Models for accurate prediction of road surfaces &pavements

: IIT-Hyderabad Tuesday said its researchers have developed models and computational simulation studies to predict performance of road surfaces or pavements and compare these predictions with conventional road designs.

This research offers a route to accurate prediction of pavement performance, which can help in construction of long lasting roads in India, a IIT Hyderabad press release said.

This research work has been recently published in the Journal of Transport Engineering, it said.

India has the second largest road network in the world after the United States nd has about 4.37 km of roads per 1,000 people.

The past two decades have seen a drive to pave the Indian roadway network, and as of 2016, 62.5 per cent of Indian roads have been paved, it said.

Construction of the road surface or pavement is a complex process as they should provide for comfortable riding quality, good skid resistance, favorable light reflecting characteristics and low noise pollution.

The pavement design is the first and essential step towards building roads that can meet the needs of the traffic demands as well as to balance the demand on natural materials used in paving them, the release said.

Prof Sireesh Saride, faculty member, Department of Civil Engineering,said a road surface or pavement typically consists of superimposed layers of various materials above the natural soil and helps in the distribution of the load of traversing vehicles for a smooth ride.

There are two types of pavements rigid and flexible.

While rigid pavements are made of high strength concrete to resist vehicle load directly, flexible pavements transmit load downwards from the surface through successive layers of materials.

"The advantages of flexible pavements are that they are adaptable to stage-wise construction, can be made of low-cost materials and can be easily opened and patched", Saride said, on the applicability of flexible pavements to Indian roads.

In modern pavement construction, accurate prediction of pavement performance has become important in order to develop robust design procedures.

"Reliability-Based Design Optimisation RBDO is a modeling technique that combines optimisation approaches with reliability assessment of structures", he said.

His team used RBDO to predict safety of multi-layered flexible pavement structures against fatigue and rutting criteria, while simultaneously considering the variability arising from individual design parameters.

The flexible pavement was modelled as containing four layers subgrade, granular subbase, base, and bitumenous layers.

Modelling studies showed that the bituminous layers thickness and resilient modulus of the base layer are the most influential parameters for the fatigue failure, it said.

The results of simulation studies were compared with data from American Association of State Highway and Transportation Officials (AASHTO) guide for the design of pavements.

"AASHTO overestimated reliability by 10-40 per cent compared to RBDO because the former did not consider the variability associated with geometrical and material properties", it said.