Soil Poisson’s ratio (lateral expansion coefficient or lateral deformation coefficient of the soil) is an indicator of soil deformability characterizing the ratio of lateral and longitudinal deformations of the soil (i.e. the ratio of relative lateral deformations to relative longitudinal deformations of the soil)
The Poisson’s ratio of the soil must be determined by the results of tests in triaxial compression devices or in compression devices with lateral pressure measurement.
In the absence of experimental data, the values of the Poisson’s ratio can be taken according to clause 5.4.7.5 GOST 12248-96 (Russian standard):
- for coarse soil is 0.27;
- for sand it ranges from 0.30 to 0.35 depending on the density;
- for sandy loam it ranges from 0.30 to 0.35 depending on the density;
- for loams it ranges from 0.35 to 0.37 depending on the density;
- for hard clay (for a liquidity index LI = 0) it is from 0.20 to 0.30 depending on the density;
- for semi-solid clay (for a liquidity index LI from 0 to 0.25) is from 0.30 to 0.38 depending on the density;
- for refractory clay (for a liquidity index LI from 0.25 to 0.5) is from 0.38 to 0.45 depending on the density;
- for soft plastic clay (for a liquidity index LI from 0.5 to 0.75) is from 0.38 to 0.45 depending on the density;
- for fluid clay (for a liquidity index LI from 0.75 to 1) is from 0.38 to 0.45 depending on the density.
Smaller values of Poisson’s ratio must be applied at higher soil density.