Method of designing a mine backfill system

Abstract

A method of designing a mine backfill system. The method 200 utilises mine design data 201 indicating if one or more stopes within a mine need backfilling. This is achieved by pre-processing the mine design data to generate a three-dimensional graph 207 containing a plurality of nodes associated with a location in the mine, then determining for each of the nodes a geological condition of the respective location. A pathfinding algorithm 211 is operated to determine a path from a backfill material preparation plant through the graph to each of the stopes on the basis of the location state. The pathfinding algorithm may calculate a node score for each neighbouring node that is based on the distance of the selected node and then calculate the total score for each path and then determine a path that minimises node score. An apparatus and computer program for carrying out the design of the mine backfill system are also disclosed.

Description

Technical Field The present invention concerns mine backfill systems. More particularly, but not exclusively, this invention concerns method of designing a mine backfill system. Background Underground mining operations are typically performed in order to enable the extraction of ore. The ore is extracted in blocks known as stopes, leaving behind voids in the earth. When extracting ore, pillars of ore must typically be left in place as structural supports to maintain the geotechnic integrity of the mine. In order to allow the ore in those pillars to be extracted, the stopes are then generally backfilled. The presence of the backfill then maintains the geotechnic integrity of the mine when the pillars are extracted. The material used in backfilling the stopes must generally be prepared at ground level and then pumped underground using a network of pipes known as a reticulation network. The reticulation network links a backfill production plant (for example, on the surface) to each of the stopes to be backfilled. Such reticulation networks can be many kilometres long and can have thousands of backfill discharge locations. Furthermore, the routing of the pipes making up a given reticulation network is a problem with a great many possible solutions and which is subject to a number competing interests. The optimisation of such networks is therefore a complex and difficult task. The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved method of designing a mine backfill system. Summary According to a first aspect of the invention there is provided a method of designing a mine backfill system, the method comprising: obtaining mine design data indicative of one or more stopes within a mine in need of backfilling; pre-processing the mine design data to: generate a three-dimensional graph comprising a plurality of nodes, each node in the plurality being associated with a respective location in the mine, and determine, for each of the nodes in the graph, a location state indicative of a geological condition of the respective location; and operating, for each of the one or more stopes, a pathfinding algorithm to determine, on the basis of the location states, a path through the graph from the stope to the backfill preparation plant. In embodiments, the method can provide more efficient techniques for designing a mine backfill system. By pre-processing mine design data to generate a three-dimensional graph of nodes and determining, for each of the nodes, a location state indicative of a geological condition of the respective location, the method can generate a digital representation of the mine and its geology. Operating a pathfinding on the basis of that digital representation can allow the method to evaluate possible paths from stopes to the backfill preparation plantin order to determine an optimal design for a reticulation network to enable backfilling of the stopes. Thus, the method can facilitate the design of a more efficient mine backfill system. It may be that the mine design data comprises one or more of: three-dimensional stope geometry, stope spatial location data, stope volume, and geotechnical stress fields / conditions of regions surrounding the stope. It may be that the path is for pumping infrastructure (for example, pipes) of a mine backfill system. Thus, the path may indicate a route through the mine for pumping infrastructure (for example, pipes) of a mine backfill system. It may be that the indicated geological condition comprises an indication of a geological structure at the respective location. Thus, it may be that each of the location states comprises an indication of whether the location associated with the respective node is in rock, in ore, in a void, in a tunnel, in a restricted area, or on the surface. It may be that the backfill preparation plant is on the surface. Thus, the method may comprise operating the pathfinding algorithm to determine paths through the graph from each of the one or more stopes to the surface. It may be that operating the pathfinding algorithm comprises calculating, for each of one or more nodes in the graph, a node score. It may be that a node score is indicative of a suitability of the respective node for use in the path. It may be that a node score is indicative of a cost associated with use of the respective node in the path. It may be that the calculating of a node score is performed on the basis of the location state of the selected node. It may be that the calculating of a node score is performed on the basis of a distance of the selected node from the backfill preparation plant. It may be that calculating a node score comprises predicting a cost associated with routing the mine backfill system through the selected node. The predicting of the cost may be performed on the basis of one or more of: the location state of the selected node, a predicted cost of pipework necessary to route the mine backfill system through the respective node, a predicted cost of installation of the pipework, predicted backfill material cost, and whether the respective node is utilised in any previously determined paths. The predicted backfill material cost may be a function of function of stope volume and backfill material composition. It may be that the backfill material composition is determined one the basis of one or more (for example, all) of geotechnical requirements, material flowability, and path routing. It may be that the node score is calculated by way of a cost function. Thus, calculating the node score of a node may comprise evaluating the cost function in respect of the node. It may be that the cost function includes a term associated with the distance of the node from the backfill preparation plant. It may be that the cost function includes a term associated with the location state. It may be that the cost function includes a term associated with one or more properties of the backfill material. It may be that the cost function includes a term associated with a predicted cost of routing the mine backfill system through the node. It may be that the cost function includes one or more terms associated with nodes scores of one or more further nodes (for example, adjacent to the node in respect of which the node score is being calculated). It may be that operating the pathfinding algorithm comprises iteratively evaluating one or more nodes in the graph (for example, on the basis of calculated node scores) to identify the path through the graph. It may be that operating the pathfinding algorithm comprises (for example, starting at a node within the stope in respect of which the pathfinding algorithm is operating), iteratively performing steps of: calculating, for each of a plurality of neighbouring nodes to the current selected node, a node score, and selecting, on the basis of the calculated node score, one of the neighbouring nodes. It may be that one or more (for example, all) of the neighbouring nodes are adjacent to the currently selected node. It may be that the plurality of neighbouring nodes includes one or more nodes which are not adjacent to the currently selected node. It may be that the plurality of neighbouring nodes includes nodes up to two (for example, up to three, five, ten, or twenty) steps away from the currently selected node. It may be that operating the pathfinding algorithm comprises recursively performing the calculating and selecting steps to determine the path through the graph. It may be that