MASS UTILISATION OF FLY ASH FOR RECLAMATION IN MINES – A CASE STUDY OF SUCCESSFUL FIELD EXPERIMENTAL TRIAL

by
*Singam Jayanthu and **Singam Jayadarshana
* Professor, Mining Engineering Department
National Institute of Technology,Rourkela-769008 –Orissa
Former Scientist of CIMFR-CSIR, NIRM-Ministry of Mines-GoI, Mining Division Board of IEI,
Presently member of EAC-Mining Industries-Orissa State Pollution Control Board (OSPCB)
**Btech-ECE-SMIT, (Mtech-EIE)CET Bhubaneswar
Workshop Facilitator
Dr. Revanuru Subramanyam
Department of Civil Engineering
NATIONAL WORKSHOP
ON
ENVIRONMENTAL IMPACT ASSESSMENT OF MINING INDUSTRIES
04-05th November, 2019
MASS UTILISATION OF FLY ASH FOR RECLAMATION IN MINES – A
CASE STUDY OF SUCCESSFUL FIELD EXPERIMENTAL TRIAL

CHALLENGES OF FLY ASH UTILISATION
 Fly ash generated from the coal based thermal power plant is of great
concern due to its disposal. Therefore proper utilization of the fly ash is
highly demanded.
 Fly ash generation and utilisation scenario indicates urgent need of
efforts from concerned agencies for reducing the gap of about 110
Million tones of Fly ash (FA) during 2011-12, and conducting need
based research for innovative measures in proper utilisation of the Fly
ash ( Table 1)
 Results of laboratory investigation, numerical analysis for understanding
the stability of overburden dump formed by mixing with 25% fly ash in
opencast coal mine at Raigarh, India along with field monitoring of such
dumps for the first time in India was found to be a better solution to the
problem of disposal of fly ash from the thermal power plants located near
opencast mine sites.
2
Indian Mining Conclave 2019-30-31 Oct’19-BBS-
Singam Jayanthu

 Surface mining is the main pillar for meeting the rising demand of metals and minerals .
 As the total production of limestone, dolomite, bauxite, and iron ore and lignite is to
come from these mines for ever while nearly 90% of total coal production.
 With rising demand of the coal, estimated to cross 1000 million tons by 2024, this share
is going to cross 95% limit and the working depth is going to cross 300 m.
 The mine size for the mission will cross on average 5 million tons per mine. Heavy
mechanization of the surface mining is therefore going to be the panacea of the mining
sector.
OPENCAST MINING TECHNOLOGY
3
Singam Jayanthu

 There is need to amalgamate the latest IT modules in these machines, improve
their efficiency, safety and economy in operation and maintenance.
 The conveyor system is found to be most economical in material transport in coal
mines and needs perfection in fabrication, operational and energy efficiency.
 In addition, the machinery/ package demand will rise in coal mining sector it can be
sustained over the next 50 years are In pit crusher conveyor package, Surface miner.
conveyor package, Dragline and auxiliary machines, High wall miner /conveyor
package etc.
 Remote Control of equipment, Fleet management, Process management, and
Proximity Detection are some of the areas requiring more research in application to
the field conditions in opencast mines.
OPENCAST MINING TECHNOLOGY
4
Singam Jayanthu

Fly Ash Scenario in India
Year FA
Generation
(Million
Tonne)
FA
Utilization
(Million
Tonne)
1994 40 1
2008 160 80
2011-2012 220 110
2031-2032 1000 --
5
Singam Jayanthu

Utilization Areas
6
12%
5
7%
4
10%
7
5% 8
1%
1
47%
2
9%
3
9%
1 cement manufacturing
2 Cement substitution
3 Road embankments
4 Low lying area filling
5 Ash bund raising
6 Mine fill
7 Brick manufacturing
8 Agriculture & others
6
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Location of Mine Site
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Typical Cross Section of the Mine
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Geo mining Conditions
 Jindal Power Open Cast Coal Mine is almost flat with small undulations
from surface. The lithological section comprises about 3-4 m
unconsolidated loose soil/alluvium. Below the top soil there is weathered
shale/sandstone up to 6–8 m depth. The weathered shale and sandstone are
comparatively loose in nature and can be excavated without blasting.
 Jindal Power Open Cast Coal Mine is captive mine of Jindal’s 1000 MW (4
x 250 MW) thermal power plant.
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Singam Jayanthu

