A Treatise On The Principles And Practice Of Harbour Engineering

PILING. 71 piles. This can be done by forming a series of grooves with the aid of rivetted connections, as exemplified in the figures shown, which represent typical sections patented by the Friestedt Co. of Chicago, U.S.A. The interlocking arrangement is extremely useful in forming a water-tight inclosure for dams. Hydraulic pressure against the outer face will generally prevent the passage of water, but where any leakage manifests itself, it can easily be checked by sprinkling ashes, sawdust, or any light material of a similar kind, upon the outer surface, whence it will be sucked into the defective joint. The driving of these piles is effected in the ordinary way by means of a falling ram ; only, it is necessary to interpose a wooden “dolly ”— a 6- or 8- Fig. 65. —Interlocking Steel Sheeting Piles. foot length of greenheart timber—between the cap of the pile and the under- side of the ram. The cap of the pile is a removable block or plate of cast steel, several inches thick, temporarily secured in position with the aid of bolts and removed after the operation of driving is finished. Metal piles, though indestructible by inseets, are subject to corrosion, with results equally disastrous in the long-run. The effects of oxidisation are most to be dreaded in the case of the outetanding piles of piers and jetties. All ironwork immersed in salt water, and especially when alternately wet and dry, undergoes chemical changes subversive of its strength and durability. Hence the manifest necessity of providing it with some protection akin to that which is accorded to timber piling. Of the methods in vogue for the prevention of corrosion in iron or steel, two stand out in greatest prominence—painting and galvanising. The former of these is only of the nature of a temporary perservative, and has to be re- applied at regular and frequent intervals; the latter cannot be renewed in the case of in situ structures, and, thouglr the initial treatment is understood to be more effective than painting, yet the environment of the seacoast is extremely detrimental to its efficacy.