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By Carrie Smith

As demand for copper continues to climb alongside the rapid expansion of artificial intelligence (AI), electrification and advanced manufacturing, the United States faces growing pressure to secure domestic supplies of the metal. Analysts expect global copper demand to increase sharply over the next two decades, as the production of electric vehicles, renewable energy and AI data centers ramps up. At the same time, new copper mines have become increasingly difficult to develop. In central Arizona, one project is taking a different approach. Located in the town of Florence between Phoenix and Tucson, Florence Copper recently became the first major new source of U.S. copper in more than a decade. In early 2026, the project began commercial operations after spending years developing its copper recovery process at a test stage. Rather than relying on an openpit or an underground mine, the operation uses in situ copper recovery (ISCR), a process that extracts copper from underground without blasting, hauling or constructing tailings facilities. The project is the world’s first greenfield commercial ISCR copper project and produces London Metal Exchange (LME) Grade A copper cathode on site, which allows the finished product to move directly to U.S. manufacturers without off-site smelting. Not only is Florence Copper a new copper operation that will help strengthen domestic mineral supply chains, but it is also a testament to whether certain copper deposits can be developed using a lower-impact approach. Traditional copper mining typically involves removing large volumes of rock from an openpit or underground workings before processing and transporting concentrate to a smelter. However, Florence Copper’s in situ process eliminates many of those steps. “Rather than extracting and processing massive quantities of mineralized rock, the ISCR process at Florence Copper leaches copper minerals into solution below ground before pumping a copper-rich solution to surface and processing it into pure copper cathode sheets on site,” said Sophie Dessart, manager of communications and public affairs at Florence Copper. The process takes place between 122 and 365 m (400 and 1,200 ft) below the surface within a naturally fractured copper oxide deposit saturated with groundwater. Operators inject a mildly acidic solution, comparable in acidity to household vinegar, through a series of wells. As the solution moves through the orebody, it dissolves copper minerals before recovery wells pump the copper-rich solution back to the surface. At the surface, the solution enters a solvent extraction and electrowinning (SX/EW) plant, where it is refined into LME Grade A copper cathodes. Once the copper has been removed, the remaining solution is recycled back into the wellfield, creating a closed-loop process that repeats throughout the life of the operation. Although Florence Copper only began commercial production this year, development of the deposit stretches back more than five decades. Copper was first identified on the property in 1969 after geologists recognized evidence of mineralization near Poston Butte. Its initial investigations focused on conventional mining methods before companies began evaluating the site’s potential for in situ recovery during the 1990s. In 2014, Trekor Metals (formerly Taseko Mines) acquired the project, and in 2017, construction of a production test facility began. Two years later, the pilot operation produced its first copper cathode using ISCR. Over the next several years, the facility safely produced more than one million pounds of copper while generating operational data that helped engineers refine commercial design. “The production test facility played a critical role by allowing Florence Copper to demonstrate the safety, effectiveness, compliance with permit conditions and overall environmental responsibility of the ISCR process while also generating valuable operational data to optimize performance at commercial scale,” said Dessart. The company completed construction of its production facility in fall 2025 and produced its first copper cathode in February 2026. Dessart said the project reached its construction and commissioning phase on schedule and within roughly 4 percent of budget. Florence Copper now expects to reach full production in 2027, with the capacity to produce 85 million pounds of copper annually. Over its projected 22-year mine life, the operation is expected to produce more than 1.5 billion pounds of copper cathode. At full production, the project is expected to increase U.S. copper cathode output by 5 percent compared with 2025 levels and make the country’s third-largest copper cathode producer. The timing of Florence Copper’s commercial launch coincides with a period of growing concern about future copper supply. According to S&P Global’s 2026 report, “Copper in the Age of AI: The Challenges of Electrification,” global copper demand could increase roughly 50 percent by 2040, reaching 42 Mt/a (46 stpy). The report projects that AI infrastructure alone will require significant volumes of copper, with a single hyperscale data center consuming as much as 50 kt (55,000 st). Without substantial new investment, the report warns the world could face a copper supply deficit approaching 10 Mt (11 million st) by 2040. But with the addition of Florence’s production, the U.S. could add a significant amount of the critical mineral to its domestic supply. “Florence Copper is emerging as a critical new source of U.S.-produced refined copper at a time when global demand is accelerating significantly,” said Dessart. “We are proud to serve as a new domestic source of U.S. copper, helping strengthen supply chains, support economic growth and ensure that the materials essential to electrification, innovation and national security are produced here at home.”

