Optimisation of haul road dimension with lime induced overburden composite material

Abstract

The current share of coal in India’s installed electricity generation of 343789 MW is about 57%. India produced 662.792 MT in 2016-17 with a projected output of 1 billion tonnes by 2020. The majority of it would be sourced from high capacity open cast mines. It needs large HEMMs that need rugged, strong and hence, durable haul roads. Haul road construction materials have not matched to the increasing capacities of heavy earth moving machineries. Conventional materials for construction of haul roads include either the mine overburden or locally available sand, gravel and/or clay. As observed, those do not provide adequate ground stability resulting in excessive stress and strain on the haul road layers. This study developed and evaluated waste byproduct based alternate haul road construction material for better performance. The developed material constitute mine overburden, fly ash, and lime of varying percentages. Their physico-mechanical properties were determined. The lime and fly ash content and curing period was observed to have direct co-relation with the strength of the developed composite materials. The composition with 27.5% fly ash, 64.2% OB and 8.3% lime exhibited maximum UCS at 3.14 Mpa and CBR at 77.08%. The critical strain limit for the haul road was determined for an operating coal mine. The best composition was evaluated to determine the maximum strain values for both static and cyclic loading conditions. The haul road dimensions were optimised for minimum adverse effect on the surface course to keep the strain limits below the critical value. The developed composite materials with enhanced geotechnical properties exhibit strong potential to replace the conventional materials in the layers underlying the surface course as well as enhance the effective utilization of fly ash.