Primary Mining Method
Sub-Level Longhole retreat.
Information
Waste rock generated from development is dumped in the mined out open stopes. The backfill is not part of the mining sequence, but a way to manage the waste rock.
Primary Mining Method
Cut-and-Fill mining method.
Information
BACKFILL SEQUENCE
- Clean the floor of all remaining ore.
- Crib the Joker chute.
- Install burlap around the chute to retain the fill and to drain the water.
- Install the hydraulic backfill line in the stope from the raise.
- Pour hydraulic fill to a distance of 0.9 m (3ft) from the back.
The specific density of the fill is 67% and the drainage occurs through the raise. The stope miners are required to do the stope preparation for the backfill and a sand crew does the backfilling.
Attached Documents
Primary Mining Method
Sub-Level Longhole stoping.
Information
- The stope is backfilled by dumping development waste rock or borrow material from the surface.
- An opening is mucked from below.
- Cemented rockfill is dumped from the top to fill the opening. This cemented pillar holds the walls and prevents the waste to be mixed with the next ore panel.
EQUIPMENT
- Bumper on the top.
- The back has to be 17.5 m (57 ft) high to dump with a truck.
Secondary Mining Method
Longhole transverse.
Information
- The stope is backfilled by dumping development waste rock or borrow material from the surface.
- An opening is mucked from below.
- Cemented rockfill is dumped from the top to fill the opening. This cemented pillar holds the walls and prevents the waste to be mixed with the next ore panel.
EQUIPMENT
- Bumper on the top.
- The back has to be 17.5 m (57 ft) high to dump with a truck.
Primary Mining Method
Long-hole bench stoping with backfill.
Information
Waste rock.
Primary Mining Method
Overhand cut-and-fill.
Information
The stope is backfilled by sections of 61 m to 76 m (200 ft to 250 ft). Paste fill with 5% cement is used. The sequence for backfilling is:
- A backfill line is painted on the wall.
- Installation of the pipe to the back of the stope: The pipe is positioned in order to be hidden in the fill after filling. This avoids the pipe being in the way when mining the next lift. In order to achieve good filling, the pouring point has to be 6 m (20 ft) from the end of the stope or of previous section.
- Construction of a barricade to isolate the section to be filled.
- Pouring of fill: The filling capacity is 127 tons/hour (140 short tons/hour). The backfill is poured up to 0.3 m (1 ft) from the back.
- Time left for curing: 3 days. The backfill pipes are 10 cm (4 in) Drisco line HDPE pipe. These pipes are 6 m (20 ft) long and are welded together underground. In proper conditions, 183 m (600 ft) of pipes can be welded in one shift.
Secondary Mining Method
Underhand cut-and-fill.
Information
Paste backfill is used with an 8% cement ratio. The backfill is done by sections of a maximum length of 61 m (200 ft) in the following sequence:
- Clean the floor of all remaining ore.
- Install the backfill pipe to the back. The unloading area has to be 6 m (20 ft) from the end of the stope or from the last section.
- A thickness of 0.3 m (1 ft) waste rocks is spread on the floor.
- In the stope where the screen is not required on the walls fro ground support, a chainlink is unrolled on the top of the waste rock in order to support the back of the next lift.
- 1.8-m (6 ft) long Dywidag bolts are installed on a 1.2 m x 1.2 m (4 ft x 4 ft) pattern. The bolts are pushed down the muck and are held vertically with wire lines fixed to the walls. The bolts are plated at their upper end. This plate will be fixed in the backfill after it is poured.
- A wall is built to retain the fill in the 61 m (200 ft) section.
- Backfill is poured up to 0.9 m (3 ft) from the back in the stope. The filling capacity is 127 t/h (140 short tons/hour).
- Time left for curing: 3 days.
The Drisco line HDPE pipes of 10 cm (4 in) diameter are used for backfill pipes. The pipes are 6 m (20 ft) long and are welded together. In proper conditions, 183 m (600 ft) of pipes can be welded in one shift.
Attached Documents
Primary Mining Method
Mechanized Cut-and-Fill.
Information
Once the lift is completely mined out, it is backfilled with either rockfill or hydraulic fill.
If rockfill is used, a scooptram unloads the fill into the stope until it reaches 30 cm to 60 cm (1 ft to 2 ft) from the back of the stope, thus leaving a free space. A line is painted on the wall to identify the waste fill level.
If hydraulic fill is used, waste rock is hauled in the access up to the next lift elevation. A layer of burlap is installed between the stope opening and the waste muck pile to retain the sand. Once the stope is ready, the hydraulic fill is poured into holes previously drilled in the ore.
Attached Documents
Secondary Mining Method
Longhole open stoping.
Information
Hydraulic fill is used to backfill the stope. In order to pour the fill into the stope, two holes are drilled from the upper level down to the stope opening. The hydraulic fill is poured into one hole (fill hole) and the other one (breathing hole) is used for air evacuation.
