Application of rock mass classification systems for design of stable openings in underground limestone mines

Rock mass classification systems, with suitable modifications, serve as a simple empirical approach for the design of various underground mine structures. There is a continuous effort both towards improving the scope of some of the existing classification systems as well as to introduce new classification systems. One of the primary objectives of the classification systems for a practicing engineer has been to make it simple to use as a preliminary design tool for underground mine structures in rockmass. A detailed survey was undertaken at the underground limestone mines. From the survey data safe unsupported span was estimated using RMR, Q and Q”. The modifications to the rock mass quality Q are suggested duly considering the influence of width-height factor on stress and strength conditions of rockmass surrounding underground openings, the joint orientation and the hydrological condition of the mine.