A probabilistic model to improve reconciliation of estimated and actual grade in open-pit mining

Many of the open-pit mines suffer from the lack of reconciliation between estimated and actual grades. In a mining operation, grade reconciliation is the comparison between the values of the estimated grade calculated in exploration stage and the actual grade obtained from more reliable data such as blast holes?? samples. Many different factors affect the degree of reconciliation in a mining operation. In this paper, the factors related to estimated grade which affect the reconciliation process in the exploration stage of the orebody are investigated. These factors constitute the sources of uncertainty for the upcoming phases of the mining life. Among these parameters, the inherent variability, statistical uncertainty, and systematic uncertainty are the most important factors. In this work, these parameters are studied in further detail, and, accordingly, for each of these uncertainties, a correction factor is determined in the proposed model. The model was applied to the study of real data taken from an iron open-pit mine in Iran. The results of the case study indicated that the systematic uncertainty, inherent variability, and statistical uncertainty are, in order, the main sources of uncertainty on grade reconciliation process. Applying the correction factors to estimated grade values has increased the amount of grade reconciliation from 10%, at original condition, to 50%, at new condition, in the case study.     

矿山露天转井下境界顶柱的数值模拟优化方法

露天底境界顶柱优化是露天转井下过渡时期的重要课题,该优化问题包括多个决策变量和多个评价指标,已有方法的优化效果不够理想。针对露天转井下境界顶柱优化特点,将遗传算法与三维数值模拟相结合,研究了境界顶柱全局优化的进化数值模拟方法,给出优化的指标和步骤,并将该方法用于大杏山铁矿的露天转井下境界顶柱的优化。工程应用表明所提出的井下境界顶柱优化方法是可行的。获得的最优方案对该矿山露天转井下的采矿设计具有指导作用。     

Assessing the accuracy of sequential Gaussian simulation and cosimulation

Sequential Gaussian simulation is widespread in Earth Science applications to quantify the uncertainty about regionalized properties. Its practical implementation relies on the screen effect approximation in order to determine the successive conditional distributions by considering only the information available in the neighborhood of the target location. A methodology is presented to assess the accuracy of sequential Gaussian simulation, by calculating the theoretical moments (expectation and variance–covariance matrix) of the simulated random vector and comparing them with the moments of the underlying model. The methodology can be applied in both the conditional and non-conditional contexts, as well as for univariate or multivariate simulation. It is helpful to determine appropriate implementation parameters, in particular about the visiting sequence and the design of the moving neighborhood for selecting relevant conditioning information, prior to performing simulation.     

Using robust kriging and sequential Gaussian simulation to delineate the copper- and lead-contaminated areas of a rapidly industrialized city in Yangtze River Delta,China

A total of 540 topsoil samples (0–15 cm), 188 subsoil samples (20–40 cm), and four individual soil profiles were collected in this study for mapping the Cu- and Pb-contaminated areas in soils of Zhangjiagang city, an industrialized city in the Yangtze River Delta region of China. Robust geostatistical methods were applied for identifying possible spatial outliers of Cu and Pb data, and then a sequential Gaussian simulation was employed for delineating the potential areas where Cu or Pb concentration was affected by diffuse pollution. The results showed that the spatial outliers of Cu and Pb were strongly associated with various types of factories. The anthropogenic input of Cu to soils at local hotspots was closely related to emissions of printing and dyeing, metallurgical, and chemical factories, whereas a lead oxide factory and a chemical factory resulted in a considerable increase of Pb in the topsoil of the study area. Approximately 30% of the total land area of the study was at potential risk from the Cu or Pb diffuse pollution resulting from rapid industrialization of the area over the past 20 years.     

A comparative study of kriging and simulation-based methods in classifying ore and waste blocks

Ore grade is the most important source of uncertainty in a mining operation which plays an important role to classify run-of-mine (ROM) material into ore and waste parcels. As a widely used method, kriging estimator is used to estimate the grade of ore blocks. In conventional mining practices, if the estimated grade of a parcel is above the cut-off grade, this parcel is classified as ore, otherwise, is labelled as a waste parcel. An alternative approach is to simultaneously consider the grade of parcels and the economic consequences of sending parcels to destinations by applying simulation-based methods. In this study, kriging and simulation-based methods including loss and profit functions are applied on a real-world case study to classify ore/waste material based on the initial exploration data. Then, the actual known data, collected from blast holes samples, are compared with the estimated results in order to validate the performance of the presented methods. Outcomes show that simulation-based methods can perform better and show more adjustability with real data.     

