Classification Based on Grain size
In general, soils may be classified as coarse-grained (cohesionless) and fine-grained (cohesive) soil. The both coarse-grained and fine-grained soils can be further sub-divided based on their grain size. According to Indian Standard Soil Classification System (ISSCS), soil with particle size > 300 mm is called Boulder. Soil with particle size in between 300 mm to 80 mm is called Cobble. The soil is calledGravel if particle size is in between 80 mm to 4.75 mm. The gravel is sub-divided as Coarse Gravel (80 mm to 20 mm) and Fine Gravel(20 mm to 4.75mm). Soil with particle size in between 4.75 mm to 0.075 mm is called Sand. The sand is sub-divided as Coarse Sand(4.75 mm to 2.0 mm), Medium Sand (2.0 mm to 0.425 mm) and Fine Sand (0.425 mm to 0.075 mm). Soil with particle size less than 0.075 mm is called Fine-Grained soil (Silt or Clay) and soil with particle size in between 80 mm to 0.075 mm is called Coarse-Grainedsoil. However, soil with particle size less than 0.002 mm is called Clay and soil with particle size in between 0.075mm to 0.002 mm is called Silt.