A Treatise On The Principles And Practice Of Dock Engineering

STEAM PILING MACHINES. 6l Head adzed off. The 15th foot of penetration required .......................213 blows. >> 18th „ „ ,, 825 „ Head sawn off. The 19th foot of penetration required .......................213 blows. „ 22nd „ „ „ 378 „ Ihe total number of blows was 5,228. A similar pile, which was not adzed or sawn, required 9,923 blows to descend to the same depth. The ram weighed 2,800 Ibs. and fell 3 feet sixty-five times per minute. The friction caused by the working of the fibres on each other, under the blows of the hammer, was sufficient to ignite and burn the interior of the head of the pile from side to side. A third type of pile driver is the Electric Pile Driver, in which advantage 18 taken of the temporary magnetisation of wrought iron to make an electro- magnet of that material attach itself by contact to the cast-iron monkey. Ihe two parts are then lifted by the winch. On switching off the current the monkey falls, and the magnet is caused to follow it down ready for lifting again. The monkey is of the ordinary kind, with an upper planed surface. The magnet is connected by wires to the motor on the winch. The illustra- tion (fig. 25) is of one manufactured by the New Southgate Engineering Co., Ltd. Hydraulic Method.—While piles readily respond to the motive force of the ram in ordinary ground, and even in stiff clay, their progress through sand and gravel is not so satisfactory, and the ordinary methods of driving have generally to be abandoned, either wholly or partially, in favour of the water jet. The principle of this method consists in transforming the sand iinmediately beneath the pile into quicksand, by saturating it with water under pressure, a condition which enables the pile to sink by its own weight 01’ with very little assistance. The water is conducted to the foot of the pile hy means of wrought iron gas piping having a short returned end, provided with a nozzle or pierced with holes, which passes underneath the pile. This last is not usually pointed, but left with a butt end, which favours perpen- dicularity in driving. The descent of the pile may be expedited by a static weight, or by the direct downward pull of a rope passing through sheaves to a winch. When the pile has been sunk to a sufficient depth, the nozzle of file water pipe is turned through a quadrant to clear the pile and brought up to the surface again by the same means which accomplished its descent, fhe sand is then allowed to consolidate round the pile, which it does rapidly and satisfactorily. No difficulty is experienced from boulders or large stones for, if met with, they can be displaced or lowered by a preliminary action of the jet below them. This hydraulic method of sinking piles is often used in conjunction with Ihe falling ram in earth of a compact nature. The pile in this case is naturally furnished with a pointed end, preferably conical. Timber piles are universally in evidence, but iron and concrete piles also