Aug 1, 2026

By Debra Struhsacker

For the last few years, critical minerals have been in the news as policymakers and the media highlight the important role critical minerals play in all aspects of the U.S. economy, technology, infrastructure, manufacturing, energy systems and national defense. These discussions focus on how critical minerals are the foundational inputs to everything modern societies build and use. They even play a role in the foods we eat because some fertilizers consist of minerals like phosphates, potash and lime. Many experts predict that the global demand for lithium, copper, rare earth elements, graphite, nickel and other critical minerals will soar in the next decade as countries pursue electrification objectives, build artificial intelligence (AI) data centers that must have massive amounts of always available electricity, and develop high-tech defense equipment built with rare earth magnets and other critical minerals (International Energy Agency, 2025). The U.S. Congress defined minerals for the first time in the National Materials and Minerals Policy, Research and Development Act of 1980, stating: “The term “materials” means substances, including minerals, of current or potential use that will be needed to supply the industrial, military, and essential civilian needs of the United States in the production of goods or services, including those which are primarily imported or for which there is a prospect of shortages or uncertain supply, or which present opportunities in terms of new physical properties, use, recycling, disposal or substitution, with the exclusion of food and of energy fuels used as such.” (30 U.S.C. § 1601(b)(2)) Although most critical “minerals” are actually metallic elements rather than minerals, this article will refer to them as “minerals” to conform to the congressional definition and the current critical minerals dialogue. Forty years later, Congress enacted the Energy Act of 2020, which amended the 1980 Act to add the following definition for critical minerals: “The term ‘‘critical mineral’’ means any mineral, element, substance, or material designated as critical by the Secretary under section 7002(c) of the Energy Act of 2020.” (30 U.S.C. 1601(2)(b)(1)) The Energy Act of 2020 directs the Secretary of the Interior, acting through the Director of the U.S. Geological Survey (USGS), to identify critical minerals, to develop a Critical Minerals List (CML), and to update the CML at least every three years or more frequently if determined necessary by the Secretary. The USGS published the first CML in February 2022 (USGS, 2022). The 2022 CML identified 50 minerals critical to the U.S. economy and national security. In November 2025, the USGS finalized its 2025 CML (USGS, 2025a, 2025b) to include 60 minerals (Fig. 1), stating: “Critical minerals underpin industries worth trillions of dollars, and import dependence puts key sectors at risk.” In developing the CML, Section 1606(c) of the Energy Act of 2022 directs the USGS to include minerals that: 1. Are essential to the economic or national security of the United States. 2. The supply chain of which is vulnerable to disruption (including restrictions associated with foreign political risk, abrupt demand growth, military conflict, violent unrest, anticompetitive or protectionist behaviors, and other risks throughout the supply chain). 3. Serve an essential function in the manufacturing of a product (including energy technology, defense, currency, agriculture, consumer electronics and health care-related applications), the absence of which would have significant consequences for the economic or national security of the United States. This law also requires the Secretary to consult with the Secretaries of Defense, Commerce, Agriculture, Health and Human Services, and Energy and the U.S. Trade Representative in designating minerals, elements, substances and materials as critical.

Sep 1, 2026

By F. D. Agrensa, J. Hadjigeorgiou, S. J. Thorpe

The recent introduction in underground mines of mechanical hybrid rockbolts has been driven by efforts to eliminate the use of resin in heavily fractured ground. Mechanical hybrid rockbolts consist of a steel tendon mechanically anchored within a friction unit. Installation of mechanical hybrid rockbolts is percussion-driven by the rock drill and the mechanical anchor is subsequently activated using rotation. The bolt configuration and installation process overcome issues associated with hole closures and the use of resin. Recent work has focused on understanding the behaviour of the rockbolts under quasi-static and dynamic conditions but there is scant information on the anticipated performance in corrosive underground environments. This paper reports the results of a comprehensive accelerated corrosion investigation of the principal components of mechanical hybrid rockbolt, which can aid in establishing the long-term suitability of mechanical hybrid rockbolt in corrosive environments.

