THIS INVENTION relates generally to the vertical transport of emulsion explosives, i.e. to the provision of explosives to underground mine workings. In particular, the invention relates to a method of providing an emulsion explosive underground in a mine having a mine shaft and a cage arranged for travelling along the mine shaft, and to an emulsion explosive facility in a mine having a mine shaft and a cage arranged for travelling along the mine shaft.

In deep level (500m+) underground mining the shaft is often the only means of transporting people, material, equipment and explosives to the underground mine workings. The shaft is also used for the removal of waste and ore to the surface for further processing. The Applicant is aware that, particularly in relation to underground mining operations, supply or conveyance of explosives to underground mining sites or underground workings, i.e. underground explosives use sites, is conventionally effected batch-wise, either by conveying the explosives along the mine shaft using a mine cage, or along a ramp or descending road system using a motor vehicle-based transportation system. Typically, the explosives so supplied are in the form of a ready to use explosive product, such as a packaged emulsion explosive, or as bulk Anfex (trade name), or as a bulk emulsion explosive.

The Applicant has found that supply systems of the type described have disadvantages, including the fact that these systems cause a decrease in efficiency of the mine's "shaft time" due to the fact that the explosives are transported in ready-to-use form. More particularly, it will be appreciated that, due to safety concerns, people and mined ore cannot be transported in the same cage or motor vehicle simultaneously with explosives. The transport of explosives therefore potentially restricts mines to after-hours conveyance of explosives. Further, transporting explosives in loading vehicles down inclined road systems has a significant cost implication with regards to wear on vehicles, as only one to two tons of explosive can, from a practical point of view, be transported at a time. One approach which can be followed to alleviate the abovementioned difficulties is to drop the explosives, particularly emulsion explosives, vertically down to the underground mining site along a pipeline or other conduit. However, this approach in itself presents further difficulties and safety concerns.

More than 30 years ago emulsion explosives were developed to replace conventional nitro-glycerine based explosives for safety reasons. These products are inherently safer and more stable to sources of ignition than previous explosives. The main reason for this comes about as a result of the physical separation of the oxidizer from the fuel by a boundary layer. In essence the two components necessary to produce an explosive reaction are still present in an admixture or emulsion although more energy is required to initiate this reaction.

Emulsion explosives however have Minimum Burning Pressures (MBP), generally in the range of 40 to 70 bar; if the emulsion explosive is subjected to a pressure in excess of its MBP, it could detonate if the emulsion explosive is simultaneously subjected to a source of heat. One of the major considerations regarding the safe usage and manufacture of emulsion explosives is thus to operate well below the Minimum Burning Pressure (MBP) of the particular emulsion explosive formulation being used. The MBP of each new emulsion explosive formulation is carefully determined in a series of analytical tests before such a product is introduced to industry. For example, extensive tests have shown that the MBP of the Applicant's underground emulsion explosive formulation, known as UG100, is about 70 bar. Pumps and equipment are specifically designed to ensure that MBP's are never exceeded. This normally requires the use of various safety devices, such as pressure trips, bursting discs and temperature sensors to ensure that operating limits are never exceeded.

The vertical drop of emulsion explosives is limited by the MBP of the particular emulsion formulation as pressure builds up with increasing depth. In essence the vertical drop can be compared to pumping of explosives. If an open-ended pipe is used for transport of an emulsion explosive from the surface to underground mine workings there is no concern with depth provided that the pipe never blocks. A blockage in such a pipe will however lead to hydrostatic pressures considerably higher than the MBP of the emulsion explosive resulting in a situation where the emulsion explosive will detonate if exposed to a heat source. In other words, if emulsion explosives are subjected to pressures above their MBP, as could happen if they are conveyed vertically downwardly for long distances, fuel-oxidiser combustion reactions in the emulsion not only initiate but self-propagate and accelerate to detonation in the presence of an underground fire or other source of heat. Deep vertical dropping of emulsion explosives is therefore extremely hazardous due to the increase in emulsion explosive pressure or hydrostatic head that can potentially take place.

