Making room for the pony - concrete and steel support of tunnels

Prior to 1842 horses were most often used outside of mines to help raise the coal up through the shafts, often with the aid of horse gins such as this.

A Cog and Run gin used for raising coal from 1775 (A Pitman’s Notebook – The diary of Edward Smith, Manager of Houghton Colliery, 1749 – 1751, Frank Graham, 1971)

As I noted in the last Technical Note, the passage of legislation in the UK in 1842 prohibited the employment of women and children under 13 in underground mines. Their labor had to be replaced, and the replacement was often with pit ponies. However, unlike women and children who could be trained to cope with working heights shorter than they were, this did not hold true for horses. And so there had to be some change in the way that the mines were operated, particularly where the coal seam was not that high. Today’s topic will discuss some aspects of how they drove that, and will end with a comment on concrete shaft liners that might have some relevance to the recent events in the Gulf of Mexico.


One of the first steps attempted to gain the extra height was to cut a deeper passage in the floor of the mine. This was often softer than the roof, and would give the additional height needed, but as I will explain later, often only for a short time.


Eighteenth century mine exposed by modern surface mining, showing the deepening of the main tunnel floors to allow the passage of ponies. (The Collier by A.R. Griffin, Shire Publications 1982)(There are two people in the shot, to give a sense of scale. )

This did not prove to be that popular, and the more common practice was to fire explosives in the overlying rock and thus drive a higher tunnel, for the passage of supplies in, and coal out. The brow of that excavation was generally kept up with the face of the mining operation, and required special support. (There was a man killed at a mine I was working at, when this area collapsed).

View of the end of the roadway leading to the working area (Modified from the Support Rules for Easington Colliery, National Coal Board) The grey area shows the height of the coal, stone packs sit behind the arch girders in an area where the coal has been mined out)

It was found that the tunnel was more stable if the overlying roof was broken out in the shape of an arch, and it could be shaped so that steel arch girders could be placed to hold the roof rock in place. There was, however, a problem in getting rid of the rock that was blasted down. Taking it out using the tubs occupied valuable space and time and earned no-one any money.

Pony hauling a tub full of rock (slack - coal contaminated with rock or other dirt) (From “The Collier.”)

It was found that if the coal on either side of the main tunnel was removed, that this would leave a space into which the overlying rock could be packed. The larger blocks of rock were used to build the walls from the floor to the top of the opening, and then the “stone man” would shovel the smaller broken rock behind it, packing it up to the roof and providing additional support. This gave a gain in production from the coal removed, while helping with disposal of what would otherwise be waste rock.

Using stone packs beside an underground roadway (The Colliery Deputy’s Handbook, D.G. Maguire, 1956)

The illustration helps illustrate another advantage of this over taking up the floor. The rock under the coal is often a shale, that can soften. When the rock weight that rested on the rock removed from the tunnel shifts, it does so to the rock immediately beside the tunnel. If that is a solid connection, then the additional pressure is applied to the underlying shale. If this is softer rock it can flow out under the pressure, pushing the rock floor of the tunnel upwards, which is known as floor heaving. This can get to the point that it reduces the height of the tunnel by over two-thirds and the tunnel floor has to be removed with a secondary mining pass. If the coal has been removed to either side of the tunnel, then the floor heave that takes place can occur in the pack area outside the area of the working tunnel, as the picture above shows. This makes it easier to maintain a clear passage.

However, there will still be some compression of the rock packs as the weight of the rock comes on them, and so the arch girders that are used to support the tunnel are put on small wooden stilts. As the weight comes on the arch, it is pushed down between the two pieces of wood, converging without distortion, and still supporting the roof.

Arch with stilts (Deputy’s Handbook).

Steel arches of this type were used in much roadway construction, both for mining and civil tunnel support (including subway systems) for many years.

However the arches, even when supported with wooden struts between adjacent arches, are not waterproof. Thus they were not of great benefit when, for example, it became necessary to sink a shaft through water bearing rock to get down to the coal. There were two ways of dealing with this, one was to weld steel plates together to give a continuous casing of the shaft, from the surface down to the seam. The other was to use concrete to pour a liner to the shaft as it went down.

However there are a couple of problems with using concrete alone as a supporting system, for while concrete is good as a support that resists loads that do not change much, and that put the support into compression it is brittle, and more vulnerable to tensile loading. It has been noted that where conventional concrete comes under a pressure, then the small fissures in the structure of the concrete can open up and extend so that the concrete becomes permeable. Part of this is due to the differential compression of the different phases of the material in the concrete. If the loading is relatively even around a cylinder in compression, then the cracks can remain quite small, but when, for example, you get the differential loading, such as that which is shown in the picture above of the pressure distribution around the arch with two walls, one can imagine how there is sufficient differential loading that cracks can open and water, or other fluid, enter the passage. As a result in mining operations concrete has proved, alone, to be an unreliable water seal and often requires additional steps to prevent water access, or ways to collect and trap the water, so that it can be carried away without interfering with workings. From personal experience, lying on your side shoveling coal, while water drips onto your back has little to recommend it.