Aug 3, 2026

By Christian Connolly

The surface office’s shift change board shows 47 workers heading underground in the next hour. Before any of them descend, a safety manager works through a familiar routine with a clipboard in hand, moving down a printed roster, checking off names, and scanning a wall of safety helmets for current inspection stickers. At the same time, a crew foreman works through a binder searching for a certification card that should have been updated a month ago, while a desk spreadsheet behind them tracks personal protective equipment (PPE) assignments by serial number, last touched by hand. The new-hire onboarding process adds another layer of work. A fresh sticker is peeled and pressed onto the back of a helmet, with the number written on a paper log that will later be entered into the spreadsheet. It takes time, not because anyone is doing it wrong or slowly, but because this is simply how it has always been done. This daily routine represents where PPE management in mining still begins for some operations across North America. The administrative burden it places on safety teams compounds across every shift, crew rotation and piece of equipment that moves through the operation. For mines running multiple shifts across several active headings, with contractors rotating in and out alongside permanent crews, maintaining accurate records through manual systems alone is not just inefficient. It is a compliance liability waiting to surface.

Aug 1, 2026

By Rajesh Raitani, Emily Haas

The Society for Mining, Metallurgy & Exploration (SME) MINEXCHANGE SME Annual Conference & Expo hosts innovationrelated content across division sessions each year. The development and integration of automation, robotic systems, artificial intelligence (AI), machine learning (ML), internet of things (IoT), digital twins, drones, remote monitoring and other intelligent systems have regularly been showcased as advancements that can be used to improve safety, efficiency and sustainability across the industry. Although the presence of these conference topics is evident, it is unclear if they are just an expressed interest of industry visionaries and experts or if they may be early indicators of emerging trends. To date, there has not been a systematic analysis of the presence, fluctuation and focus of conference topics over the years. Some sources support the analysis of conference data to help identify emerging trends, opportunities and interests. For example, the International Technology and Engineering Educators Association (ITEEA) completed an analysis of conference programs from 1978 to 2014 to highlight historical milestones and emerging trends within their profession — an effort that assisted with future conferencing planning and other professional events (Reed and LaPorte, 2015). These authors identified several topics that appeared prevalent in the peer and gray literature that were not as prominent in conference offerings. They also indicated that the conference theme had minimal influences on the submission topics (Reed and LaPorte, 2015). In another effort, creators made links between tweets that used conference title hashtags during the Association of College and Research Libraries conferences from 2011 to 2019 as a form of trend analysis (Hennesy et al., 2021). Finally, related efforts have occurred in the text mining of journal article titles to identify latent topics and unique terms in the scientific literature (Ravikumar et al., 2023). Analyzing paper and conference titles has received attention in recent years to help propose and predict research topics (Wang et al., 2022). For example, Wang and colleagues (2022) indicated that trends revealed in paper titles can be useful for proposing more authoritative sessions at major conferences to align with industry trends. Consequently, an abbreviated activity was undertaken by SME’s Industry Innovation Strategic Committee in 2025. The goal was to (1) reveal stable and shifting priorities around innovation, (2) inform respective division planning for subsequent conference sessions and (3) ascertain whether the association is meeting members’ expectations around innovation-related content throughout the year. SME’s Industry Innovation Strategic Committee focused on the identification and dissemination of these tools in the field, and reviewed technical session titles from annual conference programs from 2016 to 2026. Using keyword frequency, theme clustering and division-specific tagging, the committee identified themes that seemed to be gaining traction, fading, remaining consistent, or changing in detail and scope regarding emerging technologies. This short article serves as both a retrospective view and possible planning tool for shaping future conference programming and, if applicable, inform impactful and relevant initiatives.

Sep 1, 2026

By Jim McKinley

With a growing number of mines reaching closure and seeing closure costs materialize, regulators, lenders and banks are observing projects that fail economically by miscalculating these costs. Mine closure costs are often categorized as a type of liability, which is defined as the money owed by the company to offset effects from the project and the money available to pay for those debts, such as bonds. Often, decisions made before the first day of mining — such as co-disposal, dry stack tailings, waste segregation — can significantly change the bond calculation. Once the bond is calculated and funded, operators are encouraged to conduct closure research and use applied science for progressive bond release prior to final closure. However, the author has observed few instances of financially significant progressive bond release, as there are typically no robust procedures for bond return, either before or during closure activities. As a result, many companies decide that entering a state of care and maintenance (C&M) is less risky than attempting to fund closure activities with an unknown bond return mechanism. Although perhaps less risky in the short term, the primary long-term risk with entering C&M is that it increases the chances of the bond not covering the cost of closure and the chances of the government/regulatory agency inheriting the mine closure. Bonds are typically reevaluated on a regular cycle, such as five years, so every mining company goes through this financing challenge eventually.

