Evaluation of existing timber supports in Bogala mine and proposals for alternatives

Abstract

Rock support is an important aspect in underground mining to stabilize the ground rock to provide a safe environment. As it directly influences the safety, it is very important to evaluate the supporting system. As cost is a major issue, it is important to reduce the support cost without compromising safety. Bogala Graphite Lanka Ltd is an important vein-graphite supplier in the world operating an underground mine using Over-hand-Cut-and-Fill mining method. Steel supports, Rock bolts and timber supports are currently used for supports. Eucalyptus Microcorys (Micro) is the main type of timber used for supports. The objective was to find a cost effective type of support with the required level of strength and durability in an underground environment. Rock mass classification using Rock Mass Rating (RMR) was initially used to evaluate the intact rock. Several timber types such as Eucalyptus Microcorys, Eucalyptus Grandis, Oil treated Eucalyptus Grandis, Teak, Eucalyptus Camaldulensis and Hora were selected and their mechanical properties were determined. Concrete beams and Steel beams were also considered. From mathematical and cost analysis, it was evident that Eucalyptus Camaldulensis satisfies the requirements. It was also found to be cost effective than the existing type with a minimum cost saving of about 44%.