Design of Haul Roads in Open Cast Mines in India—A Mechanistic Design Approach

Abstract

About 80% of total mining in India is carried out in coal sector through open cast mines where heavy dumpers are plying on the haul roads. Mine haul roads have witnessed an enormous increase in traffic density as well as hauling payloads in the recent past due to increase in coal mining activities. In the Indian scenario, the majority of these large open cast mines are facing the problems of under-performance due to inadequate design of mine haul roads resulting into fast deterioration through rutting and excessive settlement. The present design methodology used in India is broadly based on an empirical CBR (California Bearing Ratio) method. This method seems to have become irrational for optimum and practical design of the haul roads which carry the present-day heavy traffic. Through this paper, an attempt has been made to develop a design based on mechanistic design approach. The main criteria to ensure the structural safety of mine haul roads has been taken as vertical compressive strain over the subgrade which is responsible for rutting failure in a pavement. The critical value of vertical compressive strain has been estimated for the Indian mine conditions. KENPAVE software has been used to design an optimum haul road cross section for existing heavy axle loads and traffic density in open cast coal mines in India. In order to have better appreciation, an example has also been given which compares the design output using conventional and the mechanistic methods.