Aug 1, 2026

By G. Danha, C. Lebudi, O. P. Oladijo, V. Moyo

Percolation vat leaching offers mid-tier artisanal and small-scale gold mining a practical compromise between heap and agitated tank systems. However, the common practice of sequentially using mercury amalgamation and cyanidation causes severe metallurgical and environmental failures. This review demonstrates that static artisanal and small-scale gold mining vats suffer critical oxygen starvation, triggering cascading geochemical hazards. Residual elemental mercury (Hg0) acts as an aggressive reagent sink, rapidly exhausting localized cyanide to generate highly mobile, toxic mercury-cyanide complexes. Concurrently, oxygen depletion retards sulphide ore oxidation, precipitating elemental sulphur (S0) and polysulfides that passivate the native gold surface. To mitigate these bottlenecks, this paper proposes low-complexity interventions: solid oxygen-release compounds (CaO2), hypochlorite pre-oxidation, and trace lead nitrate to sequester sulphur. Ultimately, formalising the sector requires the absolute decoupling of amalgamation from cyanidation and a transition toward modular, mercury-free vat systems.

Aug 3, 2026

By William Gleason

During a mining roundtable at the U.S. Department of State on Aug. 7, President Donald Trump announced that the U.S. Government will invest $3 billion in critical minerals and battery projects as part of a push to increase domestic production, boost national security and support industrial policy. Part of this investment includes $180 million earmarked for education and workforce development for the mining sector, including up to $100 million to strengthen education in critical minerals and materials from the U.S. Department of Energy (DOE) and $80 million from the U.S. Department of War (DOW) for investments in the Colorado School of Mines, South Dakota School of Mines and Technology and Johns Hopkins University. The DOE’s Office of Critical Minerals and Energy Innovation (CMEI) announced a notice of intent for up to $100 million to develop a new program called “Providing Opportunities for Specialized Education in Critical Technologies (PROSPECT).” The DOW investment will be used to build technology innovation hubs, form projectfocused partnerships between students and defense industry, develop new processes and prototypes, and certify hundreds of new students with advanced degrees in mining, geology and metallurgy. Department heads from the 14 ABETaccredited mining schools in the United States attended the meeting held at the Department of State. They were joined by Trump, Secretary of State Marco Rubio, Secretary of the Interior Doug Burgum and Secretary of Commerce Howard Lutnick as well as several industry leaders including James Litinsky, chief executive officer of MP Materials; Vicky Peacey, president of Resolution Copper; Robert Friedland, founder of Ivanhoe Mines; Mitchell Krebs, chief executive officer of Coeur Mining as well as representatives from Rio Tinto, BHP, Energy Fuels and a number of other industry leaders. “I am not aware of another time in history when the leaders of the U.S. mining education community have been brought together with a sitting President, Cabinet officials, and industry leaders to discuss the future of American mining,” said Aaron Noble, Charles T. Holland Professor Department Head - Mining and Minerals Engineering and interim department head - Materials Science and Engineering at Virginia Tech. “Mining education was not on the periphery of the conversation; we quite literally had a seat at the table where national mineral strategy was being discussed. I hope we look back on this as an inflection point for American mining education.” The historic funding announcement comes in response to a critical need for more mining and processing engineers in the United States. The DOE estimates the industry will need 6,000 more mining engineers during the next decade. Noble said U.S. programs currently graduated fewer than 200 mining engineering graduates annually. Meeting that demand has been a challenge for many years. Enrollment in U.S. mining programs has declined by approximately 45 percent since 2015, and data compiled by the Society for Mining, Metallurgy & Exploration (SME) and the Society of Mining Professors show enrollment falling from nearly 1,500 students eight years ago to fewer than 600 in 2023. The investments offer the 14 mining schools an opportunity to expand enrollment, modernize curricula, strengthen industry relationships and build a more stable workforce pipeline. Kray Luxbacher, executive director and head of the University of Arizona School of Mining Engineering and Mineral Resources, attended the roundtable. She said mining school department heads across the country are “fighting to grow enrollment to meet industry demand.” “This funding is an opportunity to change the trajectory of mining,” Luxbacher said, “to bring in students who didn’t grow up around mining, show them what a modern career in this field looks like and give our programs the resources to compete for their attention.”

