Backfill Flashcards
What is backfill
material excavated from a site and used for refilling once ore extraction has occured, it can provide ground support
What are the underground backfill options used
*paste
*hydraulic
*rock
What is rock fill
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
What is hydraulic fill
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
What is a risk with hydraulic fill
Water needs to be drained out of the fill in an efficient manner. Poor water drainage could cause fill liquefication which is dangerous
What is paste fill
comprises of full tailings it is the densest form of backfill
What determines the backfill method
*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
What are adv and dis of rock fill
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
What are adv and dis of sand fill
Adv
*negligible unless cemented
Dis
*cost
*difficult to control moisture
*environmental problems
What are adv and dis of hydraulic fill
Adv
*easy to transport
*reduces tailings disposal
*low plant cost
Dis
*high water content
*high binder content
*slow to consolidate
*extensive bulkheads construction
what are adv and dis of paste fill
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
What are the key backfill properties
UCS
Permeability
What are extra considerations for backfill
*high early strength
*sustainable long term strength
*ensuring dimensional stability after placing (by meeting/exceeding design performance requirements)
What are backfill sources from coal mines
*fly ash
*solid waste
*high water material
What are adv and dis of fly ash (granular) backfill
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