Surface coal mining necessitates the removal of several overlying materials, including topsoil, overburden, and waste rock, in order to access coal deposits (Bian et al., 2010). The overburden in coalfields is typically stratified, comprising predominantly shale and sandstone. Shale represents the most abundant sedimentary rock type, accounting for nearly 80% of such formations, and is mineralogically dominated by montmorillonite (Kesavulu, 2009). Given that montmorillonite is a highly active clay mineral (Punmia & Jain, 2005), neither shale nor clay is considered suitable for incorporation in concrete. In contrast, sandstone, which generally contains over 90% sand-sized particles, is deemed more appropriate for use in concrete production (Kesavulu, 2009).
Empirical investigations of coal mine overburden from Indian coalfields, where crushed overburden is employed for stowing purposes, have reported sand contents of approximately 93% and an average specific gravity of 2.53 (Ram Chandar et al., 2022). Compressibility analyses further indicated that such material can be effectively utilized for underground stowing, provided it passes through a 0.15 mm sieve (Prashant et al., 2010). A complementary study conducted at a separate Indian coal mine revealed that 98% of the overburden particles were retained on sieve sizes of 75 μm and above (Rai et al., 2010). Nevertheless, the same study noted minimal concentrations of essential nutrients such as nitrogen, potassium, and phosphorus, thereby limiting the suitability of the material for plantation or agricultural purposes (Yaseen et al., 2012).
Further assessments have consistently identified sand contents exceeding 80% in overburden materials (Ram Chandar et al., 2022). Long-term ecological studies on reclamation trajectories indicate that fresh mine spoil requires approximately 28 years to acquire the edaphic properties characteristic of native forest soils, provided the spoil environment remains undisturbed by external factors such as erosion or vegetation degradation (Maharana, 2013).
Reference
Bian, Z., Inyang, H. I., Daniels, J. L., Otto, F., & Struthers, S. (2010). Environmental issues from coal mining and their solutions. Mining Science and Technology (China), 20(2), 215–223. https://doi.org/10.1016/S1674-5264(09)60187-3
Kesavulu. (2009). Textbook of Engineering Geology. Macmillan Publishers India Limited.
Maharana, J. K. (2013). Physico-Chemical Characterization and Mine Soil Genesis in Age Series Coal Mine Overburden Spoil in Chronosequence in a Dry Tropical Environment. Journal of Phylogenetics & Evolutionary Biology, 1(1). https://doi.org/10.4172/2329-9002.1000101
Prashant, M., Ghosh, C. N., & Mandal, P. K. (2010). Use of crushed and washed overburden for stowing in underground mines: A case study. Journal of Mines, Metals & Fuels, 58(1 & 2), 7–12.
Punmia, B. C., & Jain, A. K. (2005). Soil Mechanics and Foundations. Firewall Media.
Rai, A. K., Paul, B., & Singh, G. (2010). A study on the Bulk density and its effect on the growth of selected grasses in coal mine overburden dumps, Jharkhand, India. International Journal of Environmental Sciences, 1(4), 677–684.
Ram Chandar, K., Gayana, B. C., & Shubhananda Rao, P. (2022, May 27). Mine Waste Utilization. https://doi.org/10.1201/9781003268499
Yaseen, S., Pal, A., Singh, S., & Yousuf, I. (2012). A Study of Physico-Chemical Characteristics of Overburden Dump Materials from Selected Coal Mining Areas of Raniganj Coal Fields , Jharkhand , India. https://www.semanticscholar.org/paper/A-Study-of-Physico-Chemical-Characteristics-of-Dump-Yaseen-Pal/23115eb27a3440a277892a37e92ac7e17a6bdc40
