Shaft sinking Preliminary Consideration

When coal has been proved to exist in sufficient quantities to be an economic proposition, it is then necessary to fix the site, shape and size of the shaft required to work the area. This requires careful consideration, and many factors have to be taken into account.

Site of shaft. a) Underground considerations. The inclination is very important. In a flat seam it may be desirable to have the shafts in the centre of the area in order to keep the roads of equal length to the boundary.

In an inclined seam it may be better to sink somewhat to the dip side, there by utilizing the force of gravity to run the major part of the coal and water to the pit bottom and having short lip haulage and less pumping.

Faults should be avoided on account of the weak strata and these areas.

If possible, sinking should keep clear of running sands, heavy watered strata, etc.

b) Surface considerations. The shafts must be reasonably near to efficient transport facilities (rail, road, canal or sea). The nature of the ground should also be carefully considered, as soft ground means costly foundations for buildings and machinery, whilst hilly ground means expensive cuttings for buildings and sidings. A good supply of water conveniently near is desirable for coal cleaning, steam raising and baths.

Shape of shaft. Shafts may be circular rectangular or elliptical in shape. In England the circular shaft is popular. It is the easing and cheapest to sink and is suitable for greater depth and water pressures. It also gives more space for ventilation during winding.

Rectangular shafts are suitable for shallow depths and timber lining and for this reason they were popular in Scotland until recent years, but in the new sinking to deeper coal they have been replaced by circular shafts. They are still extensively in the U.S.A.

Elliptical shafts have never found favour in England although there are some on the Continent.

ВАРІАНТ II