Flexible pavement design and quantity take-off for a state highway upgrade

Godavari Infra Projects has won an engineering, procurement and construction contract to upgrade 6.2 km of a state highway from a single lane to a two-lane carriageway of 7.0 m with 1.5 m paved shoulders. The existing road carries sugar-cane trucks for five months a year and has failed twice in the last four years, with deep ruts in the wheel paths and fatigue cracking near the cane factory.

The client's engineer has rejected the contractor's first pavement design because it used a single subgrade CBR for the whole length and an assumed traffic figure. The contractor needs a new design, backed by its own data, within four weeks, plus the quantities to order bitumen and aggregate.

You have: - a 7-day classified traffic count giving an average of 1,850 commercial vehicles per day in both directions, of which 35% are loaded trucks during the cane season; - an axle-load survey summary (you will build a synthetic version in task 1, with stated assumptions); - 18 soaked CBR results at 350 m spacing, ranging from 3.2% to 9.5%; - a traffic growth rate of 5% a year and a design period of 20 years.

You will design the pavement to IRC:37 for the two-lane carriageway, check the critical strains with IITPAVE, choose the bituminous layers, work out quantities and cost per kilometre, and write a design note for the client's engineer.

The same contractor bids for work in South Africa, so your note ends with a half-page comparison of how the South African mechanistic approach would treat the same road.

Done means a pavement section per homogeneous sub-section, with design traffic, subgrade modulus and strain checks shown, and a quantity and cost table the procurement team can use.