Introduction to the case histories

Case histories have been used for many years to illustrate reasons for various failures. For example, Stapledon (1976) reviewed what he called factors which contributed to dam incidents . This table illustrates the need for good geological advice and good interaction and communication between engineers and geologists, in short, good engineering geology.

The case histories which follow are presented to show how the use of the models, described in this paper, could have helped in anticipating the various geological causes of failure that were identified. These cases resulted from a considerable review of worldwide literature. There was some difficulty in choosing them since many of the cases reviewed contained insufficient geological information to make hindsight judgements on the relevance of appropriate models, and in many cases the causes of the failures were not clear. Such case histories were not used. The coverage by case histories is therefore not complete and it should be noted that:

As the models are all part of a continuous series, i.e. any one model can merge with any other model, and many of the potential check lists will repeat items. For example, sheared clay might appear in several models, as also do many situations leading to mass movements or the presence of weathered material. The case histories are not in particular order: developing a systematic scheme for presenting them was not found practical and, therefore, the case histories have been simply numbered in the order in which they appear in the text to illustrate the model. Models are presented in their figure number order related to the site scale models.

It is important to note that many of the models illustrate contemporary conditions as well as ancient, i.e. fossil conditions or activity at the time of formation. For example, 'fluvial, colluvial and lacustrine' illustrates both modern river systems and evidence of the existence of ancient river systems, now preserved in their sedimentary rocks. 'Basic volcanics' serves to illustrate both modern volcanic situations (e.g. common in island arcs) and long cooled ancient volcanic rocks. 'Hot dry climate features' illustrates both modern deserts, and ancient deserts such as those found in the Permo-Trias in Europe. In southwest England, tropical residual soils still exist in the weathered profile of near surface rocks, although the climate that was largely responsible for them ceased to exist in Britain before the Quaternary as its plate moved northward into cooler latitudes. 'Hot wet' therefore illustrates this situation, as well as modern conditions in tropical rainforests.