1. Filling of mined-out openings Dry waste fill Hydraulic fill Cemented rock fill (CRF) Paste fill

2. 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 Waste breaking Blast holes

3. 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

4. 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

5. 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

6. 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 back Distance of placement is between 10 and 30 m

7. 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

8. Hydraulic fill Direct transport by pipes High performance of filling up to 400 m 3 /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 concentration Water (up to 75% in fill) has to be pumped after filling Muddy haulage ways Additional capital cost (compared with dry rock fill)

9. Pneumatic fill car tipper conveyer belt feeder classifier aggregate silo air in feed arrangement conveyer crushers backfill aggregate silo fill feed pipeline discharge Material containing : tailings smelter slag crushed rock sands gravel of 5 to 100 mm in size is pouched through 203 mm pipes by air at 34 to 138 kPa pressure

10. 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 emission Increased pipe wear (increased capital cost) High consumption of compressed air and so energy consumption ( up to 15 kWh/m 3 ) Difficulty in producing a good working floor Equipment is large and difficult to move

11. Cemented rock fill (CRF)

12. 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/m 3 . 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 m 3 /h. Placement can by done by air assisted nozzle

13. Comparison

14. Cost of rockfill where : C rf - cost of rockfill ; c stope - cost of rockfill dumped in to the stope fill rise, c stope = 0.4 $/tonne of rockfill ; c placement - cost of placement of the rockfill in the stope by the rock loading equipment ; 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

15. 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 m 3 /hr The basic cost of sandfill in place assumed to be 2.5 $/tonne of fill

16. 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 where : C cf - cost of cemented fill ; c sf - cost of sandfill, c stope = 2.5 $/tonne of rockfill ; c cement - cost of cement ; c cement = 80 $/tonne CR - ratio of cement in the fill ; CR = 6 - 12 % for a layer of fill of 0.9 to 1.2m

17. 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