Presentation on Highwall Mining

IMPROVEMENT OF HIGHWALL
MINING METHOD
Team Name- THE RISERS
Team Members:-
1. JASMEET SALUJA
2. JASMEET SINGH CHHABRA
3. SHUBHAM CHAUHAN

Why Highwall ??
• Coal has been recognized as the most important source of energy for electricity
generation in India.
• Currently the country produces more than 550 million tonnes of coal per year,
more than 80% of which comes from opencast mines.
• Despite of having the fourth largest coal reserve and being the third largest coal
producing country in the world, India needs to import coal to meet its growing
requirement.
• Most of the opencast coal mines were started in early eighties in India. Many of
these opencast mines are reaching their pit limits.
• A significant amount of coal is blocked in non workable thin seams, in the
highwalls, below surface dwellings in these opencast mines.
• Highwall mining is a proven technology in USA and Australia to extract the blocked
coal in thin non-workable seams and the coal blocked in the highwall of opencast
mines.

What is Highwall Method of Mining??
• Highwall mining is a proven primary method for mining coal from
outcropping horizontal seams.
• In this method of mining, an Unmanned Continuous Miner is driven
underground and operated in front of the highwall.
• The highwall mining machine stands on the pit floor or on a bench,
directly in front of the exposed seam and makes long parallel
rectangular drives into the coal seam.
• A remote-operated cutter module is pushed into the seam by a string
of Push Beams (unmanned coal-conveying elements) that transport
the mined coal back to the entry of the drive onto a stockpile.

Machinery Details
1. General Details
• Length base approx. - 22 meters
• Width base approx. - 8.3 meters
• Weight base approx. - 160 tonnes
• Length of push beams - 6 meters ( 6 tonnes each )
• 50 push beams per miner
• Max. force in: approx. - 170 tonnes,
• Max force out: approx. - 350 tonnes.

Launch Vehicle :-
Mine Mode Dimensions
Width: 10 m (33.6 ft)
Height: 8.4 m (28 ft)
Length: 16.6 m (55.3 ft)
Weight: Highwall Mining System 225 000 kg
(496,040 lb)
Weight: Push Beam 5 624 kg (12,400 lb)
Weight: Low-Seam Cutter Module 21 800 kg
(48,061 lb)
Weight: High-Seam Cutter Module 43 084 kg
(93,000 lb)
Coal Seam Height Range 760 mm (30 in) to
3.05 m (10 ft)
Maximum Penetration Capability 305 m
(1,000 ft)

Cutter Head
Two types of Cutter Heads are available:
i) Low-seam cutter
{for seams 0.76 – 1.62 m (2.5 – 5.3 ft) in height}
ii) High-seam cutter
{to mine 1.3 – 3.05 m (4.3 – 10 ft) seams in height. }
 The cutter modules are interchangeable and
quickly attached to the powerhead assembly.
 The cutting cycle is fully automated, yet
allows the operator to manually adjust the
machine function using an ampere reading as
the coal seam varies.
 This proven technology allows the cutter
module to accurately follow the coal seam
and produce a clean product.
Cutting Width :- 2.9 – 3.5m

Push Beams
Push beams are 6 m long rectangular
reinforced steel box structures
Push beams are joined together to
form a string.
The string of the push beams:
a) pushes and pulls the cutter unit in
and out of the seam
b) conveys the mined coal to the
surface through two contra-rotating
augers.
c) Support the hose chain.
d) Supply air to the face to flush the
methane and keep the face cool.

The Push Beam string is the backbone of
the machine; pushing and pulling the cutter module
in and out of the highwall with retract forces up to
363 tonnes.
The push beams also transport mined coal
and support the hose chain that supplies
control and power to the cutter.
Moving coal inside the push beam (via a pair
of screw conveyors) protects the coal from
contamination and the moving mechanical
parts from rock debris, resulting in higher
availability

A strong method of attachment that is
secured and disengaged quickly.
• A horizontal hinge design that allows
the string and cutter to navigate
through coal seam rolls and
undulations
• Structural rigidity that ensures mining
in parallel drives
• A simple design free of electrical and
hydraulic connections
• Push beams that can be stacked six
high for storage in narrow worksites,
even under tough pushing and pulling
conditions

Robust Reel & Chain
Stores and protects :
 power cable for cutter head,
 control cable for cutter head,
 methane sensor cable,
 hydraulic pressure hose for cutter
 cooling water hose etc.
Hoses are protected by steel plates and
links.
Hose chain automatically unwinds and
winds during mining.

Operators Cabin
The Cat highwall mining system is equipped with a
comfortable, air-conditioned cab that offers a full view of
the mining operation and the highwall. The fullsuspension
operator seat and the two user-friendly touchscreens
create an ergonomic workplace, placing controls and system
information at the operator’s fingertips.
Salient Features:
1. Fibre Optic Gyro Navigation System
Ensure the parallelism of the galleries and maintain adequate pillar thickness throughout the gallery
2. Continuous Methane Monitoring System
Monitors the % of methane at the face. At 0.75 %, gives warning to the operator and at 1.25 %, automatically. shut
off power supply.
3. Temperature control
Monitors the temperature of the face. The face is kept cool by circulating air through augers in the push beam. The
3
augers are capable of circulating 48 m
/min of air.

Excellent Mobility
The Highwall mining system is an agile, self-propelled
machine that operates on contour benches as narrow as
18 m (59 ft). It trams easily from entry to entry and
discharges coal in tight spaces.
An optional right-angle conveyor system discharges coal
on the right or left side on narrow benches. It can also
discharge onto a stacking conveyor system, where
coal is moved to the center of the bench for stockpiling
large volumes.
Four heavy-duty, hydraulically-powered tracks articulate
independently in two operating modes – mine mode and
tram mode – and can rotate the machine 360°, which
improves maneuverability in congested areas. Mine mode
is used for moving parallel to the highwall, while tram
mode is used when moving from pit to pit.

