Ajoy Kumar Singh

Validation of RMR-based support design using roof bolts by numerical modeling for underground coal mine of Monnet Ispat, Raigarh, India—a case study

In underground coal mines, a lot of major fatalities have occurred due to roof fall in the newly developed faces or galleries of coal mines during the development or production of coal. There are around 500 underground coalmines in India, and continuous production or development or exploitation of coal depends upon the stability of the gateways developed in the form of galleries, which are supported in such a manner so that they can last up to that period, unless it has been finally extracted out with an operation called depillaring. A system of support design with roof bolting, resin bolting, and cable bolting for the aforesaid galleries is presently being decided on the basis of rock mass rating (RMR). The same support design has been attempted with the use of 3D numerical modeling technique—a tool nowadays very extensively used in geotechnical engineering to predict the stability of structures to be built or for the structures which are built against nature, i.e., underground mines. In this study, the support design system on the basis of RMR has also been validated with a numerical modeling technique for three locations of Monnet Ispat underground coalmine. After the study, it has been found that the numerical modeling technique can give better design of support system in underground coal mines in comparison with RMR-based support design system, and it will also play a major role in reducing the total cost incurred in coal exploitation from the underground coal mines.

Rock Load Estimation in Development Galleries and Junctions for Underground Coal Mines: A CMRI-ISM Rock Mass Rating Approach

Rock mass rating (RMR) plays important role in design and selection of support system (Ghosh, 2000). For stability assessment of rock mass it is very important to know the amount of rock load mobilized around the development gallery which is estimated using RMR (Singh et al., 2003, Barton et al., 1974, Bieniawski, 1984, and Ghosh et al., 1992). In Indian coal mines, Central Mining Research Institute-Indian School of Mines rock mass rating (herein after referred to as CMRI-ISM RMR) is mostly used for formulating design guidelines for supports. In this paper an attempt has been made to correlate CMRI-ISM RMR values and rock load of galleries and junctions for different gallery widths, ranging from 3.6 m to 4.8 m, at different densities of roof rocks. The proposed empirical expression can help in quick design of support system for underground coal mines working in the same regime.

A safe depillaring design for shallow depth of cover with influence of surface ground movements: a study in Jharia Coalfield

Extraction of coal from a shallow depth of cover especially under multi-seam mining condition requires intensive precautions in respect to safe working and impact on surface structures. A detailed geotechnical investigation is imperative for the design of a suitable support system during depillaring operation. A study has been exercised in Maheshpur colliery of Jharia Coalfield to assess the stability between the parting of VIIIA and VIIIB seams through numerical modeling. The support systems have been framed for split galleries, slices, and goaf edges with the help of well-established Central Mining Research Institute-Indian School of Mines rock mass rating (CMRI-ISM RMR) and NGI-Q system. A suitable method of depillaring has been designed keeping in view the safety of surface structures in respect to subsidence.