Protection Against Inrushes in the United Kingdom

IMWA Proceedings 1982 B | © International Mine Water Association 2012 | www.IMWA.info PROT!X:TI~ AGAINST INRUSHES IN THE UNITED KINGDOM DAVIES, A W H.M. SlliiOR DISTRICT INSP.EX:TOR OF MINES AND QUARRIES HV.LTH AND SAFETY EX!X:UTI VE SOUTH WALES DISTRICT U.K. ABSTRACT The paper describes an inrush o! water from old workings into current workings at a aine in Wales when 2.3 million litrea of water entered the workings. Two men were trapped by the inrush, one of whom was killed and the other was recovered uninj•xred after a period of 23 hours. Twenty five other persons received medical treatment. The precautions taken by the management of the mine before the inrush are described and the way about 2.6 million litres of water vas drained by a cross measure bore hole in the months leading up to the inrush. Further precautionary holes were ,drilled in a heading approaching the area containing the old workings in accordance with the existing statutory requirements, but when one of the holes breached the old workings water was tapped under pressure and a further 2.3 million litres entered the worl<.ings very rapidly. The peper r'wiews the statutory protection offered at tho time of the inrush and the recoJ!IIIIendations lllllde concerning the amendment of legislation. The consultatiYe document issued by the Health and Safety ExecutiYe is reviewed and the subsequent, establishment of the Mines (Precautions against Inrushes) Regulations 1979. The operation of these regulations aB they affer.t underground water situations is summarised. INTRODUCTION 1. In th~ period between 1900 and 1980 there were 258 de~ths in United Kingdom coal mines caused by inrushes of water. This figure, although l~>rge, vas dwarfed by the figures for deaths free: other causes aucil as explosions and falls of ground and the statutory protection offered against inrushes of vator was considered adequatw until 1923 when 52 persons were killed in inrushes in three llajor incidents, the largest being at Redding Colliery, Stirlingshir.,, Scotland [1) where II() persons were killed. 74 Reproduced from best available copy IMWA Proceedings 1982 B | © International Mine Water Association 2012 | www.IMWA.info 2. The Water Dangers Committee After these incidents a Committee was appointed in 1924 by the Secretary for Mines to enquire into the methods prescribed and adopted to prevent danger in mines from accumulations of water or other liquid matter and to make recommendations. The Committee consisted of leading mining engineers of the day and they took evidence from fourteen organisations representing the various interests in the mining industry. The Committee became known as the Water Dangers Coaaittee and their Report and its nineteen Appendicba (2) contained an outstandingly thorough and clear study of the subject. 3. The Report was published in 1927 and although no changes in the law of the United Kingdom relating to water dangers followed the work of the Comaittee appeared to have good effect as the number of deaths due to inrushes was reduced considerably. In the 56 years since 192.5, lt7 had no fatal accidents from this cause. 1973 however vas a bad year because there were two inrushes in the United Kingdom. One at LofthoUSe Colliery in Yorkshire [3j which claimed 7 lives and one at Cynheidre Colliery in Wales which claimed one life. In terms of deaths per 100,000 employed below ground 1973 became the third worst year of this century for deaths from inrushes in the United Kingdom. lt. Cynheidre Mine This mine is located in the Gwendraeth Valley at the Western end of the South Wales Coalfield. It is a large complex served by two pairs of shafts and three drifts lying within a circle of 5 km diameter. In 1973 the workings were confined to the Big Vein seam which was worked by mechanised longwall faces. The seam varied in thickness but normally about 2 m was extracted by shearer loaders. The seam analysis on an ash-free dry basis was about 90% carbon and 6% volatile. The seam was prone to outbursts of coal pf,a firedamp and operated under a special Code of Precautions ~It_} to protect against this phenomenon. The mine employed about 1,200 men and produced about 20,000 tonnes gross each week of anthracite and ~as owned by the National Coal Board, THE INRUSH AT CYNHEIDRE .5. An inrush of water occurred at Cynheidre Colliery on 16 July 1973 in a heading which was approaching old workings. One man was killed by the inrush and another was trapped for 23 hours. The inrush flooded an adjacent longwall face and several persons working there had difficulty in making their ~ay to safety. Of these 10 received treatment in the hospital but were not detained and 15 received treatment at the Colliery Medical Centre. 