A Treatise On The Principles And Practice Of Dock Engineering

COMPOSITE SYSTEMS. 291 The Hennebique system has been more directly applied to the formation of piles. As practised in recent examples, it consists in enclosing rows of iron rods, bound at intervals by iron ties, in a casing of concrete. Figs. 231 to 234 are the elevation and sections of a sheet pile, con- structed in this manner. There are three rows of pairs of vertical rods, connected, at 10-inch intervals, by horizontal bands or clips. The pile is moulded with cylindrical grooves in each side, in which the spur, C, of an adjoining pile engages, for guidance in driv- ing. When two consecutive piles have been driven, their combined grooves form a cylinder, which, after being cleansed by forcing water through it under pressure, is grouted with cement. The lower ends of the piles, which can be made either wedge- shaped or pointed, are protected by steel shoes secured to the body of the pile in the moulding process. In fig. 27 (p. 63) is a plan showing the method adopted for the construction of bear- ing piles. Piles of this description, 14 inches square and 42 feet long, have been driven to the number of 1,300 for a cold storage foundation at Southampton. A monkey weigh- ing 2| tons was used, and the piles were driven until 10 blows, with 4 feet 6 inches fall, failed to produce an additional inch of depression. It is better for this class of work to use a heavy weight witli a short fall, rather than a light weight with a long fall. Owing to the brittle nature of the concrete, the head of the pile during driving must be protected, as shown in figs. 235 and 236, by a sheet helmet bedded on sawdust or sand in bags on the head of the pile, with the further interposition of a wooden SHEET PILE dolly between the monkey and the helmet. The loss of energy by this arrangement is very great, though eventually the sawdust hardens into a compact mass. The brittleness and rigidity of the thin concrete covering are the only drawbacks of Figs. 231, 232, 233, and 234. Hennebique Sheeting Pile. the composite system in positions such as jetties, where it is liable to ■concussions and shocks. It has, however, been used with satisfactory