Pit limit optimization open pit design is a computerbused implementation of an algorithm that is applied to a three dimensional block model of an ore body, i. In 1986 the whittle 3d openpit optimization package was launched by whittle. In the optimization of open pit mine design, the lerchsgrossmann algorithm is the industry standard, although network flow algorithms are also well suited, efficient, and known. A genetic algorithm with zooming for the determination of.
Pseudoflow models give new life to the lerchsgrossmann pit optimisation muir 2004. Pit optimiser provides different options for financial, optimisation and analysis scenarios. Technical apers introduction academic research over the past three decades has focused on using the lerchsgrossmann algorithm as a mechanism for solving more general openpit mine scheduling problems. Also in order to show this effect, an illustration example is discussed. Determination of the optimum cutoff grade considering. A critical appraisal of the whittle 3d openpit mine optimization. Definition of the optimum open pit, whether an intermediate phase or final design, will be sensitive to many factors. The only input required is tonnage and grade information. It was developed in 1965 and implemented in the 1980s by jeff whittle. Mathematical optimization models and methods for open pit mining. The ultimate pit limit problem has been efficiently solved using the lerchsgrossmann graph theoretic algorithm. Nevada net proceeds tax and open pit optimization stope. I keep finding articles and abstracts that talk about lerchsgrossman pit optimisation that say that the algorithm has a basis in graph theory. Finally, step 4 can be assisted by optimization tools, but it mainly depends on the ability of the planner to make the best choices.
A back to basics approach to mining strategy formulation. Openpit mining is an operation in which blocks from the ground are dug to extract the ore contained in them, and in this process a deeper and deeper pit is formed until the mining operation ends. Over the past 35 years the determination of optimum openpits has been one of the most. Ore bodies are conceived to be divided into units that have significance to the mining engineer, can be geometrically described e. Cuba and clayton deutsch the calculation of the ultimatepit is the base for designing the lifeofmine plan of a surface mining project. Lerch grossman ultimate pit surface modeling medium term pushbacks ramps schedule monthday plan equipment level asbuilt surface current machine locations and activities operational decisionsupport machine guidance current face fleet management survey reconciliation drillblastloadhaul crushprocess smeltrefine metal planning metal. Performance analysis and best implementations of old and. Conventional pit optimization calculates optimal pit limits from a block model of economic values and precedence rules for pit slopes. Technical apers is openpit production inside mines. Pseudoflow, new life for lerchsgrossmann pit optimisation.
Notice we are not dealing here with the design of pit phases, which are also strongly user dependent. Mathematical optimization models and methods for openpit mining. Selection the optimal open pit contour and phase determining both softwares are based on the lerch grossman optimization algorithm. The ranked pits were then amalgamated into logical pushbacks based on mining constraints. The essence of this algorithm is that, for a given technoeconomic parameters, the most eco. The ultimate pit limit problem has been efficiently solved using the. The basic cad tools of envisage are found in the first four menu items. Request pdf lerchsgrossmann algorithm with variable slope angles one of the most. The differences in the figures are due to the widening of the pit bottom and the creation of a ramp and berms in the designed pit, which resulted in the addition of some waste, ore loss and dilution. Pit optimisation using solid modelling and the lerchs. Thus the pit optimization technique should be regarded as a powerful and necessary management tool. It is clear from the definition of our graph g that a graph closure in g represents a physically feasible pit, if not, then a block not in our closure violating the slope. The implementation of the algorithm with respect to block models is considered. The first phase results in practical npvbased schedules.
Pdf the lerchsgrossmann lg algorithm 1965 has been used for over thirty years for the optimum design of open pit mines. Optimisation, mining, stripping ratio, block model, pit design 1 introduction. I havent seen any articles that elaborate on what part of graph theory was used to create this optimisation method. Over the past 35 years the determination of optimum openpits has been one of. Mathematical optimization models and methods for openpit. Lerchsgrossmann algorithm with variable slope angles. Lerchs and grossmann 1 developed an open pit optimization algorithm based on graph theory. Algorithms to solve the open pit optimization problem have been developed by many researchers. Open pit mining is an operation in which blocks from the ground are dug to extract the ore contained in them, and in this process a deeper and deeper pit is formed until the mining operation ends. The technique, founded in 3dimensional graph theory, relies on a regular system of blocks which defines the value profit, loss and type ore, waste of material contained in the blocks. To begin, the decision to go open pit or ug very much. Pdf pseudoflow, new life for lerchsgrossmann pit optimisation. Revised ultimate pit designs were developed utilizing a lerch grossmantime value of money pit optimization routine.
