Page 26 - Minutes of Proceedings of Civil Engineers Vol CXCV 1913-14 Part 3 Correspondence

l'r,,r:oedings.] fHE " WIIITE srAR " DocK AT sourIIAMPToN. t4I rrrloptcd, beginning with a header course &t the bottom and working Mr. Robson' tt;rrvnrds with two courses to each lift of concrete. The Author did trot sly whether these courses were bedded and grouted ; being under rvnl,r.r they were doubtless laid dry. On p. 50 it was statod that at I lrnh lnrtion of the trench-rvork 3'sand " was encountered which ran lr,l'rvoen the.runners, and he would inquire how this was kept out. r\lrpnrently itwas done by filling the holes bohind the timber with grruvcl or othor goocl material, but surely this would be impractic- nlrlo rvith an excessive quantity of water. In similar crises he hlr,d rrsrxl successfully sacks of hay-sometimes nailing them over the rtrrfnces of the runners. The timbering of the trenches deserved rroticc; it appeared to be substantial, altbough the method of irrst,r'tion was open to discussion. The use of runners 4 inchesthick lry 24 feet long meant much labour in driving down. IIo con- sirluretl it could have been executed more economically with 3-inch lunucrs, in three settings instead of two, the runnels being shorter. tt Wiblr a trench 42 f.eet wide central " or king " piles were abso- '6 lrrtely necessary. IIe would limit the maximum width of a trench l,o be timbered without these piles to about 30 feet ; and then half- l,irnber struts should be used, with frequent cross struts to stiffen l,lrcm. IIe observed that in phces lvhere the bottom of the trench rvls soft and the piles showed symptoms of rising, diagonal struts rvare introduced raking downwards, to prevent such action. This rv:w a good method, and had it been adopted on other occasions some calamities might have been avoided' When timbering in s;rncl or other dangerous material he had often made it ri rulo to l:rco thc frames of timbor together vertically with stout boards or lrlnnks, a precaution which had proved invaluable in keeping the l,irnber in place. In timbering trenches too much o're could not lrc observed by the engineers in charge, rvho too often left this rnrtter to the gangers and timber-men, with their rule-of-thumb rnethods. Timbering was a class of work which was often difficult rr,ntl dangerous, and required skill and courage ; and young engi- rrccrs should dovote theirspecial attention to it, so as not to be left cntirely to the advice of such men in time of danger. Mr. G. Iler,r, Scort observed that the difficulties of the trench Mr. scott. cxcavation seemed to be very similar to those experienced with the rleep mud trenches at the Keyham Dockyard ertension.r There it rv:m found absolutely necessary, where centre piles were adopted, to provicle bulkheads at about every 100 feet, and to limit the open ttench to that length. If struts the full width of the trench rvero I Minutee of Procoedings Inst, C,8., vol. olxrii, p, 61.