Dumping of Fly Ash as Admixture with
Overburden
 Jindal Power Limited, Tamnar has already have captive thermal power
plants of 1000 MW and generating fly ash, a solid coal combustion residue
form due to the burning of coal, of nearly 16000 tons per day. Therefore,
quantity of fly ash generated requires large area for its dumping.
 Fly ash was dumped within this area surrounded by overburden in alternate
layers of height not exceeding 5 m in each layer. Therefore, each layer of
overburden was followed by a layer of mixture of fly ash and overburden
(fly ash 25%) and so on up to the height of 30 m.
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Singam Jayanthu

Ash pond in Dump AreaSite
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Dumping of fly ash through truck in the dump
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Fly Ash With OB at Dump Site
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Dozing of Fly Ash and OB Material at the
Dump Site
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Sprinkling of water in the dump area
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Top soil on the dump area
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Close View of Fly Ash and Overburden at
Dump Site
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Decks of Fly Ash with Overburden in
Dump Area
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 Various samples of overburden, soil and fly ash from the dump site were
supplied by the Jindal Power Limited for finding out various geotechnical
properties through the laboratory study. Different geotechnical tests were
conducted for the overburden and the fly ash samples collected from the site
 Laboratory geotechnical investigation was carried out for
determination of grain size distribution, specific gravity, compaction
characteristics (optimum moisture content and maximum dry density),
and shear strength characteristics following Bureau of Indian standard
(BIS) methods. The parameters like density, and shear parameters
cohesion (C) and angle of internal friction are determined for both
overburden and fly ash to analyze stability of dumped slope.
19
Experimental Investigation
Singam Jayanthu

DUMPING OF FLY ASH AS ADMIXTURE
WITH OVERBURDEN
 Jindal Power Limited, Tamnar has already have
captive thermal power plants of 1000 MW and
generating fly ash, a solid coal combustion residue
form due to the burning of coal, of nearly 16000 tons
per day. Therefore, quantity of fly ash generated
requires large area for its dumping.
 Fly ash was dumped within this area surrounded by
overburden in alternate layers of height not exceeding
5 m in each layer. Therefore, each layer of overburden
was followed by a layer of mixture of fly ash and
overburden (fly ash 25%) and so on up to the height
of 30 m.
20
Singam Jayanthu

SECTION OF THE DUMP
21
Overburden material (OB)
Mixture of Fly ash and OB
5 m
5m
Singam Jayanthu

DOZING OF FLY ASH AND OB MATERIAL
AT THE DUMP SITE
22
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CLOSE VIEW OF FLY ASH AND
OVERBURDEN AT DUMP SITE
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EXPERIMENTAL INVESTIGATION
 Various samples of overburden, soil and fly ash from the dump
site were supplied by the Jindal Power Limited for finding out
various geotechnical properties through the laboratory study.
Different geotechnical tests were conducted for the overburden
and the fly ash samples collected from the site
 Laboratory geotechnical investigation was carried out for
determination of grain size distribution, specific gravity,
compaction characteristics (optimum moisture content
and maximum dry density), and shear strength
characteristics following Bureau of Indian standard (BIS)
methods. The parameters like density, and shear
parameters cohesion (C) and angle of internal friction are
determined for both overburden and fly ash to analyze
stability of dumped slope.
24
Singam Jayanthu

COLLECTION OF FIELD SAMPLE FOR TESTING
OF PHYSIO MECHANICAL PROPERTIES OF
DUMP MATERIAL
25
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GRAIN SIZE DISTRIBUTION OF TYPICAL
OVERBURDEN (OB) AND FLY ASH
26
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COMPACTION CHARACTERISTICS OF MIXTURE OF
OVERBURDEN AND FLY ASH (25%)
27
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Numerical Analysis
 Numerical Analysis was conducted using software’s PLAXIS, FLAC-
SLOPE and OASYS.
 Different trials were made with overburden and mixture of overburden and
fly ash. The trial made for the dump prepared by alternate layer of
overburden and mixture of overburden and 25% fly ash along with the
incorporation of top soil of nearly 2 meter thickness at the top of the dump
for the reclamation purpose indicated the Factor of Safety of 1.78.
Singam Jayanthu 28

Numerical Analysis
 On the application of 25% fly ash mixture in the overburden dump
material, safety factor has increased to 1.78, which was only 1.32 with 8%
fly ash mixture with overburden.
 This increase may be attributed to the increase in cohesion of the mixture
due to self-cementing properties of fly ash generated from the combustion
of sub-bituminous coal.
 Stability analysis with Bench angle of 320 and 280 for the alternate
layers of OB and admixture of OB + Fly ash with safety factor exceeding
2 supporting the stability of dump in the field.
Singam Jayanthu 29

