3D Stockpile Modelling
Stockpile Models in MineMarket
MineMarket supports several stockpile models, such as weighted average grade (WAG), first-in, first-out (FIFO) and last-in, first-out (LIFO). These stockpile models are relatively simplistic. Transacting to and from them is a simple matter of providing a quantity to be added or subtracted. Often for interim stockpiles (such as hoppers or train loading bins) or despatches (trains, trucks, shipments and barges) these models are sufficient. MineMarket also supports a 3D stockpile model, which allows stockpile quantities and qualities to be tracked in three dimensions.
Important: Most stockpiles should be created as weighted average grade (WAG). If not carefully managed, using 3D stockpiles may create system performance issues.
3D Stockpiles
A 3D stockpile is a digital representation of a physical stockpile of mined materials, such as coal or ore. The representation is created using three-dimensional (3D) modelling and visualisation techniques, which help in calculating and monitoring the volume, mass and grade distribution of the stockpile, adjusted after each stacking or reclaiming transaction. This data enables mine managers to optimise material extraction, logistics, and quality control.
The 3D stockpile modelling engine used by MineMarket is called 'CHASM', a product of the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO). The CHASM engine models how an ideal homogeneous free-flowing material tumbles as it is stacked and reclaimed in various ways. CHASM is initialised with the shape of a three-dimensional stockpile, consisting of a base and a volume of material, and returns the result after stacking or reclaiming transactions. CHASM is designed to model 'long horizon' stockpiles, which are typically short in width and long in length, and where stackers and reclaimers move along the long axis.
MineMarket interfaces to CHASM when the following operations are performed on a 3D stockpile:
- Stacking transactions (adding material)
- Reclaiming transactions (removing material)
- Shape adjustment (altering existing material to conform to a specified shape)
For configuration, see 3D Stockpiles.
Stacking and Reclaiming Methods
CHASM supports several different stacking and reclaiming methods, which correspond to the more common types of physical stackers and reclaimers in use at various bulk material handling operations.
For each stacking or reclaiming transaction, CHASM requires information about:
- The material's physical properties: the angle of repose (the natural angle that a free-standing stockpile of this material makes with the horizontal plane)
- The stack or reclaim operation itself: the positional and volumetric constraints (X and Y positions, maximum height)
For configuration, see Stackers and Reclaimers.
Quality on 3D Stockpiles
The stacking transactions define not only the shape, but also the quality values and the contributor data of the stacked material.
A reclaiming transaction may contain more than one batch that was previously stacked, where each batch has its own set of quality parameters. When transferring this reclaimed material to the destination stockpile, MineMarket treats it as a homogeneous block of material and calculates the weighted average of these reclaimed batches to determine the overall material's quality. This is the assumed source quality for the reclaiming transaction, but like any transaction in MineMarket, it may also have sample information applied to it to override the assumed source quality.
Stockpile State
The stockpile state is the full 3D picture for the stockpile at a point in time. The state consists of the stockpile geometry information (base points, width, length and X-Y resolution) and the contents of the stockpile.
Each grid point may contain a vertical 'column' of material, with the grid point being in the centre of the column. The cross-sectional area of the column corresponds to the base resolution described earlier. A column is made up of one or more layers, where each layer represents a deposit of material due to a stacking transaction. These layers are referred to as 'batches' in MineMarket. A batch represents a homogeneous quantity of material, and is created when material is stacked onto a 3D stockpile. This stacking transaction determines the batch quality, via the best-known weighted average grade of material from the stacking transaction. A single stacking transaction in MineMarket is assumed to be homogeneous in terms of quality and contributors.
Stockpile State Queries
The State Engine in MineMarket can provide the state of 3D stockpile at a point in time. Querying the State Engine is the only way to obtain the 3D stockpile state information. Although the MineMarket database stores the state after every transaction once it has been processed by the warehousing service, it cannot be queried directly for the 3D information.
The full state after every transaction cannot be queried from the database because MineMarket only stores the full state every N number of transactions to minimise the storage requirements. Transactions in between these key states store the 'deltas' which are the differences between the stockpile shape before and after the transaction. The data is also stored in a compressed binary format, which does not lend itself to straight-forward database queries.
3D Stockpile Surveys
The shape of a 3D stockpile in MineMarket can be modified by a survey, which can adjust both the quantity of material on the stockpile and the overall shape. The shape information may be obtained by various means, such as a laser sighting survey, or data obtained from a fly-over aerial survey.
MineMarket adjusts the stockpile to conform to the overall shape, and attempts to preserve the best-known quality for the remaining volume of material. The batches are proportionately sized in a vertical direction to conform to the shape.
System Settings
The following system administration activities impact 3D stockpile modelling:
