June_1970 — Page 31

First launching soon on HK tunnel project

by K.A. Phillips

partner,

Scott Wilson Kirkpatrick & Partners, Hong Kong.

Civil engineering

Tunnel sections with spider stiffeners used during handling

IN ONE months' time the first 325ft. long, 34ft. diameter steel section of the Hong Kong cross-harbour tunnel will be launched from the slipway at Hung Hom. It will then be fitted out with concrete to bring its total weight to about 19,000 tons, and in October it will be placed in its final position on the sea bed.

From that point onwards, this operation will be repeated monthly until all 15 units of the tunnel have been launched and positioned.

In situ construction work and ser- vices installations will follow and the tunnel should be completed ready for use in the summer of 1972.

The cross-harbour tunnel will link Kowloon at Hung Hom with the island at Wan Chai. Essentially it will accom-

modate a dual two-lane carriageway with a minimum headroom of 16ft. Generally gradients are very small, ex- cept in the approach ramps where they a maximum of 6.2 degrees. In these lengths, just inshore of either ventilation building, a third climbing lane is provided for traffic leaving the tunnel.

are

Where the tunnel passes beneath the harbour the requirement has been to provide a minimum of 40 ft. clear- ance between low water level and the top of the protective rock blanket over the tunnel. This is only relaxed inshore where the existing sea bed and other marine features in any case violate the requirement.

The length of the tunnel between portals is 6062 ft, of which 812 ft. is

built in situ leaving 5250 ft. to be con- structed by the submerged tube method. The overall length of the pro- ject, from where the tunnel ramp starts to descend from ground level opposite Percival Street, Wan Chai to the north end of the toll plaza at its junction with the mainland road net- work on Hung Hom, is approximately 8000 ft.

The principal elements of the pro-

ject are:

North ramp

in situ construc- tion on Hung Hom reclamation. North ventilation building constructed as a caisson. Submerged tube tunnel. South ventilation building and south ramp

in situ construc- tion within an earth and rockfill

Far East BUILDER, June 1970

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