Slope stability -Bench angle 320 (OASYS)
Singam Jayanthu 30

Slope stability analysis -Bench angle 280
(OASYS)
Singam Jayanthu 31

Failure surface with factor of safety 1.75
(PLAXIS)
Singam Jayanthu 32

Slope stability analysis -Bench angle 280
(FLAC-SLOPE )
Singam Jayanthu 33

Slope stability analysis with Bench angle 320
(FLAC-SLOPE )
Singam Jayanthu 34

Slope Stability Monitoring By Total Station
 The height of dump at study site was about 25 m. Final stage dump consist
of 2 m top soil above the layers of OB and OB mixed fly ash material.
Stability of Dump slopes was monitored with total station and monitoring
stations fixed at an interval of 20 to 30 m on the dumps at a distance of
about 5 m from the crest of the dump slope.
 The 47 monitoring stations were installed with 1.0 m long pipes and
masonry pillars; 23 stations in the Pit 1 and 24 stations in Pit 2 and total
station was used for measuring RL of the stations.
Singam Jayanthu 35

Monitoring Stations at a Distance of 5m from
the Crest of the Dump Slope
Singam Jayanthu 36

Status of vertical displacement of dump at
the monitoring stations
Zero displacement Downward
displacement
Haphazard
displacement
Pit-1 Pit-2 Pit-1 Pit-2 Pit-1 Pit-2
AS1, AS 2,
AS 3, AS
12, AS
13,AS14,
AS 15,
A16, AS
18,AS19,
AS 20,
AS21
KJS6, KJS 7,
KJS 8, KJS 9,
KJS 10, KJS 13,
KJS 14, KJS 15,
KJS 16, KJS 17,
KJS 18, KJS 20,
KJS 22
AS4, AS 6,
AS 7 , AS 9,
AS 10, AS
17, AS 22,
AS 23
KJS 1,
KJS 4,
KJS
11,
KJS
12,
KJS
19,
KJS
23,
KJS 24
AS 5, AS
8, AS 11
KJS3
, KJS
5
37
Singam Jayanthu

Close view of the monitoring station
Singam Jayanthu 38

Singam Jayanthu 39
Monitoring Stations Installed with 1.0 m Long
Pipes And Masonry Pillars

GPS survey for monitoring the location of the
stations
Singam Jayanthu 40

Total Station For Measuring Reduced Levels
Of Monitoring Stations
Singam Jayanthu 41

Field monitoring of slopes using Total station indicated
the following:
 Displacement pattern of the monitoring stations during November
2012 to June 2013 indicated no significant displacement in the
Overburden dumps with fly ash ensuring stability of the dump near
majority of the stations.
 During November’12 to March’13, the dump was in the process of
continuous settlement near 1/3rd of the stations. About 65% , and
74% of the monitoring stations in Pit 1, and Pit 2, respectively
showed no perceptible deformation of the dump material near the
stations during March’13 to June’13.
 Decelerated movement was noticed during March’13 to June ’13
with a displacement of 1 mm in about 30% , and 26% of the
monitoring stations in Pit 1, and Pit 2, respectively. This indicates
the tendency of settlement of the dump material with 75% OB and
25% Fly Ash after March’13.
42
Singam Jayanthu

Variation of RL of Monitoring stations
up to November’13
Singam Jayanthu 43

Displacement of Monitoring Stations from
November 12 to November’ 13
Singam Jayanthu 44

Variation of RL of Monitoring stations over
the dump material
Singam Jayanthu 45

Banana and Mango grown over the fly ash
OB dump material at JPL
Singam Jayanthu 46

Monitoring Type Success Rate
 Visual Monitoring only 32%
 Prism/Crack meters only 45%
 Visual + Prism/Crack monitors 63%
 Visual + Prism/.Crack + Laser 86%
 Radar Only 93%
 Visual + Prism/Crack + Radar 97.5%
 Visual + Prism/Crack + Laser + Radar 99%
47
Singam Jayanthu

Monitoring Type Success Rate
 In this analysis, a monitoring success is where a
slope failure was identified with sufficient warning
time to successfully evaluate the mining moving
operation.
 From this, one can conclude (for this example):
1. Radar is the most successful stand alone technique
for slope hazard monitoring.
2. Radar is considerably more successful
than laser scanners in reducing the consequence of a major
slope event.
3. Use of multiple systems dramaticall increase
success rates and is encouraged by GroundProbe.
48
Singam Jayanthu

