Pit Mine Research Articles

Simultaneous multi-sector block cave mine production scheduling considering operational uncertainties

ABSTRACT The main objective of this study is to provide a practical and near-optimal mine production schedule for block caving operations considering operational uncertainty. The problem is defined in the context of goal programming optimization to meet the operational objectives, including tonnage and grade as daily production targets. The considered operational constraints include drawpoints and ore pass design, draw rate, mine production, and transportation capacities in different operational levels, tonnage and grade constraints, and mine production targets in the presence of several mining sectors. The developed model is verified and validated using historical operational data obtained from an actual block caving operation. The practicality and flexibility of the framework are examined through three different operational scenarios and compared with the real block caving operation mine plans and historical production data.

Cleat properties of the Tanjung Agung coalfield, South Sumatra Basin: implications to fluid flow

Observation of the coal cleats of the Muara Enim Formation in Tanjung Agung coalfield aims to characterize the cleat properties and interpret their implications for fluid flow. This study used the scanline method to measure cleat attributes in the form of orientation, aperture, spacing, filler, and cleat connectivity. The face cleat was dominated by NE-SW direction as an indication of the effect of paleostress, while butt cleat with NW-SE direction indicated the effect of stress release. The presence of one major fault and three minor faults trending NW-SE in the mine pit is interpreted as the main controlling factor for cleat development in the study area. These cleats have an aperture ranging from 0.4 - 2.3 mm, good connectivity, and are not filled, so they are considered to be analogous to fluid flow paths with transition and turbulent flow types with relatively NE-SW direction.

Reducing Uncertainties in Gold Plant Design and Operations

The conventional way of designing a plant is to determine the characteristics of rocks in terms of crushability, grindability and other properties that affect the mill throughput. These properties are most of the time determined from drill cores obtained during the exploration period. Such initial exploration campaigns drill to levels shallower than the real pit that will be developed. Thus, as mining pits become deeper, the ore characteristics change and begin to impact negatively on the expected mill throughput. Such situations necessitate modification of the plant, and the first intervention usually is to supplement the initial energy input with additional size reduction equipment to achieve the required throughput. However, reconsidering the inputs used in determining the initial plant selection would help in reducing the setbacks during the operational period. To help reduce uncertainties and develop a predictive tool, this study considered a greenfield drilled up to 273 m, and the core samples obtained were tested to ascertain the variations in Bond work index to depths beyond 500 m. The study showed that within the section of the Asankragwa belt investigated, Bond work indices increased from 10.3 kW/t at the surface to 16.5 kW/t at a depth of 273 m. The Bond work index was established as a function of vertical depth in a pit (x) with the relation BWI=6E-05x2 + 0.0071x + 9.8816. The predicted value at 280 m was 16.3 kW/t while that of the blend was 15.8 kW/t, giving an error of 4%. This novel relationship between the BWI and depth predicts the BWI beyond 500m with minimum mean square error. The use of the novel Bond work index and depth relationship will eliminate the uncertainty beyond the drilled depth and give a clear understanding of what the rock characteristics will be as pits become deeper. In addition, a savings of US$62,500 per diamond drill hole and US$25,000 per one reverse drilling after the 250 m depth can be made by the use of this model. This can result in massive savings considering the number of holes that would have to be drilled across the length of the pit.

Blasting and preconditioning modelling in underground cave mines under high stress conditions

SYNOPSIS Cave mining is an underground mass mining technique. The largest projects, which are known as 'super caves', produce hundreds of thousands of tons of ore per day, which involves large footprints with considerable column height, and have a life of mine of over 20-40 years. These operations are typically located deep, under high stresses and in competent rock masses, making initiation and propagation of the caving process harder to manage. These challenges must be confronted by optimizing the fragmentation of the orebody to achieve smaller size blocks that will result in consistent caving and improved flow of the ore from the drawpoints. To achieve better performance from the drawpoints, preconditioning is applied to fragment and damage the material required to cave. We present a proposed design for preconditioning in underground mines, considering the challenges that these large-scale mines are already facing, based on a comprehensive analysis of current design parameters, case studies, and sensitivity analyses using numerical models. Keywords: fragmentation, preconditioning, caving, blasting, structures, stresses, explosives.

