On the influence of the sample preparation method on strain accumulation in sand under high-cyclic loading

Abstract

A study on the influence of the sample preparation method on the cumulative strains in sand under high-cyclic loading is presented. Numerous drained cyclic triaxial tests with 105 cycles were performed on samples prepared by either air pluviation out of a funnel, air pluviation using a multiple sieve apparatus, water pluviation, moist tamping or dry loose deposition with a subsequent compaction by either vibration or tapping. The test results reveal a significant influence of the sample preparation method on the intensity of strain accumulation. While very loose samples prepared by moist tamping show much larger strain accumulation rates than their air-pluviated counterparts at same density, it is the other way around at medium and high densities. Samples prepared by procedures involving compaction in the dry state are more resistant against cumulative effects than samples directly prepared to the same relative density. The differences in the rates of strain accumulation are the result of a different initial fabric generated by the various constitution methods. A micromechanical explanation based on the distribution of contact normal orientations is provided. In contrast, the direction of strain accumulation (cyclic flow rule) and the elastic portion of deformation during the cycles (strain amplitude) are rather insensitive to the choice of the sample preparation method.