Having understood the above the Applicant at the priority date of this invention recommends that installations of a downwardly extending transfer pipe, to a maximum depth of 500m, should always for safety reasons be implemented via a separate bore-hole instead of the shaft and cage access of a mine. The potential for accidents with people in close proximity to a pipe containing emulsion explosive routed down a mine shaft is deemed to be an unacceptably high risk. The Applicant at the priority date of this invention also does not recommend dropping emulsion explosive vertically over distances greater than about 500m. As will be appreciated, two separate 500m drops in sequence, with a break between the drops, will also allow a safe method of going deeper.

A major challenge that thus still faces the emulsion explosives industry is to develop a solution to enable mines to transfer emulsion explosives beyond the 500m mark safely. Preferably, such a solution should also assist the mine with minimizing the amount of shaft time required for the transportation of bulk explosives to the underground mine workings.

A method of transporting an emulsion explosive vertically, particularly over vertical distances longer than 500m, and a facility for such transport, which avoid or at least lessen the problems mentioned hereinbefore, would thus be welcomed.

According to one aspect of the invention, there is provided a method of providing an emulsion explosive underground in a mine having a downwardly extending mine shaft and a cage arranged for travelling along the mine shaft, the method including transferring an emulsion explosive fuel underground;

transferring an emulsion explosive oxidiser along a downwardly extending conduit located inside the mine shaft from a first elevation to a second, underground elevation below the first elevation; and

mixing the emulsion explosive fuel and the emulsion explosive oxidiser underground in the mine to provide an emulsion explosive.

The emulsion explosive fuel and the emulsion explosive oxidiser are thus transferred underground separately of each other, and not as an admixture or emulsion of the two.

Transferring an emulsion explosive fuel underground may include transferring the emulsion explosive fuel underground in a cassette or a container or a tanker vehicle. This will avoid the cost of installing a conduit for the emulsion explosive fuel, which forms a minor component of the emulsion explosive compared to the emulsion explosive oxidiser.

Instead, or in addition, transferring an emulsion explosive fuel underground may include transferring the emulsion explosive fuel along a downwardly extending conduit located inside the mine shaft from a third elevation to a fourth, underground elevation below the third elevation, the conduit used for the emulsion explosive fuel being a different conduit than the conduit used for the emulsion explosive oxidiser.

Typically, mixing the emulsion explosive fuel and the emulsion explosive oxidiser underground in the mine provides a water-in-oil emulsion suitable for use as an emulsion explosive.

Preferably, the conduit for the emulsion explosive fuel, when present and the conduit for the emulsion explosive oxidiser are located against opposite sides of the mine shaft. In this way, the distance between the conduits in the mine shaft can be maximised. The conduits may be pipes. In one embodiment of the invention, the pipes are of a synthetic plastics or polymeric material, e.g. high-density polyethylene (HDPE) pipes.

The emulsion explosive fuel may be selected from the group consisting of middle distillate fuel oil, No. 2 diesel fuel oil, mining solvents, and mixtures of two or more thereof. Typically, the emulsion explosive fuel is No. 2 diesel fuel (any of the No. 2 grade diesel fuels according to ASTM D975).

The emulsion explosive oxidiser is typically a water solution of an oxidiser, with the oxidiser thus typically being in the form of a dissolved salt. The oxidiser may be selected from the group consisting of ammonium nitrate, other nitrate containing salts, and mixtures thereof. Typically, the oxidiser is ammonium nitrate.

The method may include transferring an emulsifier underground.

The emulsifier may be admixed with the emulsion explosive fuel. Thus, the method may include transferring an admixture of the emulsion explosive fuel and the emulsifier underground, e.g. along said downwardly extending conduit located inside the mine shaft from said third elevation to said fourth, underground elevation below the third elevation.

The emulsifier may include one or more PIBSA based emulsifiers.

The second underground elevation may be more than 500m below the first elevation.

The fourth underground elevation may be more than 500m below the third elevation.

The first elevation and/or the third elevation may be above ground, or at ground or surface level. The first elevation and the third elevation may be at the same elevation or level.

The second elevation and the fourth elevation may be at the same elevation or level underground.

The method may include transferring the emulsion explosive fuel into an underground fuel storage facility, e.g. located at the fourth underground elevation, or at another underground location.