Sep 1, 2026

By Paul O. Knorr

The Marine Minerals Administration (MMA), a bureau within the U.S. Department of the Interior, has responsibility over both energy and nonenergy mineral development on the U.S. Outer Continental Shelf (OCS) under the OCS Lands Act (OCSLA). The OCS extends beyond the exclusive economic zone (EEZ) and encompasses the federal seabed. These responsibilities include all aspects of the department’s offshore energy and mineral resource management and conservation, safety oversight, environmental enforcement and related activities on the OCS, including activities pertaining to offshore critical minerals. The MMA’s Marine Minerals Program (MMP) is a matrixed program that manages U.S. offshore mineral resources including hard minerals, sand and gravel. As the sole steward of OCS critical and hard minerals, the MMP is responsible for understanding where critical minerals are located, identifying and understanding their environments, managing activities that affect these resources and implementing related federal policies. Several federal laws and regulations, such as OCSLA and the National Environmental Policy Act (NEPA), govern federally authorized or regulated activities. However, there are six U.S. federal rules in the Code of Federal Regulations (CFR) that are particularly pertinent to inform MMP’s procedures: 30 CFR 580 and 280 (prospecting for minerals), 30 CFR 581 (leasing of minerals), 30 CFR 582 and 282 (operations in the OCS related to minerals), and 30 CFR 583 (negotiated noncompetitive agreements for sand).

Sep 1, 2026

By Prashant Dixit, Akhil Singh, Asim Kumar Mukherjee, Sudipta Patra, Veerendra Singh

Phosphorous is an undesired element present in iron ore used in the steel making process. It leads to an increase in overall production cost as well as deteriorated steel quality. The desired phosphorus content in iron ores used in steel making is < 0.1%. Numerous beneficiation studies are mentioned in the literature; however, there is no commercial scale technology established to beneficiate high phosphorous iron. The major phosphorous bearing minerals are apatite (Ca5(PO4)(Cl/F/OH), wavellite (Al3(PO4)2(OH)3·5(H2O)), senegalite (Al2(PO4)(OH)3(H2O), barrandite ((Fe,Al)PO4·2H2O), etc. Ultrafine grinding is required to liberate phosphorous minerals from iron ore minerals and subsequently subject it to flotation, acid leaching, and bioprocessing. The selective flotation of iron ore could successfully reduce the phosphorous content from 0.82% to < 0.20% with the combination of grinding, magnetic separation, and carbothermic reduction. Acid leaching processes are also able to remove ~80% (0.85%→0.16%) of phosphorus; however, these are relatively costly and complex processes. The mechanism of bio-extraction for phosphorous removal is reported as one of the most successful processes. This process is capable of removing more than 80% of the total phosphorous and significantly reducing the phosphorous content from 1.06% to 0.16%. The main disadvantage of this process is that it occurs at a much slower pace. In today’s scenario, ultrafine grinding followed by froth flotation seems to be the most feasible solution for the beneficiation of high phosphorous iron ore in which the concentrate obtained can be utilized for pellet making and ultimately used for steel making processes. Development of additives for leaching, roasting, and bioprocessing can be explored further to make these processes more effective and economically viable.

May 28, 2024

By Yaxiong An, Jianwen Yu, Yuexin Han, Peng Gao

This paper presents an industrial verification test, adding a high pressure grinding roll and magnetic separation operation after the third-stage fine crushing operation to reduce the particle size of ball mill feed and improve the processing capacity of grinding operation. The optimal process parameters of high pressure grinding roll and magnetic separation were determined to be a 10 mm of roller surface spacing, a 10.5 Mpa of roller surface pressure, a 14 r/min of roller surface speed, a particle feed size to the magnetic separator of P100 3 mm, and a 3000 Oe of magnetic field intensity. Under the above optimized conditions, the iron grade of magnetic pre-enriched concentrate increased significantly from 28.27% to 36.30%, and the iron recovery was 87.59%. Meanwhile, the yield of coarse tailings was 36.16%, which significantly reduced the amount of ore entering the subsequent ball mill-magnetic separation operation. The ball mill Bond work index Wib of raw materials and the pre-enriched concentrate were 11.76 kW•h/t and 10.46 kW•h/t, respectively. The relative grindability of the pre-enriched concentrate was increased by 34%.