calculating a node score in respect of a given comprises recursively evaluating a plurality of nodes. For example, it may be that a node score for the given node is based at least in part on node scores of one or more further nodes adjacent to that given node. Thus, operating the pathfinding algorithm may be said to comprise assessing nodes multiple steps (i.e. steps along a potential path) in advance. It may be that the sum of the calculated node scores in a path comprises a path score. It may be that operating the pathfinding algorithm comprises determining a path that minimises the path score. It will be appreciated that minimising, in this context, refers to identifying a minimum path score within the paths evaluated by the pathfinding algorithm. For any given stope in a given mine design there may be many thousands of possible paths from the stope to the backfill preparation plant. In such cases, it may be that the available time or computing resource precludes the evaluation of all of the possible paths. By calculating node scores and, one the basis of those scores, evaluating possible paths from a stope to the backfill preparation plant, the method can operate to determine an optimised path from the stope to the backfill preparation plant. This can reduce the cost of the mine backfill system. The method may comprise obtaining backfill data indicative of one or more properties of a backfill material to be used in backfilling the one or more stopes. In such cases, it may be that the pathfinding algorithm is operated on the basis of the one or more properties of the backfill material. The indicated one or more properties of the backfill material may comprise one or more of: a material density of the backfill material, a production rate of the backfill material, rheological characteristics of the backfill material, and geotechnical performance metrics. The material used to backfill stopes in a mine is dependent on a number of competing factors. The cement dosage in the backfill material is typically dependent on the geotechnical strength requirements for ground stabilisation as well the water content of the backfill material. The more water present in the backfill material, the higher the cement dosage needed to achieve a given strength. The water content also affects the flowability of the backfill material (for example, a wetter backfill material requires less pressure to pump). Such factors can therefore have a significant impact on the operational costs of a mine backfill system and therefore also on the design of a reticulation network for the mine backfill system. Obtaining backfill data indicative of one or more properties of a backfill material and operating the pathfinding algorithm is operated on the basis of the one or more properties of the backfill material can enable the pathfinding algorithm to account for constraints imposed by the choice of backfill material. The method may comprise, for each of the determined paths, determining one or more minimum requirements of backfill pumping infrastructure to be used in backfilling the respective stope via the path. The determining may be performed on the basis of a volume of the respective stope and the one or more properties of the backfill material. It may be that the one or more minimum requirements of backfill pumping infrastructure comprise one or more of: a minimum diameter of a pipe to be used in backfilling the respective stope via the path, a minimum pressure rating of the pipe, and a minimum class (including, for example, any wear resistance liner) or standard of the pipe. It may be that the one or more minimum requirements comprise a minimum active line pressure. It may be that the determining is performed so as to achieve the minimum active line pressure. In doing so, the method may operate to produce a mine backfill system design that avoids slack flow. The method may comprise, for each of the determined paths, selecting, on the basis of the one or more minimum requirements and the one or more properties of the backfill material, a specification of pipe to be used in constructing the mine backfill system in accordance with the path. The pumping infrastructure required to move backfill material from a backfill production plant (for example, on the surface) to the one or more stopes in the mine can vary depending on a number of factors. For example, the volume of stope to be backfilled via a given path and the flowability of the backfill material will both affect the diameter of pipe required. Thus, determining backfill pumping infrastructure on the basis of the one or more properties of the backfill material can provide a more complete mine backfill system design. It may be that the method comprises calculating, on the basis of the one or more properties of the backfill material and a volume of backfill to be pumped through the pipe, a predicted wear rate of the selected specification of pipe. In such cases, the method may further comprise determining, on the basis of the predicted wear rate, a projected remaining life of the pipe. In this context the remaining life of a pipe refers to a length of time (for example, a number of hours of use) until the pipe must be replaced. Backfill material is typically highly abrasive and can therefore rapidly cause wear on pipes in a reticulation system. Calculating a predicted wear rate of a pipe and, on the basis of that predicted wear rate, determining a projected remaining life of the pipe can enable the mine backfill system design to incorporate information on and inform maintenance planning for the reticulation network. It may be that the mine design data indicates a plurality of stopes. In such cases the method may comprise determining a respective path for each of the plurality of stopes. The method may further comprise identifying two or more overlapping paths. In this context, the term “overlapping paths” refers to paths which pass through a series of the same nodes. The method may further comprise merging the identified two or more overlapping paths. The merging of the identified two or more overlapping paths may comprise replacing the two or more overlapping paths with a single path (for example, to service all of the stopes associated with the two or more overlapping paths). Identifying and merging overlapping paths enables the system to produce a simpler mine backfill system design with reduced duplication in pumping infrastructure. Merging the identified two or more paths may comprise determining one or more further minimum requirements of backfill pumping infrastructure required in order to enable backfilling via the merged path of a combined volume of the stopes associated with the merged path. When two overlapping paths are merged, the resulting merged path must be suitable to service the needs of both overlapping paths. For example, the resulting merged path must be suitable to service the combined volume of all of the stopes serviced by both overlapping paths. The merged path may therefore require different backfill pumping infrastructure to that of either of the overlapping paths. Determining one or more further minimum requirements of backfill pumping infrastructure when merging overlapping paths can help to ensure that the merged path is allocated suitable pumping infrastructure. Merging the identified two or more paths may comprise repeating the operating of the pathfinding algorithm to reassess the merged path on the basis of a combined volume of the stopes associated with the merged path. It may be that the reassessing of the merged path comprises determining a new path, different from the merged path, from a branch point of the merged path to the backfill preparation plant. It will be appreciated that the branch point of a merged path is the final node in the series of nodes forming the merged path before it splits into a plurality of distinct paths. Merging two or more overlapping paths can alter the balance of costs on the basis of which the overlapping paths were originally determined. For example, merging two overlapping paths means that the merged path must now handle the combined volume backfill material required by all of the stopes serviced by the two overlapping paths. This increase in volume of backfill material to be handled can mean that the merged path requires more expensive pumping infrastructure. Whilst previously the optimal solution may have been to route the overlapping paths a relatively long