1. Extraction of Developed Pillars
By
Open Cast Method
I. Satyanarayana, M.Tech,MBA,MCA
Dy. Manager, Project Planning, SCCL,
isnindian@gmail.com,
visit at
www.slideshare.com/isnindian

2. SCCL OC Mines where Pillars are being
extracted by OC Method
•GK OC - KGM
•JK OC - Yellandu
•MNG OC II Extension (Phase-II) - MNG
•KTK OC - BHPL
•RG OC I Expansion - RG III
•RG OC III Extension - RG II
•SRP OC - SRP
•BPA OC II Extension - BPA
PK 1 &2 Inclines, Indaram 1 Incline, MK4 & RK -4&4A,
SMG1&1A, SMG3, KK-2&2A are the UG mines projected for
conversion to OC.

3. Why UG mines are converted to
OC
• In SCCL most of the UG mines are operating with semi mechanised
system
• Bord & Pillar system is being followed in most of the UG mines for
coal extraction
• Opencast mining is the prime source of SCCL in generating Profits as
well as wiping off losses incurred from UG mines.
• The % of coal recovery by Bord & Pillar system varies between 40-45
only
• There are nearly 3 to 3.5 BT of coal reserves in standing pillars in the
country.
• Limited Opencastable reserves
• The increased cost of production from UG mines indicates need of
opening up new opencast mines to augment the sustainable
production.
• To extract the thin seams & remnant coal pillars and to reduce the
cost of production

4. Advantages over UG method
• Seams which can not be extracted by
– UG methods can be extracted by OC Method
• No ventilation & fire problems
• No strata control problems
• Coal recovery is nearly 100 %
• Cost of production is less
• Manpower requirement is low
• Enhanced safety
• Early returns on the capital
• High capacity can be planned

5. Associated problems in conversion to OC
Collapsing of under ground galleries
(Bogging Down of Men & Machinery)
Fire Due To Spontaneous Heating
Environmental Pollution
Degradation of Coal
Loss of coal due to fire
Presence of foreign bodies in coal
(Steel, Timber, Concrete Blocks etc.)
5

6. OFF SET SURVEY & STANDING ORDERS
1. Before intended to close the ug mine for conversion to OC, a detailed
off set survey has to be conducted and the position of workings
including the disturbances and falls should be clearly demarcated on
the plan.
For safe extraction of coal and effective compaction of galleries,
standing orders for demarcation, drilling, blasting and monitoring of
compaction of galleries are framed and being implemented
scrupulously.
PLAN PARTING AND PROVED PARTINGS
Immediately after exposure of the coal seam, when ever the parting in
OB reaches critical zone, the surveyor marks the gallery junction points in
the field and demarcated with plan parting on the play cards.
After demarcation, drilling will be done to ascertain proved parting and
recorded in the book kept for the purpose.
Based on the proved parting, zones are demarcated.
6

7. MARKING OF THE ZONES
CRITICAL ZONE
When ever the parting between u/g galleries and top of the coal seam/OB
bench reaches 6 to 10 mtrs. the place is termed as critical zone which is
safe for extraction coal and OB. The zone is demarcated with yellow
flags.
DANGER ZONE
When ever the parting between U/G galleries and top of the Coal seam/OB
bench is with in 6 Mtrs, the place is termed as danger zone. Only
operations of drilling and dozing are permitted and demarcated with red
flags. No work other than the above is permitted including men and any
other machinary.
COMPACTED ZONE
After drilling and blasting, levelling of the area is done by dozer. After
inspection of the area. the area is termed as compacted zone. this zone is
permitted for normal extraction of coal/ob as it is safe.
7

8. SECTION OF GALLERY COMPACTING PROCEDURE AT COC&OC-IV
ABOVE CRITICAL ZONE
YELLOW
FLAGS YELLOW
FLAGS
CRITICAL ZONE
RED
RED
WHITE FLAGS
FLAGS ABOVE 10M
FLAGS
DANGER ZONE
COMPACTED ZONE DANGER ZONE CRITICAL ZONE

9. PLAN SHOWING THE DIFFERENT GALLERY COMPACTING ZONES

10. Collapsing Of Under Ground Galleries
(Bogging Down Machinery)
1. The
position of all UG galleries is being marked on
ground with stone dust, before taking up drilling activities.