Catchment scale geostatistical simulation and uncertainty of soil erodibility using sequential Gaussian simulation

Soil erodibility (K) affects sediment delivery to streams and needs to be appropriately quantified and interpolated as a fundamental geographic variable for implementing suitable catchment management and conservation practices. The spatial distribution of K for erosion modelling at non-sampling grid locations has traditionally been estimated using interpolation algorithms such as kriging which do not adequately represent the uncertainty of estimates. These methods cause smoothing effects through overestimating the low values and underestimating the large values. In this study observed values were used to implement a sequential Gaussian simulation (SGS) procedure to evaluate the certainty of modelled data. Soil erodibility values were computed using 41 soil samples taken from the top 10 cm soil layer regularly distributed across four catchments, 367–770 ha in area, within Kangaroo River State forest, New South Wales (NSW). One hundred realisations were applied in the simulation process to provide spatial uncertainty and error estimates of soil erodibility. The results indicated that values simulated by the SGS algorithm produced similar K values for the neighbouring cells. At the pixel level, the SGS approach generated a reliable estimation of soil erodibility in most areas. Spatial variation of the K factor in this study was strongly related to soil landscape differences across the catchments; within catchments slope gradient did not have a substantial impact on the numerical values of the K factor using pixel-by-pixel comparisons of raster grid maps.     

Sequential Gaussian simulation for geosystems modeling: A machine learning approach

Sequential Gaussian Simulation(SGSIM)as a stochastic method has been developed to avoid the smoothing effect produced in deterministic methods by generating various stochastic realizations.One of the main issues of this technique is,however,an intensive computation related to the inverse operation in solving the Kriging system,which significantly limits its application when several realizations need to be produced for uncertainty quantification.In this paper,a physics-informed machine learning(PIML)model is proposed to improve the computational efficiency of the SGSIM.To this end,only a small amount of data produced by SGSIM are used as the training dataset based on which the model can discover the spatial correlations between available data and unsampled points.To achieve this,the governing equations of the SGSIM algorithm are incorporated into our proposed network.The quality of realizations produced by the PIML model is compared for both 2D and 3D cases,visually and quantitatively.Furthermore,computational performance is evaluated on different grid sizes.Our results demonstrate that the proposed PIML model can reduce the computational time of SGSIM by several orders of magnitude while similar results can be produced in a matter of seconds.     

A comparison between cokriging and ordinary kriging: Case study with a polymetallic deposit

Cokriging is applied to the estimation of mineral resources in a polymetallic deposit. Several major steps, which should be taken in using cokriging, are highlighted as necessary practical considerations. The case study is related to an ultramafic copper-nickel deposit. Six elements, Cu, Ni, Au, Ag, Pt, and Pd, occurring in the deposit, are partitioned into three subgroups and the elements within each group are simultaneously estimated on the basis of over 4000 drill assays. A comparison was made between ordinary kriging and cokriging methods through cross-validation. The results show that cokriging has significantly improved the estimates of resources by reducing the overall estimation error by over 15% and the variance of error by over 20%.     

裂隙网络生成的随机模拟研究

网络裂隙介质的刻画是水文地质研究领域最具挑战性的难题之一。介绍布尔模拟和多点地质统计两种生成裂隙网络的随机模拟方法基础上,分别利用布尔模拟和多点地质统计方法对某一典型裂隙介质网络进行随机模拟,并通过与真实裂隙场的迹长、走向等几何参数的对比评价其模拟精度。结果表明,两种随机方法都能实现对裂隙结构特征的近似刻画,其模拟误差均在10%以内。相对来说,布尔模拟对裂隙迹长的模拟精度更高,多点地质统计模拟对裂隙走向的模拟效果更好。同时,布尔模拟较多点地质统计模拟对裂隙的已知数据要求更高。裂隙网络的随机模拟为准确刻画裂隙介质中的地下水流运动及污染物运移提供了现实可能性。     

