The void ratio of a mixture is the ratio of the volume of voids to volume of solids. It is a

dimensionless quantity A dimensionless quantity (also known as a bare quantity, pure quantity, or scalar quantity as well as quantity of dimension one) is a quantity to which no physical dimension is assigned, with a corresponding SI unit of measurement of one (or 1) ...

in materials science, and is closely related to

porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

as follows: :

e = \frac = \frac = \frac

and :

\phi = \frac = \frac = \frac

where

e

is void ratio,

\phi

, ''V_V'' is the volume of void-space (such as fluids), ''V_S'' is the volume of solids, and ''V''_''T'' is the total or bulk volume. This figure is relevant in composites, in

mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic via ...

(particular with regard to the properties of

tailings In mining, tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different to overburden, which is the waste rock or other material that overlie ...

), and in

soil science Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to th ...

. In

geotechnical engineering Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics for the solution of its respective engineering problems. It als ...

, it is considered one of the state variables of soils and represented by the symbol ''e''. Note that in

, the symbol

\phi

usually represents the angle of shearing resistance, a

shear strength (soil) Shear strength is a term used in soil mechanics to describe the magnitude of the shear stress that a soil can sustain. The shear resistance of soil is a result of friction and interlocking of particles, and possibly cementation or bonding of par ...

parameter. Because of this, the equation is usually rewritten using

n

for porosity: :

e = \frac = \frac = \frac

and :

n = \frac = \frac = \frac

where

e

is void ratio,

n

is porosity, ''V_V'' is the volume of void-space (air and water), ''V_S'' is the volume of solids, and ''V_T'' is the total or bulk volume.Craig, R. F. ''Craig's Soil Mechanics.'' London: Spon, 2004, p.18. .

Engineering applications

* Volume change tendency control. If void ratio is high (loose soils) voids in a soil skeleton tend to minimize under loading - adjacent particles contract. The opposite situation, i.e. when void ratio is relatively small (dense soils), indicates that the volume of the soil is vulnerable to increase under loading - particles dilate. * Fluid conductivity control (ability of water movement through the soil). Loose soils show high conductivity, while dense soils are not so permeable. * Particles movement. In a loose soil particles can move quite easily, whereas in a dense one finer particles cannot pass through the voids, which leads to clogging.

External links

Relation between void ratio and porosity

References

{{Geotechnical engineering, state=collapsed Materials science Soil mechanics Earth sciences Soil science Mining terminology

Engineering applications

See also

External links

References