distance through existing tunnels in the mine, the increase in the cost of the pumping infrastructure may mean that it would be more cost-effective to implement the merged path by drilling a borehole (even with the additional associated drilling costs) to allow the merged path to instead take a relatively short route. Similarly, routing a path a longer distance may necessitate use of more flowable backfill material (for example, backfill material having a lower viscosity and / or yield stress). This may be achieved by increasing the water content of the backfill material. Use of backfill material with a higher water content can require increased cement dosage to achieve the required geotechnic performance. It may be that the routing a merged path a relatively long distance results in such an increase in the required water content of the backfill material that the cost of the increased cement content of backfill material (for example, required to maintain the necessary geotechnic performance) outweighs the cost of installing shorter but more expensive pumping infrastructure (which would allow the use of a lower water content and therefore a reduced cement dosage). Thus, repeating the operating of the pathfinding algorithm when overlapping paths are merged can ensure that mine backfill system design is optimised for those changes. It may be that the method further comprises obtaining data indicative of a plurality of design scenarios. Each of the design scenarios may define at least one constraint on the design of the mine backfill system. In such cases, it may be that the method comprises operating, for each of the indicated plurality of design scenarios, the pathfinding algorithm, on the basis of the respective at least one constraint, to generate a respective plurality of mine backfill system designs. The at least one constraint may comprise one or more of: a backfill material to be used, a backfill production rate, and an indication of one or more stopes in the mine to be disregarded. An indication that a stope is to be disregarded may comprise an indication that the mine backfill design system is not required to determine a path to enable that stope to be backfilled. Repeating the operating of the pathfinding algorithm in respect of a plurality of different design scenarios can facilitate the comparison of different specifications for the mine backfill system. For example, the choice of mine backfill material can have a significant impact on the design of a reticulation network. Whilst selecting a cheaper backfill material might at first glance appear to reduce costs, it may be that the use of the cheaper backfill material (for example, due to it having less favourable rheological characteristics) has a knock-on effect of increasing the cost of the reticulation network. Providing a plurality of design scenarios having differing constraints on the design of the mine backfill system and evaluating each of those design scenarios using the pathfinding algorithm can therefore further assist in optimising the design of the mine backfill system. The method may further comprise collating the determined paths to form a complete reticulation network design for the mine backfill system. It may be that the method comprises determining, on the basis of the complete reticulation network design, a bill of materials required to construct the mine backfill system. It may be that the mine design data comprises a schedule of mining activities for the mine. Thus, the method may further comprise receiving data indicative of a schedule of mining activities for the mine. The mining activities may include excavation of a tunnel or stope. The mining activities may include a controlled collapse of a tunnel or stope. The mining activities may include removal of ventilation systems in one or more parts of the mine. It will be appreciated that areas of the mine which have had their ventilation systems removed (for example, to reduce operating costs) may be inaccessible for safety reasons. The schedule of mining activities may indicate one or areas in which pumping infrastructure is not permitted (for example, for safety reasons). Such areas may include haulage zones, tunnels for trucks / loaders / trains, ventilation shafts, hoisting shafts, emergency zones or refuge points, escape ladder ways. The schedule may indicate respective planned excavation dates for one or more (for example, all) of the stopes in the mine. The schedule may indicate respective planned excavation dates for one or more tunnels in the mine. The schedule may indicate planned dates for controlled collapses of one or more tunnels in the mine. It may be that the determining of a location state is performed on the basis of the schedule of mining activities. It may be that one or more of the location states indicates a first geological condition associated with a first period of time and a second geological condition associated with a different second period of time. Thus, it may be that the determined location states are time dependent. It may be that the operating of the pathfinding algorithm is performed on the basis of the schedule. It may be that the method comprises determining (for example, on the basis of the schedule of mining activities) an installation schedule for the mine backfill system. The installation schedule for the mine backfill system may comprise an indication, for each of one or more paths in the reticulation network (for example, for each of the determined paths), of a respective period of time for which the reticulation network associated with the one or more paths is to be in service. The installation schedule for the mine backfill system may comprise an indication of one or more dates on which the reticulation network associated with the one or more paths is to be installed and / or removed. It may be that the installation schedule is determined so as to comply with (for example, to facilitate) the schedule of mining activities. It may be that the method comprises identifying that a first path in the mine backfill system design and a second path in the mine backfill system design are not simultaneously in use. In such cases, it may be that the method comprises generating data indicating that pumping infrastructure used in constructing one of the first and second paths can be reused in the construction of the other. Operating the pathfinding algorithm on the basis of a schedule of planned mining activities for the mine can help to ensure that the mine backfill system design is in conformance with the planned mining activities. It will be appreciated that a mine is not a static construction, but one which changes and evolves over time as further excavation takes place. Similarly, existing excavations are sometimes purposely collapsed in order to maintain the geotechnic integrity of the mine. Operating the pathfinding algorithm on the basis of a schedule of such activities can help to ensure that the pathfinding algorithm is operated on the basis of an accurate assessment of the state of the mine. It may be that the method further comprises receiving data indicative of a stock of pumping infrastructure available for use in the mine backfill system. It may be that the stock of pumping infrastructure comprises one or more pipes. It may be that the indicated stock of pumping infrastructure comprises (for example, consists of) pumping infrastructure that is already owned by an intended operator of the mine backfill system. It may be that the indicated stock of pumping infrastructure is available for reuse following past use in a reticulation network of a mine backfill system (for example, a different second mine backfill system). In such cases, the operating of the pathfinding algorithm may comprise prioritising use of pumping infrastructure in the indicated stock. The prioritising may be performed by reducing a cost associated with the indicated pumping infrastructure when operating the pathfinding algorithm. Receiving data indicative of a stock of pumping infrastructure available for use in the mine backfill system and operating the pathfinding algorithm on the basis of the data can allow the method to make better use of existing stocks of the available pumping infrastructure. This can reduce the cost of the mine backfill design system by facilitating reuse of pumping infrastructure. Thus, operating the pathfinding algorithm on the basis of indicated stock of pipes available