EIACP (PC-RP) on Environmental Problems of Mining

Sodepur (No. 9, 10, &11 Pits) Colliery

This accident due to a bump occurred in the Dishergarh seam which was 3.6 m thick at the mine. The seam had been fully developed and extraction of pillars in conjunction with sand stowing had been in progress for several years.

In the No.22 Dip Section where the accident occurred, immediately above the coal seam was a weak bed of shale varying in thickness from about 25 cm to 60 cm which parted easily from the main bed of shale above it. The coal seam itself was friable and spalling from the pillar sides occurred frequently for a certain distance ahead of the pillars under extraction. This tended to make the galleries wider, and consequently, the roof more difficult to control especially when bumping occurred. In order to prevent spalling from the pillar sides and to ensure better roof control in the galleries, all galleries except haulage and tramming roads were stowed with sand for a certain distance in advance of the depillaring operations. In the haulage and tramming roadways also, the height of the roadways was reduced by raising the tracks and packing underneath with sand and stones; and the width was reduced by building stone packwalls on the two sides. The aim was to ensure that no gallery had a width more than 3 m or a height more than 2.1 m from the rails to the roof.

During his inspection of No.22 Dip Section on Saturday (20.2.1943), the manager noticed that in No.12 level some roof coal which was supported by props was showing signs of parting from the roof. There was no immediate danger from this, but he considered it better to withdraw the props and allow the coal to fall. Accordingly, the props were withdrawn at the close of the night shift, that being the most convenient time as there would be no miners underground on Sunday. The coal, however, did not fall immediately. The Mining Sirdar who inspected the district on Sunday reported that the roof coal, from beneath which the props had been withdrawn, fell down at about 1 p.m. and about 15 tones of coal was lying on the floor. Nothing unusual (like bumping or weighting) was reported in this district by the Mining Sirdars who inspected it in the second and third shifts on Sunday.

On Monday morning (22.2.1943) at about 8 a.m., before work had commenced, a small bump occurred in No.10 East Section which was about 300 m away from the No.22 Dip Section. Again at about 10.30 a.m. another severe bump was reported to have occurred in No.10 East Section but no one was injured. Work was resumed at about 11 a.m. in No.10 East section and no further bumping was experienced after that.

No.12 level, where the accident occurred in No.22 Dip Section, was at a depth of about 335 m from the surface. At about 9 a.m. the Mining Sirdar and the timber mistry examined the place where the coal had fallen the previous day. After testing the roof and dressing down the edges of the roof coal, the Sirdar asked the miners to load the fallen coal and he instructed the timber mistry to make four props ready in the meantime so that the props could be set as Soon as the coal was removed. A gang of 17 persons commenced loading the coal into tubs. This work had gone on for about 3 hours when a very severe bump occurred and caused a large mass of rock and coal to fall from the roof over a length of 12 m along the level. The fall was so large that it displaced the timber supports and broke down the stone packwalls on the two sides of the level. All the 17 men were buried under the debris, 10 of them were killed instantly, 6 received serious injuries and 1 sustained minor injuries. Of the 6 seriously injured persons, 3 succumbed to their injuries.

An inquiry into the accident revealed that at the place of the accident, all the precautions, as specified in, para 2 above had been taken to guard against bumps or at least to minimise their effects. A large number of props had also been set in the level. As was usual, the bump occurred suddenly and without any warning. The bump was caused by the breaking of the strong superincumbent strata and it transmitted a series of shock waves over a large area. Had it not been for the extra precautions taken; that is, sand-stowing of the galleries in advance, reducing the size of the roadways by stowing and building stone packwalls, the effects of the occurrence would have been much more serious and might have affected other parts of the mine also. It appeared that at the place of occurrence the shale above the coal was extra-ordinarily weak and had concealed slips and false-bedding. These factors contributed to the extensive fall of roof coal and rock which killed the large number of persons.