Coal mining - the transition to pit ponies

One of the problems that has consistently plagued underground coal mining lies in the height of the coal seam that is being mined. This was the portal (i.e. entrance) to a coal mine that we once ran a research project in, near Summersville, W Va.

Dr. Rupert and I in May 1975 at the portal of a W Va mine. (Note the kneepads).

The mine was extracting only the coal, and you can see that the entry height comes to just below our shoulder blades, which made walking into the mine (about half-a-mile or more) very tiring, since you have to walk in quite bent over. As a result, the machines that work in these low conditions, have the operators lying almost recumbent as they steer and operate them. Back in earlier times, however, before there was much machinery underground, conditions were much different. And so today I thought I would talk a little more about those early conditions and how changes began to evolve.


I’m motivated a bit in this by finding (on a market stall in Lancaster) an illustrated autobiography by James Dunn called “From Coal Mine Upwards,” that was written in 1910 by a 70-year old who began his life in a mine. As the prologue noted (abbreviated):

Over sixty years ago in a small village on the border of the Leicestershire coalfields a company of men met to discuss what was to be done with a poor lad eight years old. The richest farmer in the neighborhood said” “I should like to ask two questions before you decide. The first is, how much learning does it want to drive the plough?” and “How much learning does it need for a lad to work in the coal-pit?” The answer was very little, and to the coal pit at eight years of age I was sent to work. It was in those dismal mines, four hundred yards deep and about a mile underground from the bottom of the shaft, that I commenced to earn my daily bread.”

He was fitted with a flannel shirt, wide trousers, a cap, a smock-frock, and heavy nailed boots. He walked the two miles to the mine to be there at 6 am and he earned tenpence a day, except that the mine rarely worked more than half days, so that he made around 30 pence (when 240 pence made a pound which was worth about $4 at the time I believe) a week. After a ten to twelve hour day underground he then had to walk home.

He was lowered into the mine on a chain fitted with loops, and then walked to the working face, having been given a candle to light the way. His job was to haul at the front of a tub, so that he took off all, but his trousers, socks and boots and his flannel cap.

The man I had to work with showed me how to place a leathern belt around my loins, with a light chain attached about a yard long, which was hooked to the front of the small wagon of coal thus pulling from the front while the man pushed behind.

From James Dunn “From Coal Mine Upwards”, W. Green London, 1910. 227 pages

The mine was worked by subletting different jobs, thus a miner would work in measures of a“stint” which was two yards wide, by a yard deep to mine the coal. He loaded the tub from the face of a tunnel that he was driving into the coal, and then swopped out a full and an empty tub to continue.

Loading the coal. A sculpture in the archive at Missouri S&T

The initial rails were wooden, and the tubs were turned on steel plates at the end of the tunnel (the “flat”). Once the tubs were started back to the mine shaft, they passed through a series of folk:

this process was worked in what they called “stages”, or lengths, a man having one stage, and then two boys the next, then another miner, and then two boys, and this was continued throughout the whole length. Now it will be seen that every pair of boys were running between two men – one at each end of their stage, and the great concern of the boys was to meet the man at either end, so as not to keep them waiting. . . .(if late) The man at the other end would be waiting with his empty truck (tub) and the probability was that the boys would be beaten with his strap.

The men were paid by the ton delivered to the shaft top (a token in the tub marked who had loaded it) but the boys were paid by the day, and thus not nearly as well rewarded.

Rails were the first major improvement, transitioning from just dragging the corves on one’s back, which had been the earlier method. But the tubs had still to be moved manually. It was pictures such as this, that had led to the legislation that got women and young children out of the mines in 1842.

Woman hauling a corf, Royal Commission Report, UK, 1842.

Hauling the flat (on which a corf or two would be mounted. Note the chain) MO S&T archive

They were replaced, in large part by ponies, but there was an immediate consequence. It had been possible to use people to drag tubs along in low coal, but that doesn’t work with ponies. (And in some seams they still remained impractical).

Putting in a 2 ft 10 inch coal seam, 1929 (A Bevin Boy Remembers, Ted Holloway, Henge Publications, 1993)

The tubs were also of wood at this time, since it allowed the front planks to be removed to fill the tub, where the roof was too low to easily fill it over the walls. But the ponies had to have more height, and so the height of the roadways had to be increased. (Which also made it easier to walk down them). This was done by blasting a small amount of rock from the roof of the tunnel, giving the extra height. As James Dunn noted “My lot was never as hard again.”

