revolution: How An “Essay In Geopoetry” Led to The New Science of Plate Tectonics. Princeton Alumni Weekly, p.g. 273.
Available online:
https://geosciences.princeton.edu/sites/g/files/toruqf2391/files/about/publications/Harry_Hess_bop.pdf
