Particle Size Distribution

The particle size distribution in a given soil is determined in the laboratory by sieve analysis and hydrometer analysis. For classification purposes in coarse-grained soils, the following two parameters can be obtained from a particle size distribution curve:

(1)

(2)

where D ₁₀ , D ₃₀ , D ₆₀ = diameters through which, respectively, 10%, 30%, and 60% soil pass.

Weight-Volume Relationships

Soils are three-phase systems containing soil solids, water, and air (Fig. 1). Referring to Fig. 1

Figure 1

(3)

(4)

where W = total weight of the soil specimen, W _s = weight of the solids, W _w = weight of water, V = total volume of the soil, V _s = volume of soil solids, V _v = volume of voids, V _w = volume of water, and V _a = volume of air.

The volume relationships can then be given as follows:

(5)

(6)

(7)

Similarly, the weight relationships are:

(8)

(9)

(10)

(11)

In the preceding equations, ? _w = unit weight of water (62.4 lb/ft ³ or 9.81 kN/m ³), and G = specific gravity of soil solids, or

(12)

Relative Density

In granular soils, the degree of compaction is generally expressed by a nondimensional parameter called relative density, D _d, or

(13)

where e = actual void ratio in the field, e _max = void ratio...