Page 8 - Minutes of Proceedings of Civil Engineers Vol CXCV 1913-14 Part 3 Correspondence

I'roceedingr.l TIIE " WITITE STAR " DocK AT soUTHAMpToN. L23 :rnd a bed of mass concrete resting on a jute carpet was placed on Mr. cay. tlre top of the piles and clay, before he ventured to pump the water out ngain. Mr, CIrlnr,ns CoLsoN observed tbat one of the most difticulf, Mr. colson' ploblems in connection with dock- and harbour-rvorks wrrs tho rlesign and construction of 'rvharf-walls. The physical conditions rlifl'ered as a rule, materially if not entirely, from those spper- tl,ining to an ordinnry retaining-wall. After completion, tho conditions to lvhich a whnrf-wall was subjected were often onerous, and excessive surcharging was not uncommon; in fact, there was no fenture or deklil in connection with dock- and harbour-rvorks rvhich called for such a diversity of practice. Cases did occur in rvlrich the conditions admitted of the adoption of a similar design or method of construction; but this was no', the rule. Again, personal bi:r,s had to be reckoned rvith. From this point of view, therefore, the most valuable part of the Paper was that denling rvibh the design, the conditions governing the diff'erent sections, the method of constmction, and the rate of progress: and yery valuable lessons were conveyed by these details. In this connection there rvore ono or trvo assurnprtions rvhose r-alue was somervhat overrated. In view of- the conditions in regard to the foundation stratn, tho additional resistance, due to the sloping base, against forward movement wfl,s very problematiorl. IIe consideled that, should there be any such tendency, the material in front would move horizontally rvith the rvall. Personally, he would hnve more confidence in the greater dend rveight of material which would Itave accrued in front had the base been horizonLrl from the extreme rear level, giving 5 feet extra doptlr, or even at a mcan depth betrveen front and bnck, as shorvn in l'ig.3, Plnte 2, givin6; an extra depth of 2 feet 6 inches in front. In a foundation of absolute stability the conditions would be different; therc tho sloping baso rvould have an appreciable value n^s allording additional resistance to forward movement. Its greatest value in ftny case lay in setting brck thecentreof gravity, and thusaugmenbing the turning- rnoment. Another consideration was the volue to be placed on the ordinary backing material resting on the rear ofl'sets, which, while it added somervhat to the dead rveight qf the rvall for purposes of calculation, formed no integral part of the wall-section. fn this case, again, the width of the olllsets and the character of the material placed upon them rvould qualify the premises. On the whole, he considered that engineers would be well advised not to put too high a value on these trvo factors. The Author's romalks on depositing concrete uutler water were ver)' valuable