11. 2. The gallery junction is being marked with boards
showing the locations and parting particulars
CRITICAL ZONE DANGER ZONE
6 to 10 mtrs Less than 6 mtrs
The place is termed as critical zone. the place is termed as danger zone
Which is safe for extraction coal and Only operations of drilling is permitted
OB.
and demarcated with RED FLAGS.
the zone is demarcated with
no work other than the above is
YELLOW FLAGS..
permitted including men and any other
.
machinery

12. 3.The exact position of the gallery is being ascertained by test holes
4. Drill is being moved perpendicular to the direction of the galleries
5. The operator ensures that drill is standing on the solid pillar
6. Drills operated by Remote Control are being used
After drilling, blasting and levelling of the area by dozer , The area is
termed as compacted zone, This zone is permitted for normal extraction .

13. WORKING ON DIFFERENT ZONES
Based on the proved parting after exposure of the seam/ob bench the
coal/OB benches shall be lowered upto critical zone
When ever the area reaches to critical zone, the area is demarcated
with yellow flags to caution all the concern and to avoid hard digging,
excess drilling in the critical zone.
When ever the area reaches danger zone the area will be leveled for
drilling under the supervision of an overman then the surveyor will mark
the position of underground galleries and drill holes pattern on the
bench with stone dust, display the position and parting of gallery
junction with play cards mentioning the place and plan parting on it.
The surveyor will hand over the notice of the galleries and parting with
sketch to the overman, under manager, blasting in-charge, i/c
compacting galleries & I/C operations.
13

14. In-charge compacting galleries will instruct the necessary instructions to
the concerned shift persons regarding drilling.
Shift under manger and shift overman will inspect the place and instruct
the drill operator to carry out drilling as per the conditions.
Test holes are drilled to ascertain the parting before commencement of
actual drilling operations
Based on the above the termination of holes over the galleries will be
ascertained and will be terminated 2 m in coal and 0.5 to 1 m in OB
The drilling on pillars and galleries are done in the pattern as shown
below under the supervision of shift overman.
The overman and under manger will record the proved partings, pattern
of drilling with depths in the record kept for the purpose
14

15. PLAN SHOWING THE DRILLING PATTERN
AND MARKING OF THE GALLERIES IN THE FIELD
FACE 53D/6L
6.6m PP
Up to floor of the gallery
Test hole
0.5 to 1 m in stone or 2 m in coal less than the test
hole
15

16. DRILLING PROCEDURE OLD PRACTICE
Previously there was a practice of drilling single row of
holes over the galleries for compacting purpose but it was
found in practice that the galleries were not compacted
due to partial filling of galleries causing pot holes.
16

17. O L D S Y S T E M N o :1 (S E C T IO N )
1 M tr
C O A L
1 .5 M tr
1 M tr
C O A L
150MM
1 .5 M tr
0 .7 5 M tr
2 .4 M tr/
5 .0 M trs 3 .0 M tr
G A L L IE R Y
O LD S Y S T E M N o :1 (P LA N )
5 .0 M trs
5 .0 M trs
5 .0 M trs
G A L L IE R Y 17

18. MODIFIED PRACTICE
After experiencing the above problems, the drilling
pattern was modified to 2 rows of holes over the
galleries for compaction purpose but it was found in
the stone roof in split seam and some parts of thick
seam coal, the galleries were filled only partially due
to boulder formation.
18

19. Modified System
1 Mtr
C O A L
1.5Mtr
1 Mtr
C O A L
150MM
1.5Mtr
0.75 Mtr
2.4Mtr/
5.0Mtrs 3.0 Mtr
GALLERY
3.0Mtrs 3.0Mtrs
3.0Mtrs 3.0Mtrs
3.0Mtrs 3.0Mtrs
GALLIERY
19

20. PRESENT PRACTICE
Two rows of holes are being drilled over the galleries
One row of holes on either side of the gallery leaving a space of 1 m up
to floor of the gallery
After switching over to the present system there is a considerable
improvement in the compacting of the galleries and reduction in pot
holing and coal being extracted safely.
20

21. PRESEN T SYSTEM
(SECTION )
1 Mtr
C O A L
1.5Mtr
1 Mtr
C O A L
150MM
1.5Mtr
0.25Mtr
0.75 Mtr
0.5Mtr
2.4Mtr/
3.0 Mtr
PILLAR
G ALLER Y
(PLAN)
3.0M trs 3.0M trs
3.0M trs 3.0M trs
3.0M trs 3.0M trs
3.0M trs 3.0M trs
3.0M trs 3.0M trs
PILLAR
21

22. PRECAUTIONS WHILE DRILLING OVER THE GALLERIES
Code of practice is framed and being implemented and the
salient features are as follows
While marching the drill, drill should not be marched over the
underground galleries
Drill should not be marched over the gallery junctions.
Drilling should be carried out by placing the drill over the pillar
When ever any hole was inadvertently punctures into the
gallery a fresh hole shall be drilled 0.5 m adjacent to the hole.
Drilling on the pillars is done either in coal or OB selectively in
different bands to prevent degradation of coal.
22

