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By Ebrahim Tarshizi, Livernois Ryan, Emily Sarver, Zoe Scopa, Robert Setterlind, Leah Frost

"The mines of the future present a host of challenges, which may appear exciting or daunting, depending on one’s perspective. Whether some sectors of the public recognize it or not, the demand for raw resources is not going away any time soon. In fact, it is rising, as the global population grows, urbanizes and attempts to steadily increase quality of life. Yet, at the same time that much of the highly developed world is calling for greener goods, reduced consumption and cleaner production, in other areas there are cries for clean water and sanitation, consistent energy supply, access to health care and education, personal security and support for basic human rights. The balancing act for sustainable development of our global society is, indeed, precarious and the mining community is a key player. Fortunately, many industry members have accepted this role and the responsibility to provide leadership and a solid foundation for progress. Looking ahead, we need new generations of leaders, including many mine engineers who are ready to tackle all sorts of complex problems.There are tremendous needs just for technological innovations. Increasingly tough deposits will require that the industry continues to expand scale toward “mega pits” and “super caves;” fully develop unconventional recovery techniques like in situ leaching and gasification or deep-sea extraction and seriously consider off-earth endeavors. Such work will take entirely autonomous equipment, novel separations, processing and recycling methods, and systems that can withstand extreme physical conditions, just to name a few. It will also take a level of systems integration never-before seen in the mining industry, complete with big data issues, sophisticated predecitve analytics and modeling efforts and cyber-security challenges.Moreover, increasingly complex environmental problems will require creative solutions. Addressing issues like pollution control across multiple media, emerging contaminants, optimal management of wastes, selective mining and shared use of resources between mine operations and surrounding communities and ecosystems are among the top priorities. Really, a complete paradigm shift must occur, such that the focus is on overall improvement of environmental conditions, rather than minimization of impacts. A similar shift will be required in the social realm. How can miners be safer and healthier on-site and off? How can the industry contribute to communities such that they are better off, now and longterm, for having a mine next door? How can artisanal mining practices be transformed to also contribute to sustainable development? How can the industry’s work be a factor in increasing economic and political stability? How can the public understanding of raw resources and the need for mining enterprises be improved?Given the coming challenges, there is no doubt that the mine engineers of the future will need highly diverse skillsets — meshing traditional and contemporary competencies to a degree not previously considered in mining, or most others fields. To be sure, the scope and scale of mining projects make them wholly different than most other engineering work, aside from perhaps the largest civil and urban development projects. While on-the-job experience will continue to be essential, formal education programs (i.e., at post-secondary institutions) must lay critical groundwork."

Jan 6, 2017

By J. -B. C. Varnier, J. A. Cremeens, D. D. Overton

"Slope failures that occurred in 2008 and 2009 at the Pikeview Quarry in El Paso County in Colorado in the United States were investigated using three-dimensional discrete element modeling methods. Large-scale block sliding failures occurred along weak bedding planes that dip steeply into an excavation located at the toe of the slope. Several mining sequences at the toe of the slope were simulated to evaluate the effects of various degrees of extraction and backfill on slope stability. Slope stability back-analysis was conducted using prefailure and post-failure conditions to determine the joint shear strength properties. Laboratory testing was also conducted to determine intact rock properties. Three-dimensional discrete element analysis was uniquely applicable to this evaluation because it allowed representation of shear stress of the basal sliding surface and afforded evaluation of several scenarios of extraction and backfill at the toe of the slope. IntroductionThe Pikeview Quarry is an aggregate quarry located approximately 8 km (5 miles) northwest of Colorado Springs in El Paso County, CO, USA. The quarry has been operated by several owners since the early 1900s. According to the U.S. Mine Safety and Health Administration (MSHA, 1986), the quarry has been a major source of construction aggregate for the Colorado Springs area for many years. In the 1950s, the site was mined by Peter Kiewit and Sons to provide limestone for the construction of the nearby Air Force Academy.A large-scale slope failure occurred on Dec. 2, 2008, which stopped mining activity at the Pikeview Quarry. A second, related slope failure occurred on Sept. 13, 2009. The second slope failure was located immediately adjacent to the initial December 2008 failure.The objective of this paper is to discuss the three-dimensional slope stability evaluation. The causal relationships of slope instability are not within the scope of this publication. However, omitting the precursors to slope failure would limit understanding of the nature of the slope stability evaluation. The regional and local geology and the history of slope instability at the Pikeview Quarry aid in understanding these precursors. Two main failure mechanisms were hypothesized during the failure investigation to explain the triggering of the 2008 and 2009 large slope failures at the Pikeview Quarry, and both of these mechanisms were given equal credence in the present study. Quarry excavation and backfilling was a key factor in the slope instability for both failure mechanisms. The excavation was backfilled in stages in an effort to provide slope support. The objective of the three-dimensional model was to evaluate the effects of extraction and backfill at the toe of the slope with respect to slope stability."

