A Treatise On The Principles And Practice Of Harbour Engineering

8o HARBOUR ENGINEERING. of wet modelling clay. The depth of water was 22 feet below mean low water level, and the piles were driven by a hammer weighing about 3000 Ibs., having a uniform effective fall of about 8 feet. The experiments were spread over a period of fifty-four days, when they came to an abrupt conclusion owing to the failure of the platform under the wash occasioned by the passage of a steamship. The last observations taken showed the maximum settlement of any test pile to be about 3J inches, and that the settlement of the working platform in its vicinity was If inches. It is to be noted that this latter settlement took place under no load beyond the weight of the piles and the timber upon them, and that, therefore, the maximum settlement under load of any test pile was practically only if inches. A settlement of this amount appears to be not uncommon in local piers formed of similar piles, even before the structure is finished, or has received any other load than its own weight. Mr Bensel, from various considerations indicated in his report, concludes that the ultimate bearing power in the unlagged piles of Group I. might be taken at 20 tons per pile, and that in the remaining groups of lagged piles the ultimate bearing powers would be 30, 20Jand 30 tons respectively, per pile. The following table shows details of the observations made’during the experiments. The tons are given in American units of 2000 Ibs. Roughly their équivalent value in English units of 2240 Ibs. may be arrived at by deducting one-tenth. This modification applies also to the figures quoted in the preceding paragraph. Pile Tests at New York Harbour. Group. Pile. IDiameter of point. Diameter of butt. Approximate ! weight of pile. I Total number of Iblows to drive Total penetration i into mud. Surface contact of pile with mud. i Average penetra- : tion for each of last flve blows Load supported dur- ing latter twenty- , seven davs M v. v^ov. Settlement under load as in preced- inercolumn Settlement in working platform, during same Derind Remarks. I. ins. ins. Ibs. ft. sq. ft. ins. tons. ins. ins. 1 8 18 4200 26 48 139 8 18’3 i i Unlagged piles 6 ft. 6 in. apart; in pairs, 11 ft. 6 in. apart. 8 7 17 14 3900 2700 19 13 49'6 50'9 134 127 91 131 18'7 18-7 4 6* 17 3640 11 45'7 123 111 18-7 II. 1 6 17 3600 46 49-6 220 4 31-8 H 1A H 5 Piles spaced as above and lagged with four 5-in. x 6-in. pieces 30 ft 2 3 6i 74 15 16 2940 3450 58 46 50-1 51 -0 219 233 38 4 31-8 31-8 iff A A III. 4 8 164 3700 69 49-3 238 3 31-8 li A long. 1 7 17 3700 70 507 247 31 28 0 1* 11 Piles lagged as in Group II. and arranged in 2 8 174 4060 70 49’8 243 31 28-0 8 £ 3 74 184 4370 64 ; 49-0 241 3 28'0 11 two lines of two pairs 4 9 18 4450 80 ! 49 9 250 28 28 28'0 U each, the space be- tween each line being 11 ft. 6 in.; between the pairs in each line 5ft. 6 in. ; and between the piles in each pair, 2 ft. 8 in. Piles spaced as in Group II. and lagged with two 5 6 22 5700 90 52'6 257 28-0 Tff 1A 6 74 21 5500 67 1 49'4 247 21 28-0 111 7 54 22 5660 72 49'7 243 2.7 28'0 11 IV. 8 9 19 4870 83 48-8 245 21 28'0 11 s 1 5 164 3270 59 507 241 3f 34'6 g i 2 0 184 4870 77 49-4 247 21 34-6 3 74 19 4600 44 47-1 231 4i 34’6 IH 1 pieces 6 in.x6 in. and 4 7 174 3890 65 47'8 233 21 34'6 XTß two pieces 4 in. x 10 in. all 30 ft. long.