Cyclic behaviour of compacted black soil-coal wash matrix

Recent population and industrial growth require innovative approaches for recycling construction materials for civil infrastructure such as railways, roads, and building foundations. This study adopts a combination of expansive black soil blended with coal wash (CW), a by-product of coal mining, to produce a resilient substructural fill for railroads. When considered individually, expansive clays and CW are prone to high swell pressure, shrinking and swelling, excessive degradation, and relatively low bearing capacity, properties that would adversely affect infrastructure. This current study is a laboratory characterisation of soil and CW mixtures in relation to Atterberg Limits, Particle Size Distribution (PSD), and X-ray diffraction spectroscopy. A mini-compaction procedure is used to assess the changes in maximum dry density and optimum moisture content. This is followed by a series of consolidated-undrained monotonic and cyclic triaxial tests of the mixtures. Our findings show that CW can reduce the plasticity, susceptibility to shrinkage, and the swell pressure of clay soil. When clay is blended with CW there is a significant improvement in the undrained shear strength, resilient modulus, and yield response before failure, as well as the number of loading cycles before failure. Furthermore, the inclusion of CW to improve the mechanical properties of soil also reduced the large amount of space needed to store CW