Measurement of K₀ by triaxial strain path testing

The choice of reference stress state as datum for zero lateral strain is identified as a problem inherent in the determination of K₀ of sand by laboratory tests. A new, but simple, test method based on strain path testing is presented. This new test method enables a systematic investigation into the influence of a non-zero isotropic reference stress on the measured K₀ value. The results of such a study introduces the concept of a threshold reference stress, p′₀₀, the maximum reference effective stress that can be used to ensure the correct determination of K₀ value for a normally consolidated condition. p′₀₀ is dependent on the effective axial stress, σ'_a, at which K₀ is to be measured. The value of σ′_a/p′₀₀, however, lies within a narrow range. For an over-consolidated condition, K₀ appears to be independent of p′₀ provided the preconsolidation stress is significantly higher than p′₀₀.