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Fragmentation by blasting is a critical process in hard rock mining. The interaction between the rock mass and blast energy influences the outcomes, specifically on the rock mass response to higher stresses and loading rates, and the properties of structures. In this study, LS-DYNA is used to model the nonlinear dynamic fracturing of the rock to understand the effects of rock mass properties on the blast outcomes. The results are verified and compared with the case study, and they show that the formation of damage zones around the charge is highly influenced by rock mass strength and discontinuity properties. [ABSTRACT FROM AUTHOR]

Three hundred and twenty-four data points on the saturated hydraulic conductivity (k) of various hard rock mine tailings are collected from previous publications. The applicability of existing empirical equations for hard rock mine tailings is assessed based on this database collected. Results show that with a greater exponent of d10, the correlation between the measured and predicted k is greatly improved. An empirically modified version of the Kozeny–Carman equation is then proposed for predicting the saturated k of tailings and compared with the database. The proposed equation gives the best fit with a varying exponent greater than 2 for d10. Finally, the impact of particle shape on k is discussed. [ABSTRACT FROM AUTHOR]

Rock fragment movement during blasting operations is a major cause of ore and profit losses in hard rock open-pit mines having a complex-orebody. To address this issue, a novel multilayer dig-limit approach, which well considers blast movement in dig-limit optimization, was proposed in this study by combining machine learning techniques and practical heuristic algorithms. First, horizontal and vertical blast-induced rock movement distances were predicted using a supervised learning model. Then, the movement direction of rock fragments was computed based on the initiation sequence. After meshing the blast block into rock units, the blasted muckpile and post-blast ore boundary were determined, providing a good basis for dig-limit determination. Finally, the optimized dig-limit with maximum profit can be calculated using a practical heuristic algorithm. By applying this method in a case study, the ore recovery and economic profit were improved, compared with manually drawn dig-limit method. Additionally, the impact of equipment size, number of layers and powder factor on the application of this method was discussed. The obtained results indicated that ore and profit losses can be reduced with a decreased equipment size, increased number of layers and decreased powder factor. Highlights: A multilayer dig-limit approach considering blast-induced rock movement and dig-limit optimization was proposed. The multilayer dig-limit approach yields higher ore recovery and economic profit compared to manually drawn dig-limit. Ore losses can be reduced by decreasing the equipment size, increasing the number of layers and decreasing the powder factor. [ABSTRACT FROM AUTHOR]

Burden is one of the most important parameter which plays an immense role in rock breakage using explosive energy. It is very difficult to select the optimum burden under different geotechnical and geomining condition. The selection becomes more critical when the excavation method is underground as very few researches or studies have been carried out in such cases. Therefore, in this paper, numerical simulation-based approach has been employed to estimate the optimum burden for ring blasting. The numerical models were created under different scenario including blasthole diameter and strength of the rock. The RHT concrete constitutive model has been used in this paper to study the damage contour under different circumstances. The model output has been used to calculate the volume of rock damage along the free face. This damage volume is further correlated with various parameters. This correlation shows that the damage volume along the free face initially rises with the increase in burden and then starts decreasing after a certain value. The burden value which recorded the maximum volume of rock excavated along the free face has been considered as the optimum burden in this paper. The trial blast has been also carried out at the experimental site for twenty-four rings. The optimum burden achieved from the experimental trial for 102 mm blasthole diameter and rock having uniaxial compressive strength as 92 MPa lies between 2.4 and 2.65 m. However, the optimum burden predicted through developed empirical equation from the numerical model is 2.6 m. The study shows that the simulation-based prediction exhibits a minor deviation within 15% with the experimental result. Hence, to assess the optimum burden under various geotechnical and geomining circumstances, numerical simulation-based approach may be carried out using the proposed methodology. Highlights: Burden for ring blasting is optimised using different numerical simulation models. Volume of rock excavated along free face (EV) has been calculated in each case. The optimum burden from experimental trial and empirical data is 2.4–2.65 m. The optimum burden predicted from developed model is 2.6 m. [ABSTRACT FROM AUTHOR]

Mass spectrometry is a widely used tool for analysis of uranium isotopic composition. For solution based inductively coupled plasma mass spectrometry, uranium isotopes are typically analyzed after purification from complex matrices. In this work, we tested the ability of three mass spectrometers (ThermoScientific iCAP TQ, ThermoScientific Neoma, and Agilent 8900) to analyze uranium isotopes in an unpurified NIST reference material (SRM2780a, Hard Rock Mine Waste) digest solution. Results indicate that 235U/238U can be analyzed within 1% of the true value. 234U/238U is a more challenging analysis due to low count rates and potential isobar interferences, but strategies to mitigate these effects, such as the use of reaction gases in a collision cell and desolvating nebulizer introduction system, are effective for the triple quadrupole instruments. However, the use of the Neoma MS/MS in reaction mode using O2 gas was problematic. Nevertheless, analysis of unpurified solutions for quick assessment of uranium isotope compositions is practical, especially when high precision is not required. [ABSTRACT FROM AUTHOR]