Optimized open pit mine design, pushbacks and the gap. Client manager primethought software recommended for you. Using the lerchsgrossman algorithm during open pit mine design designxl duration. An approximate pit optimization methodology suited to the. Global optimization of open pit mining complexes with uncertainty. The most basic will include geological and mining constraints, mining and processing costs, pit slopes and product prices. The traditional pitshell optimization lerch grossman or pseudoflow is still.
An approximate pit optimization methodology suited to the slm framework miguel a. Is there a role for lerchsgrossman optimization in. Lerchs grossman method 1 applied mathematics algorithms. In the manual method, a simple optimization of economic pit depth was usually carried out by hand calculator or. This knowledge base has transferred to industry and, at present, a number of software firms, including geovia, maptek and minemax, offer produc. A comparison of conventional and direct block scheduling. Hochbaum, anna chen, 2000 performance analysis and best implementations of old and new algorithms for the. There are well established algorithms for this including lerchsgrossmann, pushrelabel and pseudo. Planning and design procedure of an open pit mining project just can be started after ultimate pit determination. Resources are stated within a lerch grossman optimized pit shell using the following parameters. Ni 43101 technical report mineral resource estimate. Lerch grossman is the name of a modeling approach for solving openpit optimization.
Abstractone of the most important design factors in open pit mining is determination of the optimal pit. The proposed system is compatible with traditional approaches to economic analysis in open pit planning, and with emerging best practices to manage technical and economic uncertainty, improve project optimization, and develop robust mine plans. In industry, two widely popular methodologies to calculate the ultimatepit limits are lerchs and grossmann and floating cone. The algorithm uses block dependencies to determine which blocks must be mined out. This is a video showing how to get an optimum pit shell in designxl given the blockmodel and the face angle constraints. Graph g with dummy node x0 and arcs added from the dummy node x0 to all other nodes. Lerchs grossman method 1 free download as powerpoint presentation.
The stochastic version of the conventional deterministic network flow algorithm is based on the use of multiple simulated realizations of the ore deposit, thus. Case studies in open pit design using lerchsgrossman pit optimization. A method of precise pit optimization commonly used in the mining industry is the lerch grossmann method. Anyone know the theory behind lerchsgrossman pit optimisation. Lerchsgrossmann algorithm with variable slope angles request. Pits may be redesigned many times during the life of a mine in response to changes in design parameters as more information is obtained and to changes in the values of technical and economic parameters. Lerchs and grossmann 1965 are the first to put forward a method to.
Using the lerchsgrossman algorithm during open pit mine. Most of the available packages rely on lerch grossman algorithms defining economic limits to underpin the time optimization algorithms, a condition that is not met in zulti north. This package utilized the lerchgrossman algorithm for the first time in a commercial. Cost effectiveness of openpit hard rock ore mining. Designxl is developed by primethought software solutions.
Secondly, an underlying assumption of open pit optimization techniques is that the mining method has a reasonable degree of flexibility. Pit shells are mostly independent of the schedule and stockpiling, and therefore can be done independently of an advanced simo optimization. The three phases of mine planning ensure that the highest value is received from an open cut mine based on a practical schedule, which is implemented in a shorter planning horizon. Different genetic procedures are applied to increase robustness, namely two typologies of admissible mutations for the elite subpopulation subjected to zooming and mutation and reproduction for the remaining individuals. These ultimate pits were then subdivided into pit shells by ranking the pits generated by the optimization routine by net present value. Due to the uncertainty in the operational and economic conditions in the mining industry there is a need to. The application of the three dimensional lerchsgrossmann pit optimization procedure to this task is described for a range. A genetic algorithm ga with nested zooming strategy is proposed for the determination of the optimal open pit mine design. Further, the pit optimization method must be highly efficient to allow for an effective sensitivity analysis. Pit optimization optimization problem that selects the blocks to be mined to maximize pit value while respecting all constraints two most popular methods. Stochastic open pit design with a network flow algorithm. The traditional pitshell optimization lerch grossman or pseudoflow is still required to create the optimal pit shell.