A Treatise On The Principles And Practice Of Harbour Engineering

PILING. 73 inland structures and for piers and jetties are by no means identical. It cannot fail to be evident that a pile driven wholly into the ground, as ni the former case, does not need to possess the same lateral stiftness which must essentially appertain to a pile only partially buried, and subject, moreover, to the incidence of forcible impact throughout a very considerable part of its length. Thus, for landwork, concrete piles may be formed by simply drilling or boring a hole within an iron shell or tube, and filling the latter with concrete, the shell in many cases being withdrawn as the work proceeds. This method, of course, is quite inapplicable to piling in water. The Hennebique bearing’ pile (fig- 66) contains a series of long, round bars, generally from four to eight in number, set parallel to, and arranged symmetrically around, the longitudinal axis of the pile. These bars are connected together and maintained in position by bonds, or ties, of iron wire and distance pieces. The bars vary from 1 inch to If inches in diameter, and the wire is usually T3T inch thick. W - W.0 Fig. 66.— Hennebique Pile. The distance pieces, which are about | inch in diameter, with forked ends, are set at a normal distance of 10 inches apart, but at and near the top of the pile the distance is reduced to 2 inches. The toe of the pile is a pyramidal block of cast iron, into which wrought iron straps have beeil inserted. The upper ends of the straps are bent inwards towards the centre of the pile. The longitudinal rods of the pile are continued as far as the casting, being deflected to the required splay. The Hennebique sheeting -pile is made on the same lines as the bearing pile. There are three rows of longitudinal rods, arranged in pairs, and connected, as before, at 10-inch intervals with iron bands or clips. The ends of sheet piles are wedge-shaped, with a down- ward splay towards one side. This is extremely useful, during the driving process, in keeping a pile in con- tinuons contact with its neighbour, towards which the resultant pressure on the splayed edge causes it to be urged. To complété the connection, piles are moulded with cylindrical grooves in each of their sides, one of which possesses a short spur or pro- jection, capable of engaging in the groove of an adjoining pile. 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. A slight variant on the Hennebique pile is the Mouchel hollow pile (fig. 67). It has the longitudinal rods, wire ties, and distance pieces of the former, but, with the object of saving material and reducing weight, it is concreted with a core, which, being withdrawn, leaves the pile hollow. Dia-