Conceptual Engineering Geological Models

Engineering geological models should form a fundamental component of any geotechnical project as they provide a systematic methodology to support all of the engineering geological thought processes that must be worked through for successful project completion. The use of models as an approach to solving engineering geological problems, with the inherent requirement for prediction and verification, is also ideally suited to training and education. IAEG Commission C25 (Parry et al. in Bull Eng Geol Environ 73:689–706, 2014) proposed that engineering geological models could be divided into two profoundly different approaches and therefore different model types. Observational and Conceptual. However, the C25 Report perhaps lacks clarity regarding the differences between these two types of models and the way in which they work together. The conceptual approach is based on understanding the relationships between engineering geological units, their likely geometry, and anticipated distribution. This approach, and the models formed, are based on concepts formulated from knowledge and experience. When these models are proficiently developed they provide an extremely powerful tool for appreciating and communicating what is known about a site, what is conjectured and where significant uncertainties may remain. The conceptual model provides a framework for the evaluation of observational data which then forms an observational model which is constrained by real data in 3D space and time. The development of conceptual models should be a core activity for engineering geologists. The paper discusses the generation of conceptual models, gives examples of the problems that can arise when they are not used, and provides guidelines for their development.