Geophysical mapping during the planning of new roads: an aid to the detection of mine-workings

Abstract

AbstractMagnetic field strength and electrical conductivity surveys have been made over an extensively mined area north of Dalton-in-Furness along parts of a proposed by-pass route. This approach was successful in detecting shafts and other workings, which were brick-lined and back-filled with debris and ash, since the magnetic field and electrical conductivity values are normally higher in the vicinity of such areas. The use of non-contacting instruments resulted in the rapid location of the geophysical anomalies associated with the contrast in the physical properties between the material in-filling the mine shafts and the surrounding rock mass. Shafts covered with debris or back-filled with the original overburden did not generally give rise to significant magnetic anomalies but often produced a conductivity anomaly associated with changes in the drainage pattern of the area resulting from the presence of the shaft.