May 31, 2024

By C. Allen, H. Zhang, L. Falk

Shock loss occurs when there is a change in the area of a drift or airflow direction. These shock losses accumulate throughout the ventilation system and will increase the mine resistance as underground development deepens or becomes more complex. Hence, shock losses should be carefully considered when establishing the resistance through a series of branches as they can be a significant contributor to the estimated mine resistance. Using computer software to simulate a ventilation system is common but applying reasonable shock loss factors in the software is not a simple or direct process. Determining shock loss values includes the consideration of historical measurements, application of factors and formulas from literature based on the geometry and complexity of junctions, and the geometry variation at different locations. For example, the shock loss at the bottom of a ventilation raise can be comprised of a 90° bend and a sudden area change. This paper presents an approach for estimating shock loss factors near raise junctions using computational fluid dynamics. Current and future work will also be compared with field measurements. Results from this approach are compared with software defaults as well as classical techniques in published literature and standards.

May 14, 2024

By Ashish Kumar Vishwakarma, Vivek Kumar Himanshu, Kaushik Dey

The accurate prediction of blast-induced ground vibration due to underground ring blasting is a prominent need for ensuring the safety of structures. Different site-specific empirical equations are available for the prediction of ground vibration. These empirical equations are best suited when the monitoring and blasting locations are present in the same medium. The change in the medium alters the behavior of wave propagation. Hence, existing empirical equations have limitations in peak particle velocity (PPV) prediction when the blasting location is an underground hard rock mine and the monitoring location is ground surface. This is because the underground metal mine comprises different levels having void in the form of excavated stope or paste-filled stope. It is very difficult to predict the magnitude of PPV on the surface in such instances. Therefore, this study has been carried out to predict the PPV at surface due to underground blasting. In this paper, PPV data was recorded at surface for 207-ring blasts. Furthermore, the PPV has also been measured at different underground locations for 47-ring blasts. Different empirical equations along with k-nearest neighbor (KNN) and random forest (RF) model of machine learning technique were developed for the prediction of PPV. Most of the empirical models have higher accuracy in the prediction of PPV at an underground location. This shows that scaled distance-based empirical predictors are best suited when the monitoring and blasting media are the same. However, the empirical models do not predict PPV accurately when the monitoring location is ground surface and the blast is conducted underground. The machine learning models are better suited for PPV prediction in such cases. Based on the analysis performed for the case study site, RF model predicts PPV at surface with the highest accuracy. The coefficient of determination and root mean square error for RF model used for predicting PPV at ground surface are 0.94 and 0.438 mm/s respectively. The RF-based model is also the best suited among all the models for predicting PPV at underground locations as well.

Apr 20, 2024

By Xiang He, Xinzhong Wang, Ning Li, Bao Cao, Hongyang Bai, Zhigang Du

Revealing the periodic fracture pattern of the main roof and the key influencing factors of the support resistance is crucial for strata control and support selection of the shallow buried working face with large mining height. Based on the cantilever beam theory, an improved step rock beam model, and the measured strata pressure data of the 12,401 working face in Shangwan Mine, the mine pressure behavior law of the shallow buried with a large mining height working face was analyzed. The results show that both ratio of maximum principal stress to load (σ1/q) and ratio of maximum shear stress to load (τmax/q) inside the main roof increase with increasing periodic advancing distance, while the ratio of maximum shear stress to maximum principal stress (K) is the opposite, indicating that the increase rate of σ1/q is higher than that of τmax/q. K is less than 1 when the periodic advancing distance exceeds 8 m, indicating that the periodic fracture of the main roof will be dominated by tensile failure. Support resistance increases with increasing immediate roof thickness, main roof thickness, periodic fracture step distance of the main roof, and mining height, and decreases nonlinearly with increasing friction coefficient of periodic fracture rock block hinge surface. The main roof thickness, the periodic fracture distance of main roof, and the friction coefficient of the hinge surface of the periodic fracture rock block are the key factors influencing the support resistance. The advance breaking of the main roof and increasing the friction coefficient of the hinged surface of the main roof can reduce the support resistance of the working face. The support resistance of the 12,401 working face in Shangwan Mine presents an arch distribution characteristic. The average periodic weighting step interval, average support resistance, and dynamic load coefficient are 15.6 m, 17,552 kN, and 1.3, respectively. Finally, the rationality and validity of the model are verified by comparing the measured and theoretical values of the support resistance in the 12,401 working face of Shangwan Mine and other shallow coal seams with large mining height.