This article delves into the debates, both in print and digital media, surrounding copper mining and its associated concerns, particularly those related to hardrock mining. Guided by agenda-building, pragma-dialectics, and stakeholder theories, this research employs topic modeling to scrutinize the media strategies and arguments employed by key stakeholders involved in an environmental movement. The aim is to unveil implicit communication activities that contribute to the emergence of public debates, shedding light on the nuanced dynamics within stakeholder discourses. The analysis shows that by referring to authoritative arguments, the local press distributes the places of power while representing conflicting standpoints and arguments. With digital media, the opponents build a pro-environmentalist network to publicize the issues relative to the mining project and the importance of defending southwestern habitats and landscape. Mining proponents similarly rely on business communities to underscore the importance of hardrock mining for things like decarbonized energy and modern living. Across groups, stakeholder communication situates differing conceptions of the relationship between humans and their natural environment. Our findings reveal that, consistently across various groups, the discourse maintains a degree of stability as topics and arguments persist over time. On one side, discussions highlight the destructive impacts of mining, while the opposing perspective underscores the significance of sustainable and resilient mining practices. This analysis of stakeholder discourses in the media helps uncover the various ways primary actors maintain their positionality and power in this particular case. [ABSTRACT FROM AUTHOR]

Background and aims: Re-vegetation of mining-impacted landscapes reduces transport of toxic elements while improving soil fertility. This study evaluated whether the planting of a native perennial grass with a consortium of diazotrophic microbial endophytes and municipal waste compost—alone and in combination—enhanced plant growth while stabilizing metal(loids) in dolomite-amended tailings from a historically mined polymetallic mineral deposit. Methods: We grew Bouteloua curtipendula seedlings in tailings with hazardous concentrations of As, Cd, Pb, Mn, and Zn. We evaluated how plant growth, organic matter accumulation, and major, minor, and trace element mobilization and phytostabilization responded to microbial endophyte and/or compost amendments after the 45-day growth experiment. Results: Although most of the added endophytes were not uniquely identified, the best plant growth and fertility outcomes were achieved with a combination of amendments: dolomite to reduce acidity, compost to increase nitrogen, and a mixed consortium endophyte seed coating to synergistically increase organic carbon and grass biomass yields. Compost reduced shoot and root concentrations—but not yields—of contaminant metals. Endophytes increased foliar Cd, Co, Mn, and Pb yields but mobilized Pb and Zn from the tailings. Root stabilization of Cd, Co, Mn did not require amendments. Conclusion: The most effective means of revegetating these acidic, polymetallic tailings with the native B. curtipendula is with a simultaneous dolomite, compost, and endophyte seed treatment. Due to potential phosphate solubilization and siderophore production by this consortium of endophytes, strategies to capture solubilized metal(loids) may be needed for sulfidic tailings with metal(loids) associated with mobile mineral phases. [ABSTRACT FROM AUTHOR]

The article explores the history of the disposal of mine waste and tailings in British Columbia during the period of 1892 to 1982. It argues that historical debates in the province over mine waste management were rooted in a settler colonial conception of land and water as resources for metaphorical and literal accumulation that influenced approaches to tailings management. It discusses the impact of the mine waste management regime on the appropriation of Indigenous lands and waters.

In recent years, with the gradual depletion of shallow mineral resources, the exploitation of deep mineral resources has become an inevitable trend. Microseismic monitoring is one of the main methods to solve high stress concentration problems such as rockbursts, roof caving and water inrush in deep mine. An accurate and fast microseismic location method is the basis of microseismic monitoring. At present, machine learning (ML) has become an important auxiliary method in the field of microseismic monitoring due to its powerful feature expression ability. Compared with other microseismic positioning methods, ML can construct a more objective positioning model. This paper uses three ML models including deep neural network (DNN), random forest (RF),and support vector regression (SVR) to construct a microseismic position method to search for the microseismic source. The travel time difference between stations is used as the input of the ML model. Since the number of field data sets is not enough to complete the training of the model, this paper uses a synthetic data set with a specific speed model as the training set and uses the field data set for testing. In order to analyze the location accuracy, we compare them with three traditional microseismic location methods. To improve the positioning performance of ML models, this paper uses a Bayesian optimizer (BO) to adjust their hyperparameters. The experimental results show that the performance of the ML model adjusted by the BO has been significantly improved. The positioning accuracy order of the three ML models is DNN > RF > SVR > traditional location method. The average positioning accuracies of the DNN inside and outside the sensors array are 27.81 m and 145.96 m, respectively. For the model proposed in this paper, the positioning accuracy inside the sensors array is significantly higher than that outside the array, which is similar to the traditional positioning method. In addition, the model has a certain tolerance to the error of the speed model. Highlights: Utilization of machine learning (ML) for accurate and objective microseismic source location. Comparative analysis of three ML models (DNN, RF, SVR) and traditional methods. Enhancement of ML model performance using Bayesian optimizer for hyperparameter tuning. Significant improvement in positioning accuracy with DNN model inside and outside the sensor array. Tolerance to speed model errors in the proposed ML-based microseismic positioning method. [ABSTRACT FROM AUTHOR]