ИССЛЕДОВАНИЕ КАЧЕСТВА ЭЛЕКТРОЭНЕРГИИ ТЯГОВЫХ ПОДСТАНЦИЙ ВЫСОКОГОРНОГО РУДНИКА

The paper presents a methodology for researching the levels of higher harmonic in networks with a voltage of 6 kV and developed measures to eliminate harmonics of the non-canonical series. According to the results of the research, it was found that the sources of high-er harmonic ones are the ATP-500 traction substations, connected to the 6 kV network in groups and alone. In the 6 kV network, the 3rd, 5th, 7th and 11th harmonics of the canonical series, as well as the 3rd, 4th, 6th and 8th harmonics of the non-canonical series, are distin-guished, the levels of which significantly exceed the permissible levels according to GOST. The presence of non-canonical harmonics is caused by the asymmetry of the bridge circuit (current asymmetry relative to the abscissa axis). An instruction has been developed for the pre-start check of the bridge circuit gates to eliminate asymmetry. The prevalence of 5 and 7 higher harmonics in the 6 kV network was established and it was recommended to take into account the possibility of resonance phenomena in the pulse-phase control circuits of electric drives connected to the 6 kV network of the mine and open pit. The implementation of the recommen-dations set forth in the work increases the reliability of the bridge circuits of traction substa-tions and eliminates the possibility of the appearance of non-canonical harmonics, which im-proves the voltage quality in accordance with the requirements of GOST.

Nutritional consequences of breeding away from riparian habitats in Bank Swallows: new evidence from multiple endogenous markers.

The Bank Swallow (Riparia riparia), a threatened species in Canada, breeds primarily in banks at lakeshores and rivers and in artificial (typically inland) aggregate mining pits. Inland pits may be ecological traps for this species, but relative dietary trade-offs between these two nesting habitats have not been investigated. The availability of aquatic emergent insects at lakeshores may have associated nutritional benefits for growing nestlings due to increased omega-3 fatty acids (FAs) in prey. We compared the diets of juvenile swallows from lakeshore and inland pit sites using assays of stable isotope values (δ13C, δ15N, δ2H) of feathers, faecal DNA metabarcoding and blood plasma FAs. Colony proximity to Lake Erie influenced the use of aquatic versus terrestrial insects by Bank Swallow adults and juveniles. Feather δ2H was particularly useful as a tracer of aquatic emergent versus terrestrial prey, and inland juveniles had feathers enriched in 2H, reflective of diets composed of fewer aquatic emergent insects. DNA metabarcoding of juvenile and adult faecal material indicated that lakeshore birds consumed more aquatic-emergent chironomids than inland birds. Lakeshore juveniles had elevated plasma omega-3 eicosapentaenoic acid levels compared with inland pit-breeding birds. We discuss the need to consider 'nutritional landscapes' and the importance of this concept in conservation of declining species and populations.

New data on minerals of the hidalgoite-philipsbornite series from the Guatomo mine near Tham Thalu, Yala Province (Thailand)

The chemical composition of three samples of minerals of the hidalgoite-philipsbornite series from the central part of the Guatomo mine pit was studied in detail by EMPA-WDS. They form yellowish-green, light green to pale blue microcrystalline crusts or hollow pseudomorphs after prismatic hexagonal crystals of mimetite in fractures of strongly altered granite or quartz. All studied samples show relatively strong, irregular to oscillatory chemical zoning in BSE, caused by S versus As substitution on T-site. Most of the zones are corresponding to hidalgoite, with only minor, outer zones represented by S-rich philipsbornite. Besides of dominant contents of Pb, Al, As and S also minor amounts of K (up to 0.11 apfu), Na (up to 0.05 apfu), Cu (up to 0.22 apfu), Fe (up to 0.09 apfu) and P (up to 0.04 apfu) were detected in studied samples.

Application of the k - nearest neighbors algorithm for predicting blast - induced ground vibration in open - pit coal mines: a case study

Blasting is considered as one of the most effective methods for rock fragmentation in open - pit mines. However, its side effects are significant, especially blast - induced ground vibration. Therefore, this study aims to develop and apply artificial intelligence in predicting blast - induced ground vibration in open - pit mines. Indeed, the k - nearest neighbors (KNN) algorithm was taken into account and developed for predicting blast - induced ground vibration at the Deo Nai open - pit coal mine (Vietnam) as a case study. An empirical model (i.e., USBM) was also developed to compare with the developed KNN model aiming to highlight the advantage of the KNN model. Accordingly, 194 blasting events were collected and analyzed for this aim. This database was then divided into two parts, 80% for training and 20% for testing. The MinMax scale and 10 - fold cross - validation techniques were applied to improve the accuracy, as well as avoid overfitting of the KNN model. Root - mean - squared error (RMSE) and determination coefficient (R2) were used as the performance metrics for models’ evaluation and comparison purposes. The results indicated that the KNN model yielded better superior performance than those of the USBM empirical model with an RMSE of 1.157 and R2 of 0.967. In contrast, the USBM model only provided a weak performance with an RMSE of 4.205 and R2 of 0.416. With the obtained results, the KNN can be introduced as a potential artificial intelligence model for predicting and controlling blast - induced ground vibration in practical engineering, especially at the Deo Nai open - pit coal mine.

