Grain size characteristics of unconsolidated soil in the humid tropical region of Tripura

Grain size characteristics form an important aspect of study in hydrological and soil sciences. Grain size refers to the single grain dimension of sediment or other grain particulate. The size of unconsolidated soil may range from boulders to gravel, as well as sand, silt and clay. Grain size analysis helps in determining the hydrodynamic state. It is also vital in determination of permeability of soil in an area. Therefore, grain size distribution is one of the textural properties of soil that affect the magnitude and direction of permeability. The present study intends to explore the characteristics of grain size and their distribution in different physiographic units of Tripura viz., hills and piedmonts, intermontane synclinal troughs, terraces and tillas; and floodplains. Although the study area receives a good amount of rainfall, the study area suffers from low permeability and porosity. This paper attempts to analyse the statistical parameters of grain size distribution and the nature of grain size gradation in different physiographic units. The statistical analysis indicated poorly sorted soil with no variation in all the physiographic units. Further, it was observed that fine sand is the predominant grain observed in all the physiographic units, which is poorly graded.