July_1970 — Page 33

Excavation for pile cap inside Bowrington Canal

L-frames north of Lockhart Road

the columns, into the ground drainage system.

Roads on the reclamation consist of 8in. thick crushed rock sub-base, 8in. lean-mix concrete base, 3in. bitumen macadam and 11⁄2in. asphaltic concrete wearing course. Elsewhere, road con- struction is similar to that of the exist- ing roads in the area.

Contracts

The project has been divided into four separate contracts, namely:-

1. Bowrington Canal extension 2. Canal Road flyover

3. Canal Road flyover extension and associated works

4. Road Connections (Island) - re- maining works.

Bowrington Canal extension

Before reclamation west of Kellett Island could be completed, it was necessary to extend Bowrington Canal between Gloucester Road and the new seawall, a length of some 1,000ft. The nullah, 40 ft. wide and 11ft. deep, is the main stormwater channel serving Happy Valley and Wan Chai areas. The existing invert level at Gloucester Road was +1.00 P.D. and that at the new out- fall was designed to be -1.00 P.D. Construction of the canal was there- fore mainly under water.

The basic design adopted is shown in Fig. 3. Piles were driven from ground level along both sides and the centre of the canal at 12ft. and 10ft. centres, respectively and capping beams con- structed to join them together. Exca- vation was then carried out in bulk down to 2ft. below the invert level.

Excavation in trench along the sides of the canal was taken down to the required level for sheeting units which formed the walls. The units were placed in the trenches and concreted into the capping beam. A crushed rock blanket 2ft. thick was put down inside the canal and, taking advantage of monthly low tides, the invert slab was cast. Finally, prestressed concrete I-beams were placed transversely on the capping beams and concrete in-fill completed the roof construction.

The two ends of the extension were supported on rubble mounds and R.C. trough construction was employed there. Since a considerable portion of the canal roof would eventually sup- port ground level roads, the roof was designed for HA loading.

The contract for the extension was awarded to Fook Lee Construction Co. Ltd. in August 1967 and the work was completed in March 1969. The cost of this project was HK$2,750,000.

Far East BUILDER, July 1970

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