ABSTRACT
Coal mining has gone on in many parts of western Europe and North America frequently for 100 years or more. Consequently, in many urban areas, there are abandoned workings at shallow depth beneath the ground surface which frequently are not recorded. These may present a potential hazard when such areas are redeveloped.
One of the modern methods of mining is longwall extraction which involves total extraction of panels within a coal seam. Subsidence consequent upon longwall mining can be regarded as more or less contemporaneous with the mining activity. What is more, unlike subsidence associated with old pillar and stall workings, it normally is predictable within about ± 10%. Of the components of ground movement developed by such subsidence tensile stress gives rise to most damage to structures. Typical subsidence damage makes its appearance in conventional structures when they are subjected to effective strains of 0.5 to l.0mm/m.
Obviously measures must be taken to avoid significant damage to structures due to mining activity. Such measures differ according to the type of subsidence problem which has to be dealt with, that is, whether it is generated by the existence of old workings or by present day extraction.