The method may include transferring the emulsion explosive oxidiser into an underground oxidiser storage facility, e.g. located at the second underground elevation, or at another underground location.

The method may include transferring the emulsion explosive fuel and the emulsion explosive oxidiser separately from each other in a direction away from the mine shaft, before the emulsion explosive fuel and the emulsion explosive oxidiser are mixed underground in the mine to provide an emulsion explosive. The emulsion explosive fuel and the emulsion explosive oxidiser may be transferred separately in a direction away from the mine shaft, e.g. along a mine gallery, which may be horizontal or inclined, towards a working face of the mine, before they are mixed. Preferably, the emulsion explosive fuel and the emulsion explosive oxidiser are transferred separately in a direction away from the mine shaft under gravity only, so that no pump is used to transfer either the emulsion explosive fuel or the emulsion explosive oxidiser away from the mine shaft. Advantageously, transferring the emulsion explosive fuel and the emulsion explosive oxidiser separately from each other in a direction away from the mine shaft, before the emulsion explosive fuel and the emulsion explosive oxidiser are mixed underground in the mine to provide an emulsion explosive, eliminates the costly and time consuming operation of moving explosives underground in the mine away from the mine shaft towards working faces of the mine.

Mixing the emulsion explosive fuel and the emulsion explosive oxidiser underground in the mine to provide an emulsion explosive may include withdrawing emulsion explosive fuel from the underground fuel storage facility and mixing the withdrawn emulsion explosive fuel and the emulsion explosive oxidiser.

Mixing the emulsion explosive fuel and the emulsion explosive oxidiser underground in the mine to provide an emulsion explosive may include withdrawing emulsion explosive oxidiser from the underground oxidiser storage facility and mixing the withdrawn emulsion explosive oxidiser and the emulsion explosive fuel.

In one embodiment of the invention, mixing the emulsion explosive fuel and the emulsion explosive oxidiser underground in the mine to provide an emulsion explosive includes withdrawing emulsion explosive fuel from the underground fuel storage facility and withdrawing emulsion explosive oxidiser from the underground oxidiser storage facility and mixing the withdrawn emulsion explosive oxidiser and the withdrawn emulsion explosive fuel to provide an emulsion explosive.

The withdrawn emulsion explosive oxidiser and the withdrawn emulsion explosive fuel may be mixed at a mixing location distanced from the underground fuel storage facility and/or from the underground oxidiser storage facility. The mixing location may be horizontally and/or vertically distanced from the underground fuel storage facility and/or from the underground oxidiser storage facility.

The method may include transferring the emulsion explosive, obtained from mixing the emulsion explosive fuel and the emulsion explosive oxidiser underground in the mine, vertically over a distance of up to 500m in a conduit. Typically, the emulsion explosive is transferred downwardly to a lower elevation or level in the mine.

In this specification, by transferring the emulsion explosive vertically is meant that the emulsion explosive is transported or transferred from a higher elevation to a lower elevation. Although the emulsion explosive may be transported or transferred along a vertical path, this is not required. In other words, where the explosive is fed from and where the emulsion explosive is delivered to do not necessarily have to be vertically aligned, although these two points will be at different elevations, typically with the delivery point being lower than the feed point, and with the difference in elevation not being more than 500m.

Mixing the emulsion explosive fuel and the emulsion explosive oxidiser underground in the mine to provide an emulsion explosive may include using a mobile or transportable underground mixing facility to mix the fuel and oxidiser. The mobile or transportable underground mixing facility may include a skid.

The underground mixing facility may include an emulsification device, e.g. a jet mixer or stir pot or the like. The emulsification device may be mounted on said skid.

A static head under which the emulsion explosive fuel and the emulsion explosive oxidiser are respectively available underground in the mine may be used to mix the emulsion explosive fuel and the emulsion explosive oxidiser underground in the mine to provide an emulsion explosive thereby eliminating the use of pumps to mix the emulsion explosive fuel and the emulsion explosive oxidiser. The elimination of pumps by relying on gravity feed of the emulsion explosive fuel and the emulsion explosive oxidiser for mixing the emulsion explosive fuel and the emulsion explosive oxidiser underground provides a more robust system, reduces maintenance, and lessens capital and operating costs.