Apr 22, 2024

By Emily Sarver, August Greth, Cigdem Keles, Setareh Ghaychi Afrouz

The characterization of respirable dust on the basis of constituent fractions and particle sizes is increasingly of concern for evaluating exposure hazards. For high-resolution particle analysis, scanning electron microscopy with energy dispersive X-ray (SEM-EDX) can be an effective tool. However, it requires particles to be deposited on a smooth, uniform substrate such as a polycarbonate (PC) filter for optimal results. While direct sampling onto PC is possible, this is not the standard approach in many situations. For example, in coal mines, respirable dust samples have typically been collected onto polyvinyl chloride (PVC) filters because they are intended for gravimetric and/or infrared spectroscopy analysis. Such fibrous substrates are not ideal for SEM-EDX (or other microscopy), but an effective method to recover and redeposit the dust particles could render such samples suitable for the additional analysis. Here, we present a simple method and compare SEM-EDX results for paired samples analyzed directly on PC and following recovery from PVC and redeposition on PC. Both laboratorygenerated dust samples (n = 10 pairs) and field samples of respirable coal mine dust (n = 44 pairs) are included in this study. Although some changes in particle size distributions were observed between samples analyzed directly and those that were recovered and redeposited prior to analysis, the results indicate the dust recovery method generally yields a representative sample in terms of mineral constituents. That said, results also highlighted the effects of high particle loading density on individual particle analysis. Considering all sample pairs, those with similar loading density between the directly analyzed and recovered sample tended to exhibit similar mineralogy distributions. This was generally the case for the lab-generated sample pairs, and the Freeman-Halton exact test of independence indicated that the samples in just three (of 10) pairs were in disagreement in terms of their mineralogy distributions. On the other hand, for the field samples, the directly analyzed sample often had higher loading density than the recovered sample; and the Freeman-Halton test showed that 25 (of 44) pairs were in disagreement. However, the effect of possible particle agglomeration on the directly analyzed samples cannot be ruled out—and exploration of this factor was beyond the scope of the current study.

May 17, 2024

By Ismail Adeniyi Okewale, Hendrik Grobler

Significant factors believed to be responsible for tailings dam failure which can lead to loss of lives, destruction of properties and assets or damage to the environment are the mechanics of material characteristics and static liquefaction. It is therefore essential to understand the tendency for the likely occurrence of liquefaction in tailings dam as well as mechanics behind the behaviour of this tailing materials (inevitable products of ore mining, mineral and metallurgical processes). This study aims to present the mechanical behaviour and susceptibility to liquefaction of a gold tailings sample. Series of oedometer tests were conducted to determine the compression behaviour and the possibility of transitional behaviour or not. Index and physical tests were conducted to determine engineering grading descriptors which was directly linked to compression behaviour and comparisons made with other tailings. Microstructure was studied to understand the effects of fabric on the behaviour of samples and the chemical composition and mineralogy were also investigated. The compression paths slowly converge and the gold tailings might be said to be less transitional. The gold tailing is less dependent on initial state. The loosest gold tailing is more susceptible to liquefaction and compared to other gold tailings, this sample is less susceptible to liquefaction.

Apr 19, 2024

By Chun Yu, Jiarui Min, Xuemin Ding, Rongdong Deng, Bao Guo, Yu Miao

Pb2+ plays a modifying role in the flotation behavior of various sulfide and oxide minerals. However, there is currently no consensus on the use of lead salts as modifiers in mineral flotation. Based on previous research, this article provides a comprehensive review of the activation effect of Pb2+ on common oxide and sulfide minerals flotation from the perspective of interfacial reactions. A theoretical model for Pb2+ activation has been proposed in this article. When the pH is less than 7, Pb2+ replaces the metal atoms in the lattice of sulfide minerals or adsorbs on the mineral surface to form PbS. When pH is in the range of 7 ~ 10, chemical adsorption of Pb(OH)+ occurs on the mineral surface, leading to the formation of Me-O-Pb+. When pH = 10 ~ 11, Pb(OH)2 precipitates on the mineral surface. Under this condition, it activates the flotation of quartz but inhibits the flotation of sulfide minerals.

