Bulk Density of Soils and Impact on Their Hydraulic Properties

Definition

Density is the ratio of mass to volume, with a dimension of (ML⁻³). A soil sample at natural conditions consists, in most of the cases, in three phases, solid, gas, and liquid. The bulk density of a soil sample, generally represented by ρ _b, is a physical property defined as the ratio of the total mass of solids (M _s) to the total volume of the sample (V _t):

$$ {\rho_{\rm{b}}} =\frac{M_{\rm{s}}}{V_{\rm{t}}} $$

(1)

The bulk density of soils is generally expressed in units of g cm⁻³ or Mg m⁻³.

The bulk density of soils is related to additional physical properties, such as porosity, n, and void ratio, e:

$$ {\rho_{\rm{b}}} = {\rho_{\rm{s}}}(1 - n) $$

(2)

$$ {\rho_{\rm{b}}} = {\frac{\rho_s} {e + 1}} $$

(3)

where ρ _s is the soil particle density defined as the ratio of the total mass of solids (M _s) to the volume of solids (V _s).

The bulk density is required to transform gravimetric water content, θ _g, into volumetric water content, θ _v:

$$ {\theta_{\rm{v}}} =...