Stokes law state that the terminal velocity of settling of spherical particle in suspension, various with the source of the diameter of the sphere, density & velocity of the fluid and density of the sphere.
Combines of sleve& sedimentation analysis:-
• It is done when soil mass consists of a particle of both course & fine grained soils.
• The slurry is sieved through 0.75mm is sieved.
• The material retained on the sieve is over-dired and the sieve is done using the set of fine sieves.
• The suspension passing the 75mm sieve is mixed with the deflocculating asent, if it is not done. The hydrometer test is performed.
• The % finer then any size can be calculated on the basis of origin mass of soil taken for cmbined analysis.
Uses of particles size distribution curve
- Particle size distribution curve extremely useful for the coarse grained soils.
- P.S.D.C - To classify the classification of coarse grained soils.
- The coefficient of permeability of a coarse grained soils depend upon the large extend on the size of the particles.
- The P.S.D.C - Used known as sensitivity of soil.
- The P.S.D.C -design of drainage filters.
- The P.S.D.C -provide index to the shear strength of soil, Generally a well graded, compacted sand has high graded soil.
- The P.S.D.C - soil stabilization and for the design of pavement.
- P.S.D.C -may indicates mode of deposition of soil. For EQ Gap-graded soil indicates deposition by two different agencies.
Relative Density:- The most important index aggregate property of cohensionless soil is its realative density.
The engineering properties of a mass of cohensionless soil depend upon large extend of relative density (Dr) also known as dnsity index(Io).
The relative density:- Dr=Emax-e/Emax-emin*100
Emax - Max void ratio of the soil in the loose condition. Emin- Min void ratio of the soil in theDenset condition. e Void ratio in the natural condition.