Jan 3, 2018

By Rick Frechette, Greg Nelson

"The 2018 Elko Roundtable was held at the Red Lion in Elko, NV on March 15, 2018. The gracious host was once again Knight Piésold. Attendance was robust with representatives from more than 14 mining properties across Nevada representing nine corporations. Total attendance was at its highest in almost a decade. A high level of interest was also gauged by the number of companies with multiple attendees.The topic of water in mining was clearly a factor in creating the large show of interest. In terms of industry trends that are tracked annually, this topic had been absent from the list for more than 10 years (Deloitte, 2018) but was squarely planted there this year. And deservedly so. Three attending companies are signatories of the International Council on Mining and Metals (ICMM) which espouses a firm stance on water stewardship (ICMM, 2017).How’s the water?It is reported that water scarcity affects more than 40 percent of the world’s population (Deloitte, 2018). Consumption of water in the United States, based on the last detailed census, entails only 1.5 percent usage by the mining industry. The largest users are reportedly thermoelectric power and irrigation, combining for more than 75 percent of the U.S. consumption. During the prior census period, water usage at mines was up dramatically (USGS, 2014).Mine water source usage is primarily a mix of ground water and saline or fresh surface water resources. Over the previous period, saline sources experienced the greatest percentage in growth as a mine water source, nearly doubling in use. Nevada ranks second as a state nationally in mine water consumption. California is the leader, and Nevada is immediately followed by Utah and Alaska (USGS, 2014).Water rights in Nevada and the ongoing litigation at the state level, particularly over the Humboldt River basin, have elevated the concern over the supply of water and have raised the interest regarding the topic of water across the mining industry as well as within other industries.The Elko Roundtable meeting began with a safety share and introductions, and included each attendee mentioned a water problem or solution that he or she would like to discuss during the day. An interesting list of subtopics was developed from this round robin and yielded the following most common themes:• Mine pit dewatering during operation and pit wall stability.• Draindown from tailings dams and heap leach pads and dealing with this at closure.• Post closure pit lakes, pit lake water quality and associated water rights."

Dec 1, 2018

By M. B. Freeman

Acrylic polymers have been found to be effective dispersants and stabilizers in a wide variety of mineral processing applications including rheology control in concentrated slurries. This paper will describe these low molecular weight, water-soluble polymeric dispersants and provide a basis for how they function in concentrated slurries based on computer molecular modeling and applications results. Data on homopolymers as well as copolymers of acrylic acid will be presented to demonstrate the optimization of a polymeric dispersant in preparing high solids slurries of inorganic materials such as kaolin, calcium carbonate, lime, and magnesium hydroxide.

Jan 1, 1996

By L. K. Lepley

A marine sonic sub-bottom profiling system and a hovercraft were used in an engineering geophysics survey of the tailings being deposited at the Mercur gold mine. Detailed density sections with vertical resolution of one meter were desired for computations of strength, permeability and potential self-compaction. The logistical problems of conducting a geophysical survey and in collection of geotechnical soil samples from an active tailing impoundment was solved by using the amphibious hovercraft for towing and transport on the impoundment. The "chirp" sonic system produced continuous, real-time geophysical cross-sections with vertical resolution of ten centimeters showing possible trapped gas. The hovercraft provided a platform over water, ice, slurry, and solid beach for collection of geotechnical information and physical samples.

Jan 1, 1994

By David De Lemos Pires

Mining is essentially a materials management process where materials are classified, excavated, moved to a desired location, processed at a cost and sold for a price hopefully to generate a profit. ?How much is that cost and can it be reduced?? is the age-old question. The requirement for a paradigm shift with regard to materials movement in search of low-cost production has not just happened by chance but, rather, has been driven by agents of change that include mining companies, consultants, governments and equipment suppliers. During the past 100 years of mining, surface mining technology has involved humans with hand tools, humans with machinery and unmanned automated equipment. In the past 50 years, surface mining technology has evolved and now takes the form of trucks and loaders (TL), in-pit-crushing conveying (IPCC) and autonomous haulage equipment (AHS).

