Production scheduling in coal surface mining using 3D design tools

Technical Report

World of Mining – Surface & Underground 57 (2005) No. 3

Production scheduling in coal surface mining using 3D design tools VLADISLAV J. KECOJEVIC, WILLIAM WILKINSON, PHIL HEWLETT, USA

Computer aided design tools have become an indispensable tool in the planning and design of surface mining operations. The powerful visualization and scenario analysis features facilitate a greater understanding of the mining operation and help the mining engineers identify leverage points. 3D production scheduling tools provide flexible evaluation of multiple design and scheduling scenarios, from the purely interactive graphical scheduling of a design,

to spreadsheet-like creation and manipulation. Such tools enable graphical output that shows where mining takes place for each scheduling time period, in the form of contours and 3D wireframes of the design. In addition to period summary reports, more detailed bench reports can also be produced. Integrated assimilation of geological modelling, mine design and schedule allows complete freedom to experiment with various what-if type scenarios.

Produktionsplanung im Kohlentagebau mittels 3D-Gestaltungswerkzeugen Computergestützte Designwerkzeuge sind zum unverzichtbaren Instrument für die Planung und Gestaltung des Tagebaubetriebs geworden. Die umfangreichen Möglichkeiten der Visualisierung und Analyse von Szenarien ermöglichen ein besseres Verständnis des Tagebaubetriebs und helfen dem Ingenieur, Ansatzpunkte zu erkennen. 3D-Produktionsplanungswerkzeuge ermöglichen die flexible Bewertung vielfältiger Gestaltungs- und Planungsszenarien, von der rein interaktiven graphischen Erstellung einer Zeichnung bis zu tabellenkalkulatorisch aufgebauten Entwür-

fen und Verfahrensweisen. Mittels dieser Werkzeuge können grafische Darstellungen erzeugt werden, die zeigen, wo in jedem schematisch festgelegten Zeitraum der Abbau stattfinden wird – in Form von Umriss- und 3D-Gitterdiagrammen. Zusätzlich zu periodischen Zwischenberichten können auch detailliertere Leistungsberichte erstellt werden. Mit der Integration von Geomodelling, Tagebaudesign und -plan verfügt man über unbegrenzte Möglichkeiten, um mit „Was wäre, wenn“-Szenarien zu experimentieren.

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the production schedule where the most commonly used target is to maximize net present value (NPV). Detailed description on optimisation techniques in production scheduling can be found in [1, 2, 3, 5, 9, 10, 11]. In the planning and design process, production scheduling is commonly supported by different types of spreadsheets [7]. However, if there are constraints on the schedule such as those that can be associated with achieving grade targets, the scheduling process can be laborious and time consuming. Even if there are no strict grade constraints, it is often next to impossible for a mining engineer to know if there is significant room for improving the value of a given schedule. The complexity of mine production scheduling in practice entails a computer solution to meet these challenges in a technologically efficient and cost-effective manner. In today’s technology-rich era, a scheduling process can be produced by computer software that enables the evaluation of all mining sequences and determines their contribution to the profitability of the surface mine. In particular, the 3D CAD tools have changed the methodology by which mining engineers plan, design, and maintain records of mining structures throughout their life cycle. Mining Engineers benefit from this progress, as parallel advancements in hardware and mining software help them to visualize the complexity and spatial distribution of data, allowing them to make engineering changes, and test or compare different concepts. In computer design of a production schedule in coal surface mining, a series of events is required to meet the specified blending or production targets, maximize the equipment usage, minimize the cost, and maximize the life of the mine. This paper discusses an approach to surface mine production scheduling that provides visual interaction, dynamic analysis and feedback between the coal geological model, surface mine design, and schedule. The authors have used fully integrated mining software such as Mincom’s MineScape to generate production scheduling [6].