To investigate the leaching rules and mechanism of a hard rock uranium ore, this paper conducted conventional leaching experiments based on the chemical composition and mineral occurrence status of the ore. Various factors affecting leaching were explored, and experimental data were fitted using the shrinking-core model. The results showed that uranium in the ore mainly existed in the form of pitchblende and coffinite, and the uranium grade of the sample was 0.15%. Under the leaching conditions of a temperature of 50 °C, a particle size of − 100 mesh, an acid dosage of 32 kg t−1, a pyrolusite dosage of 10 kg t−1, a liquid–solid ratio of 1:1, and an 8 h duration, the leaching rate of the uranium ore reached 99.12%. The leaching process was controlled by solid film diffusion, and the apparent activation energy was 11.6 kJ mol−1. Insoluble substances were present on the surface of the slag, and the solid film product was the main reason hindering leaching. [ABSTRACT FROM AUTHOR]

An experimental method is proposed to assess blasting requirements based on in-situ cratering behavior. The method relies on single hole blast (SHB) tests to derive burden-dependent relationships. A non-linear crater model of the form Y = C b s is calibrated from SHB test results to describe the cratering behavior. Parameters C and s represent characteristic blastability index parameters that depend on geomechanical and operational conditions. A series of experimental SHB tests were conducted at three hard rock mines. The craters were mapped to capture the breakout profile and calibrate the model. Results showed that coefficient C presents an inverse linear correlation with burden B , while exponent s is approximately constant for a considerable range of burden values. Experimental results are used to define burden dependent relationship for bench blast designs and blasthole placement in underground development rounds. A complementary analysis addresses the prevalence of multiple cratering mechanisms according to geology and burden dimension. [ABSTRACT FROM AUTHOR]

This study investigated the use of a limit equilibrium model to simulate the time-dependent scaling of hard rock pillars. In the manganese bord and pillar mines in South Africa, extensive scaling is observed for pillars characterised by a high joint density. It appears that the scaling occurs in a time-dependent fashion. Evidence for this is the ongoing deterioration of pillars in old areas, even after the pillars are reinforced with thin spray-on liners. Monitoring of selected pillars were conducted in an attempt to quantify the rate of time-dependent scaling. Contrary to expectations, almost no additional scaling was recorded for the pillars during a 3-month monitoring period. The scaling distance for pillars of different ages could be measured and it seems as if most of the scaling occurred soon after the pillars are formed. Only a limited amount of additional time-dependent scaling seems to occur after this. Numerical simulations of the time-dependent scaling were conducted using a displacement discontinuity code and a limit equilibrium constitutive model. The postulated exponential decay of the failed rock mass strength at the edges of the pillars resulted in simulated behaviour that is qualitatively similar to the underground observations. The results from this study are encouraging and the method can be used to investigate the long-term stability of bord and pillar excavations. Further work is required to improve on the calibration of the model and to better quantify the rate of scaling of the underground pillars. Highlights: Time-dependent scaling gradually reduces the strength of pillars. This paper presents a study of this behaviour in a hard rock bord and pillar mine. A numerical modelling approach to simulate time-dependent pillar failure, on a mine-wide scale, is described in the paper. It consists of a displacement discontinuity boundary element method with a time-dependent limit equilibrium model. The behaviour of the hard rock pillars in the manganese mines in South Africa is used to test the proposed model. It provides valuable data for researchers interested in case studies of time-dependent pillar strength. The proposed modelling methodology seems valuable to design layouts where long-term stability is a requirement. Although the focus in this paper is on hard rock mines, it can also be used for coal pillars. [ABSTRACT FROM AUTHOR]

The re-vegetation of mining wastes with native plants is a comparatively low-cost solution for mine reclamation. However, re-vegetation fails when extreme pH values, low organic matter, or high concentrations of phytotoxic elements inhibit plant establishment and growth. Our aim was to determine whether the combined addition of municipal waste compost and diazotrophic endophytes (i.e., microorganisms that fix atmospheric N2 and live within plants) could improve plant growth, organic matter accumulation, and phytostabilization of trace element contaminants in two types of hard rock mine waste. We grew a widespread native perennial grass, Bouteloua curtipendula, for one month in alkaline waste rock (porphyry copper mine) and tailings (Ag-Pb-Au mine, amended with dolomite) sourced from southeastern Arizona, United States. B. curtipendula tolerated elevated concentrations of multiple phytotoxic trace elements in the tailings (Mn, Pb, Zn), stabilizing them in roots without foliar translocation. Adding compost and endophyte seed coats improved plant growth, microbial biomass, and organic matter accumulation despite stark differences in the geochemical and physical characteristics of the mining wastes. The widespread grass B. curtipendula is a potential candidate for re-vegetating mine wastes when seeded with soil additives to increase pH and with microbial and organic amendments to increase plant growth. This study quantifies improvements to plant growth, soil fertility, and trace element stabilization with a municipal waste compost topdressing and diazotrophic endophyte seed coating in two common hard rock mining wastes of the western United States. It establishes that a widespread perennial grass, Bouteloua curtipendula, can grow despite high concentrations of phytotoxic trace elements and minimal soil nutrients, and stabilizes trace elements on or in its roots, making it a suitable option for re-vegetation or phytostabilization of hard rock mining wastes. [ABSTRACT FROM AUTHOR]

