March_1965 — Page 37

CIVIL ENGINEERING & PUBLIC WORKS

2 ft. long but every fourth was 4 ft. long. Thickness at the base was 9 in. and 6 in. on the upright section, with a 6-in. splay between.

Thickness of the footpath section was 6 in., tapering to 4 in. at the outer edge. Between the upright and footpath sections was a 3-in. splay. On the footpath section, there was a 1-in. fall towards the outer edge for drainage purposes.

Both units are set flush against each other in rows. Tongue and groove joints of 14 in. radius running the full height of each section ensure a proper edge-to-edge fit.

Before the precast units were put into position, a regulating layer of concrete was laid to provide a level foundation. Each unit was then prized into its correct position and aligned by means of crowbars.

Dowel Bars

Although both the L-units and Z- units were heavier at the base, and thus stable, for additional stability they were pinned into place by means of dowel bars penetrating 18 in. into the roadway one in the

base of each L-unit and two in each Z-unit. After the units had been finally aligned, the dowel bars were grouted into place to ensure a solid fixing.

With the precast units in place. the level of the roadway was then built up, as required, by about 2 ft. 6 in., with a 1 : 60 crossfall from east to west for drainage. To avoid excessive disruption of road traffic across the causeway, this was done in separate 4 in. layers. The material used was granite crusher run mixture of blocks up to 4 in. square) obtained from the Johore PWD quarry. Each layer was separately compacted and rolled.

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On top of the crusher run layers was placed a 2 in. premix bitumen macadam base course and, finally, a each 1 in. premix wearing course, laid by a Barber-Greene road paver. To complete the job, the L-units were topped with a low tubular-steel guard rail. On the western side, at the outer edge of the pedestrian way, a 3 ft. 6 in. high railing was erected.

Future Widening

In planning the present scheme, considerable thought was given to possible additional road widening in the future, should this become neces- sary. Provision was in fact made for widening by up to about 20 ft. more on the western side and making the road dual carriageway.

On that side, 4 ft. long (instead of 2 ft. long) precast Z-units were in- serted at 10 ft. intervals to act as end bearings for future reinforced con- crete beams supporting an additional width of roadway. The outer ends of the beams would rest on pillars set into the base of the existing causeway.

Far East Architect & Builder March, 1965

Placing the Z-units. Note the dowel bars for fixing

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Z-units in position before the road

was

raised

Causeway carriageway completed and pedestrian rails erected

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