May_1971 — Page 40

Dozers and scrapers dump material over unstable slopes, maintaining the road to a maximum gradient of 1 in 10 throughout

Ingersoll Rand drilling equipment is used prior to blasting difficult pockets

kilometre of road.

The ultimate flexible pavement specifications fall in line with most world standards for provincial high. ways and is designed for a 20-year life and a speed of 60 kms/hour. This en- tails a 10-metre formation and twin lanes with a bituminous hot mix sur- face of 7 metres width.

Satisfactory road sub-base and base aggregates are available from the in situ material which is mostly formed from sediments: silt stone and lime stone. Natural gravels are scarce in this region and will probably be supplied by sub- contractors from other quarries.

Ripping and dozing

Of a total 10 million cu.metres of cut, 25 per cent is solid rock. This material is classified by siesmic velo- city tests which register up to 9,000 ft./second. Most of this is being loos- ened with Caterpillar model D9G trac- tors fitted with 9D single and double shank ripper attachments. Although some tough pockets require blasting, the D9 rippers are being used to maxi- mum capacity and the material has fragmented better than expected.

Ripping and dozing this material is unquestionably a difficult phase which requires skilled operation and super- vision. Further, the accelerated wear on undercarriage parts and replace- ment of tips is expected to add 100 per cent repair costs to the deprecia- tion figures. Yet despite these higher maintenance costs, ripping is anticipat- ed by the supplier to budget out one third as much as an overall blasting and scarifying operation.

Refraction siesmograph tests car- ried out by the Thai/Australian per- sonnel accurately indicated not only the hardness and ripability of the rock but showed up various subsurface clea- vages and laminations vital to the sur- vey work.

The variable type, parallelogram rippers are hydraulically controlled. They were selected over the hinge types because down pressure in tough going was required. The versatility of this type of unit also permits the use of the tip to pick material from high walls and be angled to the rear to ensure ripping passes commence right at the base of a slope. It is estimated that production ranges around 200 bank cu.metres (261 cu.yd.) with trainee operators.

Cat D6 tractors with sacrifiers are used ahead of the team of Cat rubber

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Far East BUILDER, May 1971

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