From "The Miners," Anthony Burton, Andre Deutsch Ltd 1976

The ponies had the advantage that they could pull more than one tub at once, and with the restriction on height gone, they were more frequently made of metal. You may notice the lad riding on “the limmers.” That was, strictly speaking, forbidden, though I think we all did it.

As mines became more productive, so the ponies could not keep up with the number of tubs that had to be hauled down the access roads, and they were, in turn, replaced by long “endless” ropes of wire, to which we attached the tubs, and which then hauled them from around the face area down the mile or more to the shaft, where they were disconnected, loaded onto the skip and hauled to the surface. But I’ll talk about the first steps in mechanization next time.

Manually mining coal underground

Since last I wrote I have travelled to London and then up North into southern Scotland (I write this looking down at the station in Dumfries, having passed the one-time house of Scotland’s Bard). Today I would like to continue writing on some of the historic methods of mining coal, in part because, in certain parts of the world, this is still the way it is done.

Last time I had talked a little about how mining started where the coal seam came to the surface, or outcropped, and that miners worked their way into the hillside digging the coal out creating both a passage deeper into the seam, and also leaving some pillars, as they widened out the passage way to mine more of the coal. Other times, as the coal became deeper, instead of working from the outcrop, they would sink a small shaft, and mine coal out from around its walls. Because the mines thus had the narrow shaft and then widened in the coal seam they became known as bell pits. They were used in parts of Northumberland as late as World War 1. The miner would break out the coal with a pick, and hand load it into baskets, or corves, that would then, initially be carried up the ladder by children or women. However as the mine got deeper the ladder haulage would be replaced by a hand-turned winch, or later and for deeper mines, a horse gin or other winching system using an animal.

Picture of bell pit

Picture of horse gin
A two-horse gin is reported to have been able to raise some 2.5 tons of coal an hour.

As demand grew, so the underground mining pattern would grow with it. This may was from the Kehley’s Run Mine in Shenandoah, PA. The plan shows how, from the original drift into the side of the hill, the mine spread out along and behind the outcrop, leaving as small a pillar as possible to hold the roof up.

Partial plan of Kehley’s Run Colliery at the time of an underground fire in 1880. The red areas show roof falls. The cracked black are broken pillars, while solid black are pillars with some strength and integrity. (I have cleaned the image a little with Photoshop)

You can see in the illustration how the mine (the current entry is at M, the earlier entry having been closed by the roof collapse shown) mined as much coal as possible to leave the least amount of coal, and that this could cause roof falls. I mentioned one of the fires at the mine, but this mine also raised attention from one of the many riots that erupted between miners, mine owners and their security guards.

Some of these stories have been dramatized in movies such as the “Mollie Maguires”, but it was a grim and vicious set of confrontations based on grim working conditions. In one seven year period some 566 miners were killed and 1,665 were injured in Schuylkill County, PA alone.

Confrontation at the Kayley's Run colliery 1888 (after Popalis )

You might be able to get some sense of the grim conditions from the mine plan. Conditions had been worse in Europe. There are a number of nasty things that can happen in coal mines. As we recently saw and heard, one of them relates to the gas that is given off during mining. Like natural gas from other sources, in ranges from 5 – 15% this methane can be explosive and thus the levels of gas must be kept below this level (hopefully below 1%) if the miner is to be safe.

The other gas that had to be watched for was carbon dioxide, which in contrast with methane, which being lighter than air collects in the roof, is heavier and thus pools on the floor. So that if you were getting down to cut the starting slot in the bottom of the coal seam, you might just drop into a pool. It was called choke damp – though that was also the name given to carbon monoxide, which could also seep out of the coal. All these gases are colorless and odorless so that without some form of detection (the canary for example, or using a candle as a test) they can lurk to catch the unsuspecting. With the invention of the safety lamp (where the heat of the flame is removed by a surrounding mesh of copper wire) it became possible to use the lamp itself as a testing tool. One of my first mining tests was to make sure that I could tell, by the height and shape of the small blue flame of the methane burning over the lowered flame in the lamp, what the gas concentration was. (Each lamp was in a separate hood, and I remember that they had two at the same concentration in the set of around half-a-dozen I had to evaluate).

Methane caps on a safety lamp flame (Colliery Deputy’s Handbook)

When the miner saw the flame cone, he would first wave a shirt or towel to stir the methane into the air, hoping that the concentration would fall below 1%, but if the level built up, he might have to leave, or call for more drastic measures to get rid of it. Back in Medieval times there was an individual called The Penitent, who would wrap himself in wet rags and crawl into the mine with a candle on a long stick. Raising the candle to the roof, he would ignite the layers of methane that would gather there, before the rest of the miners came back into the working. Methane, being lighter than air would gather in the roof, when the air currents were not strong enough to mix it into the air and remove it.

