Page 22 - Minutes of Proceedings of Civil Engineers Vol CXCV 1913-14 Part 1

62 wENTwonrH-sHErLDs oN THE coNsrRUcrIoN oB [Minutes of the neighbouring pier was being exca,vated, this advantage was discounted to some extent by the difficulty of excavating and pump- ing inside the small pier-trenches. The want of space caused the oxcavation to be slow and expensive, especially in the cases of those piers where blows of water and sand occurred. It would have been difficult, however, to construct the wall safely by any other method, except, perhaps, by means of caissons sunk with the aid of com- pressed air, which would probably have been more costly than the plan adopted. Cu'tain-Walls anil Archee.-After the piers had been built the remainder of the work was carried out without difficulty, and it need not be tlescribed at length. The trenches forthe curtain-walls were sunk in thc usual way, the sides being supported by 4-inch timber mnners held by timber struts and walings. This was done quite err,sily, rrs the sand had been thoroughly dried by the pumps in the pier-trenches, which were at a lower level than the curtain-wall trenches. Skewbacks had been formedat the back of the piers, and the pockets thus formed were used as sumps, in which pumps were placed to keep the curtain-wall trenches dry. As soon as the oxcavation was completed the concroto was built up inside each trench to its full height. The next process was to turn the concrete arches between the piers. It was originally intended to support the centres on the sbeel joists buried in the archcs, but it was found more convenient to build the arches on earth centres laid on the dumplings between the piers. As soon as the arches had been turned, the face-wall nbove them wns built behind shuttering in the usual way. After this, the tronch-piles were drawn out, and the earth in front of thc wnll wrs rernoved by a ladder dredger. A on st rut ti t m of Re infor c e d,- C oncr ete Pl atform,-The construction of tho plrtform lrchind the rvall offered no unusual difficulties. The grorrnd wns first, excavated to the level of the underside of the deck, nntl two tlnvelling pile-engines were there erected. The piles were rnoukletl in tho contractors' yard near by, and, after maturing for 2 months, wero rlriven until the ram, which weighed 50 cwt,, produced a tret of ,ro inch with n, fall of 3! feet. The piles were 33 to 47 f.eet long, nnrl n forv of them had to be lengthened before they would pass tho tost. Most, of theIn, however, refused to go down their full length, anrl tlxr proiccl,itrg firps rvcre cut ofl. The steel joists were laid on tlro pilt's, rr,rrrl l,lrrr rrnrt.t'rrt,c lro:lms mrd slabs rvere built alound them. llllro sirlrs of l,lro lx'rr,ttts wct'tr forrnetl rvith timber shutters, but the rrutlcrsitlos of lxrth lxrnrns irnrl slabs were simply formed by the ground, lvlrich rvrw lrrorrglrt to a correct level with fine ashes.