Backfill Flashcards

1
Q

What is backfill

A

material excavated from a site and used for refilling once ore extraction has occured, it can provide ground support

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2
Q

What are the underground backfill options used

A

*paste
*hydraulic
*rock

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3
Q

What is rock fill

A

cemented and non cemented fill
Used to fill in open stope methods to provided minimisation to ground movement problems and in now engineered to improve with pillar recovery

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4
Q

What is hydraulic fill

A

slurry and dense slurry fills
made of tailings and are prepared at surface plants. The fine fraction is removed and then sent to the tailings dam the remaining slurry goes to pipelines to underground voids

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5
Q

What is a risk with hydraulic fill

A

Water needs to be drained out of the fill in an efficient manner. Poor water drainage could cause fill liquefication which is dangerous

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6
Q

What is paste fill

A

comprises of full tailings it is the densest form of backfill

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7
Q

What determines the backfill method

A

*configuration of the mining process
*stope sequence and excavation size as determined by the mining method
*depth and orientation of the orebody
*backfill material available
*cost

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8
Q

What are adv and dis of rock fill

A

Adv
*high modulus (stiff)
*can use waste rock in UG

Dis
*difficult to consolidate
*requires crushing at some point
*not always available
*tailings not used

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9
Q

What are adv and dis of sand fill

A

Adv
*negligible unless cemented

Dis
*cost
*difficult to control moisture
*environmental problems

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10
Q

What are adv and dis of hydraulic fill

A

Adv
*easy to transport
*reduces tailings disposal
*low plant cost

Dis
*high water content
*high binder content
*slow to consolidate
*extensive bulkheads construction

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11
Q

what are adv and dis of paste fill

A

Adv
*no water generated
*faster set times
*no bulkhead construction
*reduce binder requirements
*environmentally friendly as less water is used
*less underground contamination
*placement options do not have to be continuous

Dis
*difficult to transport
*pumping for horizontal runs

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12
Q

What are the key backfill properties

A

UCS
Permeability

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13
Q

What are extra considerations for backfill

A

*high early strength
*sustainable long term strength
*ensuring dimensional stability after placing (by meeting/exceeding design performance requirements)

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14
Q

What are backfill sources from coal mines

A

*fly ash
*solid waste
*high water material

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15
Q

What are adv and dis of fly ash (granular) backfill

A

Adv
*cheap material and addatives
*high strength
*backfill rate is high
*low labour system that is simple

dis
*needs special backfill support and rear scraper conveyor

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16
Q

What are adv and dis of cemented backfill

A

adv
*does not absorb water leading to reduced isolation time
*no complex filtering system required
*high strength
*readily comes in contact with the roof
*low compression ratio

dis
*complex and significant investment in early period
*high power back fill pump in needed and piplines are easily blocked

17
Q

What are adv and dis of high water content backfill

A

adv
*simple
*low initial investment
*easily transported
*low labor intensity
*readily lose water and are readily pulvarised

dis
*ratio need to control the high water content material
*backfill materials are expensive and cannot permit recycling of gangues and fly ash of coal mines