HIGHWALL MINING AN OVERVIEW

K. D. PRASADB.TECH.(MINING)

GM(Mining), BCCL(CIL)

HISTORY OF HIGHWALL MINING

Highwall mining in the form of Auger mining startedin 1983 in USA.

ADDCAR system of highwall miner started in 1990.

Superior Highwall miners started manufacturingHighwall miner in 1994.

Total coal production from highwall mining in USA= 5o – 55 million tonnes per annum.

Total population of highwall miner all over theworld in 2011 – 90 Nos.

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WHAT IS HIGHWALL MINING?

Highwall Mining is a remotely operated miningmethod to extract coal from thin seams or coal fromunderlying seams in the Highwall of surface coalmine.

Condition : Surface mining has uneconomicalstripping ratio or due to local surface constraintswhich limit further surface mining operation.

Equipments are closely related to undergroundmining machinery.

mining method is hybrid of surface & UG coalmining methods.

ADVANTAGES OF HIGHWALL MINING

This method relies upon extracting coal from a seriesof parallel entries driven in the seam from the face ofthe Highwall without roof support.

no man power is required to enter the entries madeby Highwall miner thus making it a safe miningoperation.

Operation are unmanned & remote.

Highwall is one of the safest & economical miningmethods

LIMITATIONS OF HIGHWALL MINING TECHNOLOGY

Flat seams 8 to 12 degree,

Seams free from geological disturbances,

Seams depth of 200 mtr.,

Seam thickness between 0.9 to 5.0 mtr.,

strong roof and floor,

Moderate make of water.

Length of push beam which is generally 300ms.

APPLICABILITY CONDITION

Coal blocked in Highwall due to un-economicstripping ratio

Coal blocked in boundaries of open cast.

Coal in thin seams for which no conventional miningmethod is available or economically viable

Coal seams available in hills and forest areas.

Suitable for the coal blocked below the roads,permanent surface structures ,villages.

HIGHWALL MINING EQUIPMENT

Base Unit / Advancing launcher

Reels & chains

Controls

Push beams

Cutter Unit

Anchoring

Right angle conveyor

Generator.

BASE UNIT/ADVANCING LAUNCHER

Main base unit is placed at surface where most of thedrives and all controls are positioned.

Closed operator’s main control cabin is on top of theBase Unit.

It also houses hydraulic Power-Pack to feed power toPush-beams and cutter-heads.

BASE UNIT/ADVANCING LAUNCHER

Reels and Chains

REELS & CHAIN

Reel automatically unwinds and winds consideringthe movement of the push beam and it contains : -

Power cable for cutter head.

Control cable for cutter head

Methane sensor cable

Hydraulic pressure hose for cutter

Cooling water hose for cutter motor

CONTROLS

Total operation can either be by automatic through programmable logic controller or-

Manual through touch screen technology or

Fully manual.

Contains self-diagnostic health monitoring system for the machine and u/g environment.

PUSH BEAM

Push beam plays an important role for parallel drivage of entries.

contains two contra-rotating augurs for transportation of coal from the coal face.

Articulating in-joint of two push beams provides vertical movement.

It allows the cutter head to negotiate the undulating con-tour of the coal seam.

Normal length of push beam is about 6.0 m.

PUSH BEAM (FRONT)

PUSH BEAM (BACK)

CUTTER UNIT

Cutter unit is basically the cutter head of continuousminer.

Operation is fully remote controlled from the surfaceoperator’s cabin.

Cutter modules are chosen as per thickness of coalseam.

power of cutter motors varies from 240KW to 350KW.

The entire cutter modules are interchangeable withthe machine.

CUTTER HEAD

ANCHORING SYSTEM

Two machines mounted on the front of the machine used for drilling into the pit.

Two high strength pins are inserted through the base frame of the miner into the pit floor.

During the mining cycle and retract cycle the anchoring systems stabilizes the Highwall Miner.

ANCHORING SYSTEM

CONVEYOR UNIT

Conveyor unit facilitates loading/stacking of coal on to truck/on the ground.

A new development at Highwall Miners is the Right Angle Discharge Conveyor.

It can be mounted to discharge coal on the right or left side of the Highwall Miner.

The advantage of the right angle conveyor system is the miner can work on bench of narrow width also.

GENERATOR

GENERATOR

The Highwall mining system can be powered fromeither highline power or by utilizing the Highwallminer electric generator.

