A Treatise On The Principles And Practice Of Dock Engineering

CONCRETE CYLINDERS. 195 4 feet long by 2 feet broad on the beds, and the headers not more than 10 feet apart from centre to centre. The cope is of granite, 3d feet broad oy 17 inches thick, in lengths of not less than 4 feet. ln°rease the stability of the quay walls of the Prince’s Dock, tie-rods inches diameter and 60 feet long, were put in, fixed to blocks of concrete masonry, 12 feet long by 6 feet broad and 8 feet deep (fig. 121) Where a depth of 20 feet at low water is afforded, the tie-rods are 64 feet apart, and ST6? !’61!! 18 25 feet depth at low water ’ they are 32 feet aPart. Where 28 teet depth at low water was desired, the single row of triple cylinders was supplemented behind by a row of twin cylinders, and the tie-rods were increased to 3J inches diameter and 70 feet length, and placed 64 feet apart. ncluding tie-rods and excavation of trenches, the cost of the walls £ depth at Iow water was £8° per lineal yard; to give 25 feet, £90 per lineal yard; and to give 28 feet depth, £120 per lineal yard. The same niethod of construction, with some slight modifications, has been ®mpl°yed “ constructing the later quay walls at Newcastle-on-Tyne The cylinders 111 this case were rectangular in plan, 30 feet long, 20 feet wide n 37 f®et de®P’witb a rectangular internai cavity 20 by 10 feet, leaving walls 5 feet thick (figs. 127, 128, and 129). The process of sinking was carried out as follows:—0 k lhi curb wa® 6 feet in height, the cutting edge being an iron casting of V-shaped section, 2 feet 1 inch deep, with vertical wrought-iron straps attached, and timber lining. The cast-iron toe was made in four parts which were bolted and riveted together at the corners. In constructing the curb the castings were first set and bolted temporarily together, after which the timber lining (elm or beech) was fitted and bolted upon it. The finished curb was let down into position in four parts, which were bolted together at their corners in the bottom. Sometimes a little concrete was put into the curbs before they were let down. The bottom was levelled to receive the shoes, and was made up, where necessary, to 3 or 4 feet above low-water level. Straps were put across the corners on the inside at the top of the fin 1 ^er.nt1thesldes from bulging °ut ïhe curbs’ being set level, were ed.wltb 5 , 1 concrete’ and 011 this the sides, 5 feet thick, were built all q°Unu , ttera for Concreting were 3 feet deep> and were carried on nH standard«- After each 3-foot filling sufficient time was he S ,oTt to set When the StrUCture had been built to a height of 9 or 12 feet above the top of the curb, it was stripped and sunk, the interior being taken out by grab dredgers until the top was 3 or 4 feet above low-water level.” By repeating the process of alternately building and the tlnS71 ses °f 9 or 12 feet’ the fu11 depth °f 37 feet was at“> when the toe of the curb fairly entered into a stratum of hard ballast sinking blocks were not guided or suspended in any way, but were left entire y free and were thus liable to work a little out of place. Sometimes a block would heel over considerably on one side, but could generally be “The