Measuring K𝛐 in the triaxial test

The sophistication of modern testing methods enables many types of laboratory and field tests to be carried out. However, it is sometimes the case that some types of tests are specified without questioning whether they have any meaning in a particular situation. Because of this somewhat uncritical attitude, some myths have grown up about just what it is that we can and do measure in various tests.

One such myth is that the in situ value of K_𝛐, the coefficient of earth pressure “at rest”, can be measured by reconsolidating an undisturbed sample of the soil under zero lateral strain. A natural consequence of this myth is that it is often assumed that in situ strength and stiffness properties of soil can be best examined in triaxial testing if a sample of the soil can be best examined in triaxial testing if a sample of the soil is reconsolidated to the in situ vertical effective stress while maintaining zero lateral strain conditions. This myth is demonstrably incorrect for practically all realistic situations.