This text is interdisciplinary and is restricted in scope to a discussion of the importan ce of clay in engineering geology. It is primarily addressed to geologists and mineralogists and to those civil engineers who are concemed with the geotechnical sciences.
Its object is to introduce geologists and mineralogists to the often unfamiliar terminology and literature of sorne aspects of soil mechanics and correspondingly to introduce engineers to pertinent information in geology and mineralogy which relates to clay. Geologists and engineers sometimes use the same term with a different meaning and converse! y they attach the same meaning to different words. For example, in engineering terminology compaction implies a mechanical process but to geologists it indicates decrease in void ratio due to natural causes. Likewise rock, generally regarded as a hard material, in the strict sense includes non-coherent mineral matter.
This has been termed regolith by geologists and soil by engineers to the vexation of agricultura! scientists. Confusion could be avoided by general agreement but in many instances it is likely that the question will be decided by usage.