Roads constructed by NHAI .WHY FAILING?

I dont know what was the traffic density in the said road..but it may be too heavy to mention a reason by the auther,i dont know whether the roads by NHAI designs after a detailed scientific road study. And  I think the unexpected heavy traffic may cause the road damage.

As per the others openions, htere can be several reasons. But as per my experience on Indian roads, The reasons can be as follows:

1. Inadequate dpeth of earhworks above water table, that means the water table is near to the raod layers and makes the layers to soak. This will result in local settlements

2. Improper compaction of earth layers. During rains, inadequately compacted layers will be sink

3. Improper temperature control of the bituminous layers. This will lead to improper comaction and make the bituminous layers porus. During rains, water will percolate and distroy the underlying layers.

In short, lack of quality control will lead to this type of failures. If the pavement layers are constructed as per the internationally recognised quality control guidelines, it should last for the design period of 20 years with minor maintenance works. Hope this helps 

The section of NH5 (80km to Vijayawada and 83km from Vijayawada, on which I worked) which was consructed strictly as per designs, was performing well after 5 years of construction except normal wear and tear. However, reasons for failure of road depend upon several local and construction conditions even though the design is perfect.

Good one i think u r right with out looking on ground no expert can find reasons.