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Laboratory research of porosity, porosity coefficients and water saturation of soils

Soil porosity n (%) is the ratio of the pore volume to the total volume of the soil sample. n is a classification indicator, the value of which is used to classify sandy and rocky soils as varieties.

When the value of n ≤ 3 the ground is of non-porous kind, with 3 < n ≤ 10 – poorly porous, 10 < n ≤ 30 – for moderate, and when n > 30 is highly porous (according to table B. 3 p. B. 1.3 GOST 25100). n is inversely related to the density of soil particles: the higher the density of soil particles, the lower the value of n. The value of n varies from 0% (no pores) to 99% (1% of the skeleton). n is calculated using the formula:

The formula for calculation of soil porosity

where ρS is the density of soil particles, g/cm3;

ρd – density of the soil skeleton, g/cm3.

There is also another concept – the coefficient of porosity of the soil e (u.f.). The porosity coefficient is the ratio of the volume of the presented soil sample corresponding to the pore space to the volume occupied by the solid phase of the soil. e is also a classification indicator used to classify sand as a varieties. The value of e can be equal to one (the volume of soil is equal to the volume occupied by the skeleton) and exceed it (peat, loess) e is calculated using the formula:

Formula for calculating the soil porosity coefficient

The porosity coefficient is used to calculate the water saturation coefficient Sr (u.f.). Sr is defined as the ratio of soil moisture in the natural state to the moisture corresponding to the full water saturation of the soil. Sr is used to classify sandy and coarse-grained soils into varieties according to the degree of humidity. If the value is 0 < Sr ≤ 0.5 soils have a small degree of water saturation (slightly wet), at 0.5 < Sr ≤ 0.8 – soil average degree of saturation (wet), with 0.8 < Sr ≤ 1 – water-saturated soils. Sr is calculated using the formula:

Formula for calculating the water saturation coefficient

where, W is the natural moisture content of soil, %;

ρS - density of the soil skeleton (particles), g/cm3;

e – the coefficient of porosity, u.f.;

ρw is the water density assumed to be 1 g/cm3.

These indicators are important auxiliary characteristics that are used, for example, to plot compression and calculate the modulus of soil deformation, which is necessary for making optimal design decisions when constructing buildings. Our specialists will make all the necessary calculations for you and based on the results will determine the type of soil samples according to these indicators.

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