Page 16 - Minutes of Proceedings of Civil Engineers Vol CXCV 1913-14 Part 3 Correspondence

Ilrxrvrlings,l TFE "WIIITE STAR" DocK AT soUTltAMPToN. 131 Sir Wnetnr,y ELror considered that the Paper was fl very sir whrtely vrrlrrrr.ble record of a work carried oot succes"fully, althougf, utiot' 1'rlxonting more than the usual difliculties to be expected in the nrrrstluction of ertensive dock-works, the ground at Southnmpton lrrirrc n61,6risusly unstable and the cause of much trouble in the r,lrrstluction of former dock-walls. ft appeared tha,t in this cnse tlrl r,lrief difliculties were due to the circumsL.lnces connected rvith llrr.sitt-' nnd the position of the enclosing cnrbrnkment, rendering tl, irnptacticable to onclose the rvholc arcn of the works by a cofl'er- ,lrrrrr, rnrl nocessitnting the constnrction of somc of the wnlls under runicr'. With regard to thc mcthod adopted for the constrnction of llrc south entl of berth No.43, where water hnd to be ndmil,tcd to l,lro trcnch, and concrete cnissons wete sunkl successfully to tho lrlopel depth, a somewhat similar nrethod had been adopted in a deell l,r'rrr<:h excnvatetl through rnud for one of tho dock-rvalls at l(oyhnm.l \\'lrtrn the trench had been excavated to a depth of tbout ilO feet l'r',rrn tho surface, the 6-inch sheet piles rvhich had been drivcn rlorvn to firm grounrl to form the sides of the trench began to movo irrrvlrds at the bottom, and threatenerl to collapse if the excavation rvlrrr continued. Concrete cylinders were then sunk from the surfnco ,,f the mutl inside the trench down to the rock, a further depth of rrlxrrrt 30 feet. The cylinders were 7 feet in external diameter, so rrs to fit bet,rveen tho stnrts in tbe trenclr, and four occupiod the rri,lth of the trench. 'I'hey were formed in rings 2 feet 6 inclres ,l,r,p, nnrl rfter they lrarl been sunk to the full depth required to rr,rrch the rock thoy aflbrded complete support to tho sheeting. 'l'lrc excnvation of the trench was then proceedetl lvith, the rings ,,f l,he cylintlers being removod as the strutsrvere placed in position. 'l'lrc eylinders were afterrvnrds usetl elservhere in the perrntnent rlor'l<. This work, being executed in a dry trench, rvas a simple rr llirir in comparison with sinking through water, as at Southampton. 'l'lro rvalls comprised in portion I] and constmcted rvith concrete l,lrrcks in front rnd back with a filling of mass concrete, although r'rnpleted succossfully, did not ftppear to present n methorl of lorrstmction to bo recomnended. Bven undor the most favourrrble lirr:rrmstances, with perfectly still rvater and no cunent, the deposi- I iotr of concreto rurder rvatel could not be depended on entirely for s,rrrnrl work. Concrete blocks throughout the rvholo rvidth of the rv:rll, shapetl so as to bond into ono another, rvould havo formed n solirl lrnd massive rvall, probably at less cost and with more r,s1'etlition than by using concrete in mass. It was evidont that I Minutes of Proceediugs Inst, C.E., vol. clxxii, p, 9. s2