Experiences with application of the NGI classification to coal measures

Abstract

Given are 44 case studies of coal mine roadways with their classification data and support requirement. The cases, which were originally collected for a new CMRS classification for coal measures, have been used in the paper to test the performance of the NGI system. Changes in the NGI classification are proposed so as to include horizontal stratification, joint orientation or unfavourable horizontal stress and some special geological features. A new support load equation is proposed including roadway span and rock density. Also presented are regression equations between the CMRS classification rating R and the original and modified NGI index Q.