Heterogeneity and complexity of completely decomposed rocks: a case of extrusive rock

Decomposed geomaterials are widespread globally and understanding their characteristics is very crucial due to their numerous applicability and workability in and/or on them. The heterogeneous nature and complexity in analyzing the behaviour of materials obtained from decomposed rocks have been studied. This was achieved by conducting laboratory tests on specimen from Nigeria and analyzing studies on materials of different origins and from different regions of the world. The material tested is well-graded and coarse-grained similar to related geomaterials. The fabric is homogeneous and isotropic and the elemental compositions comprise silicon, aluminium and iron in significant percentages. The mineralogy is predominantly quartz with other minerals like albite, muscovite, orthoclase and heamatite in lesser proportions. Convergent behaviour with low compressibility is observed and the effect of structure in compression is positive. The correlations between the compressibility and the engineering grading descriptors commonly used by practitioners and mineralogy are variable due to the heterogeneous nature of these materials. The heterogeneity is pronounced in the relationships between mechanical property and mean particle size and fines content and less pronounced with coefficient of uniformity. Coefficient of uniformity could be used to characterize decomposed materials. The heterogeneous and complex nature of the materials could be linked to different parent geological signatures. It is advised that geological, geochemical and geotechnical attributes of these materials should be assessed exclusively by the practitioners working on them and before they could be used for diverse applications.