Correlation Between California Bearing Ratio (CBR) Value and Index Properties of Soils for Gangetic Alluvium in West Bengal

Large scale infrastructural development by constructing huge amount of roads connecting remotest villages in rural India with the existing network of road is being pursued rigorously in India from last decade, through different government scheme, like PradhanMantri Gram Sadak Yojana. The process is involving year long selection of possible routes at block level decided from lowest administrative level district wise for making planning design, and scrutinizing them at state level before sanctioning by national authority. For such roads, near surface local soil, enroute are used as constructional material for sub-grade construction and foundation material for the road structure itself. These soils vary widely with location. In India major part of southern part is covered with Black cotton soil, while great part of north Indian planes are covered with Indo-Gangetic alluvium. Alluvial soils due to their modes of formation are very erratic and properties of such soil vary greatly along horizontal and vertical directions. To map such variation by determining their insitu properties is very costly and may be kept out of considerations generally, due to economic difficulties. But consideration of such variation in engineering properties of soil becomes important from view point of design, construction control, satisfactory performance, and cost effectiveness. There have been studies to map the possible variation for different types of soil in different countries by classification system world wise. Such investigation try to scale the variation of studied soils by zonalising so that designer and constructors can estimate possible variation of the properties of soils existing at those sites.