This document discusses the conversion of underground coal mines to opencast mines. Underground mining is becoming uneconomical, so coal reserves trapped in underground mine pillars need to be extracted through opencast mining. The key steps in conversion involve isolating underground workings, conducting surveys of workings, dividing the mine area into safety zones, compacting galleries through drilling and blasting, and extracting coal while preventing collapse of underground structures. Attention to surveying, drilling patterns, charging, blasting procedures, and marking excavated areas is important to ensure safety during conversion. The Gouthamkhani opencast project is provided as a case study, with details on its reserves, production, geology, machinery, and mine plan.

1. CONVERSION OF UNDERGROUND
TO OPENCAST
Presented by
E SUNIL 13671A2509
P AVINASH 13671A2530
ABDUL MUJEEB 13671A2546

2. Scope
Why we have to convert UG to OC?
1.Ungerground mines are uneconomical
2.In olden days, Due to lack of sufficient
technology in UG mines for the extraction of
mineral
3.Due to occurence of many GEOLOGICAL
discontinuities in UG
4.OC mines are more safer than the UG mines in
point of ACCIDENTS

3. Introduction
 The coal production of country in the financial year 2015-16 is
around 538.75 Mt. The share of opencast mines is more than 70%.
 Singareni Collieries Company Limited (SCCL) is the main source for
supply of coal to the southern region. The company produced 60.38
million tonnes of coal during 2015-16 as against 52.54 million tonnes
during the corresponding period last year
 Opencast mines are shrinking day by day due to exhaustion of virgin
coal. Extraction of coal by Underground mining is very
uneconomical.
 In future there will not be any virgin coal seam for opencast mining
and only alternative for coal production will be by open casting of
developed pillars of underground mines.
 There are nearly 3 to 3.5 BT of coal reserves in standing pillars in
the country and future of mining engineers will be very- very
challenging.

4. Favourable Conditions
 Keeping in view the disturbed geo-mining conditions,
opencast method of extraction is safe compared to
underground manual method.
 The coal seams are occurring at a relatively shallow
depth of 30mts.
 The deposit should be close to the surface. Formerly
a depth of up to 90 m was considered to be the
limiting depth in India.
 But with the advance of technology now opencast
mining of coal is considered feasible up to about 300
m depth.
 The ratio of overburden to coal should be less. A ratio
of 4: 1 is considered desirable but in some situations
opencast mining up to a ratio of 6: 1 is also
considered economic.
 The topography should be as level as possible.
 The coal seam should be of uniform thickness and
preferably flat.
 A mild climatic condition is generally favoured

5. Economical Considerations
1.Shallow Depth
2.Stripping Ratio
3.Grade (Quality)

6. Role of SURVEY in Conversion
 The U/G workings to be quarried shall be isolated by explosion
proof stoppings.
 Before intended to close the U/G mine for conversion to O/C, a
detailed off set survey has to be conducted by using latest survey
equipment's like Total Station etc.
 The U/G mine Manager should give detailed plan of underground
workings with flawless to O/C mine Manager.
 Cleaning of all coal dust and thick stone dusting before
commencement of extraction of pillars
Retaining of key personnel of U/G mine, like Surveyor, Overmen
and Officers for safe and effective operation of O/C mine.
 After completion of all legal and statutory formalities, the mine is
developed as per the permission conditions of DGMS. For safe and
systematic excavation, the mine is divided into four zones viz.
I. SAFE ZONE - White Flags
II. CRITICAL ZONE - Yellow Flags
III. DANGER ZONE - Red Flags
IV. COMPACTED ZONE - Green Flags

8. Marking Over Galleries
1.The division of mine area into zones will be done
by survey department by referring to old u/g plans.
2.When the critical zone is reached galleries are
marked by placing placards at the junctions.
3.If it is a danger zone the galleries have to be
compacted by drilling and dozing.

9. CONVERSION PROCESS
Compaction of galleries a critical activity of the U/G
underground converted opencast mine.
A. Drilling
B. Blasting

10. Role of Drilling & Blasting
(A)Drilling pattern for combined blasting when galleries
are developed in single section
(B)Drilling pattern for combined blasting when galleries
are developed in two sections with superimposed galleries
(C) Drilling pattern for combined blasting when the
galleries are developed in two sections and parting
between two sections is more than 6 mtrs
(D) Drilling pattern for combined blasting when the
galleries are developed in two sections and both the
sections are not superimposed (i.e. staggered )
(E) Drilling pattern for combined blasting when the
galleries are developed in two sections with parting more
than 6m, in the intention to reduce the number of holes
for making charging and blasting comfortable on the
same day