6. The Parts of the Mine Affected Figure 1 shows the workings in the Big Vein se8~ which were involved in the inrush. This part of the mine was served by two level 15 Reproduced from best available copy IMWA Proceedings 1982 B | © International Mine Water Association 2012 | www.IMWA.info roadways known as the 66o Horizon, which served principally as an intake airway (not shown in Figure 1 or Figure 2) and the 56o Horiz.on whJ.ch served as a return and was some 100 11 above the 66o iloriz.on. The BV1 aDd BV2 !aces had bHD worked from the adjacent Pentremawr Colliery and were abandoned in 1966 and were allowed to fill up with water tr~t was later to cause the inrush. The BV13 !ace was later worked from Cynheidre leaving a pillar to protect the 560 Horizon which was 12 11 below the seam. When the BV13 finished at a fault a connection was made for ventilation purposes to the 560 Horizon. This connection, shown more clearly in Figure 2, was known as the 1 in 1, from the gradient at which it was driven. Later still this connection was extended back, first in the seam, and then acroaa the BV13 goa! to th! other gate which was then advanced through the fault at a dipping gradient of 1 in 5 to serve the BV18 face. ~s the 1 in 1 was then no longer required for ventilation, two separation doors were erected in that part of the roadweJ which vaa in the ae... 7. In 1973 it wae decided to develop a lo~all face to be known as the BV12 to wqrk the 120 m pillar protecting the 56o Horizon by driving a heading in coal from the left hand gate of the BV13, near the top of the 1 in 1 drift, to the flooded main gate of the BV2. In addition to the usual plar~ing requirements two extra matters had to be taken into account when starting the BV12 face development heading. Firstly the drivage had to conform with the Outburst Code (4) , a consequence of which vas that the heading had to start b~tween the top of the 1 in 1 separation doors so that the products of any outburst would pass directly down the 1 in 1 into the return which was the 56o Horizon. To cater for the possibility of gas from an outbur11t backing against the ventilation into tr.e BV13 roadway an 'outburst' door vas erected inLye of the two separation doors. This was similar to these doors but opened in the opposite way (Figure 2). The heading was ventilated by intake air via ventilation tubes passing through the doors. 8. The aecond matter vas the dewatering of the BV2. It was decided by the management to do this from the BV12 development heading and a detaile4 scheme of botr. precautionary and dewatering holes was drawn up. Figure 4 shows the log of these holes that were drilled in accordance with that sch...,., and it illustrates how thoroughly this aspect vas dealt ~th. When the heading had advanced to a position 17 11 fr011 the old workings a dewatering hole, complete with stuffing box and stand pipe, would be established. When the time came !or the hole to be drilled however, it proved impossible to keep it open in the soft outburst type coal that vas encountered. ~ feature of the outburst phe~eeon which has alv&Js been present at this •ine is that bore holes, especially those of large di... ter, are oftan very difficult to drill due to cavitation ~t the drill bit and drill holes often produce very large amounts of coal cuttings. A s.aond dewatering hole vas tried fro• the heading with a similar result. 9. The plan was changed and a 62 • long cross measure dewatering hole vas bored at a calculated inclination to intersect the BV2 Reproduced from best available copy IMWA Proceedings 1982 B | © International Mine Water Association 2012 | www.IMWA.info roadway fro~ the 5GO Horizon (Figure 2) and this was successful. The initial flow from this hole was esti.. ted visually to be 550 litrH per aiaute and vu-1 ..tiaates continued to be recorded for 12 days by which time the make had reduced to 20 litres per ainute. FreE these estimates the total aake of water which c ... froa the bore hole was calculated to be 2.6 aillion litres. Tbe advance of the BV12 developaent heading had been stopped while this dewatering operation waa being done froa the 560 Hori~on. 10. When the original scheae was drawn up an estiaate was aade of the quantity of water lying in the waterlogged area. The roadways servicing the IY2 and BV1 Districts had been stopped off, and although their condition was not known, it was believed that if they had not closed completely they would be full of firedaap.

Load more