for use in the mine backfill system can help further optimise the design of the mine backfill system. According to a second aspect of the invention there is also provided a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out a method according to the first aspect. According to a third aspect of the invention there is also provided an apparatus for designing a mine backfill system, the apparatus comprising: a data retrieval module configured to obtain mine design data indicative of one or more stopes within a mine in need of backfilling; a pre-processing module configured to analyse the mine design data to: generate a three-dimensional graph comprising a plurality of nodes, each node in the plurality being associated with a respective location in the mine, and determine, for each of the nodes in the graph, a location state indicative of a geological condition of the respective location; and a routing module configured to operate, for each of the one or more stopes, a pathfinding algorithm to determine, on the basis of the location states, a path through the graph from the stope to the backfill preparation plant. It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa. Description of the Drawings Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: Figure 1 shows a schematic view of an apparatus for designing a mine backfill system according to a first embodiment of the invention; and Figure 2 shows a flow chart illustrating the steps of a method of designing a mine backfill system according to a second embodiment of the invention. Detailed Description Figure 1 shows a schematic view of an apparatus for designing a mine backfill system 100 according to a first embodiment of the invention. The mine backfill system 100 comprises a data retrieval module 101. The data retrieval module 101 is further configured to operate with a user input device (not shown) to enable an operator of the generative artificial intelligence system 100 to provide user input. The user input device is configured to receive input from the operator and generate corresponding user input data. The data retrieval module 101 further comprises a transceiver (not shown) configured to provide a communication link with one or more remote computing resources (for example, via the internet). In this example embodiment, the communication link comprises be a wireless communication link. Thus, the data retrieval module 101 further comprises an antenna (not shown). However, it will be appreciated that, in other embodiments, the communication link may comprise a wired communication link. The transceiver is configured to receive and generate transceiver data corresponding to data received or to be transmitted over the communication link. The data retrieval module 101 is configured to obtain mine design data 103 indicative of one or more stopes within the mine. In this example embodiment, the mine design data 103 indicates a plurality of stopes. The mine design data 103 further comprises a schedule of mining activities for the mine. It will be appreciated that a mine is not a static construction, but one which changes and evolves over time as further mining activities take place. Thus, the schedule of mining activities indicates change over time of the structure of the mine. The schedule of mining activities indicates respective planned excavation dates for one or more (for example, all) of the stopes in the mine and one or more tunnels in the mine. The schedule also indicates planned dates for controlled collapses of one or more tunnels in the mine. The data retrieval module 101 is further configured to obtain backfill data 105 indicative of one or more properties of a backfill material to be used in backfilling the one or more stopes. The indicated one or more properties of the backfill material include: a material density of the backfill material, a production rate of the backfill material, rheological characteristics of the backfill material, and geotechnical performance metrics. The mine backfill system 100 further comprises a pre-processing module 107. The pre-processing module 107 is configured to receive and pre-process the mine design data 103. The pre-processing module 107 is configured to generate, on the basis of the mine design data 103, a three-dimensional graph comprising a plurality of nodes. Each node in the plurality is associated with a respective location in the mine. Thus, any given location within the mine is associated with a respective one of the plurality of nodes. The pre-processing module 107 is further configured to determine, for each of the plurality of nodes in the graph, a location state indicative of a geological condition of the associated location. Thus, the pre-processing module 107 is configured to determine a plurality of location states. The geological condition is indicative of a geological structure at the respective location. In this example embodiment, each of the location states comprises an indication of whether the location associated with the respective node is in rock, in ore, in a void, in a tunnel, in a restricted area, or on the surface. As discussed above, the mine design data 103 includes a schedule of mining activities. The determining of the location states is performed on the basis of the schedule of mining activities, such that one or more of the location states may indicate a first geological condition associated with a first period of time and a second geological condition associated with a different second period of time. The pre-processing module 101 is configured to generate a data file 109 indicating the determined graph and associated location states. The mine backfill system 100 further comprises a pathfinding algorithm 111. The pathfinding algorithm 111 is configured to receive the data file 109 and, in this example embodiments, also the backfill data 105. The pathfinding algorithm 111 is configured to determine, for each of the plurality of stopes indicated in the mine design data 103, a path through the graph from the stope to the backfill preparation plant. Thus, the pathfinding algorithm 111 is configured to determine a plurality of paths. The pathfinding algorithm 111 is configured to determine the plurality of paths on the basis of the data file 109. Thus, the pathfinding algorithm 111 is configured to determine the plurality of paths on the basis of the determined three-dimensional graph and associated location states. In this example embodiment, the pathfinding algorithm is configured to determine the plurality of paths further on the basis of the backfill data 105. For example, the rheological properties of the backfill material (as indicated by the backfill data 105) may be associated with a minimum bend radius of pipe. In such a case, the pathfinding algorithm may operate to select nodes which comply with that minimum bend radius. The pathfmding algorithm 111 is configured to operate in respect of each stope indicated in the mine design data 103 in turn to determine the plurality of paths. The pathfmding algorithm 111 is configured to determine a path by iteratively evaluating one or more nodes in the graph to identify a route through the graph. The pathfinding algorithm Illis configured to determine a path by selecting a starting node within the stope in respect of which the pathfinding algorithm Illis operating. The pathfmding algorithm 111 then evaluates neighbouring nodes and, on the basis of that evaluation, selects one of those neighbouring nodes as the next node in the path. This process is repeated iteratively until the path reaches the backfill preparation plant. The pathfinding algorithm Illis configured to evaluate a node by calculating a node score. In this example embodiment, the calculating of a node score is performed on the basis of the location state of the selected node, a distance of the selected node from the backfill preparation plant, and a predicted cost of routing the mine backfill system through the associated node. Thus, calculating a node score further comprises predicting a cost associated with routing the mine backfill system through the selected node. The predicting of the cost is performed on the basis of one or more of: the location state of the selected node, a predicted cost of pipework necessary to route the mine backfill system through the respective node, a predicted cost of installation of the pipework, and whether the respective node is utilised in any previously determined