Transferring an emulsion explosive fuel and transferring an emulsion explosive oxidiser along their respective, separate downwardly extending conduits located inside the mine shaft may include allowing the fuel and oxidiser to travel down their respective, separate conduits under gravity alone. Thus, preferably, no mechanical pumping of the emulsion explosive fuel to feed the emulsion explosive fuel into its associated conduit is used. Also, preferably, no mechanical pumping of the emulsion explosive oxidiser to feed the emulsion explosive oxidiser into its associated conduit is used.

Typically, the method includes adding a sensitiser or density reducing agent underground to the emulsion explosive to convert the emulsion explosive underground from an unsensitised emulsion explosive into a sensitised emulsion explosive with a reduced bulk density, prior to the emulsion explosive being used underground. The sensitiser may be selected from the group consisting of air, a chemical gassing agent, ammonium nitrate prills, perlite, expanded plastics bodies, hollow glass bodies or spheres, phenolic microspheres, and mixtures of two or more thereof. One example of a chemical gassing agent is sodium nitrate.

The sensitiser may be added immediately before the emulsion explosive is loaded into a blast hole.

The emulsion explosive fuel may be transferred from an emulsion explosive fuel reservoir at said third elevation.

The emulsion explosive oxidiser may be transferred from an emulsion explosive oxidiser reservoir at said first elevation.

According to another aspect of the invention, there is provided an emulsion explosive facility in a mine having a mine shaft and a cage arranged for travelling along the mine shaft, the facility including

an emulsion explosive oxidiser conduit located inside the mine shaft and extending downwardly from a first elevation to a second, underground elevation below the first elevation; and

an underground mixing facility to mix emulsion explosive fuel present underground and emulsion explosive oxidiser transferred underground by the emulsion explosive oxidiser conduit to provide an emulsion explosive.

The facility may include an emulsion explosive fuel conduit located inside the mine shaft and extending downwardly from a third elevation to a fourth, underground elevation below the third elevation, the emulsion explosive fuel conduit being a different conduit than the emulsion explosive oxidiser conduit.

The emulsion explosive fuel conduit, when present and the emulsion explosive oxidiser conduit may respectively be a conduit as hereinbefore described. The first and/or the second and/or the third and/or the fourth elevation may be as hereinbefore described. Thus, the second, underground elevation may be more than 500m below the first elevation and the fourth, underground elevation may be more than 500m below the third elevation.

The emulsion explosive facility may include an underground fuel storage facility, e.g. located at the fourth underground elevation, or at another underground location.

The emulsion explosive facility may include an underground oxidiser storage facility, e.g. located at the second underground elevation, or at another underground location.

The underground mixing facility may be as hereinbefore described.

The underground mixing facility may be positioned at a mixing location distanced from the underground fuel storage facility and/or from the underground oxidiser storage facility. The mixing location may be horizontally and/or vertically distanced from the underground fuel storage facility and/or from the underground oxidiser storage facility.

The emulsion explosive facility may include an emulsion explosive fuel reservoir at said third elevation.

The emulsion explosive facility may include an emulsion explosive oxidiser reservoir at said first elevation.

The emulsion explosive facility may include an emulsion explosive conduit to transfer emulsion explosive, obtained from mixing the emulsion explosive fuel and the emulsion explosive oxidiser underground in the mine, vertically over a distance of up to 500m. Typically the emulsion explosive conduit is arranged to transfer emulsion explosive downwardly to a lower elevation or level in the mine. The emulsion explosive facility may be characterised in that the emulsion explosive facility does not have an emulsion explosive fuel pump in an emulsion explosive fuel conduit running between the underground fuel storage facility and the underground mixing facility.

The emulsion explosive facility may be characterised in that the emulsion explosive facility does not have an emulsion explosive oxidiser pump in an emulsion explosive oxidiser conduit running between the underground oxidiser storage facility and the underground mixing facility.