Apr 25, 2024

By Chenxi Ding, Chenglong Xiao, Guoli Shi, Zhiwei Zhao

This study investigates the directional blasting of a 90° slit charge structure using laboratory experiments and field tests. A 90° slit charge suitable for the corner of roadway is proposed. After the slit charge blasting, two long main cracks along the slit, and several short secondary cracks in other directions. The slit charge not only significantly reduces damage to the surrounding rock, but also improves the quality of the roadway contour. In addition, a comprehensive damage evaluation system of the roadway contour and the surrounding rock is constructed using digital image analysis, borehole televiewer, and CT scanning.

May 23, 2024

By Jarod McBride, Mike Johnston

Over the last decade the construction industry, particularly ground enhancement services such as Jet Grouting, have seen a dramatic rise in the cost of waste transportation and disposal services; increasingly representing a significant percentage of total job cost. As these costs increase and our industry continues making strides to become better stewards of the environment, one of the best ways we can contribute is by placing a priority on sustainability. Stage 3 Separation&rsquo;s unique solutions contributed to sustainability while creating new economic value. This was achieved by reducing waste, reusing materials, and accelerating production when compared to the traditional spoils pit management practice. Stage 3 Separation believes in bringing sustainable solutions to industry and was successful in teaming with HRBT South Island to meet the following project metrics: (1) reduce the overall disposal costs and associated liability, (2) recycle/reuse base materials where fit, (3) meet specified water quality for discharge, (4) do all of this in way that contributes to accelerating the production schedule in a critical job path. The HRBT South Island project overview consisted of over 650 columns, producing north of 150,000 yds3 of slurry.&nbsp; Our goal was to take the jet grout slurry waste stream and separate the liquids and solids; creating a water phase that met all environmental standards to be treated and disposed of directly into the environment and creating a dry stackable solid that could be sent directly to a landfill. Prior to Stage 3 Separation&rsquo;s deployment the Jet Grout contactor was being hampered by poor spoils management, long spoil cure times, and at the mercy of costly vac-trucks or less than partial solid loads.&nbsp; Within weeks of new process and the removal of these impediments production doubled, waste was cut in half, and numerous other efficiencies were gained. Keywords: Jet Grouting, Spoils Management, Sustainability, Waste Reduction, Production Performance

Oct 7, 2024

By Omar Conte, Roger Archabal

In recent years, numerous developers have invested in former deep quarry lake sites, particularly to develop massive new logistics and residential projects in South Florida. Due to the flat geology encountered, necessary construction materials (structural fill, sand, concrete aggregate, etc.) have been quarried from the upper limestone and sand layers encountered in the region. Considering the shallow groundwater, these quarry excavations have created numerous large bodies of water (&ldquo;lakes&rdquo;) over the decades. Restoration of these massive lake areas which are now dispersed throughout prime real estate is ideal for development. There is a strong incentive to restore these large lake areas due to the lack of available large tracts of land near Miami or Ft. Lauderdale. The redevelopment of these large and deep-water bodies has important geotechnical challenges that need to be addressed before finalizing the infrastructure and foundation design/construction. This paper will go over the investigation techniques utilized, the geotechnical evaluation, analysis, and soil improvement recommendations to allow for safe bearing support and to overcome the uncertainties associated with settlement potential.&nbsp; Several geotechnical aspects need to be considered to effectively perform mass lake backfill. These include: 1) the pre-backfill site investigation, 2) understanding the lake bottom conditions and soil layering below the bottom, 3) backfill material selection and backfill methodology, 4) quality control/quality assurance during lake backfilling, 5) post-fill ground improvement (preloading, dynamic compaction, vibro-compaction) and foundation construction are some of the key aspects for these types of projects. The geotechnical findings and lessons learned from several massive lake backfill projects will be discussed in the paper. This includes sites with measured lake bottom sediment layers of up to 15 to 20 feet thick, resulting in consolidation settlement of nearly 3 feet during ground improvement/preload settlement monitoring. The paper will present some innovative exploration and laboratory techniques to obtain important geotechnical data to cost-effectively develop these massive areas.

Oct 7, 2024