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Numerical modelling-based pillar strength estimation for an increased height of extraction

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Abstract

Underground extraction of total thickness of a thick coal seam in single lift by bord and pillar method increases pillar height during retreat. Field studies found that the increase in pillar height affects the depillaring operation adversely, especially, during caving of the strong/massive roof strata. Dilution in strength due to the increased pillar height caused catastrophic failure of barrier pillars and goaf overriding. This warrants a systematic study of pillar strength variation for the different heights of pillar. A review of different pillar strength estimation approaches for an analysis of the dilution in strength of the heightened pillar suggested that numerical modelling provides a better option for such a systematic study. Accordingly, investigations are conducted on simulated models in laboratory adopting a recognised numerical modelling procedure. The observed nature of variations in pillar strengths with the increase in its height in the numerical models and empirical formula is found to be matched. But a mismatch is found between the strength values of the two approaches with an increase in height of the pillar. Considering validity of the empirical formulation in Indian coalfields, a relationship is developed to incorporate a correction in the strength values of the numerical models. The suggested correction on the basis of this simple study of the pillar strength variation would be helpful for the use of the established simulation tool during the depillaring of a thick coal seam.

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Acknowledgements

The authors are obliged to the Director, CSIR–CIMFR, for his permission to publish this paper. The cooperation provided by the management of Singareni Collieries Company Limited during the field study is thankfully acknowledged. The views expressed in the paper are those of the authors and not necessarily of the institute to which they belong.

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Authors and Affiliations

  1. CSIR–Central Institute of Mining and Fuel Research, Dhanbad, Jharkhand, India

    Ashok Kumar, Rakesh Kumar, Arun K. Singh, Sahendra Ram, Pradeep K. Singh & Rajendra Singh

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  1. Ashok Kumar
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  2. Rakesh Kumar
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  3. Arun K. Singh
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  4. Sahendra Ram
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  5. Pradeep K. Singh
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  6. Rajendra Singh
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Correspondence to Ashok Kumar.

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Kumar, A., Kumar, R., Singh, A.K. et al. Numerical modelling-based pillar strength estimation for an increased height of extraction. Arab J Geosci 10, 411 (2017). https://doi.org/10.1007/s12517-017-3179-6

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