A simple kriging method incorporating multiscale measurements in geochemical survey

In this study, we propose a kriging algorithm, multiscale kriging model, to incorporate geochemical data observed at multiscales (multiresolutions). We assume that there are a number of measurements at different scales, and that the target scale at which the parameter values are needed may be different from the measurement scales. Several synthetic examples and the vanadium geochemical data from 8402 stream sediment samples in Zhejiang Province, China, have been used to illustrate the method. These examples demonstrate that, by incorporating measurements from all scales, the estimated field is better than the field estimated using measurements from any individual scale. This method also allows us to estimate a parameter field at the scale that does not have any measurements.     

Optimizing post-mining land use for pit area in open-pit mining using fuzzy decision making method

Open-pit mining method has severe environmental impacts which should be prevented, monitored, controlled, and reduced by mined-land reclamation process. After mine closure, a permanent post-mining land use should be implemented as an appropriate choice for using different sections of mined land. The most appropriate alternative of post-mining land use for each section of mined land is presented as the optimum post-mining land use. Pit area among different sections of mined land has more significant effects on the environment and also on defining the optimum post-mining land use for other sections of mined land. Though there are several alternatives and criteria for defining the optimum post-mining land use, the multi-attribute decision-making methods can be efficient techniques in this regard. The nature of the effective parameters used for defining the optimum post-mining land use is the same as Fuzzy numbers including incremental changes without definite limits. Thus, application of the Fuzzy multi-attribute decision-making modeling can produce more reliable results than that of other techniques. As well, pair-wise comparisons and judgments through Fuzzy numbers have proper consistency with the nature of the effective parameters; therefore, a model is developed to attain the optimum post-mining land use for pit area through Fuzzy analytical hierarchy processing. As a case study, the model was implemented in Sungun copper mine in the Northwest of Iran. Forestry?Clumber production was defined as the optimum post-mining land use containing the greatest relative importance coefficient 3.019 for the pit area in this mine.     

新疆荒漠露天矿区生态受损及砾幕层重构方法研究

露天矿开采过程中的岩土剥离、土地压占导致大面积的地表、植被及地下水系被破坏和景观格局的改变,带来一系列生态环境问题.西北荒漠矿区作为我国未来煤炭资源战略的重要接替区,若无针对性的生态修复对策,将会严重威胁到我国国土生态安全.选取西北荒漠区7座典型露天煤矿,采用实地调研与实证研究法、遥感影像法、比较研究法等,从地貌重塑、...     

Restricted kriging: A link between sample value and sample configuration

Restricted kriging provides a simple and quick remedy for the problem known as the weight independence of data in ordinary kriging. A major consequence of this problem is the effect of over-smearing in estimates, which, in turn, adds one uncertain factor to subsequent mine decisions. A detailed count is reported here on a restricted kriging system that incorporates two restrictions—one for high-grade samples and the other for low-grade samples. The restriction of high grade samples is because of their low priori likelihoods, whereas the main reason to restrict low grade samples is their nature as being waste and low analysis precisions. The two constraints reinforce each other in terms of enhancing the variables of estimates. A detailed case study on an epithermal gold deposit is carried out in terms of both cross validation and block modeling, showing that restricted kriging is superior over OK in mimicking the variables of original data.     

Fault detection in 3D by sequential Gaussian simulation of Rock Quality Designation (RQD)

