2. What is strata control?
Strata refers to rock in all the possible forms such as:
1. High strength material.
2. Very low strength material(or extremely weathered).
Strata control refers to the methods applied to manage the risks
associated with various forms of strata instability in
underground coal mines.
3. Wide stall mining :
It is the advanced method used for optimal
recovery of minerals.(eg:Coal).
The conventional method of splitting and
stooking of pillars have been replaced by wide
stall method.
Comparatively,this method is better than
splitting and stooking of pillars.
4. Let us consider the following figure :
Fig.1. Comparision of stooking and splitting of pillars and wide stall method
5. Necessary conditions of wide stall method:
Massive immediate roof is an important requirement.
If roof is moderate , reinforcement techniques such as cable bolting
and roof stitching are used to avoid local deformations.
Pillar strength should be more(can be done by increasing w/h ratio).
Wide stall method cannot be maintained under weak/laminated roof
strata.
6. Instruments used for strata control
observations in wide stall mining:
Borehole extensometer
Stress meter
Remote convergence indicator
Photographic technique
7. EAST BHUGGATDIH COLLIERY
•The first field trial of wide stall method was conducted in EBC,
situated in Jharia(Jharkhand).
•It was a successful attempt.
•It provided nearly 42% coal from a 17 m thick coal seam.
•No endangering of the surface and subsurface structures because
of appropriate strata control measures.
8. Fig.2. Dimensional information for wide stall mining (sectional view) at East Bhuggatdih with a
comparison to conventional splitting and stooking.
9. Fig.3.Top view of wide stall mining in East Bhuggatdih Colliery (Jharia)
10. Fig.4. Comparision of wide stall and splitting and stooking of pillars(w.r.t safety factor)
O yeah!! Wide stall has
better Safety factor.
11. Conclusion:
•Splitting and stooking of pillars cannot give more than 30% of coal where as,
wide stall method gives about 42% of coal.(Based on Bhuggatdih colliery).
•The instruments used for strata control observations made the method
successful.
•All the risks have been managed and no endangering of surface and sub
surface will occur if proper strata control measures are taken.
12. References:
• Salamon MDG, Munro AH. A study of the strength of coal pillars. J. S. Afr. Inst.
Mining Metall. 1967;68:55±67.
• Sinha PK, Verma RK, Jain DK. Research and development e€orts in thick seam
mining: present and future scenario. In:Singh TN, Dhar BB, editors. Proceedings
of International Symposium on Thick Seam Mining. Dhanbad, India: CMRI,
1992. p. 471±92.
• CMRI Report (unpublished). Field trial of wide stall mining of
VII/VIII seam under built-up area at East Bhuggatdih colliery.