Rock-burst is one of the most serious risks associated with hard rock tunnelling and mining at high depths. Monitoring of acoustic emissions emitted by the rock-mass during excavation and their interpretation now permits the early assessment of failure events and makes the safe management of the construction works possible. A reliable set-up of the alarm threshold is thus fundamental for the correct implementation of the procedures planned to minimise rock-burst related risk. This paper focuses on a novel in situ test specifically developed to provide an experimental basis for a more accurate assessment of the alarm threshold during tunnelling, representative of the local geomechanical conditions. The test, thanks to the compression induced by two flat jacks at the tunnel side wall, produces an artificial failure process during which acoustic emissions are measured and correlated to the mechanical response of the rock-mass, without the typical limitations of scale that characterised the laboratory experiments. The new methodology, named the Mules method, was successfully tested during the excavation of some stretches of the Brenner Base Tunnel in the Brixner granite, affected by mild spalling episodes. The case-history is fully described in the paper to illustrate the practical application of the proposed approach. Highlights: A new in situ test is proposed for the assessment of the rock-burst alarm threshold. The rock-mass is brought to failure at the tunnel side wall by two flat jacks and acoustic emissions are monitored. Two tests were carried out during the construction of the Brenner Base tunnel in a granite formation under high cover affected by mild spalling phenomena. The power spectrum density of the signals recorded during the tests displayed its maximum values before the rock-mass failure. Test results interpreted in terms of power spectrum density summation were adopted to set up the rock-burst alarm threshold during tunnel excavation. [ABSTRACT FROM AUTHOR]

In mining industries, the prime concern is to overcome the challenges of using conical cutting bits for excavating hard and abrasive rocks. In this research, a speculative investigation was performed to measure the efficiency of rock cutting and identify the wear behavior of aluminum titanium nitride-coated conical cutting bits. A newly designed and customized shaping machine is used with a triaxial force dynamometer to cut the rock samples linearly and to calculate their associated powers. Coated conical bits have a maximum hardness range of 2,291 to 2,459 HV, and uncoated conical bits possess minimum hardness range of 1,945 to 1,948 HV. Two rock samples of fine-grained sandstone with UCS of 83.77 and 97.00 MPa are used in this study. Various cutting ranges were investigated and the best range of cutting parameters are identified between the variables, such as cutting forces and extracted volume of rock, cutting effectiveness, specific energy produced while cutting, and bit wear. The percentage decrease in wear rate of a coated conical bit compared with an uncoated conical bit is 40.36%, 52.28%, and 53.30% for Rock 1 and 42.67%, 54.76%, and 60.90% for Rock 2 under varying depths of cut. The worn surface has been significantly investigated through scanning electron microscopy and energy dispersive X-ray analysis. The output of this study helps in extending the application of a surface miner for excavating harder rocks in mines. [ABSTRACT FROM AUTHOR]

Flame jet-assisted mechanical rock breaking technology is an important method to achieve efficient NECMM (non-explosive continuous mechanized mining) in hard rock mines. Therefore, it is very important to understand the physical and mechanical properties of the spalling pit surrounding rock after flame jet. In this paper, thermal spalling tests were first performed on granite blocks using a flame with a power of 13.6 kW. Then, the mechanical behaviors of the specimens at different distances from the flame jet path were measured. The result showed that the Vp (P-wave velocity), BTS (Brazilian tensile strength), UCS (uniaxial compression strength), and E (Young’s modulus) of granite increased with increasing distance. Meanwhile, the mechanical properties of the specimen at 70 mm were slightly lower than that of the untreated specimen. Therefore, it can be assumed that the damage radius of granite after the flame jet was about 70 mm. In Brazilian test, according to the strain cloud diagram of DIC (digital image correlation) system, the high strain zone expanded from the center to both ends of the specimen, and the strain value gradually increased, eventually forming a through-wall crack along the loading direction. In the uniaxial compression test, AE (acoustic emission) counts within the compacted stage increased obviously as the distance from the specimen to the flame jet path decreased. This phenomenon indicated that the thermal damage of specimens near the center of the spalling pit was more severe, and more microcracks inside the specimens were compacted. The thermal spalling and thermal damage model of the rock under the flame jet was established, which can well explain the changes in mechanical properties of rocks. The fact that thermal damage area of the rock after the flame jet is much larger than thermal spalling area is responsible for the feasibility of flame-assisted mechanical rock breaking. Damage factors based on Vp and E can well describe the weakening of the mechanical properties of granite. The results are important for guiding flame jet-assisted mechanical rock breaking in hard rock mines. [ABSTRACT FROM AUTHOR]