paths. Thus, the pathfmding algorithm 111 is configured to determine a path by, starting at a node within respective stope, iteratively performing steps of calculating, for each of a plurality of neighbouring nodes to the current selected node, a node score and selecting, on the basis of the calculated node score, one of the neighbouring nodes. Any given path can be said to have a path score comprising the sum of the calculated node scores in that path. The pathfinding algorithm Illis configured to operate to determine a path that minimises the path score. It will be appreciated that minimising, in this context, refers to identifying a minimum path score from within the paths evaluated by the pathfmding algorithm. For any given stope in a given mine design there may be many thousands of possible paths from the stope to the backfill preparation plant. In such cases, it may be that the available time or computing resource precludes the evaluation of all of the possible paths. The pathfmding algorithm 111 is further configured to determine for each of the paths one or more minimum requirements of backfill pumping infrastructure necessary to implement the associated part of the reticulation network. The determining of the one or more minimum requirements is performed on the basis of the mine design data 103 and the backfill data 105. In this example embodiment, the one or more minimum requirements are determined on the basis of a volume of the associated stope and the one or more properties of the backfill material. The determined one or more minimum requirements comprise one a diameter of a pipe to be used in backfilling the respective stope via the path and a maximum pressure rating of the pipe. However, it will be appreciated that, in other embodiments, the pathfinding algorithm 111 may operate to determine one or more other minimum requirements (for example, by determining a class or standard of pipe to be used). It will be appreciated that the one or more minimum requirements of backfill pumping infrastructure have a significant impact on the cost of implementing the reticulation network, and therefore also significantly impact the optimal path choice for the reticulation network. Thus, the pathfinding algorithm 111 is configured to determine the plurality of paths on the basis of the determined one or more minimum requirements. In this example embodiment, the pathfinding algorithm 111 does so by utilising the determined one or more minimum requirements in the calculation of node scores. Once the pathfinding algorithm 111 has determined a path in respect of each of the stopes indicated in the mine design data 105, the plurality of determined paths can collectively be considered to be a full reticulation network structure. The pathfinding algorithm 111 is configured to then further optimise the reticulation network design by identifying and merging overlapping paths in the structure. The pathfinding algorithm Illis configured to identify two or more overlapping paths by identifying paths which pass through a series of the same nodes. The pathfinding algorithm 111 is further configured to merge the identified two or more overlapping paths. The merging of overlapping paths effectively converts the reticulation network structure from a collection of linear paths into a branching network. The merging of overlapping paths further comprises determining one or more further minimum requirements of backfill pumping infrastructure required in order to enable backfilling via the merged path of a combined volume of the stopes associated with the merged path. It will be appreciated that, when two overlapping paths are merged, the resulting merged path must service the requirement of both of the two overlapping paths. In particular, the merged path much be suitable to enable backfilling of the combined volume of the stopes associated with the overlapping paths. Thus, the pathfinding algorithm 111 is configured to reassess the minimum pumping infrastructure requirements of the merged path. The pathfinding algorithm Illis further configured to repeating the pathfmding on the basis of the newly determined minimum pumping infrastructure requirements of the merged path. The change to the minimum pumping infrastructure requirements of the merged path can alter the balance of cost which led to the selection of the current path. For example, each of the overlapping paths may have had minimum pumping infrastructure requirements that were inexpensively serviced by routing the paths a relatively long distance through existing tunnels in the mine. However, the newly determined minimum pumping infrastructure requirements of the merged path may give rise to a sufficient increase in cost that it becomes be more cost-effective to implement the merged path by drilling a borehole (even with the additional associated drilling costs) to allow the merged path to instead take a relatively short route. Thus, the pathfmding algorithm Illis configured to reassess the merged path on the basis of a combined volume of the stopes associated with the merged path. The pathfinding algorithm Illis configured to output the resulting branching network as an optimised reticulation network structure 115. The mine backfill system 100 further comprises a database 117. The pathfinding algorithm 111 is configured to retrieve from database 117 a plurality of design scenarios 119. Each of the plurality of design scenarios defines at least one constraint on the design of the mine backfill system. The at least one constraint comprises one or more of: a backfill material to be used, a backfill production rate, and an indication of one or more stopes in the mine to be disregarded. The apparatus 100 is configured to operate the pathfmding algorithm 111 in respect of each of the indicated plurality of design scenarios. Operating the pathfmding algorithm 111 in respect of a design scenario comprises operating the pathfinding algorithm on the basis of the respective at least one constraint. Thus, the apparatus is configured to the pathfinding algorithm 111 to generate a respective plurality of mine backfill system designs. The mine backfill system 100 further comprises a pumping infrastructure module 121. The pumping infrastructure module 121 is configured to receive the reticulation network structure 115 and select suitable pumping infrastructure to implement a mine backfill system in accordance with the determined reticulation network structure 115. Thus, the pumping infrastructure module 121 can be said to be configured to select, for each of the paths in reticulation network structure, a specification of pipe to be used in constructing the mine backfill system in accordance with the path. The pumping infrastructure module 121 is configured to output a reticulation network design 123. The reticulation network design 123 indicates not only the structure of the reticulation network, but also pumping infrastructure to be used in constructing the mine backfill system. The mine backfill system 100 further comprises a scheduling module 125. The scheduling module 125 is configured to receive the reticulation network design 123 and determine an installation schedule for the mine backfill system. As discussed above, one or more of the location states may indicate a first geological condition associated with a first period of time and a second geological condition associated with a different second period of time. The scheduling module 125 is configured to determine the installation schedule on the basis of those location states. Thus, the scheduling module 125 can be said to determine the installation schedule on the basis of the schedule of mining activities. The installation schedule comprises one or more dates on which pumping infrastructure in the reticulation network design is to be installed and / or removed. The scheduling module 125 is configured to determine the installation schedule so as to comply with (for example, to facilitate) the schedule of mining activities indicated in the mine design data 105. The scheduling module 125 is further configured to calculate a predicted wear rate of one or more (for example, all) pipes in the reticulation network design 123. The calculating is performed on the basis of on the basis of the one or more properties of the backfill material and a volume of backfill to be pumped through the pipe. The scheduling module 125 is further configured to determine a projected