A Treatise On The Principles And Practice Of Dock Engineering

GRAVING DOCK, GLASGOW. 499 The equipment consists of the usual mooring posts, shores, capstans, and mushrooms, together with a 40-ton hydraulic crane erected by Messrs. Geo. Russell & Co., of Motherwell. No difficulties of any serious importance were encountered during the construction of the dock. The site lay to the eastwards of the Canada Dock, a short distance behind the east wall of which, the main bulk of the excava- tion, principally clay, interspersed with beds of sand, was done under normal conditions with a steam navvy and grabs. When this operation had been completed as far as possible, and the walls, floor, and sill put in, a dam of 12-inch sheeting piles was driven across the front of the entrance and was shored in the first instance to the masonry of the east wall. The water having been pumped out between the dam and the wall, the pierheads were put in. Then the old east wall was gradually demolished, the bearings of the shores being transferred to the pierheads and the sill. Finally, water was let into the dock, the dam removed, and then some little dredging at the entrance completed the undertaking. No. 3 Graving Dock, Glasgow.* This dock (fig. 502) opened in 1898, has the following general dimensions : — Length of floor, from inside of caisson at outer entrance to head of dock, .............................................................880 0 Width at bottoni,.......................................................81 8 Width at top, .........................................................115 0 Width of outer entrance at bottom and top, ..... 83 0 Width of inner entrance at bottom and top, .............................83 0 Depth on centre of sill of outer entrance at H.W.O.S.T., ... 26 6 Depth on centre of sill of inner entrance at H.W.O.S.T., ... 27 0 Level of floor of doek below H.W.O.S.T.,................................28 6 (except at gate chamber, where it is 6 inches deeper.) The dock is divided, by a pair of steel gates, into two lengths of 460 and 420 feet. The strata underlying the site of the dock consisted mainly of fine sand and gravel with occasional pockets of clay. The structure rests upon moving sand, and the wing walls and apron are founded on triple-concrète cylinders, in the manner described in Chap. v. Two of the cylinders of the apron remained unfilled till the dock was nearly completed, being used as sumps for pumping purposes. Into these wells 9-inch pipes, bedded in clean-riddled gravel, were led, in order to drain the dock area which was excavated to low-water level with side slopes, but below that level excava- tion was carried on within sheet piling, 44 feet long by 12 inches thick, driven along the sides and round the upper end of the dock. * Alston on “ Glasgow No. 3 Graving Dock,” Int. Eng. Conf., Glasgow, 1901 ; also The Engineer, May 20, 1898.