The underground mixing facility may thus be gravity fed with emulsion explosive fuel from the underground fuel storage facility and/or gravity fed with emulsion explosive oxidiser from the underground oxidiser storage facility. Instead, or in addition, the underground mixing facility may be gravity fed from the emulsion explosive oxidiser conduit located inside the mine shaft and extending downwardly from said first elevation to said second, underground elevation below the first elevation, and/or the underground mixing facility may be gravity fed from said emulsion explosive fuel conduit located inside the mine shaft and extending downwardly from said third elevation to said fourth, underground elevation below the third elevation.

The emulsion explosive facility may include underground conduits to transfer the emulsion explosive fuel and the emulsion explosive oxidiser separately from each other in a direction away from the mine shaft, towards said underground mixing facility. These conduits may for example run along a horizontal or inclined mine gallery away from the mine shaft to a working face of the mine, where the underground mixing facility may be located, so that the emulsion explosive can be manufactured at or near the working face.

The underground conduits to transfer the emulsion explosive fuel and the emulsion explosive oxidiser separately from each other in a direction away from the mine shaft, towards said underground mixing facility, may run from said underground fuel storage facility and said underground oxidiser storage facility respectively. Instead, or in addition, the underground conduits to transfer the emulsion explosive fuel and the emulsion explosive oxidiser separately from each other in a direction away from the mine shaft, towards said underground mixing facility, may respectively branch off from the emulsion explosive fuel conduit located inside the mine shaft and extending downwardly from said third elevation to said fourth, underground elevation below the third elevation and from the emulsion explosive oxidiser conduit located inside the mine shaft and extending downwardly from said first elevation to said second, underground elevation below the first elevation.

The invention extends to a mine which includes

a mine shaft and a cage arranged for travelling along the mine shaft;

an emulsion explosive oxidiser conduit located inside the mine shaft and extending downwardly from a first elevation to a second, underground elevation below the first elevation; and

an underground mixing facility to mix emulsion explosive fuel present underground and emulsion explosive oxidiser transferred underground by the emulsion explosive oxidiser conduit to provide an emulsion explosive.

The mine shaft may be substantially vertical.

The mine may include an emulsion explosive fuel conduit and/or an underground fuel storage facility and/or an underground oxidiser storage facility and/or an emulsion explosive fuel reservoir and/or an emulsion explosive oxidiser reservoir and/or an emulsion explosive conduit as hereinbefore described.

The underground mixing facility of the mine may be as hereinbefore described.

The invention will now be described, by way of example, with reference to the single accompanying diagrammatic drawing which shows a mine employing the method in accordance with the invention to provide an emulsion explosive underground, with an enlarged portion of the drawing showing a mobile underground mixing facility in more detail.

Referring to the drawing, reference numeral 10 generally indicates a mine with a vertical mine shaft 12 and a cage 14 arranged for travelling upwardly and downwardly along the mine shaft 12. A number of mine galleries 1 6.1 , 1 6.2, 1 6.3 and 1 6.4 are also shown at various underground levels or elevations of the mine 10. All of the illustrated galleries 1 6.1 to 1 6.4 branch off from the shaft 12 and are more than 500m below the surface, which is generally indicated by reference numeral 18.

An emulsion explosive oxidiser reservoir 20 for keeping an emulsion explosive oxidiser, in the form of an ammonium nitrate solution in water, is provided on the surface 18, in the vicinity of the shaft 12. Similarly, an emulsion explosive fuel reservoir 22 for holding No. 2 diesel fuel (or a similar fuel suitable for use as part of an emulsion explosive) is provided on the surface 18 in the vicinity of the shaft 12. The reservoir 20 and the reservoir 22 are physically separated by the shaft 12. Although this is not essential, it is desirable to keep the ammonium nitrate solution and the No. 2 diesel fuel as far apart as is practically possible to enhance safety.

An underground oxidiser storage facility 24, comprising a pair of vented ammonium nitrate solution tanks 24.1 and 24.2, is located in the gallery 1 6.1 . The gallery 16.1 is located off to one side from the shaft 12. Opposite the gallery 1 6.1 , the gallery 1 6.2 is located off to another side of the shaft 12 and houses an underground fuel storage facility 26 comprising a pair of vented diesel tanks 26.1 and 26.2.