remaining life of the pipe. It will be appreciated that the term “remaining life” refers in this context to a length of time until the pipe must be replaced. The remaining life may be defined in terms of time in use. The determining of the projected remaining life is performed on the basis of the calculated wear rate. The scheduling module 125 is configured to output a scheduled reticulation network design 129. The apparatus 100 further comprises a processor 129 and an associated memory 131. The processor 129 is configured to perform the above-described functions of the apparatus by executing instructions stored in the associated memory 131. Figure 2 shows a flow chart illustrating the steps of a method 200 of designing a mine backfill system. A first step, represented by item 201, of the method 200 comprises obtaining mine design data indicative of one or more stopes (for example, a plurality of stopes) within a mine in need of backfilling. It may be that the mine design data comprises a schedule of mining activities for the mine. An optional second step, represented by item 203, of the method 200 comprises obtaining backfill data indicative of one or more properties of a backfill material to be used in backfilling the one or more stopes. The indicated one or more properties of the backfill material may comprise one or more of a material density of the backfill material, a production rate of the backfill material, rheological characteristics of the backfill material, and geotechnical performance metrics. A third step, represented by item 205, of the method 200 comprises preprocessing the mine design data. The pre-processing of the mine data comprises a first sub-step, represented by item 207, of generating a three-dimensional graph comprising a plurality of nodes, each node in the plurality being associated with a respective location in the mine. The pre-processing of the mine data comprises a second sub-step, represented by item 209, of determining, for each of the nodes in the graph, a location state indicative of a geological condition of the respective location. It may be that each of the location states comprises an indication of whether the location associated with the respective node is in rock, in ore, in a void, in a tunnel, in a restricted area, or on the surface. It may be that the determining of the location states is performed on the basis of the schedule of mining activities. Thus, it may be that one or more of the location states indicates a first geological condition associated with a first period of time and a second geological condition associated with a different second period of time. A fourth step, represented by item 211, of the method 200 comprises operating, for each of the one or more stopes, a pathfmding algorithm to determine, on the basis of the location states, a path through the graph from the stope to the backfill preparation plant. Where the mine design data indicates a plurality of stopes, operating the pathfmding algorithm may comprise determining a respective path for each of the plurality of stopes. It may be that operating the pathfinding algorithm comprises, starting at a node within the stope, iteratively performing steps of: calculating (for example, for each of a plurality of neighbouring nodes to the current selected node), a node score, and selecting, on the basis of the calculated node score, one of the neighbouring nodes. It may be that the calculating of a node score is performed on the basis of the location state of the selected node. It may be that the calculating of a node score is performed on the basis of a distance of the selected node from the backfill preparation plant. It may be that calculating a node score comprises predicting a cost associated with routing the mine backfill system through the selected node. The predicting of the cost may be performed on the basis of one or more of: the location state of the selected node, a predicted cost of pipework necessary to route the mine backfill system through the respective node, a predicted cost of installation of the pipework, and whether the respective node is utilised in any previously determined paths. It may be that the sum of the calculated node scores in a path comprises a path score. It may be that operating the pathfinding algorithm comprises determining a path that minimises the path score. Where the method comprises obtaining backfill data indicative of one or more properties of a backfill material, it may be that the pathfinding algorithm is operated on the basis of the one or more properties of the backfill material. It may be that the method further comprises receiving data indicative of a stock of pipes available for use in the mine backfill system. In such cases, the operating of the pathfinding algorithm may comprise prioritising use of pipes in the indicated stock. An optional fifth step, represented by item 213, of the method 200 comprises identifying and merging two or more overlapping paths. Identifying overlapping paths may comprise identifying two or more paths which are routed through a common series of nodes. Merging the identified two or more paths may comprise determining one or more further minimum requirements of backfill pumping infrastructure required in order to enable backfilling via the merged path of a combined volume of the stopes associated with the merged path. Merging the identified two or more paths may comprise repeating the operating of the pathfinding algorithm to reassess the merged path on the basis of a combined volume of the stopes associated with the merged path. It may be that the reassessing of the merged path comprises determining a new path, different from the merged path, from a branch point of the merged path to the backfill preparation plant. An optional sixth step, represented by item 215, of the method 200 comprises determining infrastructure requirements of the mine backfill system. It may be that determining the infrastructure requirements comprises determining, for each of the determined paths, one or more minimum requirements of backfill pumping infrastructure to be used in backfilling the respective stope via the path. The determining may be performed on the basis of a volume of the respective stope and the one or more properties of the backfill material. It may be that the one or more minimum requirements of backfill pumping infrastructure comprise one or more of: a diameter of a pipe to be used in backfilling the respective stope via the path, a pressure rating of the pipe, and a class or standard of the pipe. The method may comprise, for each of the determined paths, selecting, on the basis of the one or more minimum requirements and the one or more properties of the backfill material, a specification of pipe to be used in constructing the mine backfill system in accordance with the path. Determining the infrastructure requirements may comprise calculating, on the basis of the one or more properties of the backfill material and a volume of backfill to be pumped through the pipe, a predicted wear rate of the selected specification of pipe. Determining the infrastructure requirements may comprise calculating, on the basis of the predicted wear rate, a projected remaining life of the pipe. In this context the remaining life of a pipe refers to a length of time (for example, a number of hours of use) until the pipe must be replaced. An optional seventh step, represented by item 217, of the method 200 comprises collating the determined paths to form a complete design for the mine backfill system. An optional eighth step, represented by item 219, of the method 200 comprises obtaining data indicative of a plurality of design scenarios and repeating the operating of the pathfinding algorithm in respect of each the design scenarios in the plurality. Each of the design scenarios may define at least one constraint on the design of the mine backfill system. The at least one constraint may comprise one or more of a backfill material to be used, a backfill production rate, and an indication of one or more stopes in the mine to be disregarded. It may be that the operating the pathfinding algorithm in respect of a design scenario is performed on the basis of the respective at least one constraint. Thus, the repeating of the operating of the pathfinding algorithm may comprise generating a respective plurality of mine backfill system designs. An optional ninth step, represented by item 221, of the method 200 comprises determining, on the basis of the complete design, a bill of materials required to construct the mine backfill system. An optional tenth step, represented by item 223, of the method 200 comprises determining (for example, on the basis of the schedule of mining activities) an installation schedule for the mine backfill system. It may be that determining the installation schedule comprises receiving data indicative of a schedule of mining activities for the mine. It may be that determining the installation schedule comprises determining (for example, for each of the determined paths) a period of time during which reticulation network associated with a path must be in place in order to comply with the schedule of mining activities. It may be that determining the installation schedule comprises determining installation and / or removal dates for one or more elements of the mine backfill system. Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described. It will be appreciated that not all elements of the illustrated embodiments need necessarily be present in all embodiments of the invention. For example, other embodiments of the apparatus 100 do not include one or more (for example, all) of the database 117, the pumping infrastructure module 121, and the scheduling module 125. In some embodiments, the apparatus 100 is not configured to evaluate a plurality of design scenarios. In some embodiments, the apparatus 100 is not configured to specify pumping infrastructure for use in constructing the mine backfill system. In some embodiments, the apparatus 100 is not configured to determine an installation schedule for the mine backfill system. In some embodiments, the apparatus 100 is configured to determine a bill of materials required to construct the mine backfill system. The determining of the bill of materials may be performed on the basis of the reticulation network design 123. The bill of materials may comprise a list pumping infrastructure (for example, pipes) required to construct the mine backfill system. It will be appreciated that the method of the present invention may also be utilised in respect of applications other than design of mine backfill systems. For example, the method of the present invention may be used in the design of other types of mine infrastructure. Such other mine infrastructure may include water pipes, electrical power lines, and communication wires (for example, optic fibres). Thus, the present invention also provides a method of designing a mine infrastructure system, the method comprising: obtaining mine design data indicative of one or more service consumers within a mine; pre-processing the mine design data to: generate a three-dimensional graph comprising a plurality of nodes, each node in the plurality being associated with a respective location in the mine, and determine, for each of the nodes in the graph, a location state indicative of a geological condition of the respective location; and operating, for each of the one or more service consumers, a pathfinding algorithm to determine, on the basis of the location states, a path through the graph from the service consumer to a service provider. It may be that the service consumer is a consumer of services. Similarly, the service provider may a provider of services. The services may comprise electrical power. Thus, the service consumer may be a location within the mine in need of connection to electrical power supply. The service provider may be an electrical generator or other source of electrical power. The services may comprise water supply. Thus, the service consumer may be a location within the mine in need of connection to a water supply. The service provider may be a water pump or other source of water. The services may comprise communication service. Thus, the service consumer may be a location within the mine in need of connection to a communication network. The service provider may be connection point of the communication network. The method of the present invention may also be used in contexts other than mining. For example, the method of the present invention may be used in the design of irrigation networks. Thus, the present invention also provides a method of designing a reticulation network. It will be appreciated that the apparatus 100 may comprise one or more processors and / or memory. In embodiments, apparatus 100 comprises a processor 129 and an associated memory 131. The processor 129 and the associated memory 131 may be configured to perform one or more of the above-described functions of the apparatus 100. Each device, module, component, machine or function as described in relation to any of the examples described herein (for example, data retrieval module 101, preprocessing module 107, pathfinding algorithm 111, database 117, pumping infrastructure module 121, and scheduling module 125) may similarly comprise a processor or may be comprised in apparatus comprising a processor. One or more aspects of the embodiments described herein comprise processes performed by apparatus. In some examples, the apparatus comprises one or more processors configured to carry out these processes. In this regard, embodiments may be implemented at least in part by computer software stored in (non-transitory) memory and executable by the processor, or by hardware, or by a combination of tangibly stored software and hardware (and tangibly stored firmware). Embodiments also include computer programs, particularly computer programs on or in a carrier, adapted for putting the above-described embodiments into practice. The program may be in the form of non-transitory source code, object code, or in any other non-transitory form suitable for use in the implementation of processes according to embodiments. The carrier may be any entity or device capable of carrying the program, such as a RAM, a ROM, or an optical memory device, etc. The one or more processors of the apparatus 100 may comprise a central processing unit (CPU). The one or more processors may comprise a graphics processing unit (GPU). The one or more processors may comprise one or more of a field programmable gate array (FPGA), a programmable logic device (PLD), or a complex programmable logic device (CPLD). The one or more processors may comprise an application specific integrated circuit (ASIC). It will be appreciated by the skilled person that many other types of device, in addition to the examples provided, may be used to provide the one or more processors. The one or more processors may comprise multiple co-located processors or multiple disparately located processors. Operations performed by the one or more processors may be carried out by one or more of hardware, firmware, and software. The one or more processors may comprise data storage. The data storage may comprise one or both of volatile and non-volatile memory. The data storage may comprise one or more of random access memory (RAM), read-only memory (ROM), a magnetic or optical disk and disk drive, or a solid-state drive (SSD). It will be appreciated by the skilled person that many other types of memory, in addition to the examples provided, may also be used. It will be appreciated by a person skilled in the art that the one or more processors may each comprise more, fewer and / or different components from those described. The techniques described herein may be implemented in software or hardware, or may be implemented using a combination of software and hardware. They may include configuring an apparatus to carry out and / or support any or all of techniques described herein. Although at least some aspects of the examples described herein with reference to the drawings comprise computer processes performed in processing systems or processors, examples described herein also extend to computer programs, for example computer programs on or in a carrier, adapted for putting the examples into practice. The carrier may be any entity or device capable of carrying the program. The carrier may comprise a computer readable storage media. Examples of tangible computer-readable storage media include, but are not limited to, an optical medium (e g., CD-ROM, DVD-ROM or Blu-ray), flash memory card, floppy or hard disk or any other medium capable of storing computer-readable instructions such as firmware or microcode in at least one ROM or RAM or Programmable ROM (PROM) chips. Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

