Stress-path effects on the grading of an artificial material with crushable grains

Granular materials forming part of natural slopes, embankments, foundations, pavement structures, and rail track structures are subjected to both static and dynamic loads. As a result of this particle breakage may occur. This work shows the results of an experimental investigation into the mechanical behaviour of an artificial granular material, consisting of crushed expanded clay pellets, commercially known under the brand name LECA (Light Expanded Clay Aggregate). The maximum particle size of the material tested was 2 mm; the material was reconstituted to obtain grading curves with the same mean diameter D50, and different coefficients of uniformity, U (= 3.5, 7, 14, 28) or the same coefficient of uniformity, U, and different D50 (= 0.5, 1 mm). The constant volume friction angle and the minimum and maximum densities corresponding to each grading were determined before testing in one dimensional and triaxial compression at different stress levels. The changes of grading of the material after testing were described using two parameters defined as the ratio of the mean diameter and coefficient of uniformity of the current particle size distribution and initial distribution, which were both assumed to be consistent with self-similar grading with varying fractal dimension