Compressive behaviour of very dense structured granular geo-materials

Abstract

The isotropic compression behaviour of dense structured geo-materials and the associated degradation at failure is addressed in a non-qualitative manner. To this end, the general behaviour of fully de-structured geo-materials, e.g. sands, as an accepted reference is thoroughly investigated. The parameters affecting the behaviour of de-structured materials such as mineralogy, gradation and fines content, and relative density are discussed. The isotropic compression behaviour of a weathered weak sandstone, representative of a structured granular geo-material, is then investigated along the isotropic compression stress path under a range of pressures from nil to 100 MPa. Both structured and fully de-structured states of the material are tested implementing the proposed quantification method. The effect of structure on the compressibility of the material is found to be tangible. By plotting the specific volume versus natural log of the mean effective stress, the onset of structure collapse and the successive degradation of the structure are captured. By increasing the pressure, compaction bands throughout the sample increasingly develop and the compression curve asymptotically approaches to that of the fully degraded state of the material. At elevated pressures, the rate of compressibility will increase significantly due to particle crushing.