June_1966 — Page 61

CIVIL ENGINEERING AND PUBLIC WORKS

HARCOURT ROAD FLYOVER

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OMPLETED in April this year, the Harcourt Road flyover is the first stage of the Government's Gar- den Road Complex a multi-million dollar project for improving traffic flow in the central area of Hong Kong.

Garden Road Complex represents a comprehensive road system between Harcourt Road and Robinson Road. incorporating a new road to be called Kapok Drive running approximately on the alignment of the Albany Nul- lah between Harcourt Road and Mac- donnell Road, the widening and im- provement of Garden Road and the related flyovers and link roads.

The original Statutory Town Plan showed the junction of Harcourt Road and Kapok Drive as a round- about design with future provision for an east/west flyover in Harcourt Road.

While the roundabout design was considered adequate at the time the planning layout was first conceiv- ed, subsequent traffic volumes in the city centre have increased consider- ably during the ensuing years, and from traffic counts carried out in the area it has been established that a roundabout without a flyover would he over-loaded immediately on open- ing to traffic. To resolve this problem the most practical solution was to omit the roundabout entirely from the design and provide at the outset a flyover for westbound traffic in Har- court Road.

The flyover measures a total length of 960 ft., including the two ramps. and provides a 24 ft. wide carriage- way, a 10 ft. wide bus stop and a 9 ft. wide footpath, the latter being design-

Far East Architect & Builder June, 1966

This feature describing the design and construction of the Harcourt Road flyover is based on a paper presented to the Engineering Society of Hong Kong by Mr. G. Chien, BSc(Eng), AMICE, and Mr. P. Connor, AMICE, of the Roads and Drainage Division, Public Works Department, Hong Kong.

ed to link up with the podium level of the buildings to be developed in the two adjoining lots.

Site Investigations

Prior to the actual design of the flyover, site investigation by percus- sion boring was carried out. Both disturbed and undisturbed soil sam- ples were taken at regular intervals and standard penetration tests were carried out at 10 ft. intervals.

At a depth of 70 ft. below ground level the general N value recorded was 65 blows/ft. and at 80 ft. depth the corresponding value was as high as 138. At the latter depth the soil samples taken revealed that a very hard stratum of decomposed granite had been reached. It was apparent from the information obtained that the maximum length of piles to be driven would not exceed 80 ft.

The general water table recorded was at 4 ft. above Principal Datum, i.e. approximately 12 ft. below ground surface. Near the junction of Har- court Road and Kapok Drive, a 145 ft. wide ex-naval dry dock and a 26 ft. wide culvert are located directly under the flyover. The invert of the dock was found to be 53 ft. below ground level and the depth of con- crete construction measured 16 ft.

View from Connaught Road C. looking east

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