ABSTRACT
The newly developed open pit coal mines in India, use: 35, 50, 85, 120 and 170 tonne trucks for coal haulage. Standard specifications for the design of flexible pavements for these heavy load trucks are not available, as of yet. This paper describes the relationship between the thickness of flexible pavement (the California Bearing Ratio, CBR, value of the sub-grade soil), and both the tire contact area and inflation pressure, the last two being related to truck wheel load. Equivalent wheel loads (EWL) for trucks of different capacity have been worked out, using the equal deflection criteria. A relationship between the CBR and the thickness of the flexible pavement for different types of trucks has now been established. From the economic analysis of surfaced and unsurfaced roads, it has been concluded that vehicle operation cost can be reduced considerably, by providing a bituminous surfacing layer.
