Page 12 - Minutes of Proceedings of Civil Engineers Vol CXCV 1913-14 Part 3 Correspondence

f 'r,u:oorlings.l TIIE "WIIITE STAIi" DOCK AT SOUTIIAI\IPTON. 127 rl'nr()nt seemed to have been tho guiding consideration, and it was \Ir.copelantl. ,rlso shr,ted that the concrpte was never stressed to its safo limit ,'rr,l w:r,s not required to be specially watertight. fn the first place, lro rssumed that the specification determined in what proporbions tlro tlift'erent classes of concrete were to be mixed, and stipulated tlr:r.t tho sand and motal should be gauged in cubical boxes, etc., ,rrrrl it wns, therefore, dillicult to understa,nd why the question of rrsirrg unscreencd gravel should have been raised, as the slmo ,1rr:r,rrtity of concrete had to bo put into the wall, no mttter of rvlurt it \yas composed. It was apprrrcntly a dep:lrbure fronr the r;lrccification rvhich was not :r,nticipatod when the contract draw- irrgs were rnade. With regard to tho stanchness of the rvall, llrcre wts great dillbrenco of opinion about the act,ion of sea- rv:uter on concrete-as to whethel the lime was replaced by nurgnesir-and in a rvork of this chnracter it should be considered :r.lrsolutely necessary to make the wall as hourogeneous ts pos- silrle. Wh:rtever safe linrit of stress the Author hatl in his ruind rvts arrived at as the result of experiments on concrete made of the best materials nnd mixed in proportions of mathomatical ir,ccurri,cy. 'Where ho was relying on concrete made of Thames glnvel, in which the proportions of sand and gravel in each g:r,uging of concrete varied considerably, one being in excess of the other, the factor of safety might not exist, and tho wall as con- structed might be called upon to bear more than its snfo limit. The high cost of tho wall was stated to be due to the extraordinury tlifliculty of sinking through running sand, and the question arose rvhether more use miglrt not be rnade of the expcrience gained lry rnining-engineers. ft was always expected by thour, wherr sinking deep shnfts, that water-bearing stratr would have to be lrierced, and the most recently tested methods of ernying out such rvork wero worthy of the considerltion of dock-engineors. 'I'he two processes which had been proved to bo reliable wcre I'oetsch's freezing process and the grouting process. Little rvas l