Soil deformation characteristics in compression tests

Conclusions

1. The proposed interpretation of the processes of uniaxial and overall compression satisfactorily agrees with experimental data. The graphs of S_i, constructed in accordance with theoretical formulas, possess all the properties of the experimental relations.

2. The inclusion of the specimen surface irregularities makes it possible to explain the nonlinear behavior of the graphs of S(σ_z), observed in overall compression tests on soil specimens made from normally consolidated clays having a liquidity index I_L<0.5, the basic mass of the material of which is linearly deformed over the entire load range, that is, for a constant value of the modulus of deformation.

3. The function of the effect of the contact surfaces ϕ(σ_z) can be obtained experimentally and its form agrees satisfactorily with the predictions from the theory.

4. The effect of the contact surfaces can be excluded by performing tests on specimens having different heights, as well as by testing specimens under loads increased in comparison with the ordinarily applied loads, so that

$$\lim \varphi (\sigma _2 ) = \delta for \sigma _2 \to \infty .$$

5. The existence of structural strength for the investigated soils has not been confirmed experimentally. The absence of displacements under small loads is due to insufficient measurement accuracy, constructional characteristics of the equipment, and effects connected with swelling and sticking of the soil to the sleeve.