With the increase in mining depth and the deterioration of mining conditions, thick and hard overburden movement frequently induces mine earthquakes and rock bursts. Some mines are expected to prevent and control super thick hard rock mine earthquakes through vertical ground well water fracturing technology. However, the dynamic underground disaster appears more intense. Taking the '11.30' mine earthquake in a mine in Shandong Province as the engineering background, the dynamic disaster mechanism of an extraordinarily thick and hard roof induced by hydraulic fracturing of vertical wells on the ground was studied utilizing field investigation, accident case analysis, similar material simulation test, and theoretical analysis. The main conclusions are as follows: (1) After hydraulic fracturing vertical wells on the ground, the movement mode of thick and hard roofs changed from layer-by-layer to overall sliding movement; (2) The influence range of the advanced abutment pressure of the working face is reduced by the hydraulic fracturing of the vertical shaft, and the peak value of the advanced abutment pressure increases. Furthermore, the advanced abutment pressure's peak is far from the coal wall; (3) The hydraulic fracturing technology of cross-arranged vertical surface deep and shallow wells and the hydraulic fracturing technology of cross-perforated surface multi-branch horizontal wells are proposed to avoid the dynamic disaster of overall sliding movement of an extremely thick hard roof induced by surface hydraulic fracturing. Therefore, these research results provide significance for preventing and controlling mine earthquakes and rock bursts in super thick hard roof mines. [ABSTRACT FROM AUTHOR]

The article reports that the General Mining Law of 1872 of the USA the recent administration has embarked on reforming the law to promote the sustainable and responsible domestic production of minerals and to ensure a fair return to the taxpayer. Topics include examines the Mining Law was to encourage mineral exploration and development on Federal lands and the settlement of the West.

The increasing salinization of freshwater streams from anthropogenic land uses and activities is a growing global environmental problem. Increases in individual ions (such as sodium or chloride) and combined measures such as total dissolved solids (TDS) threaten drinking water supplies, agricultural and economic interests, and the ecological health of freshwater streams. Because the toxicity of high ionic strength waters depends on the specific ion composition, few water quality standards exist to protect freshwater streams from salinization. In the present study, we used a novel approach to develop site‐specific and ecologically relevant TDS thresholds for the protection of aquatic life. The first step of the approach was to characterize the ion composition of the waterbody or region of interest and prepare artificial samples to match that composition. Using a combination of standardized toxicity test species and more ecologically relevant field‐collected species, toxicity tests were then conducted on these artificial samples prepared at a range of TDS concentrations. The advantage of this approach is that water quality criteria can be developed for easy‐to‐measure generalized parameters such as TDS while ensuring that the criteria are protective of instream aquatic life and account for the complex interactions of the various ions contributing to salinization. We tested this approach in Sand Branch, Loudoun County, Virginia, USA, where salinization from hard rock mining and urban runoff has impaired aquatic life. Acute and chronic TDS thresholds of 938 and 463 mg/L, respectively, were developed in this stream and used for total maximum daily load development in the watershed. The approach provides a potential model for establishing protective thresholds for other waterbodies impacted by salinization. Environ Toxicol Chem 2022;41:2782–2796. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Underground mining operations are a very problematic task, especially in poor geotechnical conditions. The right choice of excavation and support techniques leads to adequate and secure mining operations. This should ensure the overall stability of the underground mine with the best productivity and stability performance. In this paper, an empirical model for obtaining support systems for underground galleries was applied. Then, a numerical model for the evaluation of the performance of support measures for rock masses in the Boukhadra iron mine was introduced. Extensive field and laboratory tests were performed to obtain geological, geotechnical, and mechanical data on the entire geologic formations of the (1105 m) level. The performance of the design is supported by the selection of a common support plan between RMR, Q, and UBC systems for each geotechnical unit. Therefore, the rock masses classification based on the geo-mechanical model has determined the suitable support systems. The finite element model (FEM) was used for the analysis of rock mass behaviour, displacements, stress, and plastic point distribution. The results permit the optimization of the plastic zone thickness around the gallery. The outcomes of this study could improve the stability of the mine by choosing the right direction of excavation in consideration to the direction of the discontinuity planes. In order to choose between the current and the recommended mining operations, an equivalent calculation sequence was verified. Our study demonstrated that the consideration of discontinuity sets in the orientation of excavation highly improves the mining conditions with or without support. [ABSTRACT FROM AUTHOR]

