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Falls of Ground Incidents - Reporting Year 1997/1998

Contents

Introduction

This report summarises the fall of ground dangerous occurrences and fatal and major injury accidents reported at mines during the 1997/98 reporting year.

All statistics are provisional.

Dangerous occurrences

Any fall of ground, not being part of the normal operations at a mine, which results from a failure of an underground support system and prevents persons travelling through the area affected by the fall or which otherwise exposes them to danger, was introduced as a dangerous occurrence at Part II/40 in RIDDOR 1995, with effect from April 1996. This is the second full year that such incidents have been reported to HM Inspectorate of Mines.

Twelve falls of ground were reported at mines during the year, eleven at coal mines and one at a miscellaneous mine.

Seven of the falls occurred in places that had recently excavated, two occurred in places excavated within the last 6 - 12 months and three of the falls occurred in places that had been driven more than five years ago.

In coal mines, most incidents occurred in roadways supported by free standing passive support such as arches, props and bars etc. Nine falls occurred in places supported passively and two in places supported by rockbolts (see table). Three of the falls occurred in bord and pillar roads, two on facelines, five in main/gate roadways and one in a development drivage.

At the miscellaneous mine the fall occurred at a junction which relied upon natural rock strength for support. This junction had originally been enlarged to house a crusher installation penetrating the normal overlying gypsum and permitted weathering and weakening of the upper soft marl.

The recorded roadway falls varied in height from 1m up to 6.6m, in length from 1.7m to 11m and in width up to a maximum of 6m.

Fall of Ground Dangerous Occurrences

Age of Excavation
Recently driven 7
6 - 12 months 2
Over 5 years 3
Total 12
Type of Support
Free-standing support 9
Rockbolting 2
Miscellaneous 1
Total 12
Warning of Collapse
None -
Less than 24 hours 3
Over 24 hours 9
Total 12
Type of Excavation
Junction -girders 2
Junction - rockbolts 1
Junction - natural support 1
Roadway - props and bars 3
Roadway - arches 3
Roadway - rockbolts 1
Faceline 1
Total 12

Accidents

There was one fatal and 22 major injury accidents at coal mines compared with 2 fatal and 29 major injuries in the previous year.

There was one major injury reported for other mines compared with two the previous year.

At coal mines, 13 of the accidents occurred in places supported by free standing supports, five where powered supports were used and four where rockbolts were used. The fatal accident occurred at the main gate end of a longwall retreat face where there was a sudden failure of the forward face side rib in the roadway which was supported by rockbolts. At the time of the accident the face had not reached the 'square' position and was negotiating a minor swilley. The rib, some 7m × 1.4m × 1.4m, failed without warning and trapped a workman against the stage loader.

1996/1997 1997/1998
  Fatal Major injury Fatal Major injury
Coal mines - free standing supports (arches, props and bars etc) 1 15 - 13
Coal mines- powered supports - 11 - 5
Coal mines- rockbolts 1 3 1 4
Miscellaneous mines - 2 - 1
Total 2 31 1 23
1996/1997 1997/1998
Coal Mines - place of accident Fatal Major injury Fatal Major injury
Longwall face - 14 - 7
Headings 2 13 - 13
Elsewhere - 2 1 2
Total 2 29 1 22

Conclusions

The number of falls of ground dangerous occurrences have remained virtually the same at 12 reported this year against 13 last year. The majority of these falls occurring in places passively supported.

There has been a noted reduction in the number of falls of ground accidents with the most notable reduction in the powered supports category.

H C EVANS
HM Principal Inspector of Mines
17 June 1998

2012-11-27