446 ENGINEERING GEOLOGY/Overview The compendium of case histories published in 1939 by Robert Legget has become an important milestone, helping establish the subject’s profile, soon to be followed by ‘A Geology for Engineers’ by Blyth (in 1943) and the Berkey Volume (in 1950) The latter volume, entitled ‘Application of Geology to Engineering Practice’, was published by the Geological Society of America (GSA) in memory of the stimulating contributions by Charles Berkey, whose main professional work had been the provision of consultancy advice for dam construction but had also published his important paper, ‘Responsibilities of the geologist in engineering projects’ (AIME Tech Pub 215) Collations of published works then followed in the early 1960s, notably the ‘Reviews on Engineering Geology’ series published by the Geological Society of America and the ‘Engineering Geology Special Publications’ produced by the Geological Society of London The first Congress (in 1970) of the International Association of Engineering Geology (IAEG) established the discipline at an international level, since when it has provided a framework for promotion and development of the subject The IAEG added ‘and the Environment’ to its title in 1997, thereby acknowledging the wider remit of the organisation Engineering Context Ground behaviour of concern arises from the adverse combination of geological processes and ground conditions precipitated by human activity with the potential to cause harm Examples may be drawn from a wide range of situations selected from many parts of the world These include slope instability, subsidence, volume change, hazards relating to water, erosion, seismicity, volcanism, glacial and periglacial phenomena, and pollution Knowledge concerning several processes, notably slope instability and subsidence, have reached a level of maturity but others, such as natural pollution, are still underrepresented and are in need of further research and development The causes of adverse ground behaviour are of scientific interest, but it is the consequences which are of greatest concern to the engineering profession The properties of the geological profile and the processes operating within it determine where and when an adverse combination of circumstances might become linked together, quite possibly induced by human action, so bringing about an imbalance that triggers failure Taking into account the likelihood of a geologically-related hazard occurring, together with an assessment of the vulnerability of people, property, and environment in the vicinity, provides support for decisions as to what should be done to mitigate the consequences Engineering geologists essentially interpret geological information for use by others, applying judgement as appropriate to provide the knowledge necessary for effective decision-making concerning resource abstraction and identification of constraints on development and regeneration In essence, the aim is to identify the most probable geological conditions together with the most unfavourable conditions that might be plausible, and an estimate of their likelihood This informs the broader hazard assessment and risk analysis procedures undertaken for most major engineering projects The general approach adopted is to build a threedimensional model in advance of the site investigation, using existing knowledge of the distribution and properties of the geological materials and the geological processes acting upon them Geological materials comprise three components: solids, liquids, and gases Of equal relevance to the natural geological materials classically studied by geologists (bedrock, or ‘Solid’, geology) are the Quaternary deposits (superficial, or ‘Drift’ geology), artificial deposits (‘Made Ground’) and the weathered profile The conceptual ground model can then be used to plan the site investigation in an interactive way to reduce uncertainty without adopting unnecessarily expensive approaches (for example, close-spread fixed separations between boreholes) The potential exists for financially-based decision-making in terms of value, for example by linking reduction in geostatistical error of estimation with improvement in uncertainty (that is, risk reduction), and so develop an optimal site investigation design Social Context The social and economic significance of ground failure is still largely underestimated, particularly in urban and suburban areas Essentially the impact of each of a series of possible strategies which could be pursued needs to be measured, including the option of doing nothing The aim should be to establish cost effective and socially acceptable management of the built environment The scale of the effect brought about by the occurrence of adverse ground behaviour determines who might be affected and therefore who needs to know This could range