An emulsion explosive oxidiser conduit 28, in the form of a high-density polyethylene pipe, runs from the emulsion explosive oxidiser reservoir 20 to the ammonium nitrate solution tanks 24.1 and 24.2. The conduit 28 is routed along one vertical side of the shaft 12. Against an opposite vertical side of the shaft 12, an emulsion explosive fuel conduit 30 in the form of a high-density polyethylene pipe provides flow communication between the emulsion explosive fuel reservoir 22 and the diesel tanks 26.1 and 26.2.

A twenty ton batch metering device 32 is located in the conduit 28 between the reservoir 20 and the tanks 24.1 , 24.2.

A mobile or transportable underground mixing facility 34 is shown in the gallery 16.3. An enlarged portion of the drawing also shows the mixing facility 34 in more detail. The gallery 16.3 is at a lower level than the galleries 16.1 and 16.2 and the mobile underground mixing facility 34 is thus vertically and horizontally spaced from the underground oxidiser storage facility 24 and the underground fuel storage facility 26.

The mobile underground mixing facility 34 includes a skip 36 carrying an emulsification device in the form of a jet mixer 38, an ammonium nitrate solution meter 40 and a control panel 42. Although a jet mixer is illustrated in the drawing (or more accurately a container within which the jet mixer is housed), any suitable mixing device or emulsification device may be used to mix ammonium nitrate solution and diesel fuel oil to provide an emulsion. Preferably however, the mixing device should have few, if any moving parts.

A vented transfer pipe 44 establishes flow communication between the underground oxidiser storage facility 24 and the mobile underground mixing facility 34. Similarly, a vented transfer pipe 46 establishes flow communication between the underground fuel storage facility 26 and the mobile underground mixing facility 34.

An emulsion explosive conduit 48 runs from the mobile underground mixing facility 34 down into the gallery 1 6.4 to feed into an emulsion explosive storage tank or silo 50. A homogeniser 52 is located in the conduit 48, between the jet mixer 38 and the emulsion explosive storage tank 50.

As shown in the drawing, the emulsion explosive conduit 48 splits to provide the potential to load emulsion explosive into an underground tanker vehicle 54. Another underground tanker vehicle 56 is shown in the gallery 1 6.4, being loaded with emulsion explosive from the emulsion explosive storage tank 50.

The drawing also shows an ammonium nitrate solution plant 58 and a surface tanker vehicle 60 for transporting ammonium nitrate solution from the ammonium nitrate solution plant 58 to the emulsion explosive oxidiser reservoir 20.

The reservoirs 20, 22, the conduits 28, 30, the storage facilities 24, 26 and the mixing facility 34 form part of an emulsion explosive facility by means of which the mine 10 can be provided underground with an emulsion explosive. For clarity, the drawing does not show all of the valves, pressure gauges, flow meters, bursting discs, pumps and the like that would typically form part of such an emulsion explosive facility. The use of these components is however well known to persons skilled in the art and need not be described for an understanding of the invention.

Ammonium nitrate solution, as an emulsion explosive oxidiser, is transferred from the ammonium nitrate solution plant 58 by means of the tanker vehicle 60 by road to the mine 10, where the ammonium nitrate solution is pumped from the tanker vehicle 60 into the emulsion explosive oxidiser reservoir 20. No. 2 diesel fuel oil is transferred in similar fashion to the mine 10 and pumped into the emulsion explosive fuel reservoir 22.

The ammonium nitrate solution is transferred in 20-ton batches, as measured by the twenty ton batch metering device 32, by means of the emulsion explosive oxidiser conduit 28 to the ammonium nitrate solution tanks 24.1 and 24.2. Typically, the ammonium nitrate solution is fed by means of gravity only to the ammonium nitrate solution tanks 24.1 and 24.2. In other words, typically, a pump is not required to transfer the ammonium nitrate solution from the surface 18 to the ammonium nitrate solution tanks 24.1 and 24.2.

The No. 2 diesel fuel oil, already admixed with an emulsifier such as a PIBSA based emulsifier, is similarly transferred under gravity only by means of the emulsion explosive fuel conduit 30 from the emulsion explosive fuel reservoir 22 to the diesel tanks 26.1 and 26.2.

