300 DOCK ENGINEERING.
Wharfs at Hull.
The splayed wings of the entrance to the Alexandra Lock, at Hull,*
are lined with timber wharfs, which are returned for a length of 300 feet
up and down the River Humber. The wharfs (fig. 246) were constructed
in bays, generally 10 feet in length, but 3 feet at the corners, the framing
being braced both longitudinally and transversely, and covered with a
5-inch decking. The river bed in front of the wharfs had been dredged
away to about 40 feet below the top of the piles, so that the piles, which
were 61 feet in length and about 15 inches square, penetrated only about
Fig. 246. —Wharf at Hull.
20 feet into the ground. Grooved and tongued sheet piling, 25 feet long
and 8 inches thick, was driven along the front, the top being just above
low water. The sheeting was driven in lengths of 6 feet at a time all
the piles in one bay being previously pitched in position so as to ensure
tight contact. This sheeting held up the material at the back when the
river bed was deepened in front. During construction the mud accumu-
lated so rapidly, in the recesses behind, that whole-timber sheeting had to
be driven at the back to retain it, the space enclosed between the front
and back piles being excavated to enable the cross bracing to be fixed at
the lowest possible level. The wharfing was constructed from a staging
on piles driven by piling machines on barges. The sheet piling was driven
by piling machines with telescopic leaders.
* Hurtzig on “ The Alexandra Dock, Hull,” Afin, Proc. Inst. C.E., vol. xcii.