Download - Filling
Filling of mined-out openings
Dry waste fill
Hydraulic fill
Cemented rock fill (CRF)
Paste fill
Dry waste fill coming from the same stope
Any material size is satisfactory : usually between 60 and 150 mm and up to 300 mm
No transport or specific equipment
Reduced cost
High compaction : up to 50% of volume
Fill is weak
Impossible to control the material gradation (grain size distribution)
Impossible to drive the fill tight against the back
Transport of supplementary waste into the stope or extra waste from the stope doesn’t excluded
Ore body
Stope
Waste
Ore breaking
Wastebreaking
Blast holes
Dry waste fill coming from outside of the stope
material from underground development
1500 m niveau l 12
main shaft
waste pass
fill pass
material from surface quarries
Material size between 60 and 150 mm and up to 300 mm is satisfactory
Material gradation can be controlled
Fill is stronger due to a better size distribution
Volume of fill by stope is controlled
Specific fill passes, storage and other facilities are needed
Underground transport is indispensable
Higher cost
Dry waste fill coming from outside of the stope :placement by gravity
Material size between 60 and 150 mm and up to 300 mm is satisfactory
Material gradation can be controlled
Fill is stronger due to the better size distribution
Volume of fill by stope is controlled
High compaction : up to 50% of volume
Specific fill passes, storage and other facilities are needed
Underground transport is indispensable
Higher cost
Dry waste fill coming from outside of the stope : slinger belt placement
Fill is stronger due to better compaction if gradation of material is proper
Fill can be placed tight against the back
Material size is more restricted ( up to 100 - 200 mm)
Material compaction can reach 20 % to 30 %
Specific equipment is needed
Distance of projection is limited to 6 - 10 m
Dry waste fill : Placement by loading equipment
Fill is stronger compared to gravity placement due to better compaction if gradation of material is proper
Fill can be placed against the back
Material compaction can reach 25 %Material size is restricted to 60 and 150 mm in order to create a strong floor for the LHD
Placement by LHD
Material size between 60 and 150 mm and up to 350 mm is satisfactory
Placement by slusher
Material compaction can reach 30 to 40 %Impossible to drive the fill tight against the backDistance of placement is between 10 and 30 m
Hydraulic fill
mine water storage
aggregate silo
pipeline for cleared water
water recovering device
pumps
backfill
fill feed pipeline
mixer
slurry recovering
discharge
discharge
Material containing :
crushed rock of up to 50 mm, granulated smelter slags of up to 30 mm,sands of up to 2-3 mm,mill tailings of up to 0.5 mm
cement can be added
is mixed with water with ratio varying from 0.6 to 4 parts of water for 1 part of solid (in weight)
pulp is pumped through 150 mm (75 to 250 mm) pipes up to 1500 m vertically and 600 m horizontally
speed of particles 2.5 to 4 m/sec
Hydraulic fill
Direct transport by pipes
High performance of filling up to 400 m3/h
Fill is stronger compared to dry rock fill with gravity placement
Good wall support and working surface are achieved
Good ventilation control
Full automation is possible
Very sensitive to water concentrationWater (up to 75% in fill) has to be pumped after fillingMuddy haulage waysAdditional capital cost (compared with dry rock fill)
Pneumatic fill
car tipper
conveyer belt
feeder classifier
aggregatesilo
air in feed arrangement
conveyer
crushers
backfill
aggregatesilo
fill feed
pipeline
discharge
Material containing :
tailingssmelter slagcrushed rocksandsgravelof 5 to 100 mm in size
is pouched through 203 mm pipes by air at 34 to 138 kPa pressure
Pneumatic fill
Density of filling is better compared with gravitational dry rock fill
No excess water (compared with hydraulic fill)
Improvement of face ventilation
Fill can be placed tight against the back
High dust emissionIncreased pipe wear (increased capital cost) High consumption of compressed air and so energy consumption ( up to 15 kWh/m3 )Difficulty in producing a good working floorEquipment is large and difficult to move
Cemented rock fill (CRF)
High-density or paste fill
Mill tailings including slimes, sand, waste rock or gravel from 0 to 25 mm are dewatered down to 12-15% of water content, classified and concentrated by elimination of light particles.
In resulting mixture the volume of fine material must exceed the pore-volume of the coarse fraction. So the fill material attains a density of 2.1 t/m3.
3 to 6 % of cement is added to form a stronger fill.
Concrete or mud pump is used to transport the material (85% of solids) by pipeline of 60 to 200 mm diameter with a rate of 20 to 50 m3/h.
Placement can by done by air assisted nozzle
Comparison
Young’sModulus inMPa
Compaction in %
Concret 3000-9000 0
Cemented fill 300-6000 3-5
Hydraulic fill 10-60 10-20
Uncemented rockfill 10-30 15-50
Cost of rockfill
where : Crf -cost of rockfill ;cstope - cost of rockfill dumped in to the stope fill rise,
cstope = 0.4 $/tonne of rockfill ;cplacement - cost of placement of the rockfill in the stope by the rock loading
equipment ;
filloftonne/$,ccCplacementstoperf
The waste material is dropped by gravity to the waste pass
At the underground level the waste is trammed from the waste pass and dumped to the fill rise of the stope
Than the fill is placed in the stope by LHD or slusher
Cost of sandfill
Sand and mill residues are stored in silos on the surface
Sand is drawn into the mine through a vertical sans pass
At the underground mixing station the sand is mixed with water to produce a pulp of 70% solids
The pulp is piped by gravity to the stopes to be filled with a rate of 100 m3/hr
The basic cost of sandfill in place assumed to be 2.5 $/tonne of fill
Cost of cemented fill
The fill of a cement/sand ratio of 1/20 to 1/4 is prepared in the mixing tank on the surface
The fill is pumped in to the mine through 51 to 127 mm diameter feed lines placed either in boreholes or shafts with outlets at all of the mining levels
Than the fill is delivered to different stopes by horizontal drifts
filloftonne/$,CRccCcementsfcf
where : Ccf - cost of cemented fill ;csf - cost of sandfill, cstope = 2.5 $/tonne of rockfill ;ccement - cost of cement ; ccement = 80 $/tonneCR - ratio of cement in the fill ; CR = 6 - 12 % for a layer of fill of 0.9 to 1.2m
Preparation of stope for the cemented fill
Stope preparation can include the installation of stringers, stulls, mesh, cables ...
Cost of the mesh is assumed to be 2.3 $/m²
Cost of stringers, stulls, cables is assumed to be 50 % of the mesh cost
Extra labor to install stringers, stulls, mesh is assumed to be 4.5 hr x 2 workers for 5 meters of stope advance