Question

Coarse grained soils behave differently than fine grained soils. What is the primary soil property responsible for the different engineering behavior of coarse versus fine grained soils, and why is it important?

Answer 1

The primary property responsible for different engineering behavior of coarse grained soil is its particle size distribution and of fine grained soil is its mineral composition . The different engineering properties which are of concern are permeability, compressibility, shear strength, consolidation,plasticity, etc.

Coarse grained soil: By knowing the particle size distribution of coarse grained soil, it gives a rough idea of the behavior of soil under different conditions instead of a lengthy analysis of soil. For example, if soil is SW according to Unified Soil Classification System, then the engineer knows that the soil is well graded sand having high shear strength and low compressibility.

Fine grained soil: By knowing the type of mineral present in fine grained soil its degree of swelling, shrinkage, plasticity, activity, etc can be thought of before hand. For example, if mineral montmorillonite is present in soil it can be assumed that soil has high swelling and high shrinkage characteristic.