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Online Training Geohazards: Coal hazard - mining subsidence plus fault reactivation

20 April 2021
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Event type:
Contributes to CPD, Lecture
Organised by:
Geological Society Events
Virtual event
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CPD Geohazards Lecture Series presents Coal Hazard Mining Subsidence Plus Fault Reactivation by Dr. Pete Brabham

Start time: 17.00 hrs

From 1750 to the 1970s the UK coal industry was the lifeblood of the Industrial revolution and UK energy, peak extraction taking place in 1912-13. Coal mines varied from single tunnels (adits) driven into hillsides over time to collieries employing 1000s of men with twin shafts to depths of over 3000ft. In South Wales alone there are over 1400 recorded mines. Before 1840, there was no legal requirement to make any maps of mining activities. Due to the large number of tragic accidents, in 1840 a law came into force that coal mines had to maintain an accurate underground map. When mines closed these maps were often discarded, so the law was amended in 1872 that on abandonment all mine plans had to be deposited in a central datastore. With privatisation of British Coal in 1994 all mine plans were transferred to the Coal Authority in Mansfield. Today the detailed paper plans are now available in digital format and can be incorporated into modern GIS.

When coal is extracted underground, the subsequent collapse of the strata can result in surface deformation or subsidence, this can take the form of crown holes or troughs. Often coal mining zones (takes) were naturally bounded by geological faults. Differential subsidence has caused some of these faults to become reactivated, resulting in a linear scarp on the land surface. Old mine shafts that were infilled with wooden rafts can potentially fail many decades later. In operation, mines were either naturally draining or kept dry by pumping. On abandonment over a period of 30 years, the groundwater can rebound. This minewater is often polluted by Iron Pyrites that can result in a red ochre staining polluting of local rivers. Waste from the mining process was usually deposited in tips without any careful engineering. Failure of tip on a steep valley side culminated in the tragedy of the Aberfan disaster in October 1966. After Aberfan many of the tips were reprofiled but with recent heavy rainfall events we have seen a re-occurrence of tip failures in South Wales.

Speaker - Dr Peter Brabham

Peter Brabham was born in the Rhondda Fawr Valley South Wales in a coal mining family, his grandfather was killed in a coal mining accident in 1956. As a child he played on the local abandoned colliery site throwing stones down the open shaft. Peter graduated in 1982 with a degree in Exploration Geophysics from Cardiff University. He then spent four years at Durham University researching into the application of seismic surveying to shallow onshore coal deposits. His time at Durham coincided with the UK miners’ strike of 1984-5. After gaining his PhD he took up a temporary post teaching at Cardiff University and 33 years later he is still there. In 1992 his geophysics research students formed the Terradat geophysical survey company. For the past decade, Peter has been the Director of the highly respected MSc Applied Environmental Geology programme. His expertise in South Wales coal geology is now being utilised by the FLEXIS Energy programme in Wales to investigate the ground heat potential of minewater in the abandoned coal mines.


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