As part of the general improvements and expansion of the international airport at Delhi, one of the main take-off and landing runways is being modernized. The main contractor, GMR from Hyderabad contracted several companies to lay the 80 kilometers of cable required for the automated landing system.
The cables were to be laid in trenches 25 cm deep by 25 cm wide cut into cement treated base (CTB), a soft concrete with a compressive strength of between 5 and 10 MPa. Traditionally such trenches in India are dug manually using pneumatic breakers.
One of the sub-contractors, Advanced Construction Technologies (P) Ltd from Chennai decided to try an ER 1500-1 drum cutter
, fitted with a 250 mm wide cutter wheel,
mounted on a Volvo EC 140 excavator for this work. To achieve an exact depth of 250 mm, Erkat designed and manufactured a cutter wheel with a diameter of 980 mm specifically for this application.
Before starting work with the cutter wheels, the standard ER 1500-1 cutter drums had to be removed and a specially made wear protection cover fitted. The wear protection cover was supplied by Erkat so that the shafts exposed after removal of the cutter drums as well as the exposed areas of the main housing, would be protected from wear and damage while operating with the cutter wheel. This would also ensure that the standard rock cutting drums could be refitted at the end of the project without any delays or additional costs. The cutter wheel was then fitted.
The pick pattern on the cutter wheel was designed to provide a smooth cutting action, optimum cutting force, wear protection on the steel body of the wheel and minimum wear to picks and boxes. With a single excavator operator assisted by a labourer, a cutting rate of 125 meters per hour was achieved. The labourer’s main task was to stop the marks showing the line of the trench from being covered by dust and debris so they were always visible to the excavator operator. This productivity rate was equivalent to 100 labourers using pneumatic breakers and several compressors.
Pick type W 6E from Wirtgen were used and, in this material, the consumption rate was 60 picks for 4,000 m of trench or 250 cubic meters of cut material.