Introduction

Surface mining operations involve complex and multi-faceted processes that must be planned, designed and evaluated to provide the exploitation of the ore deposit at a minimum cost with a view to maximizing profit. Production scheduling in surface mining is an important facet of the planning and design process. It determines mine life and therefore cash flows including capital and operational costs, and revenues [4]. Commonly, the production scheduling involves sequencing of ore deposits to be mined in each period over the life of the surface mine subject to precedence and other physical constraints imposed by the mining system [8]. Many variables must be considered and the efficient planning and design of ore removal over the life of the mine must be implemented to achieve predetermined targets with minimum costs. Mining engineers often seek an optimal solution within DR.-ING. VLADISLAV J. KECOJEVIC, College of Earth and Mineral Sciences, The Pennsylvania State University, 154 Hosler Building, University Park, PA 16802-5000, USA Tel. +1 (0) 814-865-4288, Fax +1 (0) 814-865-3248 e-mail: vuk2@psu.edu DIPL.-ING. WILLIAM A. WILKINSON, JR., Mincom, Inc., 9635 Maroon Circle, Suite 100, Englewood, CO 80112, USA Tel. +1 (0) 814-940-8727, Fax +1 (0) 814-940-8726 e-mail: waw@mincom.com DIPL.-ING. PHIL HEWLETT, Mincom, Inc., 9635 Maroon Circle, Suite 100, Englewood, CO 80112, USA Tel. +1 (0) 303-446-9000, Fax (303) 446-8664 e-mail: peh@mincom.com 2

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Scheduling procedure

Generally, there are two principle scheduling modes including target scheduling (TC) and equipment scheduling (ES). Within the TC, it is required to nominate production targets for each mining area, activity or equipment item being scheduled. This is achieved by assigning a sequence of blocks to each item, and allocating each block to a time period. ES shares some similarity with target scheduling, but is more suited to short term planning and budget applications where greater detail is required. A roster is used to specify the weekly operating pattern of each scheduled equipment item together with roster exceptions (holidays), availability and utilization. Each item of equipment can perform one or more of the modeled activities, which can vary from block to block, between material types, and period to period. The entry point for production scheduling is a geological model of the coal deposit inside the so-called ultimate mine limits. Such a model contains a number of geometric blocks where appropriate data values are assigned to each block. These data include block spatial coordinates, block size, volume, tonnage, heating value, ash and sulfur content, etc. Such resource data are imported into a schedule database, which represents the starting point to form the base framework for schedule definition, accumulation and appraisal. Figure 1 shows a typical block model, Figure 2 shows the ultimate mine limits, Figure 3 presents ash content values as-

signed to the block model; while Figure 4 shows all values of the specific geometric block within the geological model. After importing a block model, there is a number of constraints that have to be set including both mining and economic. These requirements correspond to rules according to how overburden and coal can be mined, tonnage and volume targets, allowable quality range, losses, dilution, blending, stripping ratio, cut-off requirements, etc. Additionally in some situations, it is prudent to update the blocks database via surveyed face locations rather than re-reserving (Figure 5). This is particularly true for short term scheduling when the engineer is under pressure to produce the schedule for the next week in a short turnaround time. Associated data for mining equipment include production rates, performance criteria and cost data. Equipment performance can be a function of mining conditions, moderated by availability and productivity considerations, or simply read from a table of measured performance. Cost data contain equipment costs, overburden and coal loading and haulage costs, stockpile costs and coal processing costs. An analysis of data within the database is often generated by different types of reports, including numeric tables, spreadsheets, graphs, and 3D plans. Figure 6 shows an example of using 3D visualization tools to view block model within ultimate mine limits. The calendar database needs to enable definition of the time periods including days, weeks, months or years that must be scheduled

Fig. 1:

An example of a cross-section taken through the geologic model

Fig. 2:

Ultimate mine limits

Fig. 3:

Ash content values assigned to the block model

Fig. 4:

Values of specific geometric block within the block model

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Fig. 5:

An example of blocks data update based upon surveyed face locations

Fig. 6:

An example of 3D graphics showing block model within ultimate mine limits

Fig. 7:

An example of calendar database

Fig. 8:

Graphical interpretation of scheduled time sequences

Fig. 9:

Interactive and automated equipment scheduling

Fig. 10:

Equipment schedule represented by time chart

and the targets that must be achieved during each of these periods. This database may also be defined using detailed shift rosters for each piece of equipment (including scheduled maintenance, crib breaks, etc.) for short term planning or by using a user-structured 4

calendar of equipment availability. Figure 7 shows the example of data definition within the calendar database; Figure 8 presents graphical interpretation of scheduled time sequences; while Figures 9 and 10 show the examples of equipment scheduling.