23. PRECAUTIONS WHILE DRILLING OVER THE
FIERY GALLERIES
• Adequate pool of fire extinguishers is being kept near
to the drill machine.
• Fire fighting ranges with necessary fire hoses are
extended near to the fire area with sufficient number
of water jets.
• Water tanker with necessary hoses with turbo jets are
kept ready at the site.
• Drilling is carried out under the constant supervision
of an overman.
23

24. PRECAUTIONS WHILE CHARGING AND BLASTING FOR COMPACTION
• At the beginning of the shift, the blasting in-charge will take the report of
the drilling of previous shifts
• The surveyor along with his team inspects the place and makes a sketch
of the area with actual depth of the holes.
• After ascertaining the perfectness of the drilling, in-charge gallery
compacting will permit for charging and blasting of the area.
• Blasting in-charge along with overman will inspect the blast site and
instruct the overman regarding the amount of explosive to be charged in
various depth holes.
• Blasting overmen then takes the measurements of temperature of each
hole and note down in the field book irrespective of whether galleries
under fire or not with the help of non-contact digital thermometer
specially procured for the purpose.
• Whenever the temperature of the hole exceeds 800 the holes are filled
with water and charging will be done after temperature reduced to below
800.
• When temperature of hole exceeds 800 even after watering the holes, the
holes are left uncharged.
24

25. PRECAUTIONS AFTER BLASTING
• Immediately after blasting, blasting in-charge, overman and in-
charge compacting galleries will inspect the site and ensures proper
compacting and permit for levelling of the area.
• The levelling operations shall be conducted under the supervision of
an overman and experienced dozer operator.
•
• The dozer operator will level the area from outcrop to dip side to
ensure proper filling of the galleries and to prevent bogging down of
dozer.
25

26. PRECAUTIONS WHILE EXTRACTING IN COMPACTED ZONE
• After ascertaining the effectiveness of compactness a limit line of
extraction is marked on the ground keeping 5 m safe distance from
the compacted area. the limit line is demarcated with white flags.
• No extraction is permitted beyond the limit line.
• In-charge compacting galleries will permit the extraction of area
26

27. COMPACTING NEAR FAULT/DISTURBED AREAS
• After experiencing pot holing even though the partition is more than
10 m near the fault area.
• It was decided to compact the galleries upto 15 m on either side of
the fault irrespective of zones immediately after exposure of seam
27

28. SAFETY EDUCATION AND PROPAGANDA
• Every month incharge compacting galleries will conduct
safety meeting on gallery compacting, programme for the
month and areas compacted during the previous month and
also experiences. all the members were educated by
explaining them the programme on the plan with all details.
• Suggestions are invited from the supervisors/ executives.
The following information will be handed over to the members
– Gallery compacting programme sheet
– Part plan showing the compacted galleries, proposed
compacting programme, rl’s of the benches and plan
partings
– All the minutes are recorded in a bound paged book kept
for the purpose.
28

29. EXPERIENCES
• Only with the experience and visual observation SCCL officals are
acertaining the effectiveness of gallery compacting
• It is not possible to acertain the compactness by drilling as drilling is
not possible in the compacted zone.
• It is observed that sometimes the compaction is not effective at
galleries filled with water
29

30. RECOMENDATIONS
Before converting the under ground mine as a
opencast the traversing and offset survey of the under
ground mine must be done and the following details
shall be marked on the plan specially prepared for the
operational purpose.
• Complete off set survey details including the
heights of the galleries.
• All major faults, slips, disturbances
• All major falls, air crossings, area heightened for
the hauler places, cross overs
• All iron girders, w-straps with roof bolts, roof
bolts, roof stitching used for supporting the under
ground galleries and junctions. 30

31. – Diesel operated shovels and drills are preferred.
– High density explosives are to be used in watery
holes.
– Sand bags stemming is preferred instead of normal
drill cuttings in watery holes.
– Automatic fire suppression system should be
mandatory on HEMM used over fiery galleries.
– Heavy duty magnetic separators shall be installed in
the hopper and on the running belt conveyors.
– Controlled dewatering of the mine is most important
to prevent fires in galleries and to improve safety in
gallery compacting.
31

32. Conclusion
To avoid collapsing of under ground galleries
and bogging down of men and machinery
effective compaction of galleries is to be
done meticulously and scrupulously to
liquidate coal from standing pillars by
opencast method safely.
32

33. Thank you all,