The bottom of the stope is sealed with a backfill barricade. The barricade is built with cement blocks fixed together with steel rods in an arch shape. Once the blocks are assembled, shortcrete or cement is applied on the surface of the barricade.
Primary Mining Method
Sub-level long-hole retreat with backfill.
Information
In order to achieve a high percentage ore recovery in the Darlot stopes, two types of backfill are used. Once a stope has been mined out, it is generally filled with CAF (Cemented Aggregate Fill) or rough waste (blasted rock from development headings). Generally, stopes with pillars separating them are filled with rough waste, as there are no free faces that need to stand until the adjacent stope is completed.
If it is deemed that no pillar is required, a stope will be filled with CAF. CAF is generated by crushing waste rock to a size of 40 mm (1.5 in), and then mixing this with a cement mixture to achieve a consistency of 5% cement by weight. This mixture sets and allows a stope to stand unsupported while an adjacent stope is being mined. The backfill is delivered to the stopes from the top of each mining block with haul trucks.
Primary Mining Method
Open stope.
Information
No backfilling.
Primary Mining Method
Retreating Longhole.
Information
The waste rock is dumped directly into the stope from the upper drift.
Primary Mining Method
Long-hole.
Information
No backfill is used at that time. When the stope reaches a length of 20 m to 25 m (66 ft to 82 ft), a pillar of 3 m to 5 m (10 ft to 16ft) is left.
Primary Mining Method
Long hole open stope.
Information
No backfilling.
Primary Mining Method
Long-hole sublevel retreat.
Information
The stopes must be backfilled with waste rock and its sequence is to be determined. Firstly, the stopes are opened on a length of 25 m (82 ft) and are backfilled. This distance may vary and, if the conditions allow it, the panel will be entirely blasted before being mucked. The waste rock is stored in the ramps or at the surface.
EQUIPMENT
- Elphinstone scooptram (1700, 2800, 2900).
- Bell 40B truck.
Primary Mining Method
Longhole modified Avoca.
Information
Uncemented rock fill is used as backfill. The waste is brought by truck to a waste pass. The waste pass is accessible from each of the access drifts. A scooptram takes the waste rock from the drawpoints to the stope.
The filling of the stope is done from the superior sub-levels to the open stope. Before proceeding with the mucking, a metal stopper is installed at a distance of 2 m (6.6 ft) from the limit of the open stope. The stopper is anchored to the floor using metal rods and chains attached to the wall. The stopper is kept until the height of the fill reaches the floor elevation. The metal stopper is then removed and replaced by piles of rock created as the waste rock advances.
When the opening is completely filled, a rolled up conveyor belt is attached to the walls above the mucked portion. This is done to position the belt in a way that it will unroll over the muck pile following the blast of the first section of broken ore. Refer to the description of the method in the section «Step by step» for detailed sketches.
Attached Documents
Primary Mining Method
Modified Avoca.
Information
Unconsolidated fill is being placed directly into the open stope from the top level by a scooptram. The stope is filled to the top level reaching a 25-m (82 ft) length to stabilize the walls. Muck bays are developed off the main ramp at every 100 m (328 ft), these bays also serve as rockfill storage.
DIMENSIONS OF THE BAYS:
- Length: 18 m (59 ft).
- Width: 5 m (16 ft).
- Height: 5.5 m (18 ft).
In order to fill a stope, the scooptram must travel on the upper drift. Usually, production holes are previously drilled. To protect hole integrity, steel plates are welded to a metal pipe on each hole.
EQUIPMENT
3-yard scooptram.
Primary Mining Method
Mechanized cut-and-fill stoping.
Information
Once a lift is completed, a scooptram carries the waste rocks in the stope leaving a clear height of 1 m (3.3 ft). The waste rocks from the development is stored underground as much as possible. Since there is insufficient accessible stockpile underground for the backfilling, allowance has been made to truck waste rock from surface.
To optimize the mining sequence of the zone, two 3.3-m (11 ft) crown pillars have to be left. In order to recover these pillars, the mined lift above is filled with cement backfill. Where cement pillar is required, the run of mine mullock will be mixed in the nearest stockpile with cement supplied by an agi-truck. The loader will mix the two constituents together before tramming the fill into the stope. The cement fill placement consists of meshing the floor to reinforce the base of the cement pillar. An initial 1.5 m (5 ft) layer is put in place in order to ensure compaction of the material. Thereafter, the backfill is placed within 1 m (3.3 ft) from the back, retreating to the access. The cement to rock ratio is 10%.
EQUIPMENT
3-yard scooptram
WANNAWAY NO2 LODE
Two cemented backfill pillars are planned in the mining sequence of the zone in order to recover two crown pillars.
Attached Documents