Estimation of rock load for junctions based on roof failure cases for safe mining operation
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ORIGINAL PAPER
Estimation of rock load for junctions based on roof failure cases for safe mining operation Avinash Paul 1
&
Vemavarapu Mallika Sita Ramachandra Murthy 2 & Amar Prakash 1 & Ajoy Kumar Singh 1
Received: 7 January 2020 / Accepted: 18 September 2020 # Saudi Society for Geosciences 2020
Abstract Coal mine roadway junctions in bord and pillar mining, in particular, are more vulnerable to roof fall due to the excavation induced stresses as well as general stress loading pattern inherent to the typical cross section achieved in practice. Roof fall incidences are generally more in junctions of development galleries and a cause of concern as they provide access to faces in different directions (dip/rise). The CMRI-ISM rock mass classification system, popularly known as Rock Mass Rating (RMR), is being used for the design of support system in underground coal mines for the last 30 years in India. In spite of the well-defined guidelines, it has been observed that roof failures are still a major concern in many underground coal mines. In this research, an attempt has been made to develop a new rock load prediction model for junctions of bord and pillar workings based on the geoengineering investigations carried out in 63 coal mines. After analysis of failure and stable cases, a best suited rock load predictor equation was developed. Analysis indicated that the maximum roof failure cases occurred for RMR values in between 30 and 45, and this zone is considered as highly unstable zone. Assessment of stable and unstable class is also done with respect to rock load for varied RMR. A general support design has also been suggested as per the RMR and severity of the roof fall. The suggested approach can help designing a rational support system for underestimated and overestimated zones thus minimising the roof fall cases leading to improved safety and productivity in underground coal mines. Keywords RMR . Rock mass classification . Junctions . Roof failure . Support design . Safety
Introduction Roof fall in underground coal mines is always a matter of concern and subject of research for mining engineers while designing the support system (Murkute et al. 2005; Prakash et al. 2018). The fatality due to ground movement still contributes a very high percentage (41%) during the process of excavation (Dash et al. 2016) (Table 1). When the extraction is made in underground workings, particularly in the layered strata such as in coal measure rocks, re-distribution of stresses takes place which disturbs the state Responsible Editor: Murat Karakus * Avinash Paul [email protected] 1
Central Institute of Mining and Fuel Research (CSIR), Dhanbad 826 015, India
2
Indian Institute of Technology (Indian School of Mines), Dhanbad 826004, India, Dhanbad 826004, India
of equilibrium of stresses (Ventakteswarlu and Raju 1987). Thus, soon after the excavation is made, the coal mine roof should immediately be supported by installing an appropriate system of support. Any time lag may cause the roof to deform and fail resultin
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