A Treatise On The Principles And Practice Of Dock Engineering

DOCK ENGINEERING. 258 Unless the sense absolutely precludes such an interpretation the reader will consider the principles laid down as applicable and common to all forms of narrow dock waterways. In one respect alone does a passage materially differ in design from a lock. A lock provided with gates has them all (with the possible exception of storm gates) pointing in the same direction, whereas, in a passage, the gates point in opposite directions in order to exclude water from either of the docks which it serves to connect. Having commented as fully as is practicable within the limits imposed by restrictions of space, upon the various matters appertaining to the design and construction of locks, we now pass on to a brief review of some prominent examples selected from harbours in various parts of the world. Canada Lock, Liverpool. Constructed in 1857, with a single chamber, having an effective length of 498 feet, a width of 100 feet, a depth of 35 feet 9 inches below coping, and a draught of 26 feet 9 inches on sill at H.w.o.S.T., this lock was deepened in 1895 to a draught of 33 feet on sill, lengthened to 602 feet, and divided by a pair of intermediate gates into two chambers of 200 and 402 feet respectively. In addition to the three pairs of gates, the lock pierheads are fitted for the reception of ship caissons in the event of repairs being necessary to the outer sills. Fig. 183. —Section of Old Canada Lock, Liverpool. The old lock was constructed entirely in masonry and intended to serve the additional purpose of a graving dock. Hence the peculiar form of section adopted and shown in fig. 183. The recessed panels in the side walls were for the abutments of shores to the sides of vessels. In the course of alteration these panels were filled up, as also were the lower sluicing culverts, except for short lengths on each side of the gates, where they are now utilised as levelling culverts. The improvement work of 1895 consisted in removing the old masonry floor and replacing it by one of concrete, at a depth of 3 feet 3 inches lower than the new sill level, founded on the boulder clay which underlies the whole site. The concrete was composed of 8 parts of gravel to 1 of Portland