8.20
8.21
8.22
8.23
8.24
8.25
The vertical piles are designed to take up to 250 tons each and the rakers up to 200 tons. The inshore 18 ft. of the deck is in the form of a slab supported on beams spanning from the rear row of piles to the top of the concrete-block seawall. The seawall itself is con- structed on a rubble-mound foundation and comprises 6 rows of precast-concrete blocks laid one on top of the other to a level of 5.5 ft. above Chart Datum and above this, mass concrete cast in-situ to the required level. The lower blocks are designed with keys along both horizontal and vertical joints and suitable filter material is dumped behind the wall to prevent soft material escaping through joints and the rubble mound.
For the remaining containership berths as well as the southern 150 ft. of the first phase, a cellular steel-sheet-pile form of construction is recommended because:-
(a) There is a considerable depth of mud on the proposed line of the quaywall at these positions and this type of construction requires the least amount of dredging and is comparatively quick to build.
(b) There is little danger of settlement of the crane rails which would be on piled founda-
tions.
Details of the design proposed for the second-phase quaywall are shown on Drawing 19. It would be constructed with flat-type steel sheet piling varying in length from 70 to 80 ft. with a width of 15.7 ins. and a weight of 36.4 lbs per ft. run. These piles are driven with interlocking clutches to form a cellular bulkhead 76-ft. wide.
The soft material within the cells is removed and replaced by granular material and/or rock. The crane beams would be 42-in. wide × 48-in. deep, supported on 42-in. diameter hollow prestressed-concrete piles of about 110-ft. length driven at 15-ft. centres. An apron of rip rap could be deposited on the seabed immediately in front of the quaywall later if local scouring should occur.
The proposed cope level is +14.25′ C.D. with a 9 in. upstand kerb. It is calculated that with the worst storm waves, overtopping would occur only when the tide level reached about +6 ft. C.D. but the average flow over the quay would be only about 0.3 cusec/ft. run when the tide reaches +8 ft. C.D. A 1-ft. cross fall on the 100-ft. working apron is proposed in order to limit possible flooding of the marshalling area.
The fendering system shown for both types of quaywall comprises vertical 10 in. × 8 in. timber rubbing pieces backed by 12 in. × 12 in. timber walings and hollow rubber blocks. The system has been designed to absorb blows from 54,000-ton-displacement containerships berthing and to withstand the vertical movement of the ships alongside as they load and unload; it should therefore ensure rapid and safe berthing of containerships. Bollards capable of taking a pull of 100 tons would be sited at 120-ft. centres along the cope. It is understood that containerships would have self-tensioning mooring winches to cater for the rise and fall during loading and unloading.
The wave observations being carried out in the summer of 1969 or subsequent operating experience may indicate that there would be undue interruption of loading on account of movement of ships during periods of swell. In that case the fendering and mooring systems described in the previous paragraph may have to be altered to reduce ship move- ment to an acceptable amount.
8.26 The test piles driven, on which the estimates of pile lengths in paras. 8.19 and 8.22 were based, were about 12in. × 15in. section. The piles now proposed would be 42-in. diameter. Because of this difference and the variable nature of the soil as indicated by the site in- vestigations, further pile-driving and loading tests should be carried out before finally deciding the pile lengths.
Marshalling Area
8.27
With straddle carriers stacking containers 2-high, the marshalling area for Stage 1 shown on Drawing 16 would provide space for 1,800 20-ft. containers per berth or the equivalent of larger sizes. With proper recording and control, it would not be necessary to provide lanes between blocks of different categories of containers as proposed by the Container Committee and shown on Drawing 4. It is not practicable of course to use all the space fully in a marshalling area, but it is considered that the area proposed for each berth
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