In underground mines, stability problems can cause unplanned dilution, increasing the costs of mining operations, such as loading, transport, crushing and grinding. This is usually dealt with by simply increasing investments with support. However, the design geometry of stopes and drifts also has a great effect on a stope's stability. The use of empirical stability methods is a very common practice, however because of their few input parameters, it cannot predict the actual performance related to each stope and drift design. This study has as main goals a back analysis of the actual dilution, using the Equivalent Linear Overbreak Slough (ELOS) method and analysis in the drift developments at the hanging wall contact, using numerical models. The case study is an underground hard rock gold mine, with a pillar-less Transversal Stope method. The hanging wall failure was quantified using a database from 19 stopes measured by the Cavity Monitoring System (CMS). Numerical finite elements models (FEM) were used, and 5 primary stopes were selected to calibrate models. The volumes of actual dilution showed a good correlation with the volumes of the relaxation zones produced by the models. Then, new optimized drift geometry layouts at the hanging wall contact were proposed, showing a decrease in 2.35 times in the relaxation zone of the numerical models, therefore justifying the use of these models as a dilution optimization tool. This methodology also proved to be useful in the definition of cable bolt length. [ABSTRACT FROM AUTHOR]

Rock bursts are often encountered in coal mines worldwide. (10) Li, L. et al., Study on Overburden Movement and Fissure Evolution Law of Protective Layer Mining in Shallow Coal Seam [[10]]. 10.3390/en15051803 10 Li L., Wu G., Liu Q. Study on Overburden Movement and Fissure Evolution Law of Protective Layer Mining in Shallow Coal Seam. 10.3390/en14164832 3 Xiong Y., Kong D., Cheng Z., Wen Z., Ma Z., Wu G., Liu Y. Instability control of roadway surrounding rock in close-distance coal seam groups under repeated mining. [Extracted from the article]

The goaf volume in the vacancy method of hard rock mines is significantly larger than the filling capacity, forming layered and inclined planes during the large-scale filling process. This results in unclear mechanical impact mechanisms on the backfill. To investigate the effect of interface inclination angle on the mechanical behavior of backfill, a set of cemented tailings composite backfill (CTCB) samples with interface inclination angles of 15°, 30°, and 45° are prepared. Uniaxial compression tests and digital image correlation techniques are used to investigate the influence of various interface inclination angles on the strength, deformation behavior, and failure mode of the CTCB. The results show that: (1) The uniaxial compressive strength (UCS) of the CTCB weakens with increasing interface inclination angle but consistently shows exponential growth with curing age (CA) regardless of the interface inclination angle. (2) The interface inclination angle controls the behavior and classification characteristics of the stress-strain curve of CTCB samples, and the increase of interface inclination angle weakens the elastic modulus. (3) The interface inclination angle significantly influences the failure mode and classification characteristics of the samples compared to CA and tailing-to-cement ratio (TCR), with shear slip failure induced by the former and axial splitting failure induced by the latter. The research provides a theoretical basis for understanding the mechanical behavior and stability control of inclined CTCB in underground mining. • A series of CTCB samples with varying interface inclination angles are prepared. • Relationship between interface inclination angles and mechanical properties is investigated. • A matrix correlation between elasticity modulus and strength is obtained. • Types of stress-strain curves and types of failure modes for CTCB samples are classified. [ABSTRACT FROM AUTHOR]

The selection of mining equipment is one of the most important parts for decision-makers, which can affect the mine and the entire planning. Underground mines are usually divided into two categories; hard rock and soft rock, each of which has its equipment according to the type of exploitation method used. There are different ways to make decisions and choose mining equipment. One of the practical approaches can be the use of the Multi-Criteria-Decision-Making models (MCDM). The main aim of this research is to develop a decision support system based on MCDM methods and use FUZZY logic to resolve uncertainties in the Underground-Hard Rock Mining Equipment Selection (U-HRMES). In this paper, the U-HRMES model has been used in Anguran underground lead and zinc mine as a case study. At present, the drilling and loading-hauling equipment of the Angoran mine does not perform properly. Therefore, to improve the performance and speed up the mining operation, it was tried to suggest suitable equipment using the U-HRMES. For this purpose, effective criteria were obtained based on a literature review, and according to the conditions of the Anguran underground lead and zinc mine, these criteria were filtered, and then, Twenty-two subcriteria with four groups of main criteria; technical specifications of the machine, economic and environmental issues, stope conditions and finally management and operational issues were obtained. It should be noted that the types of preference functions in the selection process of underground hard rock mining equipment were determined based on expert groups. Using the U-HRMES, two series of decisions were evaluated for the options of drilling equipment and loading and hauling equipment for the Anguran underground stopes. Finally, single-arm drilling with a score of 0.870 was chosen as the appropriate choice for drilling equipment, and LHD WX04 with a score of 0.252 was selected for loading and hauling equipment. Also, by analyzing the sensibility of the model results based on the change of criteria weights from ±10 % to ±20 %, there was no change in the results. The observations were that the drilling equipment selection has more sensitivity and reaction to changes in weight of the stope conditions. At the same time, the loading and transport equipment selection has this reaction and this sensitivity to changes in the weight of technical specifications of the machine. [ABSTRACT FROM AUTHOR]