The mobile generator is housed in a super silencedcontainer.

The mobile generator is mounted on crawlers forhigh maneuverability in rough terrain.

MECHANISM OF WORKING

In high wall mining the coal seam is penetrated by a continuous miner propelled by a hydraulic push beam transfer mechanism.

cycle includes sumping (launch pushing forward) and shearing (raising and lower the cutter head boom to cut the entire height of the coal seam).

the push beam transfer mechanism (PTM) automatically inserts a 6.01m long rectangular push beam (screw conveyor segment) into the centersection of the machine between the power head and the cutter head.

MECHANISM OF WORKING (contd)

The push beam system can penetrate nearly 300m into the coal seam.

High wall mining system use auger enclosed inside the push beam that prevent the mined coal from being contaminated by rock debris during the conveyance process.

Using a video imaging and/or a gamma ray sensor and/or other geo radar system like a coal-rock interface detection sensor the operator can see ahead projection of the seam rock interface and guide the continuous miner’s progress.

METHOD OF MINING

Contour mining

Trench mining

Bench mining, and

Highwall mining.

CONTOUR MINING

Contour Mining (contd)

Highwall mining follows the contour of the coalseam, method is known as contour mining byHighwall method.

When any coal seam, particularly thin seam appearsat incrop/outcrop, conventional method of miningcontour mining can be done economically and safely.

TRENCH MINING

TRENCH MINING

Entries can be made by excavating a trench to expose the coal seam and Highwall mining can be done both along the exposed coal seam available at dip and rise side.

This is commonly known as trench mining.

BENCH MINING

Mining by preparation of benches in each seam for multi-seam working is called bench mining.

For working multi seam deposit, a bench is prepared in the top seam and mining operation is taken top downwards.

Highwall mining can also be done by preparation of benches from bottom upwards but there is a possibility of damages to the coal of upper seams if there is any failure of web pillars at the bottom seams.

Bench Mining

Mine Floor Coal

Highwall Mine Seam

Highwall Mine Seam

Blast 2nd Bench

Blast 2nd Bench

Mine Floor Coal Bench 2

Highwall Mine Seam 2

Highwall Mine Seam 2

STRIP SEAM 3

Strip Seam 3

Strip Seam 3

Highwall Mine Seam 3

Highwall Mine Seam 3

Ready!

Blast Bench

HIGHWALL MINING

When the open pit mining has reached beyond thestripping ratio or the limit of mining operation, thecoal blocked in the Highwall, can be taken outeconomically and safely by this method.

HIGHWALL MINING

SPECIAL FEATURES

Machine is fitted with FOG ( Fiber Optic Gyro)navigation system.

Ensures the parallel drivages automatically. Machine is controlled by PLC, to avoid

human error . Auger system is unique for the wet coal

transportation. GPS ensures faster positioning of the machine

at desired angle of drivages. An inbuilt device to measure the roll, pitch, and

Cutter head angle .

SAFETY

Operations are carried out by remote control.

Operator’s cabin at 6 mtr height and about 20 mtraway from Highwall.

No person is required to go inside the drivages.

Persons are not exposed to hazards like roof falls,gas, dust, irrespirable atmospheres, etc.

Manpower requirement for the whole operation is aslow as 4 per shift.

One of the safest mining methods.

PROTECTION AGAINST METHANE CONCENTRATION

Continuous monitoring of the methane by DGMSapproved methane Sensors

Intrinsically safe & fail safe in design

Methane sensor device interlocked with PLC controlsystem

Power to UG will be “ON” only if:

The Methane sensor is “ON”

Working properly

Methane level is below 1.25%

Protection Against Methane Concentration

When Methane level:

=0.8% Operator get audio-visual alarm

>1.25% U/G part of the machine will be powered “OFF”

Protection Against Methane Concentration

In case methane sensor switched off or is in fault mode all electrical powersources including signal & control will be shut off (fail safe)

COAL DUST SUPPRESSION

Water spraying on the cutter head – at a flow rate of 19

litre per minute at a pressure of approx 20 Bar.

It is interlocked with power supply to the cutter head

PROTECTION AGAINST FALL OF OBJECTS

The construction of the operator’s cabin protects operator

Area of operation of the grounds man is below the steel structure of the machine

NAVIGATION SYSTEM

The machine is capable of making parallel drivages

without navigation system.

However, Fibre Optic Gyro (FOG) system can be

provided for auto Steer control

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