|The colliery was near Mansfield, Nottinghamshire and there were two shafts each 15 feet in diameter which were sunk in 1874 to the Top Hard seam by the Skegby Colliery Company and deepened during 1896 to 1897 to the Low Main seam at 467 yards deep. The Top Hard, Deep Hard, Deep Soft, Low Main and Piper seam had all been worked and the Top Hard had been exhausted many years before. At the time of the explosion the daily output was 1,200 tons of which 850 tons were from the Low Main seam which had been worked for 40 years. The remainder of the output came from the Piper seam.
The district in which the disaster took place was known as 28’s and was one and a quarter miles inbye in the Low Main seam 580 yards below the surface. Up to a month before the disaster, the seam had been worked by machine cutting at floor level, blasting and hand filling onto conveyor belts which fed a trunk conveyor. The system was changed when an Anderson shearer coal getting and loading machine was stated on the 28’s face on the 28th. January 1957. The district usually employed 30 men on the day shift, 12 on the afternoon shift and 10 on the night shift but o the 21st. February during the day shift when the explosion occurred there were 40 persons in the district including and electrician, a fitter and the undermanger.
The mine was ventilated by an exhausting direct coupled steam driven Davidson Sirocco double inlet fan which was situated at the surface and circulated 115,000 cubic feet of air per minute at 3.3 inches water gauge. A new fan, driven by a diesel engine which was designed to circulate 175,000 cubic feet per minute at a water gauge of 7.7 inches. This had been installed and was ready to use. The fan as first used three days after the explosion. The workings in the colliery were not particularly gassy but firedamp was found and safety lamps were used throughout the colliery. Those in general use were Oldham G.W. electric cap lamps. as firedamp detectors, Protector Type No.6 flame safety lamps, fitted with pyrophor bar internal igniters. Gauzes of all the flame lamps were of 28 mesh. Automatic firedamp detectors, Ringrose 47/125 Type, were provided but there was some reluctance on the part of the men to use them. There were only two in use in the mine at the time and neither of them were in the district involved.
The colliery was in the National Coal Board No.4 Area of the East Midlands Division and the principle officers at the time were Mr. F.D. Severn, Area General Manager, Mr. T. Wright, Area Production Manager, Mr. C. Round, Deputy Area Production Manager (Operations), Mr. J. Atkinson, Deputy Area Production Manager (Planning), Mr. T. Frith, Group Manager, Mr. A. Stone, Acting manager and Mr. W. Bacon Acting undermanager. The previous manager, Mr. E. Maiden, had left the pit to take charge of another colliery on the 1st. February 1957 and the undermanager Mr. Stone, was temporally appointed as manager.
The officials in the low Main No. 28’s district, day shift were Mr. T, Buckley, overman, Mr. J.W. Kirk, deputy, Mr. S. Derbyshire, shotfirer. On the afternoon shift, Mr. W. Warren, overman, Mr. J. Aldred, deputy and on the night shift, Mr. A. Walker, overman and Mr. M. Cox, deputy. As was customary on these mechanised faces, the face work was spit up into stints, each about 30 yards long. Ten men working in pairs were employed for advancing the conveyor and for setting and withdrawing supports, five men were employed to fill the coal at the loader gate stable hole, remove the original left side pack of the loader gate and take up the floor of the loader gate so that the conveyor driving engine could be advanced. Four men were employed filling out the coal at the return gate stable and two additional men were working at the left end of the face where it was slowly being extended. At the time there were 34 men, a shotfirer, a deputy, an acting undermanger, two electricians and a fitter making a total of forty men in the district at the time of the disaster.
The coal in the Low Main seam was 3 feet 3 inches thick with a medium clunch floor and a roof of 9 inches of clunch, 4 feet 6 inches of coal and 35 feet of grey bind with 60 feet of sandstone above. There was a variable but thin section of sandy material between the grey bond and the sandstone. A double until coal face, 280 yards long, and was known as 30’s face had been advanced 1,250 yards to the north-west, rising at about 1 in 100, by orthodox machine cutting, blasting and hand loading on to a face conveyor belt. There were three roads or gates of this face, the middle and right hand gates were the intake airways and the left gate was the return. The middle gate was the loader and conveyor gate. Electricity was used to operate the machinery in the district.
On the 11th June 1956, at a point 120 yards inbye from the junction of 30’s loader gate and old 28’s face trunk road, a scouring was started from 30’s loader gate, driven through the waste to 30’s right side gate and for a further 15 yards to the solid coal on the right of 30’s right side gate. This road continued in the coal for about 10 feet and as about 12 feet wide. The face was then widened to about 30 feet and the road, still 12 feet wide, was carried forward with stone packs about 9 feet wide on each side. It was dipping about 1 in 8 and was supported by 12 foot steel arches which were 9 feet high. The ventilation came from an auxiliary fan 18 inches i diameter driven by a 5 H.P. electric motor which forced air though canvas ducting to the face. By 14th July 1956, this road had reached a point 63 yards from 30’s right side gate where it stopped. A coal face, now called Old 28’s face, had been worked to the north-east but had been abandoned owing to difficulties in maintaining the roads. It was intended to develop a new face to replace Old 28’s face advancing in the same direction but leaving solid coal 80 yards wide between the ends of the Old and the New 28’s faces and also 50 yards of coal to the right of the 30’s right side gate to protect the gate from damage. Plans were changed two or three times both on the layout and the direction of advance of the New 28’s face and also as to the scheme of ventilation. Eventually it was decided to open New 28’s face 150 yards long, immediately to the right side gate, leaving no coal for protection of this road and extending to the left of the original development road.
