RECENT IMPROVEMENTS IN COALMINING.

New Zealand Times, Volume XXXIII, Issue 5394, 11 July 1878, Page 3

RECENT IMPROVEMENTS IN COALMINING.

( Communicated ). The difficulty of sinking pit-shafts through strata heavily laden with water has in many cases proved an ■ insuperable .obstacle to the winning of new fields, and has frequently led to the abandonment of undertakings on which a large amount of capital has been expended. The method ordinarily employed has been to put down ' heavy pumping machinery powerful enough to overcome the amount of water, and by constant pumping to keep the pit sufficiently dry for the men to work on the" bottom. .. This is obviously attended with great inconveniences ; the wet state in which the sinkers have to work prevents their being down as long as they otherwise would be, and any breakages of the machinery are attended with cessations of work. , To overcome these difficulties, Messrs. Kind and Chaudron have devised a method’ by which the pit is sunk through the water-bearing strata, and “ tubbed” — i.e., lined—with metal, entirely under water. Several shafts have been successfully put down in Belgium by this means, and recently it has been introduced into England. The apparatus used consists of a 40-inoh vertical engine, with 40-inoh stroke, placed about 23ft. from the centre of the proposed shaft. The piston-rod of this engine is coupled to one end of a beam working as a simple lever, 12ft. on the side of the engine, and lift, on the side of the borer. To the borer end of the beam the rods hearing the cutting tool are attached. The admission of steam to the top of the piston depresses the engine end of jthe beam, and raises the rods and cutter, which are then allowed to fall by their own weight. There are two cutters, the -smaller of which is about 6ft. in diameter, and is composed of a bar of wrought iron, into which steeled teeth are secured by a pin. This bar is attached to the lower ends of a wrought iron V piece, the upper end of which is attached by a length-ening-screw to the rods. The necessary rotatory motion is given to the cutter by men standing on a platform at the pit’s mouth. The hole made by the small cutter is nsnally kept about ten yards in advance of the main shaft. When this smaller hole is sufficiently advanced, the instrument is withdrawn by a small capstan engine, and the hole is ‘emptied by a “sludger” or pump of sheet-iron, having at the bottom two valves opening inwards. - This is lowered and raised by the rods.-'

The large cutter then comes into operation. It is similar to the small one, but larger according to the desired size of the pit; one 14ift in diameter, weighs 16 tons. Tho teeth are so arranged os to always give a sloping surface to the bottom of the shaft, in order to allow the debris to fall into the smaller hole, where it is caught by a sheet-iron bucket. The shaft having been by these means sunk through the water-bearing strata to a bed of rack sufficiently hard to allow of the first metal ring being placed upon it, the most remarkable part of the operation is commenced. This consists in placing and securing a succession of metal rings under water, and without the use of pumping engines, hut in such a manner as to effectually dam back the water in the measures sunk through.

■ The first ring (which is like those above it cast in one piece) has at the bottom an outward turned flange. This flange is planed accurately, and rests upon the bed of rook mentioned above. The space outside this ring is filled with well-picked moss. The second ring is large enough to slide down outside the first, and has also an outward turned flange which presses upon the moss, and causes it to form a watertight joint. On this foundation the whole of the tubbing is built up, and the enormous weight compresses the moss into a compact mass. To enable the rings to be lowered with less danger a false bottom or diphragm is bolted bn to the lower flange of the ring, which causes it to float on to the water ; a central equilbrium tube passes np the shaft, having cocks at intervals, through which water may be admitted into the centre of the tubbing, so as to aid its descent. By this means much of the weight is taken off the lowering rods. The space between the walls of the shaft and the tabbing is then filled with cement, which'ls allowed to‘ set; after which the diaphragm is removed. The water is then drawn out, the moss-box foundation examined, and if all is found secure, the pit is ready for continued sinking by tho ordinary method. Thoadvantagesbf thissystem are very numerous. As has already been pointed out, no pumping engines are required ; in addition, great savin l * of labor, leas risk to life and limb, neighboring wells are not interfered with, and last, but not least, an economy of 50 to 75 per cent, in the outlay as compared with the ordinary systems has been obtained. The writer has in the present year seen the Kind-Chaudron method in successful operation in the North of England. A colliery shaft having been commenced in the magnesian, limestone close to the sea-shore, a very large amount of salt water was met with. Pumping machinery was put down, until the water raised to the surface amounted to 600,000‘gallons per hour, when the services of Messrs. Kind and Chaudron were, called in, aud the pit is now being successfully sunk under water as de-. scribed. ■