Repeated damage of fulbari by-pass road: causes and measures for restoration

The Fulbari by-pass road is a service road running parallel with Tista-Mahananda canal of West Bengal, India. The road has been damaged repeatedly for the last few years. There are huge depressions on the road surface and it now look like a sine curve. Field investigation, field tests indicate huge seepage is flowing under the road throughout the year, ultimately leading to piping and consequent soil loss. The adjoining canal lining is severely damaged leading to huge seepage. Field and laboratory tests suggest that the sub-grade soil is poor, un-compacted heterogeneous sub-soil of very loose compactness and thus unfit to act as a sub-grade material under severe traffic load. A combination of these factors is jointly responsible for the damage of the road, even after repairing every year. Two alternative suggestions have been given by the author. Either construct rigid pavement on supporting piers founded on a firm-soil. Also absolute leak proofing of the adjoining canal was suggested to be mandatory. Or search for a new location, where there will be no seepage effect. A new flexible pavement could be constructed, which might be cheaper than the first suggestion and keep the aforesaid road to serve just like a service road.