Dec 1, 2013

By Chris Howell

PotashCorp?s Aurora phosphate mine, in Beaufort County, NC, operates four low pressure boilers and four high pressure boilers to meet its process steam requirements. Maintaining these boilers is critical to meeting production demands. Processing phosphate ore into phosphoric acid requires large amounts of sulfuric acid and steam. Ore is mined from the phosphate deposit with large bucket excavators after 9 to 30 m (30 to 100 ft) of overburden is removed. The phosphate ore is mixed with water to make a slurry that is pumped to the mill. Elemental sulfur is burned in the presence of air to make sulfuric acid. This process is highly exothermic and boilers produce steam while cooling the process. The phosphate ore is reacted with sulfuric acid and the resulting products are refined into different grades of phosphoric acid for fertilizers, feed stock and food additives. Plant operators at the mine were challenged with boiler feed water that was high in silica and other contaminants. As a result, boiler operations were experiencing difficult, labor-intensive operations and equipment deterioration. This resulted in higher operating costs and diminished processing performance. The facility was operating an aged boiler feedwater pretreatment system that included warm lime softening followed by pressure filtration and a cation/anion/mixed bed demineralizer system. The demineralizer required frequent regeneration and chemical usage was high and costs were difficult to predict. Depressurized well water (DPW water), used for plant utility water and boiler makeup, is very high in silica, in the range of 60-70 ppm. Silica can form scale at pressures below 600 psig. Above 600 psig, silica starts to volatize, carrying over with steam to potentially form deposits on downstream equipment and processes. Mine officials decided to upgrade the boiler feedwater pretreatment system to a state-of-the-art reverse osmosis (RO) membrane system. This new system, which started up in March 2009, has improved operating performance and reduced water consumption and overall operating expenditures.

Jan 1, 2011

By James A. Kiger

We at Colowyo would like to thank you for the opportunity to share with the Society of Mining Engineers of A.I.M.E. the progress of reclamation at Colowyo Coal Company's multiple seam open pit coal mine which is a general partnership of W.R. Grace and Co., and the Hanna Mining Co. First, a brief history of Colowyo Coal Company (Colowyo). The Colowyo operation is located approximately 28 miles southwest of Craig, Colorado, which is in the northwest corner of the state. The Colowyo operation produces coal from a Federal Coal Lease, a portion of which has experienced previous coal mining by underground methods. The underground coal mines were known as the Red Wing Mine and The Streeter Mine, and supplied coal to numerous locations in the Rocky Mountain region.

Jan 1, 1984

By T. B. Linde

The Morenci In-pit Crusher and Conveyor System has been designed with safe production and cost savings in mind. Large open pit mines around the world have been installing semi-mobile crushers and linking them with a pit conveyor system to lower unit cost. At Morenci two 60/89 in. gyratory crushers are incorporated into the semi-mobile crushing plants. The ore is reduced to -8 in. and transported out of the mine on a 60 in. steel cable belt. This paper includes an overview of the Morenci In-pit Crusher and Conveyor System from the drawing board to open pit installation and finally a discussion on operating and repair considerations.

Jan 1, 1990

By D. F. Scott

Spokane Research Center personnel have been investigating the use of seismic tomography to monitor the behavior of a rock mass, detect hazardous ground conditions, and assess the mechanical integrity of a rock mass affected by mining. Seismic tomography can be a valuable tool for determining relative stress in deep (> 1220 m) underground pillars. If high-stress areas are detected, they can be destressed prior to development or avoided. High-stress areas can be monitored with successive seismic surveys to determine if stress decreases to a level where development can be initiated safely. There are several benefits to using seismic tomography to identify high stress in deep underground pillars. The technique is reliable, cost-effective, efficient, and non-invasive. Also, investigators can monitor large rock masses, as well as monitor pillars during the mining cycle. By identifying areas of high stress, engineers will be able to assure that miners are working in a safer environment.

Jan 1, 1997

By Irina Chernyshova, Erik Larsen, Hanumantha Rao Kota, Vladislav Slabov, Garima Jain

The mining industry faces pressure to provide metals for the green digital shift using sustainable technologies. This study evaluates biosurfactants as collectors for ultrafine and coarser particles of hematite and malachite, aiming to improve the flotation of ultrafine particles.

Jun 1, 2023

By Karin Bäppler

Hydropower produces almost two-thirds of the world’s renewable electricity generation and delivers a major contribution on the ambition of the Paris Agreement and Sustainable Development Goals (SDG) with a range of benefits to society and environment. These include clean and flexible generation and storage in addition to reduced dependence on fossil fuels and avoidance of pollutants. The Limberg III PSP is one of the European projects that addresses the implementation of the UN SDGs. The challenge of the project is the construction of a 770 m long pressure shaft to be excavated with a TBM at an inclination of 42°.

Jun 13, 2023

By K. Johnson, B. Schiffer

Demonstrating aquifer restoration is an essential component of regulatory approval needed to mine uranium, copper, and other minerals by in-situ recovery (ISR). A PHREEQC geochemical model provided a useful means of forecasting the time for restoration and predicting future groundwater quality following low pH mining at Strata Energy’s Ross ISR Project in northeast Wyoming. The model simulated groundwater quality at three phases of the process: at the end of mining; during restoration; and post- restoration. The model utilized the one-dimensional reactive transport and dual porosity features of PHREEQC. Mineral surface ion-exchange, dissolution/precipitation reactions, and adsorption processes were simulated to estimate water quality as the pH was shifted from circumneutral to acidic during mining and back to neutral during restoration. The model results showed that cost-effective management of mine water could meet regulatory requirements. Additionally, the model was used to interpret results from a field trial and inform operational decisions. The predictive approach and geochemical understanding developed have application in assessing aquifer restoration for other ISR projects.