Advantageously, during transfer of the emulsion explosive oxidiser and the emulsion explosive fuel respectively in conduits 28 and 30, it is not necessary to stop the transport of people, equipment or ore by means of the cage 14.

When it is required to have emulsion explosive available for blasting purposes underground, ammonium nitrate solution is transferred under gravity from the ammonium nitrate solution tank 24.1 or 24.2 to the mobile underground mixing facility 34 using the vented transfer pipe 44, and diesel fuel oil is transferred under gravity from the diesel tank 26.1 or 26.2 by means of the vented transfer pipe 46 to the mobile underground mixing facility 34. In the jet mixer 38, the ammonium nitrate solution and the No. 2 diesel fuel oil are emulsified to provide an unsensitised water-in-oil emulsion explosive. The emulsification process is controlled by means of the control panel 42 and the ammonium nitrate solution meter 40 is used to ensure the correct ratio between ammonium nitrate solution (the major component) and No. 2 diesel fuel oil (the minor component). The unsensitised emulsion explosive is transferred from the jet mixer 38 through the homogeniser 52 to the emulsion explosive storage tank 50, from where it can be transported by means of an underground tanker vehicle (i.e. a mobile charger unit or vehicle for loading blast holes with emulsion explosive) such as the tanker vehicle 56 to a place where blasting is being done. Alternatively, or in addition, emulsion explosive can be transferred directly from the homogeniser 52 into a tanker vehicle such as the tanker vehicle 54 for transporting to a blasting area.

Immediately before blasting, the emulsion explosive is sensitised. Any one of a number of conventional sensitising methods, such as chemical gassing for example, may be used to reduce the bulk density of the emulsion explosive, whereafter the emulsion explosive is used for underground blasting purposes. Typically, sodium nitrate is added to the emulsion explosive by the tanker vehicle 54 or 56 to gas and hence to sensitise the emulsion explosive.

Advantageously, dropping the emulsion explosive oxidiser to depths of more than 500m by means of the emulsion explosive oxidiser conduit running down the mine shaft 12 poses no safety threats from an explosives perspective as the emulsion explosive oxidiser is not admixed with any fuel and thus does not have a Minimum Burning Pressure. At this stage, the oxidiser is not classified as an explosive. Also the dropping of the emulsion explosive fuel by means of the conduit 30 running down the mine shaft 12 does not pose any particular safety concerns from an explosives perspective. The transfer of diesel fuel in this manner is an everyday practice in deep- level mining.

Advantageously, the emulsion explosive oxidiser and the emulsion explosive fuel on their own are Newtonian fluids. Both of these components have a rheological behaviour similar to water and thus flow like water, meaning that they can be transferred with ease under gravity alone using conventional conduits such as PVC or HDPE conduits.

The mixing technology used for the mobile underground mixing facility 34, as illustrated, is known and requires little modification to be adapted for underground use and modularisation for ease of transport underground.

Location of the underground oxidiser storage facility 24 and the underground fuel storage facility 26, as well as location of the mobile underground mixing facility 34 and the emulsion explosive storage tank 50 underground enhances security as access to the equipment and to emulsion explosives is limited.

The emulsion explosive oxidiser and the emulsion explosive fuel can advantageously be transferred underground over large distances to locations horizontally remote from the mine shaft 12, using gravity flow only, before being mixed at or near a working face. This saves so-called tramming costs or transport costs of emulsion explosive from the mine shaft 12 to the working face.

If required, the emulsion explosive produced by the mobile underground mixing facility 34 can be transferred vertically and underground for distances of up to 500m, as illustrated by the emulsion explosive conduit 48, with relative safety.

Although not shown in the drawing, the mine 10 can employ a number of mobile underground mixing facilities 34 to manufacture the required quantities of emulsion explosive close to where they are needed.

Advantageously, management of the mine 10 can control the amount of emulsion explosive required to be manufactured on a daily basis. This allows for development and manufacture of a more cost-effective explosives product with a short shelf life.

In the mine 10, as illustrated, available shaft time is increased as no time is required to transport the bulk emulsion explosive to the underground workings.