PILE (AS. pit, from Lat. pi/um, javelin, pestle. from piscre, pin:5ere, to pound). In engi neering and architecture, a long post generally of wood, but often of iron, driven into soft soils to support a load or to form an inclosure against the entrance of water. Piles are known by different names, according to their character or use, the more important being: Bearing pile, one used to sustain a vertical load and the one generally meant when the word pile is employed qualification; .sheet piles, thick boards or timbers driven in close contact, often tongued and grooved, to inclose it space, to prevent leak age. etc.: screw pile, an iron shaft to the bottom of which is attached a broad-bladed screw with or two turns; disk pile, an iron shaft to the hotton, of which is attached a circular disk to give additional hearing power. The most com mon form of pile is the hearing pile of, usually, a roughly trimmed, slender tree trunk, o•, less usually, of a squared or other dressed timber shape. The woods used for piles are spruce and liemloek for soft soils, pines, elm, and beech for firmer soils, and oak for compact soil. Engineers usually require that piles shall not he less than ten inches in diameter at the smaller end. Gen erally the pile is shaped for driving. and some times a pointed iron shoe is attached to the pointed end ; the top is frequently bound with an iron band to prevent browning.
Piles are sunk into the soil by several methods, the most common of which is driving by a ham mer. The machines used to drive piles by a falling weight or hammer are known as pile drivers. There are two general forn, of such machines known as drop-hammer pile-drivers. In a drop-hammer pile-driver a heavy hammer of iron is pulled to the top of a lofty frame by hand or power and allowed to fall freely on to the head of the pile. The frame consists of two uprights called leaders about tw•o feet apart and from ten feet to sixty feet long, which guide the falling weight. These leaders are usually braced back to the pile-driver platform hy diagonal timbers. The sides of the hammer are grooved to slide between the leaders, and it weighs front 500 to 4000 pounds, usually about 2000 pounds. It is hauled to the top of the frame by a rope or chain attached to its top and passing over a pulley at the top of the frame, and thence to a hand windlass or the drum of a hoisting engine.
In one kind of pile-driver the rope is attached to the hammer by a sort of tongs which is automatically opened by a tripping device when the top of the frame is reached, thus allowing the hammer to fall. In another form the rope is lierumnently attached to the hammer, which is set free by loosening a friction clutch. thus allow ing the drum to unwind the rope which is pulled down with the hanuner. The latter form of driver is the one least commonly used, and is the most expensive in first cost, but is generally regarded as the most efficient. Drop-hammer pile-drivers are mounted on seows or cars, or may be skidded about on the plat form timbers. A steam hammer pile-driver consists of a steam cylinder in which a piston works, earrying a heavy weight. or hammer on the end of the piston rod. This steam eylinder is vertical with the piston rod, extending downward, and is held between the tops of two or four uprights which serve to guide the hammer. The bottoms of these uprights are held together by a cast block pierced with a conical hole which fits over the partly sharp ened head of the pile. The ham mer has a cylindrical projection which passes through the hole in the base block to strike the pile. The piston stroke is usu ally about three feet, and the weight of the striking parts is commonly about one and one half tons. This whole appara tus is swung between the leaders of a pile-driver frame by a rope exactly as is the hammer of a drop-hammer pile driver. In operation the apparatus is lowered on to the pile until the pile carries its entire weight. By of flexible hose connections with a steam boiler steam is admitted tinder the piston, raising it with its attached piston-rod hammer until at the top of the stroke a trip cuts olf the steam and the hammer falls by its own weight, striking the pile a heavy blow. At the end of the down stroke the valves are automatically reversed and the stroke repeated. In this way the machine can deliver from sixty to eighty blows per min ute, as compared with front six to fourteen blows for a trip drop-hammer driver, and from twenty to thirty blows for a friction drunt drop hammer. While the steam-hammer driver strikes blows having much less energy than those of a drop-hammer driver, it strikes its lighter blows so much more rapidly that it compares with the best friction drum drop-liammer drivers in eflicieney.