Natural and artificial cavities as ground engineering hazards

The occurrences of natural and artificial cavities are reviewed and their causes are assessed. Natural cavities are found principally in carbonate rocks and the processes of sinkhole formation are described. Solution cavities in non-carbonate rocks and cavities in insoluble rocks are also considered. Extraction methods for coal, metalliferous minerals and salts are described in relation to the creation of underground cavities. An outline procedure for locating cavities emphasizes the importance of the desk study in this type of investigation and the difficulty of proving the absence of cavities beneath a site.