Conclusion
 Considering the importance of mass utilisation of Fly ash in the coal mining area, and
limitations of available technology for its utilisation it is recommended to undertake
experimental studies for mass utilisation of the ever increasing Fly Ash production in India.
One such experimental trial conducted for the first time in India at M/s JPL mines proved
stability of the dumps with 25% Fly ash as admixture in the OB dumps as discussed in the
present paper.
 Displacement pattern of the monitoring stations using Total station during November 2012 to
November 2013 indicated no significant displacement in the Overburden dumps with fly ash ensuring
stability of the dump. Based on the above monitoring results, it is recommended to undertake further
process of laying top soil and plantation, subsequently.
 Similar procedure may be adopted in other mine sites for utilisation of fly ash as back filling material
with a scope of additional studies for continuous dumping of fly ash and OB material eliminating the
need of creation of ash pond in near future.
 In view of impetus on the application of innovative technologies at the earliest in India,
there is an urgent need to formulate expert committees in various disciplines including
academia, research, regulatory and field personal besides CFARM-DST for formulating
reliable guidelines near future.
 Meticulous monitoring and Assessment of Environmental parameters through various approaches
including application of transdisciplinary research areas of ECE, CSE, EIE etc to the mining industries
is the need of the hour for sustainable mining in the world .
Singam Jayanthu 49

Thank you
Singam Jayanthu 50

BRIEF ABOUT THE FIRST AUTHOR
 Mining Engineering) from Kothagudem School of Mines-Osmania University with first rank in 1986. He worked as a
ventilation officer and in-charge of machine mining districts of coal mines (Singareni Collieries Company Limited)
for a couple of years before taking up M. Tech (Mine Planning & Design), from Banaras Hindu University in 1990. He
was awarded OU, IDL, MGMI/SCCL Gold Medals. Dr Jayanthu worked as a scientist since 1989 in premier research
institutes of India (Central Mining Research Institute-Dhanbad, and National Institute of Rock mechanics-Kolar
Gold Fields). He was awarded Masters Degree in Counselling & Psychotherapy from Kuvempu University in 2006.
Research areas of interest include Design of support system and methods of mining: long wall/Bord & pillar/Blasting
Gallery/Wide stall; Strata control, Caveability, EMP, mine closure management, Underground instrumentation and
monitoring,numerical modelling , Fly ash and bottom ash management, transdisciplinary research applicationsto
mining industries etc. He was conferred with National Mineral Award in year 2000 for his distinguished contributions
in the field of mining technology in India. Being holder of Mine Managers certificate of competency, he presented on
issues of mining techniques and transdisciplinary research and innovations during 1998 –2018, in various
international seminars/conferences including research and academic institutions such as NIOSH, MSHA-USA,
Aachen University-Germany, World conference on Multidisciplinary research and innovations in Dubai etc. He has
completed over 90 Research & Development Projects sponsored by Various Ministries of Govt of India, and
Consultancy projects sponsored by various coal and metal mines of India, and authored over 180 technical papers
published in various national/international journals and Proceedings of conferences/seminars.
 At present he is working as Professor in Mining Engineering Department of National Institute of Technology,
Rourkela. He is member of Technical Committee Environmental Appraisal for Mining Industries of Orissa State
Pollution Control Board since 2007. He is Principal Consulting Editor during 2007-2011- and Chief Editor since
January 2012 of Indian Mining and Engineering Journal and being Fellow of IE(I), he also extended his services as
Honorary Secretary of The Institution of Engineers (India), Rourkela Local Centre, and co-opted Council member,
Mining Division Board of IEI. Worked as Head of the Dept of mining Engg of NIT-Rourkela for three years during
2007-2010. At present conducting research also on applications of trans-disciplinary areas including EE, ECE, CSE, EIE
to mining industry such as Power Quality improvement, Wireless Sensor Networks with IoT, Soft Computing
techniques, TDR etc for improving safety in the mines. Associated with four patents provisionally filed related to “A
Novel Seismic-Data Acquisition Sensor (S-DAS) for Monitoring Ground Vibration due to Blasting using Sensor Field
Network in IoT Framework”, “Wireless Distributed Time Domain Reflectometry (WDTDR) Sensor Node for
Distributed Real-Time Monitoring of Slope Behaviour”, and A Novel Roof Sag Sensor (RSS) for Real-Time Monitoring
of roof sags in Underground Mines and Tunnels using Mine Sensor Network in IoT Framework”, Design and
Development of an IoT based Mine Environment Safety Monitoring Device- (MESAMONSYS).
51

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