Page 22 - Minutes of Proceedings of Civil Engineers Vol CXCV 1913-14 Part 3 Correspondence
P. 22
r'',',r,trlings,l TIIE IYIIITE STAR" DoCK AT SOUTIIAMPToN. 137 (. ',, ,rirrnrm load the foundation could bear safely, orwhat w{rs the}Ir,Lotch. ,, 1.r' of safety with any given load. The maximum load per lrr,rrc foot on the foundation of the block-faced wall, Fig. 8, I'l rl'ti 2r *ppeared to be higher than the figure given for the wall l,,,tn irr Fig.3. A betterdistribution of the loacl on the founda- r.rr, :rrd some. economy of materinl, would have been obtained by ,rtirrs the wall farther back on its foundation, reducing the '.,, |i oll'.set from 4 to 2 feet, and stepping the back block-face at , \r't'\'irlbernate course, reducing the thickness of the wall to 18 feet ,r l()w rvnter of ordin&ry spring-titles. The pier-and-arch con- r'rrr:tion, with a plntforrn behind (Fig. 11, Plato 2), appeared to i,, nr)t entirely sltisfnctory. Probably the platform reduced the l,lclrrl pressure on the rvall by about 40 per cent., and there might lr;r\'o been special reasons for its +doption. Otherwise, it rvould L1'p:rlsnfly have beerr prefet'able to increase the depth of tho piers I r.rrr 35 to 45 feet, to reduce the thickness of the curtain-rvalls to .i lt,trt, rt the centre, and to omit the thicker lower portion. With- ',rr1, tlris portion the weight of the curtain-walls would be borne mainly l,r'the piersr the distribution of the load on their foundations would 1,,'irnproved. It was not clear whether the piles under the plat- l oln w€r6 driven beforo or after the completion of the wall in ll,rrrt, of them, If they were driven before, tbeir safe load might i,,'nr:r,terially reduced by loosening of the ground at the back of the during its construction. If they lvere driven after, they would ",rll ,,'nrl)l'ess the ground and increase the lateral pressure against the rrrrll in flont, The reasons explessed by the Author for preferring ., -loping brso below tho tluay-rvnlls seemed doubtful. The depth ,,l tlre foundation rrt the toe should be adjusted in accordance with r lr{} rl:l,ximum load per square foot to be provided for. Froquently tlrc tlepth so arrived at wl,s sullicient to secure tho wnll against l,,,irrg pushed forward, without any dipping of the bnse fronr front r,r b:rck, beyond the srnall amount required for trench-drainage. If rr, \\'cle not sullicient, sloping the bnse, ns shown in Figs.3 and 8, l'lrrto 2, increased ths resistance of the wall to latelal pressure, rvith , lrc ltltlition of less concrete than any oiher method required. But tlrc srrnre end might bs athined by rnaking the wholo foundrtion ,11'1r1rtrr nnd keeping the b:rse nearly levol. This required more .rrcr'oto, but affbrded a larger margin of safety for the load on the ' l,)rrn(lltion at the toe, which rvas usually the principal source of , r r r x ioty. Ee agreed with the Author's view that a wall entirely of l,lrrck rvork would have been better and cheaper than one partly of rrrss concrete: it would probably have been economical to use for it It)- to 12-ton, instead of 6- to 8-ton blocks. With more block work to
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