The face was opened out by driving a road in the coal about 12 feet wide from the left side of the developing road from 150 yards to the north-east in the same direction as the 30’s face and then to make a connection through the pack back into 30’s right side gate. This was completed on 29th. December 1856 and this the new face was arranged to be ventilated with the original development road at the right end as intake, the air passing along 28’s face, along 30’s face and out along 30’s left gate as a return airway. This meant that 28’s and 30’s were ventilated in series. At the time the Coal Mines act, 1911 was still in force and therefore under the Electrical Regulations under the Act notice was required to be given of intention to introduce apparatus into the mine or any ventilating district of the mine, but in this case 30’s and 28’s districts were part of the same ventilating district and electricity was already in use in that district. After 28’s face had been advanced 10 feet by hand getting, and Anderton shearer coal getter loader, mounted on an armoured chain conveyor, both of which were electrically driven, was installed with what was known as the prop free front method of support to allow the conveyor to be advanced broadside following each cut of 20 inches by which the face advanced.
The roof at the face was supported by coupled 3 feet 3 inch long bars set to a triangular system on hydraulic props fitted with castellated heads. They system required rows of bars to be set at maximum intervals of 3 feet with 6 feet maximum intervals between props in the same row. The necessary authorisations and exemptions had granted under the provisions of the Coal and Other Mines (Support) Regulations. The maximum interval between the front row of props and the face was authorised to exceed 3 feet but not to exceed 5Å feet. Alternate bars were to be advanced after each cut of 20 inches.
The original development road was both intake and loader gate, with the face conveyor discharging into a stage loader and then into the gate conveyor which extended to a common trunk road conveyor at the junction with 30’s face loader gate. To enable the original loader gate to function as loader gate it was necessary to remove a 3 yards wide pack at the face on the left side of the gate to allow the face conveyor and it’s driving machinery to be advanced after each cut. This roadside pack was rebuilt behind the face conveyor after each day’s coal getting, the original road having to be remade by taking up the floor and ripping the roof and putting in new steel arches, 12 feet wide and 9 feet high. The return gate at the left side of 28’s face was also roof ripped and packed on each side as the coal face advanced. 12 feet by 9 feet steel arches were set 3 feet apart, but within 20 feet or so of the face a similar sized arch was used. Strip packs, 3 yards wide, were built 9 yards apart in the waste between the two gate ends for the first 15 feet of advance of the coal face with the Anderton shearer.
Mr. Maiden was the manager at the time and he informed the Inspector for the District that he intended to stop the intermediate packs once the face had advanced far enough establish proper control of the roof. The full caving system extended from the left side of the pack, 9 feet wide, of the loader gate to the right side of the pack of the return gate, a distance of about 130 yards was started on 11th. February 1957 and was continued up to the time of the accident during which time the coal face had advanced a further 44 feet. The management claimed that full caving between the roadside packs was introduced earlier than originally intended because the roof wastes between the intermediate packs was not breaking down regularly to provide packing material. The waste edge support by chocks was doubled and the roof at the face improved.
The loader gate was already difficult because of the need to take out the 3 yards wide left side of the pack to enable the face conveyor and its driving machinery to discharge through to the stage loader and to rebuild it behind the conveyor. As might have been expected, these difficulties became much more serious after caving was started. Indeed large falls of roof occurred in the loader gate and continued as the coal face advanced. the road was widened to 17 feet by extending on the left side as the cavity left by the falls widened on this side. To cover this width, 5 feet long horizontal joists were inserted between the steel arches sections. For several days before and also between 6 and 7 a.m. on the morning of the explosion, falls occurred and had left a cavity about 36 feet long, 9 to 12 feet wide and 10 to 12 feet high, above the steel arches of the roadhead. To top and sides of this large cavity were only partly and inadequately secured by two wooden chocks built on the wood lagging pieces laid over the steel arches.
People had to work at the face under the edge of this cavity and the electric cables from the driving gear of the face conveyor were under it with only steel arches covered by boards to protect them against the a danger of further falls. A fall occurred between 6 and 7 a.m. and partly buried the face conveyor engine and closed access to the coal face, so that the miners had to withdraw for a time and under the supervision of the undermanager and the deputy they helped to remove enough debris to enable the face conveyor to run again. This fall was liable to damage the machinery including the electrical gear in the roadhead. The fall was also liable to injure workmen but an electrician and a fitter examined the machinery and found it safe and it was agreed that it was safe to restart work. This was done without anything being done to secure the roof.