ABSTRACT
An understanding of the shear strength characteristics of geomaterials forming overburden dumps in coal mines is required for assessing the stability of overburden dumps. The effective shear strength of dump materials depends on a wide variety of interrelated parameters including: fragment size, intact particle strength, gradation, compaction density, water content, degree of saturation and others. In this study, an investigation was carried out to assess the effect of fragment size and moisture content on shear strength behavior of the coal mine overburden dump rock material by conducting a series of small and large scale direct shear test on samples differing in average fragment size, uniformity coefficient and moisture content. The overall mobilized shear strength was found higher in case of samples having larger average fragment size and lower moisture content. The angle of internal friction of all the tested samples was found to be increased with the increase in average fragment size while reduction in the same was noticed with the increase in moisture content.