Migration of sand mining pit in rivers: An experimental, numerical and case study

Irregular, unauthorized and non-technical mining of sand and gravel from rivers play an important role in undesirable changes in morphology and environment. The present experimental study investigated sand mining pit modelling in the different scenarios. A two-dimensional flexible mesh, depth averaged model was set-up to simulate the experiments. The results exhibited an acceptable agreement between the numerical and experimental results, so that the maximum error was limited to less than 10%. After verifying the numerical model, a critical reach in Helleh River was selected as a case study. The effect of sand and gravel mining on a bridge at the site was studied. The results also indicated that for a flood event with a return period of 25 years, sand and gravel mining changed the bed profile up to 1.27 m at the bridge foundation. Moreover, initial signs of river meandering emerged in one scenario.

Spatial distribution of agricultural yields with elevated metal concentration of the island exposed to acid mine drainage

An island province in the Philippines exposed to acid mine drainage for about 22-25 years, uncovered new discovery in selected agricultural yields. The acid mine drainage was from two open mine pits of higher elevation flowing to Boac and Mogpog River system. A total of 78 various agricultural yields samples with 234 specimens were collected and analyzed from six municipalities of Marinduque, Philippines in 2019. These agricultural yields were (A) vegetables, (B) root crops, (C) fruits, and (D) rice. Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES) Perkin Elmer Optima 8000 with ICP multi-element standard solution IV were used to detect metals concentration in the agricultural samples. Digestion of samples followed the EPA Method 200.3. Results were compared with the WHO/FAO limit followed by the identification of yields and areas that pose risks to public health. Determination of the spatial distribution was by ArcGIS. The six municipalities; i.e., Boac, Buenavista, Gasan, Mogpog, Torrijos and Sta. Cruz, were labelled as B, BV, G, M, T and S, respectively. Record showed that Sample A from G contain higher metal concentration among other yields. Manganese concentration in Samples A, B, and D were found to be higher than WHO/FAO limit. However, copper and zinc concentration in Sample C in all municipalities exceeded the allowable limit. Elevated total chromium concentration was found in Sample D collected from G, T, and S. These results would help relevant government agencies and units design strategies to mitigate the degraded agricultural lands and protect public health.

Morphological Variation of Blue Panchax (Aplocheilus panchax) Lives in Different Habitat Assessed Using Truss Morphometric

Blue panchax ( Aplocheilus panchax Hamilton, 1822) lives in broad ranges of habitat from open waters to closed waters, including at ex-tin mining pits in Bangka Island, Indonesia. Variable habitats might cause morphological variations due to different ecological factors. This study aimed to assess the morphological variation of blue panchax collected from different habitats using truss morphometric characters. Fish samples (70 individuals) were collected from abandoned ex-tin mining pits of different ages and a river in Bangka Island. Twenty-nine truss characters were analyzed using the Kruskal-Wallis test and post hoc with Dunn’s test . The results showed that almost all of the body parts of blue panchax found in ex-tin mining pits and rivers were significantly different (p-value < 0.05), except some truss characters of caudal peduncle . The post hoc of Dunn’s test showed a positive correlation between habitats and truss characters (adj. sig < 0.05). Some truss characters of killifish were different between ex-tin mining pits with different ages chronosequence, and some other characters were different between pits and river. This study provides the first data about the morphological variation of blue panchax in ex-tin mining pits of different ages. The data is valuable as a scientific basis of further utilization of ex-tin mining pits in the areas.

Социально-экономическая эффективность реализации проекта по использованию отвалов вскрышных пород для нужд транспортного строительства на территориях нового освоения

The objective of the paper is to demonstrate a cost efficiency assessment methodology adapted to a major integrated mining and transport project. The sources of social and economic efficiency of the project to use overburden dumps for the needs of transport construction in the areas of new development are stated in the article. In order to assess such a large-scale and complex project, it is not enough to rely on a universal general project methodology; the methods must be adapted and customized. In particular, cross-sectoral and indirect effects arise that will require an adequate organizational and economic scheme for the project to be implemented. It has been concluded that a complex assessment of economic efficiency is only possible with the view of the entire national economy, taking into account not only direct but also indirect, including non-transport, effects. However, the basis for accepting the project for a detailed study is to compare the cost of the ballast material delivered to a specific point in the project network infrastructure of the development territory from the dumps of the mining pits and from the roadside pits, i.e. following the traditional method.

