Page 15 - Minutes of Proceedings of Civil Engineers Vol CXCV 1913-14 Part 1
P. 15
l\ucoodinge.l THE '( WI{ITE sTAR " DocK AT souTEAMPToN. 55 rvlrich at the back occurred about 20 feet below the bottom of the rlrrrrlgctl cut. The ground at this point was mostly fine s:r,nd, so that a rvnter-jet had to be used to get down the piles, rvhich were of whole I,irrrlrcr. In front the depth was only about 15 feet, so that here lrnlf-timber piling was used and the water-jet was not reqrrired. llrtrveen these two rows of piling a trench was excavated down to l,lro rvtll-bottom, by means of grabs aided by helmet divers armed rvith water-jets, who blew the sand oui from corners where the grab rrrtrkl not reach. As the trench was sunk its sides were supported lry struts and walings similar to those in an ordinary trench, but rull fixed by divers (Figs. 9). The struts were placed about 10 feet npnlt horizontally and about 6 feet apart vertically. They t'ere plovided with bottle-jacks at one end to facilitate fixing. This rrrrnngement of timbering prov€d to be convenient and quite srrllicient to support the sides of the trench safely. Conueting.-Nter being cleaned up by divers the trench was lilled to dock-bottom level (40 feet below low water) with 5-to-l rnass concret€, the struts and walings being removed by divers as the work proceeded. The timber piling was left in, however, so as to avoid disturbing the ground and thus placing undue loads on the green concrete, the front piles being bored off so as not to foul l,ho fairway. The concrete was lowered by the titan cranes in lxrxes with bottom doors, which were unlocked automatically when tlre box came to rest on the wall, and opened as the crane lifted tlrem. A diver was sent down to direct where each box was to be lrllced, so that the concrete sbould be kept as still as possible whilst it was being discharged from the box. After the concrete had been deposited in this manner to within :r,bout I foot of dock-bottom level, a layer of 4-to-l concrete, made lvith crushed gravel, was placed and carefully levelled to receive the face-blocks. This was effected by laying two lines of rails on the concrete, packed on small blocks and wedges, so that the upper surface of the rails was exactly level with the bottom bed of the first course of blocks. The concrete was then discharged from bores between these two lines of rails and levelled to a true surface by a screed or straight edge, which was drawn across the ll.ils by divers. fn this way a fairly perfect bed was obtained on rvhich to build the blocks. The rails, which were placed just out- sirle the bed for the blocks, were afterwards removed. Block-Setting.-On the bed thus formed, the blocks w'ere laid by rlivers with the aid of the titan cranes. The blocks were arranged for English bond, and it will be noticed (Figs. 9) that the back pu,r't of the headers has a slight upward slope on both top and
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