The statistical analysis and summarisation of geotechnical databases

Geotechnical databases are compilations of mainly numerical results of tests carried out in the field or laboratory on small volumes or quantities of ground materials. These values are regarded as 'samples' from the relatively infinite volumes of actual ground present. Most of the databases compiled to date by the Engineering Geology Group have been as components of the applied geology mapping projects, in which they are used to provide broad geotechnical assessments of the principal geological formations encountered. It is a prerequisite of these databases that each numerical item of data is allocated to an engineering geological 'unit' that can be taken to possess some degree of coherence in its origin, occurrence, properties etc. and which can be meaningfully distinguished from other such units. The source for such databases, of necessity, has been limited to the existing available site investigation reports. To a much lesser extent, relatively small databases have been used in in-house research projects, where the data acquisition can usually be planned and closely controlled. This report is concerned primarily with the former type of database, although many· of the aspects discussed will be relevant to the latter.