DRIVAGE OF INCLINES IN MANDLA NORTH COAL MINEof

Jaiprakash Associates Limited, Noida

by M N Jha & M S Sandhu*

COAL MINING SCENARIOCoal mines were nationalized during 1971-73.80% of coal production came from underground mine during that era.Emphasis was given to develop Opencast mining to meet rising demand.This trend continued with high level of mechanization resulting into only 10% share of coal production from underground mines as of now.Ministry of Coal identified Coal blocks for allocation to be developed scientifically through underground method only.*

GENERAL INFORMATIONMandla North coal block with coal seams at a depth varying from 210 to 300 m was allotted to M/S Jaiprakash Associates Ltd.It covers an area of 10.41 sq. km.Coal seams are highly disturbed with 29 faults in the property. The major fault (F2A) with 100m throw divides the property in two parts.The mine has been planned to extract 1.5 mtpa deploying 3 sets of Continuous Miner.One set of inclines with one ventilation shaft are proposed to access coal seams.*

COAL SEAMSBarakar formation contains 5 coal seams splitted in to 19 workable/non-workable seams occurring at a depth varying from 173-350m.The following distinct horizons formed by coal seams are found workable.

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COAL HORIZONCOAL SEAMTOP SET1Seam I B2Seam I C3Seam II4Seam III BBOTTOM SET5Seam IVA/A26Seam VA/A17Seam VB/B1

METHOD OF WORKINGIt is planned to develop Seam IC initially having found in all 24 sectors with Gross reserve of 45.48 mt since Seam IA has not developed into workable thickness and Seam IB coalesced with Seam IC at various places.Life span for extraction of IB/IC is estimated at 25 years @ 1.5 mtpa.Extraction of II/IIIB shall be planned after a lapse of 5 years on completion of depillaring of the first panel of Seam IB/IC. This sequence will be followed for the remaining lower seams.It has been decided to work this mine by Bord & Pillar method with deployment of Continuous Miner for driving Trunk headings along rise and dip of the property.Panels comprising a set of 5 headings with cross connecting galleries will be opened on either side of the main trunk roadway for lateral development.3 sets of Continuous Miners will be deployed to achieve the targeted Mine capacity of 1.5 mtpa.*

METHOD OF WORKING (Contd)VENTILATIONThe proposed Mandla North Coal Mine has been considered as Degree-II Gassy Mine for assessment and planning of ventilation requirements.18000cum/minute of air is required to be produced by Mechanical system installed in Ventilation shaft.3.3 kv, 350kw motors shall be installed.These figures has been arrived taking into account all relevant DGMS requirements.

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METHOD OF WORKING (Contd)EVACUATION OF COALContinuous Miner shall convey the coal into Shuttle cars through its bridge conveyor.Loaded Shuttle car will discharge coal onto the feeder-breaker via coal hopper.Coal will be discharged uniformly onto the gate belt conveyor from feeder breaker.The gate belt in turn will discharge the coal onto the trunk belt conveyor and to bunker on the surface.Mechanically covered trucks will carry the coal from bunker to Railway siding for loading into the railway wagons.*

INCLINE DRIVAGEA single set of inclines measuring 5.2mX3.5m at a gradient of 1 in 4.5 are being driven in the centre of the property.The above parameters will restrict the length of the inclines to 903mx2 with optimum level of efficiency both for evacuation of coal and man riding system. The inclines will pass through Deccan Traps (495mx2) and Moturs (348mx2) before intersecting the coal bearing Barakars.

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INCLINE DRIVAGE (Contd)TECHNOLOGYDeployment of Road header - This option was not considered because of its unsuitability in Basalt having hardness >8.Drilling, blasting with combination of SDL and conveyor belt The frequent shifting of Conveyor belt along with high level of maintenance makes this option unviable. Deployment of Jumbo drill, SDL and 150kw haulage with 10t skips This has been adopted being the most suitable for Indian condition and subsequently to be used for man riding.*

INCLINE DRIVAGE (Contd)EQUIPMENTS-HAULAGEHaulage with man riding provision with following specifications have been installed.Haulage rating 150 kwRope Speed 2.2 to 2.5 m/secRope pull 20 Tonnes in 1 in 4.5 gradientRope diameter 25 mmMotor RPM 1000Drum diameter 1500 mmRope length 1200 m

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INCLINE DRIVAGE (Contd)EQUIPMENTS-JUMBO DRILLOne Jumbo drill capable of drilling both face and roof holes in two inclines with following specifications has been deployed.Make Sandvik HL 510Percussion pressure 120-175 barRotation (max) 175 barImpact power 16 kwFeed length 3900mm+860mmFeed force 9 Kn/120 barWater pump 1 x Water booster pumpLength 8015 mmWidth 1700 mmHeight (without canopy) 1800 mm*

INCLINE DRIVAGE (Contd)EQUIPMENTS-SIDE DISCHARGE LOADERTwo SDLs to load the broken rock into the 10 t skip with following specifications. Overall length 5428 mmHeight over canopy 1850-2100 mmGround clearance 205 mmBucket capacity 0.66 cum (side tipping rock bucket)Gradient to be negotiated 1 in 4.5Track width (grouser pads) 330 mm*

INCLINE DRIVAGE (Contd)EQUIPMENTS-VENTILATION FANIn order to get air flow of 8cum/sec at the face end of 900 m long drift, fans of 37.5 kw with following specifications are installed in respective inclines.Fan Pressure 3200 PaRPM 2950Voltage 415 VRating of fan motor 37.5 kw *

INCLINE DRIVAGE (Contd)BLASTING PATTERN

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*INCLINE DRIVAGE (Contd)BLASTING PATTERN

INCLINE DRIVAGE (Contd)*

Time Study ActivityTotal Time (In minutes)Tramming05Water connection15Scaling (Dressing)20Face Drilling52Roof Drilling20Roof bolting50Water dis-connection15Tramming07Face charging60Blasting10Entry after blast20Face clearance after blast30Mucking(Blasting muck clearance)240General work(Ducting, lighting etc)60Total Time604 (Say 600 minutes) i.e 10 hours.

CONCLUSIONWe expect to achieve a progress of 90m per month in each incline to touch coal seam within a time span of 10-12 months.Continuous Miner will be deployed to drive trunk heading and for formation of panels.3 set of Continuous Miner along with allied equipments shall be commissioned to achieve the target production of 1.5 mtpa.

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