Design of remnant pillar in mechanized depillaring using continuous miner


Affiliations

  • Department of Mining Engineering, IIT (BHU), Research Scholar, Varanasi, India
  • Deptt. of Mining Engineering, IIT (BHU), Associate Professor, Varanasi, India
  • Department of Mining Engineering, IIT (BHU), Professor, Varanasi, India

Abstract

Ribs and snooks are the critical natural support at the goaf edge in the mechanized depillaring operation of the bord and pillar mining system. The pillar extraction has been carried out by taking the slices and leaving ribs and snooks during the depillaring operation. Remnants are the remaining portion of the extracted pillar. The depillaring operation leads to an unsupported roof, and the immediate unsupported roof imposes its weight on the pillar (remnant) under extraction. The remnant’s purpose is to provide a necessary reaction to the overhang to restrict roof failure until the pillar’s final slice. The remnant’s stability during depillaring operation has been accessed in the study using three-dimensional numerical simulations. A scheme has also been proposed in the study to evaluate the factor of safety (FOS*) of the remnant pillar in the residual phase at different stages of slicing operation. A case of an Indian coal mine using the fish-bone method has been chosen for the study. A typical depillaring stage has been selected for the extraction of the pillar using the fish-bone method. The numerical simulation of the considered panel provides the vertical stress and yielding profile on the pillars at different stages of depillaring. The simulation results show the influence zone up to one pillar from the goaf edge. The immediate intact pillar shows considerable yielding of about 60% of the pillar area. The remnants have completely yielded during the slicing operation but provide a reaction to the immediate strata. The remnant should provide the reaction to the immediate roof till taking the final slice from the pillar. The remnant’s FOS* is calculated by taking the ratio of reaction offered by the remnant (numerical simulations) and the weight of the overhang (estimation). The area’s borehole section shows two layers of medium to coarse-grained sandstone as an immediate stratum. The weight of the immediate strata has been estimated in the study considering the immediate strata’s thickness. Two different scenarios of immediate strata thickness (i.e., 4.75 m and 9 m) have been considered in the study to evaluate the remnant’s FOS at different depillaring stages.

Keywords

Remnant, ribs/snooks, fish-bone pattern, continuous miner, mechanized depillaring, numerical simulation

Full Text:

References

Chawla S, Jaiswal A, Shrivastva B K (2017): Design of snook in the depillaring panel using continuous miner. Journal of the Institution of Engineers (India) Series: D. 99(1):39-49.

Garg P, Jaiswal A (2016): Estimation of the modulus of the caved rock for underground coal mines by back analysis using numerical modelling. Journal of the Institution of Engineers (India) Series: D97(2):269-273.

Islavath SR (2019): Stability of Continuous Miner Workings using Numerical Modelling Approach. Journal of Mines and Metals Fuels. 67(8):360-365.

Itasca (2000): FLAC (Fast Lagrangian Analysis of Continua). Itasca Consulting Group Inc.Minneapolis Minnesota 55401 USA Version 3.0.

Jaiswal A, Sharma S K, Srivastava B K (2004): Numerical modeling study of asymmetry in the induced stresses over coal mine pillars with the advancement of the goaf line. International Journal of Rock Mechanics and Mining Sciences 41:859-864.

Jaiswal A, Srivastava B K (2009): Numerical simulation of coal pillar strength. International Journal of Rock Mechanics and Mining Sciences 46:779-78

Kushwaha A, Singh S K, Tewari S, Sinha A (2010): Empirical approach for designing of support system in mechanized coal pillar mining. International Journal of Rock Mechanics and Mining Sciences 47(7):1063-1078.

Mandal P K, Das A J, Kumar N, Bhattacharjee R, Tewari S, Kushwaha A (2018): Assessment of roof convergence during driving roadways in underground coal mines by the continuous miner. International Journal of Rock Mechanics and Mining Sciences 108:169-178.

Mandal P K, Singh A K, Ram S, Singh A K, Kumar N, and Singh R (2004): Strata behavior investigation of India’s first depillaring face with continuous miner and shuttle car. Minetech 25(6):3-12.

Mark C, Zelanko J C (2001) Sizing of final stumps for safer pillar extraction. In: Proceeding of 20th International Conference on Ground Control in Mining. Morgantown WV USA, pp. 59-66.

Medhurst T P, Brown E T(1998): A study of the mechanical behaviour of coal for pillar design. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts 35:1087-105.

Murali Mohan G, Sheorey P R, Kushwaha A (2001): Numerical estimation of pillar strength in coal mines. International Journal of Rock Mechanics and Mining Sciences 38:1185-92.

Ram S, Kumar D, Singh A K, Kumar A, Singh R (2017): Field and numerical modelling studies for efficient placement of roof bolts as breaker line support. International Journal of Rock Mechanics and Mining Sciences 93:152-162.

Sheorey PR, Das MN, Barat D, Prasad RK, Singh B (1987): Coal pillar strength estimation from failed and stable cases. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 24(6):347-355.

Sheorey P R (1994): A theory for in situ stresses in isotropic and transversely isotropic rock. International journal of rock mechanics and mining sciences and geomechanics abstracts 31: 23-34.

Singh A K, Singh R, Maiti J, Kumar R, and Mandal P K (2011): Assessment of mining-induced stress development over coal pillars during depillaring. International Journal of Rock Mechanics and Mining Sciences 48:805-818.

Singh R, Singh A K, Coggan J, Ram S (2016): Rib/snook design in mechanized depillaring of rectangular/square pillars. International Journal of Rock Mechanics and Mining Sciences 84:119-129.

Singh R, Singh A K, Maiti J, Mandal P K, Singh R, and Kumar R (2011): An observational approach for assessment of dynamic loading during underground coal pillar extraction. International Journal of Rock Mechanics and Mining Sciences 48:798-804.

Singh R, Singh A K, Mandal P K, Singh M K, and Sinha A (2004): Instrumentation and monitoring of strata movement during underground mining of coal. Minetech 25(5):12-26.

Singh S K, Agrawal H, Singh, Awanindra P (2017): Rib stability: A way forward for safe coal extraction in India. International Journal of Mining Science and Technology 27(6): 1087-1091.

Smart B G D, Singh R N, Issac A K (1978): A borehole instrumentation system for monitoring strata displacement in three dimensions. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts 15(2): 77-85.

Van-der-Merwe J N (2005): Fundamental analysis of the interaction between overburden behaviour and snook stability in coal mines. Journal of the Southern African Institute of Mining and Metallurgy 105(1):63-73.

Yu Z., Chugh Y. P., Miller P. E., Yang G. (1993): A study of ground behavior in longwall mining through field instrumentation. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts 30(7):1441-1444.


Refbacks

  • There are currently no refbacks.