April_1966 — Page 73

CATWALK

CATWALK

CATWALK

CATWALK

TAKTA

+

म

MOORING DOLPHIN

MOORING DOLPHIN

SCALE OF PTET

ELEVATION OF TANKER BERTH

and sideways rakes as well as ver- tically.

Discussions were held with the contractor before piling started to ensure that the piling layout, in so far as it was possible, enabled him to use his plant to the best advantage. In fact some small adjustments were made which helped to speed the driving of the piles.

The decision to use steel piles was amply justified during construction.

-lighter and easier to handle than

concrete piles of similar length; --relatively simple to extend or trim: -withstood the heavy driving that is almost unavoidable when pass- ing from an easily penetrated formation straight on to rock. All bearing piles were driven to refusal which was defined as when the average penetration per blow for five consecutive blows of the hammer does not exceed 0.05 in.

The large diameter piles for the breasting dolphins are cased cast in- situ reinforced concrete piles. A thin-walled casing about 75 ft. in length and fitted with a cutting edge was driven by the forward-and-back- ward twisting motion of a "Hoch- strasse" unit fixed to the top. The soil and soft mud and were then mucked out by means of a grab.

At greater depths where rock was encountered, a chisel was used to break the rock up into fragments be- fore using the grab to muck out. The final cleaning out was done by means of pumping.

The steel reinforcement cage, the

Fig. 3

grout pipes and, where required, the 4 in. diameter ducts for Macalloy rods were then lowered into the pile casing after which the whole length was filled with aggregate graded from 21⁄2 in. to 1 in. Four 14 in. dia- meter grout pipes were used in each pile: two were placed with their lower ends close to the foundation, one was 20 ft. up and the remaining one was a further 20 ft. up from the bottom.

To start the grouting operation, a cement-water grout serving as a lubricant was first pumped for a few minutes after which normal grouting proceeded using 1:1.75 cement-sand grout. Additive was used to retard the setting time of the grout so that throughout the grouting operation no back pressure would be created be- cause of a partial setting of the up- per layer of grout.

Rock anchorages

The fixing of these anchorages is still in progress. Each anchorage is formed by first drilling at least 30 ft. into rock below toe level through the 4 in. diameter ducts cast into the piles and then inserting the Macalloy rod and grouting in the bottom 15 ft.

When the grout has developed full strength the rod is then stressed by stages to the required load and final- ly the entire anchorage is grouted up. In drilling for the anchorages some of the holes have required grouting and redrilling before inserting the rod. The reason for this is that where the rock surface slopes steeply it has

not always been possible to obtain a complete seal at the base of the cas- ing and in some case partially de- composed surface material has wash- ed in during drilling. This problem has been overcome successfully by injecting a sand-cement grout at pressures of about 80 lb./sq. in. and afterwards redrilling.

Plant

The principal items of plant brought out to site were:

Reclamation:

2 No. Cat 977

1 No. Cat D7E

2 No. Mobile Cranes Crushing plant

Concrete batching plant 7 cu. yd. grab dredger Marine Works: Piling barge

Costs

1 crane barge

2 Hochstrasse rigs

1 concreting barge

7 cu. yd. grab dredger

Site Investigation

Reclamation, tank

foundations, dyke

HK$

24,000.00

walls, drainage etc. 3,000,000.00* Marine facilities

* estimated final costs

3,600,000.00*

APPENDIX I

Design criteria

Dimensional characteristics of

tanker:

Summer deadweight

Far East Architect & Builder April, 1966

PIER HEAD UNLOADING PLATFORM

Fig. 4

O

1

100_

SCALE OF FECY

SECTION A-A

65