The Penitent – an etching by Hildebrand

But, as they mined coal from further away from the shaft, the air would not easily move around the workings, and since the coal would give off other gasses, as well as methane, there needed to be some way of circulating the air. And so the miners began to run sets of tunnels out into the coal that ran parallel to one another, but with cross tunnels (cross-cuts) between them so that they could circulate air around and up to the working area.

For many years, starting in around 1810 the motive power for the air was created by having a fire in the bottom of the shaft, in a special furnace room. Usually these were underground, although there was the occasional one at the surface. Unfortunately if the fire ignited the surrounding timber that was being used for support, then a major fire could result, killing everyone underground. This was the case with the Avondale mine disaster in 1869, at the time the worst industrial accident in American history, 110 people died.

At first there was only one shaft or tunnel leading in and out of the workings, but a major accident occurred at New Hartley in Northumberland, UK in 1862 where the main beam for the dewatering pump fell into the shaft, blocking it. The 199 men and boys in the mine, virtually the entire working male population of the village, were all killed, It was a result of those deaths that legislation was passed that required that there be two separate ways to get out of a mine. Where the mine is deep underground this means that there are generally two shafts, or more from the workings to the surface. (My Dad was manager at the resurrected mine, and the village school was the first primary school that I went to).

Initially men broke the coal from the solid with picks. To mine more efficiently they would first swing the pick along the bottom edge of the coal, and cut a slot that would be perhaps a couple of feet deep. Then they would drive the pick into the cracks in the main seam section and break the coal to the edge that they had created. When they worked this efficiently, a man can be very effective in breaking out the coal (about 4 joules/cc specific energy, for those that are interested, The machines mine at around 1,000 joules/cc of coal removed).

As the working face grew away from the shaft, it became too slow to rely on women and children to carry the baskets, on their backs, to the shaft and up out of the mine. ( A woman was reported to be able to carry about 56 lb of coal at a time. So first rails were used to slide the baskets along. Then wheels were added, first to flats, and then to small tubs. At first these were of wood, but then were changed to metal.

Although there are still parts of the world where this type of primitive mining still occurs, and where women and children are used to help get the coal out, in most countries they have been banned from underground work. (This was the Act of 1842 in the United Kingdom) . Taking the coal from the miner or hewer to the shaft was known as putting or hurrying. (I learned it as putting).

Six year old girl:
"I have been down six weeks and make 10 to 14 rakes a day; I carry a full 56 lbs. of coal in a wooden bucket. I work with sister Jesse and mother. It is dark the time we go."

Jane Peacock Watson.
"I have wrought in the bowels of the earth 33 years. I have been married 23 years and had nine children, six are alive and three died of typhus a few years since. Have had two dead born. Horse-work ruins the women; it crushes their haunches, bends their ankles and makes them old women at 40. "

Maria Gooder
"I hurry for a man with my sister Anne who is going 18. He is good to us. I don't like being in the pit. I am tired and afraid. I go at 4:30 after having porridge for breakfast. I start hurrying at 5. We have dinner at noon. We have dry bread and nothing else. There is water in the pit but we don't sup it. "

With time horses (or pit ponies as they were called) were taken underground and used to haul the tubs. Ponies were used for haulage well into my working career, and leading one was the first underground job that I had, when I worked in the mines before going to college. They served two purposes, being used firstly to haul the coal from the face, but also to haul wood back to the working area, where the miner would cut the wooden props to length and then wedge them against the roof to hold it up while he worked under it.

Because of low cost, the tubs had very crude axles, and so, to go around a turn, one had first to stop the pony, then switch the points on the rail, then start the pony round the turn, then run back to the back end of the tub, and manually twist the tub so that the axles turned to align with the turn. Fail to do any one of those and the tub came off the rails, meaning you had to unload it, put it back on the rails, and then reload it – all the while with the pony standing there enjoying the break.

Because a man with a pick is, though efficient, quite slow, machines were developed where a large number of picks were set into a chain, rather like a large chain saw, and this was used to undercut the coal seam about a hundred years ago. Then holes were drilled into the coal above the slot, filled with a stick of dynamite, and the blast would break the coal into pieces, that the miner could load into tubs. Typically he might load some 20 tubs in a shift, and these were hauled out of the working area by one of the lads, who would then attach those from several of the faces, and pull the resulting train to the shaft using a pony.

He would put his “token” in the tub before he would fill it, and so, when the tub was emptied at the surface, he would be given credit for that coal, providing it did not have much stone in the pile.