UNIFORMITY COEFFICIENT: - CU=D60/D10, the particle size range is measured by this uniformity coefficient. For well graded soil it is near 1. A soil having CU =more than 10 is well graded soil.
COEFFICIENT OF CURVATURE = D30 2 /D60 XD10. For a well graded soil it is 1 to 3.LIQUID LIMIT: - An arbitrary limit between liquid limit and plastic limit of consistency of soil. It is defined as the minimum water content at which a part of soil cut by a groove of standard dimensions will flow together for a distance of 12 mm (1/2 inch) under an impact of 25 blows in the device.
PLASTIC LIMIT: - Arbitrary limit between plastic limit and semi solid limit of consistency of soil. It is defined as the minimum water content at which a soil just begins to crumble when rolled into a thread of approx 3 mm diameter.
SHRINKAGE LIMIT: - It is defined as the maximum water content at which a reduction of water content will not cause a decrease in the volume of a soil mass. It is the lowest water content at which a soil can still be completely saturated.
PLASTICITY INDEX: - The range of consistency within which a soil exhibits plastic properties. . i.e. Ip = =WL – WP.
CONSISTENCY INDEX: - The ratio of the liquid limit minus natural water content to the plasticity index is called consistency index or relative consistency. When it is zero soil is in liquid limit; when more than 1 it is in semi solid state; if equal to 1 it is in plastic limit. i.e. IC =( WL –w)/ IP
LIQUIDITY INDEX: - It is known as the ratio of natural water content of a soil minus its plastic limit, to its plasticity index expressed as a percentage and also known as water plasticity ratio. i.e. IL = (w - Wp) / Ip
SHRINKAGE INDEX = WL – WS ;
FLOW INDEX (If )= (w1–w2)/log10 n2/n1 (shear strength variation with water content) ;
COMPRESSION INDEX Cc =( e0 –e)/log10 ( ’/ 0) ;
TOUGHNESS INDEX = Ip / If
PERMEABILITY is the property of soil which permits the passage or seepage of water through interconnecting voids. Clay is practically impermeable
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