The paper primarily considers the diagnosis and evaluation of shallow workings from which coal, ironstone and fireclay have been extracted by underground methods close to outcrop. Instability problems affecting normal structures are mainly attributed to 'room and pillar' workings, and current work on the behaviour of the latter is briefly discussed. The resultant compaction of collapsed strata (goaf) is problematical and evidence is presented which throws doubt on the compaction of 'bell-pit' workings of probable mediaeval age.
Investigation techniques are discussed in detail and attention drawn to the importance of geological structure, particularly faults. Associated 'steps' caused by differential movements are not always fully appreciated. The detailed case histories are taken from the Yorkshire coalfied and consider urban development, re-development and a major road project.
It is concluded that exploration on an areal basis is necessary if all the factors connected with shallow workings and other industrial legacies are to be fully elucidated. In order to rationalize techniques it is advocated that larger investigations should comprise more than one stage. A detailed pre-survey appreciation of the available mining, industrial and geological literature is an integral part of this type of project, and the full co-operation of all the parties involved should stem from this period.