Grain shape effects on the mechanical behavior of compacted earth

The main purpose of this paper is to experimentally explore the effects of grain shape and size on the mechanical behavior of compacted earthen materials. Sand-earth, natural rounded gravel and crushed angular gravel are the three materials used in this study. Both gravels are from the same site and characterized by the same grain size curve. The uniaxial compression tests, the results of which are presented and discussed in this paper, were performed on cylindrical specimens of three materials: sand-earth mixture, rounded gravel-earth mixture and angular gravel-earth mixture. The tested specimens were prepared under optimum compaction references, using the Proctor test procedures. For each compression test, four parameters are determined: the compressive strength, the initial tangent modulus, the secant modulus at maximum stress and the peak axial strain corresponding to the maximum compressive stress. The results obtained show that the mechanical behavior of gravel-earth mixture may be influenced by grain shape of the gravel used, thus introducing a new parameter to be taken into account when preparing unstabilized rammed earth material. Further experimental studies are recommended to better assess these results. Keywords: Rammed earth, Mechanical behavior, Grain shape, Compressive strength, Initial tangent modulus, Secant modulus, Peak strain