Patent ID: 8082167

Claim:
A method of scheduling the extraction of a resource in a mine medium comprising the steps of: obtaining drillhole grade data relating to the resource contained within the medium; creating a plurality of different block models of the mine with a processor, each formed of a plurality of blocks, each block in each model having a resource grade, each of the block models honouring the drillhole grade data; and generating a single schedule for extraction of blocks from the mine with the processor based on a cut-off grade policy to increase expected net present value having regard to all of the plurality of different block models, wherein the single extraction schedule is determined by the following: Maximise ⁢ ⁢ ( 1 N ⁢ ∑ n = 1 N ⁢ ∑ i = 1 P ⁢ ∑ j = 1 G ⁢ ∑ t = 1 T ⁢ V ij n ⁢ x ijt ⁢ d t ) ( 1 ) subject to the following constraints: 1 N ⁢ ⁢ ∑ n = 1 N ⁢ ∑ i = 1 P ⁢ ∑ j - 1 G ⁢ ⁢ R i n ⁢ ⁢ x ijt ≤ R t 0 , for ⁢ ⁢ all ⁢ ⁢ t 1 N ⁢ ⁢ ∑ n = 1 N ⁢ ∑ i = 1 P ⁢ ∑ j = 1 G ⁢ ⁢ Q ij n ⁢ ⁢ x ijt ≤ Q t 0 , for ⁢ ⁢ all ⁢ ⁢ t y i , t - 1 ≤ y it , for ⁢ ⁢ all ⁢ ⁢ i ⁢ ⁢ and ⁢ ⁢ t ∑ τ = 1 t ⁢ ∑ j = 1 G ⁢ x ij ⁢ ⁢ τ ≤ y it , for ⁢ ⁢ all ⁢ ⁢ i y it ≤ ∑ j = 1 G ⁢ ∑ t = 1 T ⁢ x kj ⁢ ⁢ τ , for ⁢ ⁢ all ⁢ ⁢ i , t ⁢ ⁢ and ⁢ ⁢ k ⋐ S i ∑ j = 1 G ⁢ δ jt = 1 , for ⁢ ⁢ all ⁢ ⁢ t x ijt ≤ δ jt , for ⁢ ⁢ all ⁢ ⁢ i , j , and ⁢ ⁢ t ( 2 ) ( 3 ) ( 4 ) ( 5 ) ( 6 ) ( 7 ) ( 8 ) wherein; T is the number of scheduling periods; N is the number of simulations; P is the total number of panels; G is the number of all possible cutoff grades; R i n is the total rock in the panel i in simulations n, Q ij n is the total ore in the panel i, simulation n, when mined with the COG j; V ij n is the value of the panel i, simulation n, when mined and processed with the COG j; R t 0 is the maximum mining capacity in period t; Q t 0 is the maximum processing rate in period t; S i is the set of panels that must be removed before starting the panel i; d t is the time discount factor; x ijt is the fraction of the panel i is extracted with the COG j in period t; y it is a binary variable equal to 1 if the extraction of the panel i has started in periods 1 to t, and equal to 0 otherwise; δ jt is a binary variable controlling the selection of the COG applied in period t.