Five decades of settlement and subsidence

During the late 1960s and 1970s consideration of land instability in Great Britain was dominated by coal mining-related problems. Subsequently, as the pace of development and infrastructure has increased, there has been a greater awareness regarding collapses due to mining for resources other than coal and also due to karstic features in soluble rocks. This has been highlighted by reference to national and regional studies. In addition, there has been an improvement in the number of recorded occurrences of sinkholes and crown holes. The hazard of ground collapse in certain geological settings, together with the size of collapses and resulting damage to development and infrastructure, has become more evident as case studies have been published. Whereas a range of subsidence triggers are evident, the principal causal agency is usually water from rainfall or leaking utilities. Wider-ranging studies, both in Britain and overseas, have identified ever broader causes of land instability, including those related to glacial and periglacial features, and also uncontrolled groundwater exploitation. This review provides a useful summary of land settlement and subsidence activity to warn practitioners where caution should be applied when carrying out ground investigations and providing design advice.