Page 18 - Minutes of Proceedings of Civil Engineers Vol CXCV 1913-14 Part 3 Correspondence
P. 18
l'rrroorlings.l TIIE "WIIITE STAII" DocK AT SOUTHAIIPTON. 133 llrnot'otical calculation would suggest, and it might more than com- trIr. Elli6. lrrr11;;1f,s for the oxtra cost involved, and the slight inconvenience .rrrrxod b/ having broken lines to the back of the trenches. The l,rkr Sir Benjamin Baker once remarked that almost every existing r,,truining-wall (of more than a certain age) on & soft foundation n,rrrltl be found to have moved more or less out of its original ,rligtrurent;and it rvould be interesbing, at sorne future time, to lr,rrr',, ruhurh"r the nerv quer,y-rvalls of the White Star dock had l,'llorved the ex*mple of the Empr.ess dock walls in coming l'r'wru'd to a noticerblo.extent. IIad the Author anticipated such rr rrrovcrrrent by setting out the walls on a slight concave curve, as rvrs rrsull at Liverpool with walls not on a rock foundltion ? The Irrr:b tha.t not infrequently forward movement took place in dock- rr:rlls after a lapso of time, might be accounted for by an argument irr the Appendix. The Author gave the resistance to forrvard rrrovcnrent due to wlter-pressure as 22.8 tons, which no doubt held g,rotl rvhen tho rvall was now and the backing lvas dry. IJut when irr course of time the backing, especially if it rvere a porous rrrutcri:rl, such as the ship's ashes mentioned in tho Paper, becarre "rrtrrr:rted with water, it was evident that the resultant water- lrr'(|ssure in front of the wall must be diminished considerably, and irr cxceptionrl cases it might vanish entirely (except for its efrect irr l,dding rveight to the earth in front of the toe of the wall) ; xr that the Author rvould appear to havo placed undue leliance on I.lris factor as & permanent measure of stability. \Yith regard to tho driving of :'einforced-concreto piles to carry the platform behind tlro pier-and-arch wnll, were the heads of the piles damaged irr dliving, rnd wlrat means wer.e tlken to a,vert such damu,go? l)r'iving to a final set of ,ru inch with a, 3|-foot frtll of a 50-crvt. r';rnr seemed to be unnecessalily severe, and likely to shatter tho rl,ncl'ets instead of er,using further penetnrtion, l\Ir. \Y. Hr:mry Iluxrr:n had read tho P:r,per with more than Mr. Eunter. ,rrrlinlry interest, and wts sure that it would harvo permanent value irr tLe Proceedings ts a frank and faithful r.ecord of engineering ,rperations carried out zr,midst advelse conditions, as rvell as of sclious risks boldly flced and dificulties gr:rppled with and over- r.()ure. The Author had abstained from any st:rtement of the totol r.rrst of the works, or any suggestion as to the value of the ltnd ,r:cupied by them. If reasons of policy were the ca,use of this :rlrstention, there was no mor€ to be said. But the value of the l)lper, already great, would be increased if such figures could be srrpplied, as the cost per berth in the dock must have been very rrrrrsiderable. This was a case very much in point in the controversy
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