Time-Dependent Stability Assessment of Coal Mine’s Gallery Using New Geotechnical Classification

Abstract

Geotechnical classification of the roof of an underground coal mine is of utmost importance for the assessment of the roof support requirement. Forty-five published cases of the Indian coalfield have been taken for analysis. It has been observed from the cases that stand-up time with CMRI–RMR is not properly correlated, particularly, for short-term stable cases. After re-looking the data set, it has been perceived that the influence of a single weak parameter is sufficient enough to reduce the strength of the roof rock mass. Therefore, the summation of the ratings for estimation of the overall rating of the rock mass is not appropriate. Keeping this in mind, a new geotechnical classification of the coal roof index (CRI) has been proposed similar to the Barton ‘Q’ system of rock mass classification. A multiple regression analysis has been done by considering five independent parameters and one dependent parameter and using the developed new equation to assess the rating range. This study reveals that the newly developed classification system has shown a good correlation with recorded stand-up time compared to CMRI–RMR classification. The range of the proposed CRI classification is varying from 0.001 to 3000. It has been divided into five classes. An exponential correlation between the proposed CRI and CMRI–RMR has also been observed. © The Institution of Engineers (India) 2024.