Clive N. Edmonds, 2020. "Chapter 12 Subsidence – chalk mining", Geological Hazards in the UK: Their Occurrence, Monitoring and Mitigation – Engineering Group Working Party Report, D. P. Giles, J. S. Griffiths
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Old chalk and flint mine workings occur widely across southern and eastern England. Over 3500 mines are recorded in the national Stantec Mining Cavities Database and more are being discovered each year. The oldest flint mines date from the Neolithic period and oldest chalk mines from at least medieval times, possibly Roman times. The most intensive period for mining was during the 1800s, although some mining activities continued into the 1900s. The size, shape and extent of the mines vary considerably with some types only being found in particular areas. They range from crudely excavated bellpits to more extensive pillar-and-stall styles of mining. The mines were created for a series of industrial, building and agricultural purposes. Mining locations were not formally recorded so most are discovered following the collapse of the ground over poorly backfilled shafts and adits. The subsidence activity, often triggered by heavy rainfall or leaking water services, poses a hazard to the built environment and people. Purpose-designed ground investigations are needed to map out the mine workings and carry out follow-on ground stabilization after subsidence events. Where mine workings can be safely entered they can sometimes be stabilized by reinforcement rather than infilling.
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Geological Hazards in the UK: Their Occurrence, Monitoring and Mitigation – Engineering Group Working Party Report
The UK is perhaps unique globally in that it presents the full spectrum of geological time, stratigraphy and associated lithologies within its boundaries. With this wide range of geological assemblages comes a wide range of geological hazards, whether they be geophysical (earthquakes, effects of volcanic eruptions, tsunami, landslides), geotechnical (collapsible, compressible, liquefiable, shearing, swelling and shrinking soils), geochemical (dissolution, radon and methane gas hazards) or georesource related (coal, chalk and other mineral extraction). An awareness of these hazards and the risks that they pose is a key requirement of the engineering geologist.
The Geological Society considered that a Working Party Report would help to put the study and assessment of geohazards into the wider social context, helping the engineering geologist to better communicate the issues concerning geohazards in the UK to the client and the public. This volume sets out to define and explain these geohazards, to detail their detection, monitoring and management and to provide a basis for further research and understanding.