1. A method of designing a mine backfill system, the method comprising: obtaining mine design data indicative of one or more stopes within a mine in need of backfilling;pre-processing the mine design data to:generate a three-dimensional graph comprising a plurality of nodes, each node in the plurality being associated with a respective location in the mine, anddetermine, for each of the nodes in the graph, a location state indicative of a geological condition of the respective location; and operating, for each of the one or more stopes, a pathfinding algorithm to determine, on the basis of the location states, a path through the graph from the stope to the backfill preparation plant.

2. A method according to claim 1, wherein operating the pathfinding algorithm comprises, starting at a node within the stope, iteratively performing steps of: calculating, for each of a plurality of neighbouring nodes to the current selected node, a node score; andselecting, on the basis of the calculated node score, one of the neighbouring nodes.

3. A method according to claim 2, wherein the calculating of a node score is performed on the basis of the location state of the selected node.

4. A method according to claim 2 or 3, wherein the calculating of a node score is performed on the basis of a distance of the selected node from the backfill preparation plant.

5. A method according to any of claims 2 to 4, wherein the calculating of a node score comprises predicting a cost associated with routing the mine backfill system through the selected node.

6. A method according to claim 5, wherein the predicting of the cost is performed on the basis of one or more of: the location state of the selected node, a predicted cost of pipework necessary to route the mine backfill system through the respective node, a predicted cost of installation of the pipework, and whether the respective node is utilised in any previously determined paths.

7. A method according to any of claims 2 to 6, wherein:the sum of the calculated node scores in a path comprises a path score; and operating the pathfinding algorithm comprises determining a path that minimises the path score.

8. A method according to any preceding claim, wherein:the method comprises obtaining backfill data indicative of one or more properties of a backfill material to be used in backfilling the one or more stopes; andthe operating of the pathfinding algorithm is performed on the basis of the one or more properties of the backfill material.

9. A method according to claim 8, wherein the indicated one or more properties of the backfill material comprise one or more of: a material density of the backfill material, a production rate of the backfill material, rheological characteristics of the backfill material, and geotechnical performance metrics.

10. A method according to any preceding claim, wherein the method comprises, for each of the determined paths, determining one or more minimum requirements of backfill pumping infrastructure to be used in backfilling the respective stope via the path.

11. A method according to claim 10 and claim 8 or 9, wherein the determining is performed on the basis of a volume of the respective stope and the one or more properties of the backfill material.

12. A method according to claim 10 or 11, wherein one or more minimum requirements of backfill pumping infrastructure comprise one or more of: a diameterof a pipe to be used in backfilling the respective stope via the path, a pressure rating of the pipe, and a class or standard of the pipe.

13. A method according to any of claims 10 to 12, wherein the method comprises, for each of the determined paths, selecting, on the basis of the one or more minimum requirements and the one or more properties of the backfill material, a specification of pipe to be used in constructing the mine backfill system in accordance with the path.

14. A method according to claim 13 when dependent on claim 8 or 9, wherein the method comprises:calculating, on the basis of the one or more properties of the backfill material and a volume of backfill to be pumped through the pipe, a predicted wear rate of the selected specification of pipe; andon the basis of the predicted wear rate, determining a projected remaining life of the pipe.

15. A method according to any preceding claim, wherein: the mine design data indicates a plurality of stopes; and the method comprises:determining a respective path for each of the plurality of stopes, identifying two or more overlapping paths, and merging the identified two or more overlapping paths.

16. A method according to claim 15 when dependent on any of claims 10 to 14, wherein merging the identified two or more paths comprises determining one or more further minimum requirements of backfill pumping infrastructure required in order to enable backfilling via the merged path of a combined volume of the stopes associated with the merged path.

17. A method according to claim 15 or 16, wherein merging the identified two or more paths comprises repeating the operating of the pathfinding algorithm to reassess the merged path on the basis of a combined volume of the stopes associated with the merged path.

18. A method according to claim 17, wherein the reassessing of the merged path comprises determining a new path, different from the merged path, from a branch point of the merged path to the backfill preparation plant.

19. A method according to any preceding claim, wherein the method further comprises:obtaining data indicative of a plurality of design scenarios, each of the design scenarios defining at least one constraint on the design of the mine backfill system; andfor each of the indicated plurality of design scenarios, operating the pathfinding algorithm, on the basis of the respective at least one constraint, to generate a respective plurality of mine backfill system designs.

20. A method according to claim 19, wherein the at least one constraint comprises one or more of: a backfill material to be used, a backfill production rate, and an indication of one or more stopes in the mine to be disregarded.

21. A method according to any preceding claim, wherein:the mine design data comprises a schedule of mining activities for the mine; andthe determining of the location states is performed on the basis of the schedule of mining activities, such that one or more of the location states indicates a first geological condition associated with a first period of time and a second geological condition associated with a different second period of time.

22. A method according to claim 21, wherein the method further comprises determining, on the basis of the schedule of mining activities, an installation schedule for the mine backfill system.

23. A method according to any preceding claim, wherein each of the location states comprises an indication of whether the location associated with the respective node is in rock, in ore, in a void, in a tunnel, in a restricted area, or on the surface.

24. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out a method according to any preceding claim.5 25. Apparatus for designing a mine backfill system, the apparatus comprising:a data retrieval module configured to obtain mine design data indicative of one or more stopes within a mine in need of backfilling;a pre-processing module configured to analyse the mine design data to: generate a three-dimensional graph comprising a plurality of nodes, 10 each node in the plurality being associated with a respective location in themine, anddetermine, for each of the nodes in the graph, a location state indicative of a geological condition of the respective location; anda routing module configured to operate, for each of the one or more stopes, a15 pathfinding algorithm to determine, on the basis of the location states, a path through the graph from the stope to a backfill preparation plant.

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