ABSTRACT
For many thousands of years, the main subterranean activities of man were cave dwelling, mining and tunnelling. Mining was often carried out at considerable depths in ancient rocks, and the cavities excavated for this purpose were generally stable, with some form of structural lining being used as a means of preventing local falls of the roof or sides. Many mining galleries could be left unlined, just as the galleries of burrowing animals are unlined, and many only needed local roof props.