The study involves developing a framework of research methodology for enhancing the capability of spaceborne integrated DInSAR and PSI approach for better detection, monitoring, and analysis of land surface deformation in the underground mining environment. First component of the framework involves pre-feasibility assessment of the integrated approach followed by selecting suitable InSAR data sets considering three significant parameters, i.e., terrain, deformation, and system characteristics. The other essential components are preprocessing of the selected & acquired InSAR data for its quality check, the scheme for better detection as well as monitoring of mining subsidence trough(s) using Coherent Small Baseline-DInSAR Time Series (CSB-DTS), scheme for better in-depth monitoring of detected and undetected mining subsidence trough(s) using PSI, and result validation & analysis. Effectiveness of the proposed framework has been validated in the assessment of subsidence due to underground mining activities in one of the largest copper-ore producing belts in India, Khetri Copper Belt. [ABSTRACT FROM AUTHOR]

The article discusses the effect of divestiture on partial or full disposal of a business unit through sale, exchange, closure, or bankruptcy. Topics include the difference between the technicalities of the terms exit and divesture; strategic moves of late to focus on its core surface mining and underground hard rock mining equipment products, technologies, and systems.

In Canada, many mines have adopted the sublevel stoping method, such a blasthole stoping (BHS), to extract steeply deposited minerals. Sill pillars are usually kept in place in this mining method to support the weight of the overburden in underground mining. To prolong the mine's life, sill pillars will be recovered, and sill pillar recovery could cause failures, fatality, and equipment loss in the stopes. In this paper, three sill pillar recovery schemes—SBS, SS1, and SS2—were proposed and conducted to assess the feasibility of recovering two sill pillars in a hard rock mine by developing a full-sized three-dimensional (3D) analysis model employing the finite element method (FEM). The numerical model was calibrated by comparing the model computed ground settlement with the in situ monitored ground settlement data. The rockburst tendency of the stope accesses caused by the sill pillar recovery was assessed by employing the tangential stress (Ts) criterion and burst potential index (BPI) criterion. All three proposed sill pillar recovery schemes were feasible and safe to recover the sill pillars in this hard rock mine, and the scheme SBS was the optimum one among the three schemes. [ABSTRACT FROM AUTHOR]

In case of extra-thick Carboniferous coal seam mining, the hard rock strata of 50-100 m existing above the coal seam roof in upper layer, simple roof caving controlling technology can hardly achieve the engineering needs. To solve the strong abutment pressure in mining induced by multiple hard rocks overlying strata in coal mine, the structure and lithology of the overbeding hard rock strata were explored. Based on the engineering background of fully mechanized caving coal mine in Datong coalfield of China, a technical scheme of strata control of multiple hard roof fracturing was formulated. A ground and underground combined hydraulic fracturing technology was carried out. Results show that the deformational behavior of lower strata is closely related to the movements of the upper hard rock strata. The development and expansion of the cracks within upper hard rock strata is the dominant factor to the abutment pressure of the working face according to microseismic monitoring data. The working resistance of the hydraulic supports, deformation of the roadway and the pressure of the advanced support in tailgate were used to verify the effectiveness of the proposed controlling technology. The conclusions obtained in this study provide a novel method for the joint control of the multilayer of rigid roof and provides a means of precise control of hard rock strata. [ABSTRACT FROM AUTHOR]

The demand for minerals has never been so high and is expected to increase in the coming decades. Karlsson et al. adapted the commonly used hydrogen peroxide-ammonium citrate extraction method from ore exploration practices to the characterization of mine waste rocks, and demonstrated that it can be efficient in the evaluation of the risks of sulphide-related element mobilities from waste rock material during the preliminary phase of a mining project [[11]]. 10.3390/min11050495 11 Karlsson T., Räisänen M., Myöhänen T., Alakangas L., Lehtonen M., Kauppila P. Hydrogen Peroxide Ammonium Citrate Extraction: Mineral Decomposition and Preliminary Waste Rock Characterization. [Extracted from the article]

In this study, based on the example of the ground vibration damage response of a thick and hard rock layer fracture type mine quake, and by applying the theories of mine pressure, rock mechanics and vibration energy principle, the concept of "vibration damage boundary" of mine quake ground, which uses particle vibration velocity to evaluate the vibration damage, is proposed. In addition, the quantitative prediction method of the ground vibration damage boundary is preliminarily established. The research results reveal that the elastic deformation of the fixed support end of the thick and hard rock layer structure in the stope is the main energy source for the formation of mine quakes, and that the particle vibration velocity caused by the propagation of focal energy to the ground can reasonably reflect the response degree of vibration damage. The proposed prediction method considers the "instantaneous" motion characteristics of mining thick and hard rock layer and the dynamic load effect of "mine quakes." The method can deepen our understanding of mining ground damage prediction, and increase the reliability of ground damage boundary prediction. Finally, the results are used to predict the ground vibration damage boundary of limestone primary fracture in the longwall 16101 face of the Fuping Coal Mine. [ABSTRACT FROM AUTHOR]

The article presents the discussion on high level of strategic thinking, planning, communication and problem-solving skills. Topics include successful candidates being required to complete the background screening showing a criminal check and validation of qualifications; and working with the project's mine engineers, hydrogeologists, geologists, infrastructure geotechnical and tailings specialists.