IMPLICATIONS OF CORAL REEF MINING PITS ON 2D HYDRODYNAMICS

Small Island Developing States (SIDS) are among the most vulnerable areas to the impact of natural hazards and climate change. Flooding due to storm surges and extreme waves, coastal erosion, and salinization of freshwater lenses are already a serious threat and could lead to irreversible consequences in the coming decades. On the other hand, reef flat mining is one of the most common practices to source the required material for the implementation of coastal protection measures on SIDS. There are strong concerns about this practice, because partial removal of the protective reef could increase wave impacts on the islands. However, the available data and knowledge on the effects of these mining pits are currently very limited. Klaver et al. (2019) studied the effects that pits may have on nearshore hydrodynamics and wave runup. Results obtained via numerical modeling indicate that excavation pits cause a decrease in infragravity wave energy around the fundamental mode of the reef, which is partly caused by reduced wave transmission. Similarly, changes in sea and swell (SS) wave energy are attributed to reduced transmission, as well as a decrease in wave dissipation and (triad) wave-wave interaction. Earlier studies by Ford et al. (2013) and Yao et al. (2016) point out that mining pits may lead to additional two-dimensional effects. In this presentation, we present the potential 2D effects of reef flat excavation pits on nearshore hydrodynamics. More specifically, we aim to assess the impact of excavation pits on nearshore circulation patterns, which could be an indicator of coastal morphological changes.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/85-IMM66eWE

Models for prehistoric lithic quarry development

Archaeologists have struggled to find meaningful and cost effective ways to analyze and interpret prehistoric quarry sites. Quarry site deposits typically contain large quantities of broken rock fragments that generally lack morphological attributes commonly used for lithic debitage analysis. Remnants of quarry pits often overlap and converge, forming complex cultural landscapes that are difficult to document and understand. Archaeological excavations near Glens Falls, New York, uncovered evidence of prehistoric mine pits, dense layers of chert quarry debris, and intensively battered bedrock surfaces. High resolution mass analysis was used to analyze large quantities of quarry debris. A new classification for prehistoric quarry sites and new models for quarry site development are proposed.

Operational mine planning in block cave mining: a simulation-optimisation approach

ABSTRACT Block cave mining operations face challenges to meet daily operational production targets. The optimistic long-term and medium-term plans along with uncertainty and the synergistic effect of the mechanical and structural failures in operational levels of the mine cause a significant deviation from production plan targets. The on-site tuning of the mining production targets in real time are neither the best practice nor the optimum approach to compensate for shortfalls in production. The objective of this paper is to develop a methodology that generates practical and near-optimal short-term mine plans for block caving operations in the presence of operational uncertainty. To accomplish this goal, we propose a simulation-optimisation approach using a Monte Carlo simulation model and a multi-objective non-linear goal programming model that takes into consideration operational constraints and uncertainties. In a case study, we compare the results of the proposed methodology against the mine plan and the historical production data of a copper block cave operation. The strengths and weaknesses of the model are presented and discussed.

Diurnal and Seasonal Variation of Area-Fugitive Methane Advective Flux from an Open-Pit Mining Facility in Northern Canada Using WRF

Greenhouse Gas (GHG) emissions pose a global climate challenge and the mining sector is a large contributor. Diurnal and seasonal variations of area-fugitive methane advective flux, released from an open-pit mine and a tailings pond, from a facility in northern Canada, were simulated in spring 2018 and winter 2019, using the Weather Research and Forecasting (WRF) model. The methane mixing ratio boundary conditions for the WRF model were obtained from the in-situ field measurements, using Los Gatos Research Ultra-Portable Greenhouse Gas Analyzers (LGRs), placed in various locations surrounding the mine pit and a tailings pond. The simulated advective flux was influenced by local and synoptic weather conditions in spring and winter, respectively. Overall, the average total advective flux in the spring was greater than that in the winter by 36% and 75%, for the mine and pond, respectively. Diurnal variations of flux were notable in the spring, characterized by low flux during thermally stable (nighttime) and high flux during thermally unstable (daytime) conditions. The model predictions of the methane mixing ratio were in reasonable agreement with limited aircraft observations (R2=0.68). The findings shed new light in understanding the area-fugitive advective flux from complex terrains and call for more rigorous observations in support of the findings.

