A Treatise On The Principles And Practice Of Harbour Engineering

8o HARBOUR ENGINEERING. of wet modelling clay. The dcpth 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 expérimente 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 31 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 lf 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. I Diameter of point. Diameter of butt. Approximate weight of pile. I Total number of I blows to drive. Total penetration I into mud. Surface contact of pile with mud. | Average penetra- tion for eacli of last I Ave blows Load supported dur-! ing latter twenty- ! seven days of test. ins. ins. Ibs. ft. sq. ft ins. tons. 8 18 4200 26 48 139 8 18-3 8 17 3900 19 49'6 134 9J 18-7 7 14 2700 13 50-9 127 134 18-7 61 17 3640 II 45'7 123 144 18-7 6 17 3600 46 49'6 220 4 31-8 64 15 2940 58 50-1 219 3g 31-8 74 16 3450 46 51 -0 233 4 31-8 8 164 3700 69 49’3 238 3 31'8 7 17 3700 70 50'7 247 31 28 0 8 174 4060 70 49'8 243 3J 28-0 74 184 4370 64 49'0 241 3 28-0 9 18 4450 80 499 250 21' 28-0 6 22 5700 90 52'6 257 23 28'0 74 21 5500 67 49’4 247 2f 28-0 64 22 5660 72 49'7 243 2Ï 28-0 9 19 4870 83 48'8 245 24 28-0 5 164 3270 59 507 241 38 34'6 10 184 4870 77 49-4 247 2A 34-6 74 19 4600 44 47T 231 48 34'6 7 174 3890 65 47'8 233 28 346 CO s ins. i 1 « 1Ä H « 1* li 11 Ir<i 1A IH 11 li g g 1H 1rs Settlement in working platform during same period. Remarks. Unlagged piles 5 ft. 6 in. apart; in pairs, 11 ft. 6 in. apart. Piles spaced as above and lagged with four 5-in. x 6-in. pieces 30 ft long. Piles lagged as in Group II. and arranged in two lines of two pairs each, tlie space be- tween eacli 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 pieces 5 in.x6 in. and two pieces 4 in. x 10 in. all 30 ft. long.