Correct Answer - Option 1 : 75 micron
(i) Mechanical analysis is defined as the determination of the mass of particles in the fraction containing particles of only a certain size.
Sieve Analysis: Suitable for coarse soil (greater than 75-micron particles) e.g. sand, gravel
Sedimentation Analysis: Suitable for fine soil (fines - particle size less than 75 microns) e.g. clay, silt
(ii) Sedimentation analysis is used only for the soil fraction finer than 75 microns.
(iii) The sedimentation analysis procedure is as follows:
- Soil particles are allowed to settle from a suspension.
- The decreasing density of the suspension is measured at various time intervals.
- The procedure is based on the principle that in a suspension, the terminal velocity of a spherical particle is governed by the diameter of the particle and the properties of the suspension