Numerical modelling based rock load height estimation at the goaf edge in a mechanised depillaring panel
Ram Sahendra, Kumar Dheeraj, Kumar Rakesh, Kumar Ashok, Rajendra Singh
Available Online November 2016.
- https://doi.org/10.2991/rare-16.2016.30How to use a DOI?
- mechanised depillaring (MD); roof bolt-based breaker line supports (RBBLS); goaf encroachment; rock load height (RLH); numerical modelling; spalling
- Presence of different openings along the extraction line (goaf edge) in a mechanised depillaring (MD) panel provides an easy path for the goaf to encroach the working area during caving. A number of continuous miner based MD operations are adopted in Indian coalfields in last thirteen years, where roof bolt-based breaker line supports (RBBLS) is used to restrict the goaf encroachment. Different field studies by CSIR-CIMFR found that the performance of a RBBLS is significantly influenced by extension of spalling in coal pillars/fenders at the goaf edge. Development of higher induced stresses around the goaf edge during a MD operation creates the spalling in natural supports resulting a dilution in its competency at the goaf edge. It is observed that the RBBLS works satisfactorily under the shadow of stable natural supports only. Accordingly, the field studies have found that the positions of the RBBLS at the goaf edge need to be adjusted as per expected extent of the spalling. Under these conditions, estimation of rock load height (RLH) with respect to proposed position of a RBBLS at the goaf edge is a difficult task in the field. Therefore, a laboratory study, based on numerical modelling, is done using the FLAC3D package. The elastic model incorporating the Sheorey's failure criterion for the rock mass is used to analyse the rock mass behaviour at the goaf edge. Here, a criterion of 1.5 safety factor is used to obtain the RLH value. It is found that the value of RLH gets almost saturated after 2 m out-bye from the goaf edge for the considered site conditions. Therefore, an attempt is made to estimate the RLH at three positions 0 m, 1 m and 2 m out-bye from the goaf edge. This parametric study is conducted with a variation in depth of cover from 100 m to 450 m and rock mass rating from 20 to 70. This study in the laboratory supported the field observations that a RBBLS works satisfactorily under the shadow of stable natural supports. A comparison of the RLH values for different selected positions of the RBBLS provided an idea to decide its suitable position of the RBBLS for a given site conditions. Discussing important findings of the field studies, this paper presents results of the numerical modelling for estimating the RLH at the goaf edge. Strength and weaknesses of this study for the design of a RBBLS are presented on the basis of a simple analysis of the simulation results
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Cite this article
TY - CONF AU - Ram Sahendra AU - Kumar Dheeraj AU - Kumar Rakesh AU - Kumar Ashok AU - Rajendra Singh PY - 2016/11 DA - 2016/11 TI - Numerical modelling based rock load height estimation at the goaf edge in a mechanised depillaring panel BT - Recent Advances in Rock Engineering (RARE 2016) PB - Atlantis Press SN - 2352-5401 UR - https://doi.org/10.2991/rare-16.2016.30 DO - https://doi.org/10.2991/rare-16.2016.30 ID - Sahendra2016/11 ER -