The Severn Tunnel/Chapter 8

by Thomas Andrew Walker

CHAPTER VIII.

FURTHER PROGRESS AND GREATER TROUBLES.

Progress of the work—1883.The first nine months of the year 1883 were comparatively uneventful months. The progress of the works was constantly increasing, and they were now in full swing throughout.

The rate of progress rose from £23,000 per month at the end of 1882, to £31,000 by mid-summer, and continued at the rate of about £30,000 per month through the remainder of the year.

The most rapid progress was made on the Gloucestershire side of the river. More shafts were sunk at intervals of 60 or 80 yards from the existing heading to the new gradient, and the whole of the bottom heading was completed down to the ‘Shoots.’

The heading through the gravel which had run in, in November, 1882, was secured and safely driven to the extreme eastern end of the tunnel, where a junction was made with a small shaft sunk by the Company in 1879.

The bridges over the open cutting were commenced, and the cutting itself lowered to the right Progress of the work—1883. level from its eastern end for a length of rather more than a quarter of a mile, when two steam-navvies were brought upon the works, and started to take out the excavation. A shaft was sunk at a point rather more than a quarter of a mile east from the eastern tunnel face, where a public road and one of the main drains of the level crossed the railway.

At this point it had been originally intended to build an ordinary bridge; but after the lowering of the gradient, it was found necessary to execute a short length of tunnel instead of this bridge. The shaft was sunk for the purpose of constructing this tunnel.

The invert of this tunnel was just on the top of the red marl, and the whole of the tunnel itself in gravel, with great volumes of water. Above the gravel was soft running sand, and then mud.

It was ground that required the greatest care, and could only be safely executed by being kept perfectly dry.

Two 15-inch pumps were therefore fixed in the shaft; and before the end of the year a break-up was started in the middle of this tunnel, and about 20 yards of completed tunnel executed.

Before the end of the year rather more than a mile of full-sized tunnel was completed from the Sea-Wall Shaft. The arch was finished under the whole length of the ‘Shoots,’ and all but 100 yards from there to the Sudbrook Pit. The tunnel was Progress of the work—1883. completed for rather more than 100 yards westwards from the Sudbrook Pit, and the bottom heading from the same point, towards the point where the Great Spring had broken in, was commenced.

At 5 miles 4 chains, more than 200 yards of full-sized tunnel were put in, and about 100 yards of arch turned.

Another break-up was also started, and the brickwork commenced in it, at about 250 yards westwards from this shaft.

Very good progress was made from the Marsh Pit. By the end of the year more than 200 yards of the tunnel were completed east from this pit, and about 700 yards westwards.

From the Hill Pit about 70 yards of tunnel were completed east from the pit, and more than 400 yards westwards.

The cutting on the Monmouthshire or Welsh side of the river was commenced in March.

On the 9th February, a terrible accident happened to some men who were working at the 5 miles 4 chains pit. The men were gathering round the bottom of the pit at one o’clock (after midnight) to come up to supper; the one cage was at the bottom, and four or five men had just got into it; and the other cage was on the upper level, from which the skips were taken to the clay-crushing machine, when the banksman at the ground-level (a steady man, who had worked a considerable time at the same employment), seeming to forget the position Progress of the work—1883. of affairs, and thinking that the cage on the one side was standing on the ground-level, suddenly took hold of and pushed an iron skip right into the mouth of the pit. The iron skip, falling about 140 feet, crushed the bonnet of the cage at the bottom, and killed three of the men who were in the cage; and the skip then rebounding among the crowd of men who stood near, killed another man and seriously injured two others.

The holes which had been stopped in the bed of the river once or twice this year required further attention, the tide washing away the clay and bags which had been placed over them; and it may be as well to state here, that in the following year, before the tunnel was completed, when this clay was supposed to have settled as far as possible, the hole at the top was slightly enlarged and sealed with a thick layer of concrete.

The works being thus in a very advanced condition, except the length of about 200 yards adjoining where the Great Spring had broken in, it was decided to open the door in the head-wall, which had been built across the heading in December, 1880, and to take in hand the length passing the Great Spring.

At the end of May an attempt was made to open this door, but it was at once found that a quantity of rock and shale had fallen down behind it, and that it was impossible to open it. On the 30th May holes Progress of the work—1883. were bored through the door with augers, and a piece 12 inches across was broken out. Through this a considerable quantity of soft material was forced by the pressure of the water behind, and now and then large rocks were brought down which stopped the hole. For more than two months the men continued to work, taking away material which was forced through the door by the pressure of the water behind, having continually to break up with long bars and ‘jumpers’ the lumps of rock which blocked the hole. At last it became evident that it would be an endless matter to attempt to work in this manner, so the bottom heading was pushed forward until it passed well beyond the point where this door was built.

A hole was then broken up from the bottom into the top heading, and all the water from behind the door allowed to pass that way.

Men then got up into the upper heading, and found that a length of 50 or 60 feet of the roof had fallen in, and that there was an enormous cavity above, but that little water was coming from that direction.

To obtain better access to the upper heading than was afforded by the hole broken up from the bottom heading, we then drove a small side heading round the end of the head-wall, and thus had double access to the heading beyond.

We commenced at once to pole and secure a heading through the mass of débris that had fallen from the roof. We also drove a rising heading from Progress of the work—1883. the end of the brickwork of the tunnel, up at an incline of about 30 degrees from the horizontal, and so broke into the great cavern that had been left above the top of the tunnel by the falling down of the roof of the heading. Up this sloping heading we carried all the old timber that we could obtain in short lengths, and threw it forward into the cavern, hoping to fill it up, and to support the roof before further mischief occurred.

We continued to drive the bottom heading 9 feet high by 9 feet wide, and in it we built a head-wall with a door, almost directly under the door in the upper heading.

We then restored and properly timbered the upper heading, repaired the head-wall, and hung a new door in place of the one which we had broken in our endeavours to get through. We cleared down also to the top of this head-wall from the sloping heading, and built another head-wall across that to guard against accidents.

The total quantity of material forced through this door by the pressure of the water behind was 2,000 yards, showing the enormous extent of the cavity above, and the damage that had been done by not properly timbering the heading at first.

While this work was going on, on the 30th September, another serious accident occurred, happily without loss of life or injury to any of the men. A ‘bond’ or wire-rope, used for lifting the large cages at the Sudbrook Winding Shaft, broke about Progress of the work—1883.

midnight. The two cages were adjusted by additional wire-ropes to balance each other, so that the engine only had to lift the weight contained in the cages, and not the cage itself. The bond broke just as the one cage, containing four loaded skips of rock, had reached the top; the other cage was at the bottom. The first cage was not sufficiently high to allow the banksman to turn the tumblers under it, and when the bond broke, the upper cage being loaded, and the other empty, the loaded cage rushed down the pit with terrible velocity, throwing the light cage up against the head-gearing at the top of the pit, smashing the pulleys and the other wire-rope; and then the light cage also fell to the bottom, and both cages lay together broken.

It is noteworthy that the wheels under the loaded skips of rock which fell 200 feet into the tunnel, being made of Hadfield’s steel, were not broken.

As the work was now so far advanced, I decided not to replace these large cages, and fixed instead two single cages, only large enough to carry the cobs that were used in this part of the work for hauling the skips. While the alterations were being made, four of these cobs had to be stabled at the bottom of the pit.

The following pages will show how fortunate it was that at this very time we had taken these precautions with regard to the head-walls and doors, Progress of the work—1883. and the security of the work generally between Sudbrook and the Great Spring.

Of course all possible precautions were taken at all times, but it seemed an extreme one at the moment to push forward these three head-walls, one above the other.