Building the geological model: case study of a rock tunnel in SW England

• Published in: Land Surface Evaluation for Engineering Practice Vol. 18; pp. 123 - 128
• Main Authors: Fookes, P. G., Shilston, D. T.
• Format: Book Chapter
• Language: English
• Published: The Geological Society of London 01.01.2001
• Series: Geological Society, London, Engineering Geology Special Publications
• ISBN: 9781862390843; 1862390843
• ISSN: 0267-9914; 2041-4730
• DOI: 10.1144/GSL.ENG.2001.018.01.18

Objectives A ‘geological model’ is a representation of the geology of a particular location. ‘The form of the model can vary widely and include written descriptions, two-dimensional sections or plans, block diagrams, or be slanted towards some particular aspect such as groundwater or geomorphological processes, rock structures and so on’ (Fookes 1997, p. 294). Formal creation of a geological model is one of the fundamental processes by which geologists, geomorphologists and other Earth scientists assemble an understanding of the ground conditions at a site. It is a powerful and cost-effective vehicle for conveying this understanding, often in simplified form, to other disciplines such as civil and structural engineers and planners. Geological models are not always easy or straight-forward to create. This is particularly so at the desk study and field reconnaissance phases of site investigation. However, it is during these early phases that a model (or models) can be particularly useful by helping to set out what is known, what is conjectured, and where significant gaps in knowledge may lie. Geological field-work provides important information for the model, yet much of the geological interpretation of such fieldwork is necessarily subjective. The case study described here illustrates how the vagaries of geological exposure and ground investigation programmes can be evaluated to give an understanding of the completeness and reliability of such data. This evaluation of data is called here the ‘determinability’ of the geology.