EIACP (PC-RP) on Environmental Problems of Mining

Rawanwara Colliery

This accident resulted from the extension of collapse of goaf over unextracted pillars. A coal seam 0.9 m to 1.2 m in thickness and dipping at 1 in 5 was being worked through inclines. The maximum thickness of strata overlying the coal seam was about 18 m and except for a small thickness of the immediate roof, the overlying strata were soft and weak. The seam was developed on the Bord & Pillar system by driving 2.4 m wide galleries and forming 12 m square pillars. Subsequently, each pillar was divided into 4 stooks, each 4.8 m square, and finally these stooks were reduced as much as safety permitted. During these operations, props were used to support the roof and when coal extraction from an area was finished, the props were withdrawn and the area was abandoned. The abandoned area eventually collapsed.

The area of workings was roughly 180 m x 140 m and about three- quarters of it had already collapsed.

In October, 1921 the Inspector of Mines found the condition of the mine unsafe and the working of the mine was discontinued. The mine was re-opened on 13.3.1923 and working was confined to the reduction of pillars near one of the inclines.

On 14.4.1923 an overman inspected the workings at about 8 a.m. and gave orders to the contractor for props to be set up preparatory to extracting a small pillar. He did not notice any signs of crushing of the pillars, nor did he think that there was any immediate danger of collapse. At about 10 a.m., the contractor re-entred the mine with two timbermen for the purpose of setting the props. Before he went in, he told the rest of his gang to remain outside the mine until the timbering had been completed. Consequently, a group of 14 persons remained sitting in the shade in the cutting of the incline. A few minutes after the contractor had – gone into the mine, an area of the workings, measuring 55 m x 38 m, collapsed suddenly causing a terrific blast of air through the incline. The extraordinary violence of this blast may be judged from the fact that all the 14 persons sitting in the incline cutting were lifted into the air and thrown over a distance varying from 6 to 60 m. 11 of these persons were killed outright and the remaining 3 received serious injuries. One of the injured persons died subsequently.

Shortly after the collapse a rescue party entered the mine and found that one of the 3 me, who were in the mine at the time of the collapse, was still alive and was pleading to be taken out. The party began digging their way towards him. They could proceed to a distance of about 4.8 m and; thought that they were quite close to the trapped man when they were obliged to retreat owing to the insecurity of the roof. At about 2 a.m. a fall occurred closing the excavation which they had made and even extending the area of the original collapse. After this fall they could get no answer from the entombed man and, believing that he was dead, work was given up for the day. Attempt to reach the buried men was made again the next day but in vain. On the third day the rescuers could reach upto the body of the contractor but as the work was highly dangerous and it was almost certain that the entombed men were dead, the rescue operations were discontinued.

The Court which inquired into this accident was of the opinion that the main cause of the accident was the faulty method of working. In order to render this system safe, it is necessary that pillar extraction should proceed only where the pillars are large enough to avoid the extension of a collapse to the spot where work is going on. In this mine the pillars had been reduced in a wholesale fashion and when a collapse occurred, it extended over the pillars at which work was going on the previous day and in the vicinity of which the three unfortunate men who were trapped, were at work.

The overman and the contractor undoubtedly thought that the work-people were perfectly safe at the mouth the incline. It is not likely that it ever occurred to the management that in the event of a collapse of the workings, an air-blast might result which would endanger the lives of people outside the mine. The Court therefore did not hold the staff of the mine culpably responsible for the deaths caused by the air-blast. However, the Court found serious failures on the part of certain individuals to comply with the Regulations and suggested that criminal prosecutions should follow.

Later on, criminal proceedings were instituted against the owner, the manager and the former manager of the mine and they were convicted and punished.

The Court recommended that the possibility of such air-blasts occurring in mines in which pillar extraction is being done should be considered by the concerned mine management. Mine owners and managers should be warned to be on their guard against bringing about conditions which might possibly lead to large air-blasts. In particular, it would be a good practice to limit the extent of an unsubsided goafed area by bringing down the roof at suitable intervals.