Question

The average particle size of Soil A is Less than 0.005mm ,Soil B is between  0.005 mm and 0.05 mm ,Soil C is 0.05 mm to 2.0 mm. Find the soil which has least water holding capacity.​

Answer 1

Answer:

There are several systems of soil classification which are based generally on particle size or on some additional soil properties such as plasticity and compressibility. Soil classification based on particle-size characteristics is widely used, especially for preliminary or general descriptions (see Section 6.4). However, any system based on particle size alone is likely to be misleading because the physical properties of the finest soil fractions depend on many factors other than particle size. This has led to the development of the Unified Soil Classification (USC) which is considered today to be the most useful of the engineering soil classification systems. The USC permits reliable classification on the basis of relatively few and inexpensive laboratory tests.

11.1 The Unified Soil Classification

The Unified Soil Classification identifies soils according to their texture and plasticity. The USC soil groups are based on:

Percentages of selected ranges of particle sizes (see below);

Shape of the particle-size frequency curve (see Section 6.7);

Plasticity-compressibility characteristics (see Sections 8.5 and 10.3).

For engineering use, four ranges of particle sizes are recognized. They are:

Cobbles: particles with a diameter larger than 75 mm;

Gravel: particle sizes from 4.75 to 75 mm;

Sand: particle sizes from 0.075 to 4.75 mm;

Fines: particles smaller than 0.075 mm (silt and clay).

The particle sizes used in the Unified Soil Classification are somewhat different from the other classification systems shown earlier in Table 2. The USC particle sizes correspond to US Standard Sieves, 3 inches (76.2 mm), No. 4 (4.76 mm) and No. 200 (0.075 mm) respectively, as follows:

GR000200.JPG (11719 byte)

Soils in the USC are classified in three basic soil types. They are:

Coarse-grained soils (CGS) which contain 50 percent or less of fines;

Fine-grained soils (FGS) which contain more than 50 percent fines;

Highly organic soils which are peat, muck, humus or swamp soil.