Now , Let’s move on to the Real Method

Push Beam
Highwall Miner
standing on Pit
Bottom

Highwall Mining
Trench
Mining
Opencast
Mining
Contour
Mining

The three methods for
commencing of Highwall
Mining are clearly
shown in the picture.

1. Trench Mining  Trench mining is practiced for
mining thin, reasonably flat coal
seams which may not be
amenable to opencast mining.
 In this method, an artificial
highwall is created by making a
trench up to the coal seam.
 The miner is positioned on the
floor of the seam within the
trench and galleries are driven on
both sides of the trench

2. Contour Mining Contour mining is used to
extract outcropped coal seams
in hilly area.
The highwall mining follows
the contour of the seam along
the hill side.

3. Open Pit Mining Highwall mining is used to
work the coal blocked in the
highwall of an opencast mine.
In this method the highwall
miner is positioned on the floor
of the seam and in front of the
highwall and galleries are
driven in the exposed seam in
the highwall.

Method’s Shortcomings
Problems in Highwall Mining :-
1. Highwall Mining near old Underground mines,
2. Multiple-seam and Multiple-lift Highwall mining,
3. The width and frequency of barrier pillars.
4. The width of hole and web pillar
5. Machine getting trapped under Highwall
6. Coal blocked in Web & Barrier Pillars
Highwall stability is the major ground control related safety concern.
Ground control plans for highwall mining must specify hole width, web pillar width,
barrier pillar width and number of holes between barriers.

In this article, we have focused particularly in Determining
the Web Pillar and Barrier Pillar Width, There Frequency in a
Panel and Highwall Stability.
Using Mark-Bieniawski formula as a standard, we have devised a Computer
Program for calculating the above mentioned factors.
A user just needs to enter the following informations:
i) Height of Coal Seam
ii) Maximum and Minimum Overburden Height
iii) Hole Width
iv) Panel Width

Mark-Bieniawski Formulas
• Coal Pillar Strength
Sp = Si [ 0.64 + 0.54 W / H ]
Where:
Sp = web or barrier pillar strength
Si = in situ coal strength
W = web or barrier pillar width
H = mining height

• Coal Pillar Stress
Swp = Sv (Wwp + We) / Wwp
Where:
Sv = in situ vertical stress
Wwp = web pillar width
We = highwall miner hole width.
• Overburden depth
Ddesign = 0.75 * Dmax + 0.25 * Dmin
Where:
Dmax = maximum overburden depth
Dmin = minimum overburden depth.

• Stability Factor for Web Pillars
SFwp = web pillar strength / web pillar stress
• If the number of web pillars in a panel is selected as “N”, then the Panel Width
is given by :-
Wpn = N (Wwp + We) + We

• Neglecting the stress carried by the web pillars (i.e. assuming that they
have all failed), the average vertical stress on a barrier pillar is
Sbp = Sv (Wpn + Wbp) / Wbp
Where:
Wpn = panel width
Wbp = barrier pillar width
• Similarly, the stability factor for barrier pillars against strength failure is
simply
SFbp = barrier pillar strength / barrier pillar stress

Our Innovations
1. Roof Bolting Technique :-
• Considering the average height of holes in highwall mining which
normally varies from 0.9 to 3.05 m , and the instability of Immediate
Roof at that hole heights with the length of extraction.
• The Mechanized Roof Bolt Technique can be applied to keep the
immediate roof intact that is prevent separation which is the main
cause for failure.
• The Roof Bolts shall be inserted into the roof by proper drilling
arrangements provided along the length of the push beams . The
bolts would be of minimum length when inserted vertically upward.
The length of bolts can even be increased by inserting them slantly
upto the limits permissible.

2. Back Filling Measures :-
• Keeping in mind the use of push beams to transport or carry the
coal from the face to the mouth .
• By reversing the direction of the auger motion the supply of
filling material from the mouth to the face might be done to
provide for the back filling of the material.
• Various improvisation techniques for the back filling can be
obtained by practical application of this method at the site and
can further be developed on the basis of results so obtained so
that the filling material be dumped efficiently with some
compactness.

3. Two Trench Technique
• So far we have seen the highwall technique in the light of single
trench technique in which, in a panel, multiple parallel holes are
made with desired web pillars in between them.
• In case of hills, where trenches on both the sides of the seam are
possible, in panel, a hole can be drawn from first trench and now
after leaving the desired web pillar width , next hole can be made
from the opposite side upto the acceptable depth .
• This might decrease the loads on the web pillars and subsequently on
the barrier pillars. This extra safety might be utilized in enhancing the
further coal extraction by robbing the barrier pillars at last or even
working parts of barrier pillars.

Presentation on Highwall Mining

4. Controlled Caving
• Most of Highwall Mining sites are under previously worked Opencast
mines or Hilltops ( Outcrops ). These areas are isolated ones which do
not contain any Property of Importance on the surface.
• Hence, using the method of PLANNED & CONTROLLED BLASTING
regular caving can be managed as this will reduce a great amount of
overlying pressure on the pillars and will contribute to Safety of Pillars
and increase in Percentange Extraction.
• This may also eliminate the need for leaving web pillars for the
Overburden support.

Conclusion
• Thus we conclude that , by introduction of these techniques
the stability and safety in Highwall Mining Operations can
significantly be improved.
• Further, in near future Highwall Mining may prove to be a
significant method for coal production.

Presentation on Highwall Mining

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