Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Geotechnical Engineering > Coal Pillar Lecture Notes > Flashcards

Coal Pillar Lecture Notes Flashcards

1
Q

What can underground mining accidents cause (geology)

A

Severe windblast and seismic activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what has reduce the fatalities in Australia when mine failures occur

A

That the events occured over shut down periods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the key differences between mining and other engineering structures

A

Mining changes the loading conditions of the rock mass and does not have consistent well defined properties.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What were the fundermental principles of the research undertaken to address the intrinsic properties of rock mass

A
  1. identification of the primary variables
  2. pysical processes involved in the failure
  3. reviews of field performance where operating mines are utilising full-scale mine testing
  4. undertake rigerous probalistic analysis to quantify levels of risk
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are not deemed appropriate design tools on their own?

A

Trial and error, curve fitting and experimental panels are not adequate on their own.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is it essential to understand to design appropriate pillars in coal for the risk levels

A

understanding the functions of each pillar system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are pillar systems for local support

A

*bord and pillar
*pillar extraction (face line pillars, stooks and fenders)
*retreat longwall (chain pillars, sacrificial pillars)
*special purpose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are pillar systems providing regional stability

A

interpanel pillars
barrier pillars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the main function of the pillars in a bord and pillar system

A
  1. restrict surface movement
  2. protect infrastructure from high load abutment stresses
  3. prevent hydraulic connections of overhead water sources going through the strata
  4. provide temporary support of the roof in thick seam workings
  5. provide partitions to ventilation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the two pillar extraction methods

A

Face line pillars
Stooks and fenders

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are face line pillars utilised for

A

control abutment stresses around the goaf edge
through
1. act as a leverage point to break off roof strata
2. protect access and egress paths
3. act as venitalion partitions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are stooks and fenders implemented for

A
  1. control convergence through reducing roof span
  2. function as temporary roof supports
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the retreat longwall pillar types

A

Chain pillars
Sacrificial pillars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are chain pillars used for

A
  1. protect future roadways from high abutment stresses
  2. protect access and egress to coal face
  3. act as bentialtion parititons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the purpose of special pillars

A
  1. create protective pillars below specific surface features (like dams and cliff faces)
  2. shaft pillars
  3. crown pillars
  4. yeild pillars
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What pillars provide regional stability

A

Inter panel pillars
barrier pillars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What do inter-panel pillars control

A
  1. ventilation control
  2. regional instability control
  3. water control
  4. pressure outburst control
  5. fire control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What to barrier pillars provide

A

a regional load bearing framework to the mined to create a buffer for:
*mininimising adjacent mine holing into each other
*protect from risks of other mines (water, fire, gases)
*restrict stresses between collieries
*protect critical mine infrastructure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How is stress transferred over an excavation

A

The weight is transfered to the abutments, this weight increases as excavation width increases. As futher increases the roof might cave.
When excavation becomes very large centre excavation stress is transferred through goaf while edges still support some undermined sections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does the stiffness of the roof strata control

A

Influence on the magnitude and distribution of the abutment stresses around the excavation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What determines the roof strata stiffness

A

modulus of elasticity, panel width, depth, thickness of roof strata

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How do typical panels seperated by a barrier pillar have the abutment stresses interact

A

They dont interact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What happens with the stress in addtional ‘normal’ panels

A

as pillar width decrease there is a relation to other abutment stress profiles. The profiles are additive and result in an increase in pillar stress.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does width height ratio govern

A

the stiffness and strength of the pillar

25
What occurs with stresses when roadways are very close together creating a small pillar between
The small pillar will yeild as it is so narrow it will start to unload and transfer the stress to the abutments
26
What are the two pillar failure modes
gradual and controlled sudden and uncontrolled
27
If the failure of a pillar can be controlled what may be formed
a yield pillar may be formed
28
How can major interactions be controlled
*roadway width *rib control *roof control
29
What is it essentials for the database
reliable database of both failed and unfailed pillars
30
What does the coal pillar system comprise of
pillars, roof, floor, and contact surfaces
31
How are pillar failure initiated
failures initiated by roof and floor failure and they develop gradually
32
What occurs when the pillar suddenly collapses
it occurs when the pillar itself fails
33
How will a pillar failure appear
may still appear intact
34
what happens to the stress when the pillar fails
load is reduced on the overburden and is then transferred to adjacent pillar
35
What is the domino effect
if adjacent pillars are already highly loaded any increase may have the effect of transferring the additional load it may also fail. This results in failures are sudden rather than gradual.
36
What are a means of controlling pillar failure progression
barrier pillars
37
How is managing of the risk done
probabilistic design approach
38
What are the key elements to the iterative decision process
*Decide tolerable or acceptable levels of risk *mining dimensions *pillar load and strength *pillar FOS *stability compliance *operational compliance
39
What is the equation for risk
Risk = probability of failure X consequences of failure
40
What does the UNSW pillar design procedure comprise of
competent roof and floor strata
41
What are the three main geotechnical decision steps in the pillar design process
Pillar working load Pillar strength Design Factor of Safety
42
Pillar load is commonly used to describe what
pillar stress
43
How does a uniform pattern of pillars distribute the stress
shared equally
44
What is Tributary area theory
When the layout is regular the overburden supports the load/stress over an area of influence
45
What is the pillar load highly dependent on
rate of extraction
46
why does strength decrease in coal or fissure rock (for a fixed shape specimen) as the volume increases
as volume increases the amount of irregularities present increase
47
what generate resistance to the lateral expansion of coal under loads
friction and cohesion
48
As the w/h ratio increases and the reliance on friction and cohesion diminises what does the pillar rely on
becomes dependent on geometry and is less affected by coal properties
49
What is the empirical mechanistic approach
utilising methods of statistically based approach that assessed a likelihood of failure
50
While prior studies utilised the minimum width what do new studies consider
there is incremental increase in strength for non square pillar and this was accounted for with an effective width
51
What is FOS equation
FOS = pillar strength / pillar load
52
what were the steps to the functional approach
1. identify purpose 2. pillar life expectancy 3. have acceptable levels of risk and the probability and consequence 4. Factor of Safety
53
What is a stook pillars purpose and life expectancy
Maintain roof control of the goaf and fail once goaf moves through 1-3 days
54
What is a fender pillars purpose and life expectancy
goaf edge control, assist break off of roof strata, protect road from goaf induced damage 3-5 days
55
What is a bord and pillar pillars purpose and life expectancy
local roof and floor stability, restrict some sub-surface movement 6-12 months (extraction) or 1-5 years (working)
56
What is a chain pillars purpose and life expectancy
long term stability, protect sub-surface features and can prevent ventialtion leakage 10-20 years
57
What is a barrier pillars purpose and life expectancy
regional load bearing structure, partition for isolation, protection of surface features 1-20 years
58
What is a subsidence pillars purpose and life expectancy
protect major sub surface and surface features Life of the structure up to permeant life
59
what are other consideration for design
operational requirements geotechnical requirements

Geotechnical Engineering (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions