A Treatise On The Principles And Practice Of Dock Engineering

VELOCITY OF EFFLUX FROM SLUICES. 243 H=(l + F)^ = 2-175 x ^ = -544 foot, or 6| inches. The head required to produce the same velocity through a simple sluice opening, as in a gate, will be as follows : — -v2 H=(1^^^ F, = -055. 1 055 x ^ = -264 foot, or a little over 3 inches— about one-half of the head required in the former case. It may be interesting to compare the foregoing problems with a kindred one calculated by Kutter’s formula. Suppose the culvert, as above, to have an inclination equal to that afforded by the head—viz., 61 inches—or, to simplify calculation, say 7 inches in 100 feet. , 1'811 -00282 x 100 x 12 41-6 + + ---------7------- „ -00282 x 100 x 12\ '01 + 41'6 + -----------=— - 7= \ 7 /71-2 / -12 x 7 V 100 x 12 223-18 1-38 V'007 = 161 x -084 = 13-52 feet per second. The difference, even allowing for the additional J inch fall, is very marked, but the results are not really comparable, being calculated on widely divergent lines from dissimilar conditions. A very complète and interesting example of sluicing on an extensive scale is shown by the plan in fig. 173, which refers to the Canada tidal basin at Liverpool.* The main culverts are constructed partly in masonry and partly in iron. Those of iron are circular in section and lined with a layer of Portland cement f inch thick, which is secured by dovetailed ribs or keys at close intervals along the castings. This work, although completed twenty years ago, is still sound and intact, exhibiting no signs of erosion or decay. The centre of the basin is brought within the scope of the discharge by outlets in the floor of the northern portion, which is laid with concrète. The sluicing pipes are arranged in radiating lines beneath the floor (fig. 172), each being provided with a series of upper outlets along its length, and terminating in a splayed opening. To protect these openings heavy frames or discs of greenheart (fig. 174) are laid over them as covers, being secured by four strong links to foundation anchorages. When the sluices are not in use, these discs lie at rest upon their respective outlets, but under the pressure of flowing water within the culvert they are raised to the full extent allowed by the links, and the water rushes out in the form of annular jets, sweeping the circular area within its range. This arrangement has been found extremely effective for the purpose G, F. Lyster on “ Dock Extensions at Liverpool,” Min. froc. Inst. C.E., vol. c.