Stability of underground working depends on geomechanical properties of rocks as well as geometrical and operational parameters of excavation. In this study, a fuzzy rule-based method, minimizing the subjectivity in rock engineering system (RES) is proposed to address the uncertainty in determining stability of underground pillars. A total of 243 elastoplastic 3D numerical models are analyzed by varying attributes of five input (leading) variables: (1) rock mass strength, (2) depth (in situ stress), (3) height of excavation (stope), (4) sequence of excavation with or without filling, and (5) crown pillar thickness. Interaction matrix between the leading input variables are evaluated using fuzzy "IF–THEN" rules considering the results of finite-element models (FEMs) and the "cause–effect" plot of the variables are also determined. Average equivalent plastic strain (EPS) over two consecutive pillars is the target output variable indicating the stability of the excavated zone (stope)–pillar system. Results of FEMs are plotted in the existing stope stability number graph and show that ESP¯≈0.06−0.07 denotes the boundary between "stable" and "transition" zone and ESP¯≈0.09−0.1 represents the boundary between "transition" and "caved" zone. A rib pillar stability index (RPSI) is formulated based on the vulnerability of a pillar for the evaluation of EPS¯ indicating the "stable" or "unstable" condition. Results show that plastic strain decreases exponentially with increasing RPSI having R2 of 0.824. The proposed concept is applied to determine the stability of stopes of a hard rock mine by estimating RPSI and EPS¯ and finds that they are placed in "stable" zone for the given geomining conditions. [ABSTRACT FROM AUTHOR]

The use of asymmetrical disc tools for the mining of hard and very hard rocks is a promising direction for developing mechanical mining methods. A significant obstacle in developing mining methods with the use of asymmetric disc tools is the lack of adequate computational methods. A deep understanding of rock–tool interaction can develop industrial applications of asymmetric disc tools significantly. The fundamental problem in designing work systems with asymmetric disc tools is the lack of adequate analytical models to identify tool loads during the mining process. One reasonable approach is to use computer simulation. The purpose of the research was to develop a simulation model of rock cutting using an asymmetrical disc tool and then evaluate the developed model. In the article, the Discrete-Element Method (DEM) in LS-Dyna was adopted to simulate rock cutting with asymmetrical disc tools. Numerical tests were conducted by pushing the disc into a rock sample at a given distance from the sample edge until the material was detached entirely. Two types of rock samples were used in the simulation tests: concrete and sandstone. The independent variables in the study were the disc diameter and the cut spacing. To validate the simulation model, analogous laboratory tests were carried out. The article presents a comparison of the results of simulation and laboratory tests. The given comparison showed good accordance LS-Dyna model with the experimental studies. The proposed test results can be input data for developing simulation models on a larger scale. Thus, it will be possible to consider the complex kinematics of the dynamics of the rock-mining process with disc tools using the DEM simulation. [ABSTRACT FROM AUTHOR]

A methodology using three-dimensional elasto-plastic analysis has been formulated to assess the required strength parameters for a stable backfill wall for various dimensions of a stope. The numerical modelling results show linearly increasing trend for the required backfill cohesion with respect to stope height for longer stopes and curvilinear with flattening trend for shorter stopes. Comparison of the numerical modelling results with those of a popular theoretical equation shows that the theoretical equation fails to represent the interface friction and tension. The numerical modelling methodology is a better tool which can capture a gamut of aspects. The developed methodology has been used to estimate the required pastefill strength and binder percentage for a hard rock mine in North India, where it has been successfully implemented in over 50 stopes without any significant case of backfill failure. [ABSTRACT FROM AUTHOR]

Management of potentially acid-generating (PAG) waste rock is an important element of environmental stewardship at hard rock mines. Mixing this material with non-PAG rock is common, but there appears to have been limited analysis of acceptable ratios, in particular where the waste rock is overwhelmingly non-PAG. The mine model for the Gold Acres Complex in Nevada was used to determine the most likely and worst-case PAG:non-PAG ratios. Humidity cells (HCTs) were run for PAG (144 weeks) and non-PAG (67 weeks) end members, together with mixtures at ratios of 2:98 (the most likely case; 47 weeks), 4:96 (reasonable worst-case; 136 weeks) and 10:90 (an unreasonable case; 47 weeks) to evaluate leachate quality; all of the mixtures remained pH-neutral. Incremental mineralogic changes over the course of the HCTs could not be ascertained because the samples had undergone 37 years of weathering in the open pit. However, a mass balance demonstrated that lower solute concentrations were released than expected based on the end-member leachate chemistry. A review of three other mines that layered, rather than blended PAG and non-PAG rock, shed light on process and characterization constraints. [ABSTRACT FROM AUTHOR]