In 2013, Gayatri was selected by the National Highways Authority of India (NHAI) for the widening of the Panikoili to Rimuli section of the NH215 highway in Odisha. This highway is considered an economic lifeline for the mineral-rich area.
In addition to widening the road from two lanes to four, the project required building facilities including flyovers, underpasses, bridges, bus bays, rest areas and service roads. The project also included Highway Traffic Management Systems, Highway Patrolling Service and Accident Vehicle Recovery Service.
In order to widen the road, the Gayatri team had to lay each layer of material precisely, starting with the sub-base course, base course and finally the surface courses. To prepare the sub-base course, Gayatri conditioned the soil and mixed material, and loosened up the hard layer of material, so that the subsequent material could bind properly. There was a 250-millimetre layer of soil and the next layer was an embankment top layer, 70 millimetres in thickness. Five full-time surveyors surveyed the NH215 site initially.
Traditionally, road-building projects require this initial survey, plus ongoing subsequent grade checking of the project site. Not only is surveying, running and resetting stakes costly, it is time-consuming and means the motor grader is often running — but not being utilised. This burns fuel and adds wasted time to the project. With the grade-control system, only the first pass requires a grade stake and checker.
The rest of the passes reference the first pass, using an auto mode. The machine-mounted sensors calculate the necessary blade position to achieve the desired cross slope of the sub-base course and surface layers.
Here, Gayatri, in consultation with its technology partner SITECH India North & East, adopted the Cat AccuGrade 2D Cross Slope system for its motor grader. The system uses sensors on the machine to control the slope of the blade during operation.
The system makes automatic adjustments to the left or right lift cylinder as the operator runs the grader. It delivers all of the information to the in-cab display so the operators can quickly spread material or cut at the correct cross slope, which reduces manpower utilisation. Real time cut and fill data and in-cab guidance give the operator the opportunity to work more confidently and achieve greater accuracy with fewer passes, using less material.
To monitor the effectiveness of the technology, Gayatri tested the system-laying material for a 140-metre long by 15 metre wide bed. The surface course layer material was 250 millimetres aggregate and had to maintain a tolerance of +/- 25 millimetres; the slope was approximately 2 per cent.
With the grade control system on the motor grader, the operator made 21 passes in 50 minutes, compared to manual grading, which requires 33 passes and took 89 minutes. The result was 36 per cent fewer passes required and 44 per cent less machine runtime. In addition to decreasing passes and runtime, accuracy improved by 25 per cent.
With the sensor, Gayatri is getting accurate tolerance limits (+/- 10 millimetres), which has helped them in reducing manpower requirements. Once the peg marking is done, it runs automatically by auto sensors of hydraulic systems, so no manpower is required later, which means engineers can utilise that manpower somewhere else.
Overall, Gayatri was able to stay on grade and improve productivity and accuracy by 42 per cent, compared to conventional methods. Further, they were able to increase accuracy and decrease both fuel consumption and grading time, while building a better road that is expected to have a longer life and overall lower long-term maintenance costs.
With less rework, Gayatri saved costs on the final embankment layer material. Fuel consumption for that same embankment layer went from 19 litres to 10 litres, a 47 per cent increase in efficiency. The team also used the motor grader to cut and maintain the road ditch slope when building the road drainage systems. This was needed to remove material from the bottom of the ditch.