11. (A)Drilling pattern for combined blasting when
galleries are developed in single section
TOP VIEW
SECTION
VIEW

12. (B)Drilling pattern for combined blasting when
galleries are developed in two sections with
superimposed galleries
TOP VIEW
SECTION
VIEW

13. (C) Drilling pattern for combined blasting when
the galleries are developed in two sections and
parting between two sections is more than 6
mtrs
COMPACTING ONLY TOP SECTION GALLERIES
COMPACTING BOTTOM
SECTION GALLERIES IN
COAL AFTER EXPOSURE

14. (D) Drilling pattern for combined blasting when
the galleries are developed in two sections and
both the sections are not superimposed (i.e.
staggered )

15. (E) Drilling pattern for combined blasting when
the galleries are developed in two sections with
parting more than 6m, in the intention to
reduce the number of holes for making charging
and blasting comfortable on the same day

16. CHARGING & BLASTING
OPERATION
 After completion of drilling, Blasting In-
charge shall inspect the area and shall make
estimation of explosives required on the
basis of depth of holes.
 As per DGMS circular no slurry or emulsion
explosives shall be used in fiery holes and
we can’t avoid fire in holes drilled for
combined blasting purpose. Hence,
 Temperature of the holes shall be measured
with Infrared based thermometer and if it
exceeds 80C, the charging shall be stopped.

17. CHARGING OF HOLES ON
PILLARS
150mm 250mm

18. About GKOCP
1. Mineable Reserves : 71.01 M.T.
2. Area of extraction : 410 Ha.
3. Maximum depth of the quarry : 240m.
4. Gradient : 1 in 10 to 1 in 5
5. No. of coal seams : Three (Top, Middle & Bottom)
6. Total Over Burden to be removed : 391.30 M.cu.m.
7. Average stripping Ratio : 1 : 5.51
8. Annual targeted coal production : 2.00 M.T. to 2.5 M.T
9. Annual Over Burden removal : 11.72 M.cu.m.
10. Life of the project : 41 years
11. Total capital investment : Rs. 158.94 Cr. As per RCE 2001.
12. Date of starting the mine : 17.09.1993.
13. Man power planned at mine level : 922.
14. Quality of coal : ‘E’ grade
15. Technology adopted : Shovel Dumper combination

19. Production Details
I. Total OB quantity to be excavated : 391.30M.cu.m.
II. Extracted up to 30-11-2016 : 251.37M.cu.m.
III. Balance quantity to be extracted : 139.93M.cu.m.
IV. Total coal reserves : 71.0MT
V. Extracted up to 30-11-2016 : 49.71MT
VI. Balance coal to be extracted : 21.29MT
VII. 2016-17 Coal target : 22.5LT
VIII. Achieved upto 30-11-2016 : 17.85LT
IX. 2016-17 OB target : 52.00 + 122.05 (Dept + Off-loading)
X. Achieved upto 30-11-2016 : 21.45 + 115.42

20. Geology
 Gouthamkhani Area has three coal seams viz., Top seam, Middle seam and
Bottom seam Out of these three seams, Bottom and Middle seams are
workable coal horizons. Top seam has restricted occurrence in the centre
of main block.
 The property is of basinal in structure and sloping from three sides. The
maximum gradient is 1in5 and the average gradient is 1in10. The seam
thickness as well as the parting between seams varies within a wide range
as shown in table given below.
seam
Thickness of seams (in mtrs.) Thickness of partition (in mtrs.)
From To From To
Top seam 3.20 11.80
10.00 23.00
Middle seam 1.80 11.40
4.30 44.50
Bottom seam 2.40 29.0

21. Machinery
The mine working under SHOVEL-DUMPER
combination method and The mine having,
1.ROPE SHOVEL-1(10cum)
2.HYDRAULIC SHOVELS-7(6.5cum)
3.DUMPERS:-100t-7,60t-7,35t-23

22. Mine Plan

23. Precautions
After proper compaction of the area, again
gallery and junction shall be marked with stone
dust and with `White` flags
The blasted galleries shall not be kept exposed
unnecessarily.

24. Conclusion
To avoid collapsing of under ground galleries
and bogging down of men and machinery,
effective compaction of galleries will be done
to extract coal from standing pillars by
opencast method. Surveying is very-very
important in U/G turned O/C mine. The plan
submitted by the U/G mine manager should be
very handy and informative. Surveying should
be conducted with latest instrument like, Total
Station etc.

25. THANK YOU