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Porosity is the ratio of pore volume to its total volume. Porosity is controlled by: rock type, pore distribution, cementation, diagenetic history and composition. Porosity is not controlled by grain size, as the volume of between-grain space is related only to the method of grain packing.
Micro CT of porous medium: Pores of the porous medium shown as purple color and impermeable porous matrix shown as green-yellow color. Pore structure is a common term employed to characterize the porosity, pore size, pore size distribution, and pore morphology (such as pore shape, surface roughness, and tortuosity of pore channels) of a porous medium.
Porosimetry is an analytical technique used to determine various quantifiable aspects of a material's porous structure, such as pore diameter, total pore volume, surface area, and bulk and absolute densities. The technique involves the intrusion of a non-wetting liquid (often mercury) at high pressure into a material through the use of a ...
This measured pressure permits obtaining the pore diameter, which is calculated by using the Young-Laplace formula P= 4*γ*cos θ*/D in which D is the pore size diameter, P is the pressure measured, γ is the surface tension of the wetting liquid and θ is the contact angle of the wetting liquid with the sample. The surface tension γ is a ...
The pore space of soil contains the liquid and gas phases of soil, i.e., everything but the solid phase that contains mainly minerals of varying sizes as well as organic compounds. In order to understand porosity better a series of equations have been used to express the quantitative interactions between the three phases of soil.
At the microscopic and macroscopic levels, porous media can be classified. At the microscopic scale, the structure is represented statistically by the distribution of pore sizes, the degree of pore interconnection and orientation, the proportion of dead pores, etc. [4] The macroscopic technique makes use of bulk properties that have been averaged at scales far bigger than pore size.
Pore size varies considerably; the smallest pores (cryptopores; <0.1 μm) hold water too tightly for use by plant roots; plant-available water is held in ultramicropores, micropores and mesopores (0.1–75 μm); and macropores (>75 μm) are generally air-filled when the soil is at field capacity.
Porosity gives a measure of the water storage capability of soil but not all the water present in the soil pores is available for extraction by pumping for the use of humans or draining by gravity. The pores in the soil hold back sufficient quantity of water on account of forces like surface tension and molecular attraction. Hence the actual ...