Gazestan phosphate ore deposit (Central Iran) is an apatite deposit which is instrumental in selecting the method of excavation. The position of fault systems and the condition of rock quality also play a role in the method used for mineral resources and ore reserves estimation. Conversely, the Rock Quality Designation (RQD) is a parameter that provides a quantitative judgment of rock mass quality obtained from drill cores. This factor can be applied to detect the fractured zones which occur due to fault systems. Additionally, the faulted areas can be determined by surface geological map and a few by core drilling. Some of the faulted areas are not distinguishable in the surface and are covered by soils, especially within 3D modeling and visualization. In this study, an attempt has been made to establish a relationship between the RQD percentages which were geostatistically simulated and faulted areas through the region. In comparison, the results showed that low RQD domains (RQD <20 %) can be interpreted as fault zones; high RQD domains (RQD >50 %) correspond to less fractured areas, and the contact between high and low RQD domain is gradual. Therefore, this categorization of RQD domains can be incorporated to detect the faulted zones in 3D models for mine design. Based on the categorization, the uncertainty within the area was calculated to introduce two new core drilling points for the completion of this phase of exploratory grid from the fault structural viewpoint, in order to have a proper model of ore reserve to estimate. It was concluded that this procedure can be utilized for conceptual comprehension of fault trends in 3D modeling for the method selection of excavation and complete the estimation procedure phase.     

Hydraulic variations in permafrost due to open-pit mining and climate change: a case study in the Canadian Arctic

Acta Geotechnica - The paper deals with numerical computations of hydraulic variations and groundwater flow changes in continuous permafrost due to climate change and open-pit mining in the cold...     

和尚桥露天铁矿地下水疏干方法研究

和尚桥铁矿是一个大型露天磁铁矿,由于矿区的特殊位置,建设生态矿山、最大限度地减少矿山生产对环境的扰动势在必行。矿山工业布局、独特的水文地质环境和安全生产需要,均给矿山地下水疏干提出新要求。根据该铁矿露天采矿场不同地段的地质、水文地质和工程地质条件,提出了地表和地下联合疏干的方法。利用所建立的地下水疏干预测模型,模拟该方案疏干矿坑地下水的可能,为矿山安全生产、地下水综合利用提供决策依据。     

江苏句容石砀山矿区-300 m以上铜多金属矿体探采对比

选取江苏句容石砀山铜矿标高-300 m以上Cu①号主矿体,基于普查、详查、生产勘探及开采各阶段的地质资料,将地质勘查资料与生产勘探及开采后确定的构造、矿体特征、开采技术条件、矿体资源储量等参数进行对比研究,探讨勘查期间勘查类型划分、方法手段、工程间距选择的合理性,分析探采不同阶段的矿体形态、规模、控制程度及资源储量估算的误差率,为今后该矿床深部及类似矿床的勘查及开采提供借鉴。     

江苏句容石砀山矿区-300m以上铜多金属矿体探采对比

选取江苏句容石砀山铜矿标高-300 m以上Cu①号主矿体,基于普查、详查、生产勘探及开采各阶段的地质资料,将地质勘查资料与生产勘探及开采后确定的构造、矿体特征、开采技术条件、矿体资源储量等参数进行对比研究,探讨勘查期间勘查类型划分、方法手段、工程间距选择的合理性,分析探采不同阶段的矿体形态、规模、控制程度及资源储量估算的误差率,为今后该矿床深部及类似矿床的勘查及开采提供借鉴.     

Ordinary kriging and indicator kriging in the cartography of trace elements contamination in São Domingos mining site (Alentejo, Portugal)

The abandoned pyrite mine of São Domingos, in the southeast Portugal is still an acid mine drainage generator and a source for trace elements pollution. This study aims to evaluate and map the soils and sediments chemical pollution. With this purpose three test sites located in the vicinities of the mine were sampled for soils, sediments and mining waste materials. The samples were analysed for pH, organic carbon, iron oxides and total content of As, Cu, Cr, Hg, Pb, Sb, U, Zn, Mn, S, Fe Al, Ca, K, Mg and P. The hyperspectral image of the test sites was acquired using the aero transported sensor HymapTM. Chemical analysis and hyperspectral images data were processed to estimate the contamination maps by multivariate data analysis, ordinary kriging, cokriging and indicator kriging methodologies.The test sites located downstream the mine open pit, are highly contaminated mainly in As, Hg, Pb and Sb, but no contamination was found in the third test site, upstream the mining site. The acid mining drainage seems to be the main spreading agent of chemical contaminants mostly originating from the mine waste materials. Factorial analysis and the geostatistical methodologies allowed several approaches for the contamination cartography of mining areas.