398 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



the water-jet was largely used for putting down the sheet and 

 other piles. Before this means was adopted, the operation of 

 driving a panel of sheet-piling 9 feet high and 6 feet wi< It- 

 required 900 blows of a monkey weighing about 12 cwt., while 

 the average time occupied in the driving was eight hours and 

 a half. The resistance offered by the sand was so great that 

 the thickness of the piling had to be increased from 3 inches to 

 5 inches. By the injection of water under pressure through 

 two 1-inch pipes, with indiarubber prolongations to the pumps, 

 the time occupied in getting down a panel was reduced to an 

 average of one hour, while in many Ccises the operation was 

 completed in fifteen minutes. The blows of the monkey were 

 only required to overcome the friction between the adjoining 

 panels. As a rule, the weight of the 12-cwt. monkey resting on 

 the top of a pile 10 feet long was sufficient, with the water-jets 

 in use, to force it down to its place. 1 



In sinking some piles for a bridge foundation at Berlin, in 

 a position where ordinary driving was undesirable ; after 

 experiments with different-sized pipes and pressures, a 2 5-inch 

 pipe was used connected with the town water service under a 

 pressure of four atmospheres. With this arrangement, in five 

 minutes, a pile sank about 11 feet 6 

 inches without loading, and in ten minutes 

 more it sank an additional 4 feet 6 inches. 

 In one hour, it reached a total depth of 

 22 feet 6 inches. Afterwards a 2-inch un- 

 tapered pipe was adopted, and the pile- 

 shoes were abandoned. The piles were 

 easily rotated and lifted while the water 

 was flowing. 2 



For fixing the screw-piles of the Birken- 

 head landing-stage, after failure to get 

 them to the depth required by other means, 

 the water-jet was applied with success. 

 The first experiment was made by cutting 

 off the point of the screw.(Fig. 350), thus forming a hole of about 

 3 inches diameter, through which a pipe of If -inch interim! 

 diameter was passed. This pipe reached to the top of tho 

 working-stage, and was connected by a rubber tube to an ordinary 

 steam injector. 



1 Engineering, vol. xlvii. p. 550; and M.P.I.C.E., vol. <M. p. 335. 

 M.P./.C.K.vol. Ivi. p. 335. 



FIG. 350. 