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Fig. 12: Fig. 11:

Production data represented as a numerical report in Excel spreadsheet

Schedules may be presented in a variety of forms, including bar and Gantt charts, reports of any prescribed content and format and plan, or 3D plots shaded by time. Exporting the data to Excel is most often used for numeric reporting. Graphical output is normally progress plans, a shading plan by period for a bench or machine, but may also include Gantt and time charts. Figure 11 shows scheduled production data represented as a numerical report in an Excel spreadsheet. Schedule design may be aided by visual cues such as shadings by grade/quality ratio, current face positions highlighted within the 3D surveyed mine image and any other output such as contours and 3D wireframes of the design. Alternatively, scheduling and targeting using predefined sequences of mining may be used for quickly ranking a choice of mining scenarios. The mining sequence can also be shown animated on-screen, and each frame automatically saved at a user-defined resolution for export to other multimedia presentation software. Detailed mining operations may be simulated using a technique that advances all active operations and activities concurrently, through a user-specified time slice, for example, one shift. The feasibility of a mining plan considering inter-equipment dependencies and possible contention may be fully evaluated. Material flow may be modelled by assigning destinations to each unit of material being mined. Stockpiles may be managed, blending alternatives studied and dumping plans (including pit backfilling) generated. Backtracking and undoing provides complete freedom to experiment with various what-if type scenarios. Figure 12 shows an example of incorporating 3D visualization with mine production scheduling and projected mine topography data.

[2]

CHANDA, E. & DAGDELEN, K. (1995): Optimal Blending of Mine Production Using Goal Programming and Interactive Graphics Systems. – International Journal of Surface Mining, Reclamation and Environment, 9: 203-208.

[3]

FRIMPONG, S., ASA, E. & SUGLO, R. (2001): Numerical Simulation of Surface Mine Production System Using Pit Shell Simulator. – Journal of Mineral Resources Engineering, 10, 2: 185-203.

[4]

FOURIE, G. & DOHM, G. (1992): Open Pit Planning and Design. – In: HARTMAN H. (Ed.): SME Engineering Handbook, 2nd edition, Vol. 2:1274-1297; (SME).

[5]

FYTAS, K, PELLEY, C., CALDER, P. (1987): Optimization of Open Pit Short- and Long-Range Production Scheduling – CIM Bulletin: 55-61.

[6]

Mincom: MineScape Schedule, http://www.mincom. com/products/minescape, 2003.

[7]

MineMax: Mine Schedule Optimization, White paper, Bentley: pp. 1-12, 1998-2000.

[8]

RICCIARDONE, J. & CHANDA, E. (2001): Optimising Life of Mine Production Schedules in Multiple Open Pit Mining Operations: a Study of Effects of Production Constraints on NPV. – Mineral Resources Engineering, 10: 301-314.

[9]

THOMAS, G. (1996): Optimisation of Mine Production Scheduling. IIR Dollar Driven Mine Planning Conference: p. 12.

[10]

WANG, D. (1996): Long Term Open Pit Production Scheduling Through Dynamic Phase Bench Sequencing. Transactions of the Institute of Mining and Metallurgy: pp. A99-A104.

[11]

WESTCOTT, P. (1991): Mine Scheduling and Optimisation. Mining Industry Optimisation Conference, Australasian Institute of Mining and Metallurgy: pp. 55-58.

References [1]

CACCETTA, L., KELSY, P. & GIANINI, L. (1998): Open Pit Mine Production Scheduling. Proceedings of the Third Regional APCOM Symposium, Australasian Institute of Mining and Metallurgy: pp. 65-72.

Mining schedule progression showing anticipated mine topography surface, dates of completion and equipment location

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