Lowland gravel-bed river recovery through former mining reaches, the key role of sand

Whereas the geomorphic effects of in-channel mining have been widely documented, very few studies have focused on recovery trajectories after mining ended. This paper describes and quantifies the channel adjustment of extended and over-widened mining pits located in a low energy gravel-bed river, and identifies the factors that control their recovery rate. The study was based on aerial photographs and LiDAR analysis, grain-size sampling, bedload computation and geophysical measurements made during ground penetrating radar (GPR) and electrical resistivity tomography (ERT) surveys. We describe the spatio-temporal changes in the morphology of former pits as well as the current surficial longitudinal grain-size pattern in pits and in neighbouring upstream and downstream reaches. Our results show a wide range of geomorphic readjustments. Between 23 and 47 yr after the end of mining, the mining reaches have still not yet fully recovered. The planimetric recovery rate is closely correlated with the ratio of the volume deposited in the pits to their original volume. Finally, the infilled material is only partly composed of bedload and the mainly sandy fine sediments play a primary role in the recovery process. The abundance of sand, controlled by the lithology of the watershed, explains the unexpectedly high recovery rates of some pits despite the low energy of the river.

A novel soft computing model for predicting blast - induced ground vibration in open - pit mines using gene expression programming

The efforts of this study are to develop and propose a state - of - the - art model for predicting blast - induced ground vibration in open - pit mines with high accuracy anf ability based on the gene expression programming (GEP) technique. 25 blasts were conducted in the Tan Dong Hiep quarry mines with a total of 83 blasting events that were collected for this study. The GEP method was then applied to develop a non - linear equation for predicting blast - induced ground vibration based on a variety of influential parameters. A traditional empirical equation, namely Sadovski, was also applied to compare with the proposed GEP model. The results indicated that the GEP model can predict blast - induced ground vibration in open - pit mines better than the Sadovski model with an RMSE of 0.986 and R2 of 0.867. Meanwhile, the traditional empirical model (Sadovski) only provided an accuracy with an RMSE of 1.850 và R2 of 0.767.

Role of mineral flotation technology in improving bitumen extraction from mined Athabasca oil sands III. Next generation of water‐based oil sands extraction

AbstractCurrent water‐based oil sands extraction operations are unsustainable, due to their consumption of large quantities of water and energy, generation of large volumes of fluid fine tailings, and rapid expansion of tailing ponds. From a brief analysis of the historical evolution of water‐based oil sands extraction, it has been identified that the use of conventional dispersed air flotation to recover liberated bitumen from oil sand slurries is mainly responsible for the high consumption of water required and the fluid fine tailings generated. Based on mineral flotation principles, a new concept is proposed, whereby water‐based oil sands extraction is simplified as a process of transferring hydrophobic bitumen from hydrophilic surfaces (sands) to hydrophobic surfaces (bitumen carriers). Compared to existing bitumen extraction technologies, bitumen liberation from sands is accelerated by attrition/scrubbing, and the liberated bitumen is recovered from the oil sand slurry by hydrophobic coagulation and heavy media separation. This concept is verified from preliminary laboratory tests for processing (above) average grade oil sands. The water required is significantly reduced from 100 to 150 wt% of the ores processed (as seen in current commercial operations) to 30‐40 wt% of the ores. Virtually no fluid fine tailings are generated, with the potential of eliminating tailing ponds. The tailings produced after bitumen extraction are paste‐like, containing &gt;60 wt% solids, which can be directly disposed of in the mining pit, with little or no further treatment. Future research is needed to justify and refine the concept in large‐scale tests and engineer it into commercial operations.

Study of flow turbulence around a circular bridge pier in sand-mined stream channel

Experiments were performed in a sand bed channel to investigate the effects of a mining pit on the hydrodynamics around circular bridge piers. Mean velocity profiles, Reynolds stresses, kinetic energy fluxes and scales of turbulence were analysed at critical locations along the channel bed as well as in the proximity of the pier. At the approach location where flow had passed over the pit and was approaching the pier, substantial increments in the near-bed velocities, bed shear stress and Reynolds stresses were observed. Dredging of the pit increased the strength of the horseshoe vortex in the scour hole region and also amplified the shedding frequency of trailing vortices at the rear of the pier. These effects may be instrumental in the alteration of local scour as well as erosion and deposition patterns around bridge piers.