Early mining methods

Only seams lying near the surface would be worked in the early days of coal-mining. At first the coal was got by open-cast working. Where the coal became too deep for opencast working, tunnels were driven from the outcrop to the seam.

Where possible these tunnels were driven on a slight rising gradient to allow of drainage as no pumps were then availa­ble. The coal was carried along the underground roadways to the surf ace on the backs of women, boys and girls known as bearers. Where the coal was more or less flat but lay at a depth too great for opencast working, shallow pits were sunk. These shallow pits were sunk to the coal seam and then were widened to remove as much coal as possible without supporting the roof, after which the pit was abandoned, and another one sunk nearby.

The coal was still carried by the bearers along the adits and up the shafts until about the middle of the 14th century, when windlasses or jack rolls, similar to those used for wind­ing water from wells, were introduced for hoisting the coal up the shafts in baskets; this method of winding was employed until the 19th century. The coal was got by wooden picks tipped with iron and by iron wedges.

For the sinking of shafts and driving of levels or tunnels ill rock, fires were lighted in contact with the rock or stone to be broken, and these fires were extinguished and the rock cooled by water, thus causing it to split.

Little progress was made in mining methods for several centuries largely owing to lack of tools and equipment, and the miners or pit men who were more or less serfs.

About the middle of the 17th century horses were employed for winding coal from mine shafts.

With deeper and somewhat more extensive area of working around the shafts difficulties of ventilation and drainage arose.

Exercises

I. Answer the following questions:

1. What seams would be worked in the early days of coal­mining?

2. When were tunnels driven from outcrop to the seam?

3. Whom was coal carried by?

4. By what means was the coal got at that time?

5. When were horses employed for winding coal?

6. When did the difficulties of ventilation and drainage arise?

II: Answer the following questions in written form:

1. Why was little progress made in mining methods for several centuries?

2. How were tunnels driven in rock?

3. What method of winding was employed until the 19th century?

Modern methods of working coal-seams

The main classification of methods of working coal-seams is as follows: (1) Board and pillar; (2) Longwall advancing; (3) Longwall retreating; (4) Semi-longwall; (5) Horizon mining.

Hard and fast rules¹ distinguishing between these various methods cannot be laid down in some cases as so many modi­fications and combinations of the methods exist at various collieries working under different conditions. The general principles underlying² the three chief systems may be brief­ly outlined as follows:

Board and pillar mining, variously called "room and pillar", "pillar and stall", "post and bank" and "stoop and room", consists of driving "boards", "stalls" or "rooms" to split up the area to be worked, so as to leave "pillars" or "stoops", which may or may not be extracted at a later date.

Under normal workings by this method, no packing is employed. Thus pillars when extracted are generally "retreat­ed", that is the pillars farthest away from the shafts are then taken out before those nearer the shafts.

Longwall advancing working consists of long faces or "wide places" from which all the coal is removed for a given working section and the necessary roads are made through the goaf where formerly coal lay. The roof near the working face is supported by props, bars and chocks, and by packs built up of material which falls from the roof, or may be imported.

Packs may be such as to support only the roadways left for the further extractions of the mineral and for ventilation pur­poses, when the system is referred to as³ "caving". They may also be built at varying intervals, i.e., "strip packing", or the void of goaf may be packed solid, i.e. "solid packing".

Longwall retreating working consists of first driving road­ways through the solid coal at such intervals as may be nec­essary for the extraction of the coal in a later operation, and of such lengths as may reach either the boundary of the area of coal to be worked, or an arbitrary boundary. The blocks of coal thus formed are then worked on the longwall principle, but the direction of advance of working is from the boundary towards the shafts.

Notes

1. Hard and fast rules—твердо установленные правила (критерий)

2. principles underlying — принципы, которые легли в ос­нову

3. the system is referred to as — система называется