Mar 2, 2022

By I. Cameron-Clarke

This paper describes the design of a wellfield to provide a water supply for a new mine in southern Africa. A hydrogeological investigation was conducted that included the drilling and test pumping of eight wells located within a highly jointed pyroxenite aquifer. The wellfield was designed using a simple probabilistic analysis. This approach allowed the variability of the aquifer parameters to be taken into account. A risk assessment analysis was then carried out to evaluate the level of assurance that a reliable water supply could be provided by the wellfield. The analysis was also used to assess the effects of supplementing the water supply by pumping from nearby flooded workings.

Jan 1, 1992

By J. A. Cremeens, D. D. Overton, J. C. Varnier

"Slope failures that occurred in 2008 and 2009 at the Pikeview Quarry in El Paso County, Colorado, USA were investigated using three-dimensional discrete element modeling methods. Large scale block sliding failures occurred along weak bedding planes that dip steeply into an excavation located at the toe of the slope. Several mining sequences at the toe of the slope were simulated to evaluate the effects of various degrees of extraction and backfill on slope stability. Slope stability back analysis was conducted using pre-failure and post-failure conditions to determine the joint shear strength properties. Laboratory testing was also conducted to determine intact rock properties. Three-dimensional discrete element analysis was uniquely applicable to this evaluation because it allowed representation of shear stress of the basal sliding surface and it afforded evaluation of several scenarios of extraction and backfill at the toe of the slope. INTRODUCTION The Pikeview Quarry is an aggregate quarry located approximately five miles northwest of Colorado Springs in El Paso County, Colorado, USA. The quarry has been operated by several owners since the early 1900s. The Pikeview Quarry has been a major source of construction aggregate for the Colorado Springs area for many years (MSHA 1986). In the 1950s, the site was mined by Peter Kiewit and Sons to provide limestone for the construction of the nearby Air Force Academy. A large scale slope failure occurred on December 2, 2008, which stopped mining activity at the Pikeview Quarry. A second, related slope failure occurred on September 13, 2009. The second slope failure was located immediately adjacent to the initial December 2008 failure. The objective of this publication is to discuss the three-dimensional slope stability evaluation. The causal relationships of slope instability are not within the scope of this publication. However, omitting the precursors to slope failure would limit understanding of the nature of the slope stability evaluation. The regional and local geology and the history of slope instability at the Pikeview Quarry aid in understanding these precursors. Two main failure mechanisms were hypothesized during the failure investigation to explain the triggering of the 2008 and 2009 large slope failures at the Pikeview Quarry. Both mechanisms are given equal credence in this publication. Quarry excavation was a key factor in the slope instability for both failure mechanisms. The objective of the three-dimensional model was to evaluate the effects of extraction and backfill at the toe of the slope with respect to slope stability. GEOLOGY Regional and local geology are both important factors in slope instability at the Pikeview Quarry. Geologic structure at the quarry is related to regional mountain building and basin development associated with the Laramide Orogeny and the Rocky Mountains. Lithologies at the Pikeview Quarry are also related to regional trends. Localized geologic features, primarily related to weathering and erosion, have also been major contributing factors to slope instability at the Pikeview Quarry."

Jan 1, 2017

By D. M. Carris

Since the Buffalo Creek incident in February, 1972, Federal and state environmental agencies have had the pressure on the coal industry in the Appalachian area to close the coal processing plant water circuits. In an attempt to comply with this requirement, Eastern .Associated Coal Corp. decided to install a vacuum disc filter system at its Kopperston plant to eliminate the tailings pond and reduce the amount of plant make-up water. It was recognized at the time that the plant static thickener tailings would be a very difficult slurry to dewater because of its unusually high clay content. The following is a case history of the Kopperston installation and the refinements Eastern has made in its vacuum disc filter operation to increase efficiency.

Jan 1, 1979

By Edwin B. Wilson

The purpose of the panel's examination of coal mining research and development is to explore how the various groups that make up this research community might work together more efficiently and be more productive. The community, as defined here, includes federal and state governments, coal producers, manufacturers, unions, universities, and industry sponsored research organizations. The framework chosen for these discussions consists of brief presentations by the panel members on their views of the proper role and function of the group they represent. The panel members were also asked to highlight the economic, technical and institutional constraints that affect the performance of research and development and the use of the results. Following these presentations, a number of prepared questions will be discussed by the panel, and audience participation is invited. These questions were given several weeks ago to the panel members for their study. Before proceeding with the panel member reports, a brief review of the importance of R&D to the coal mining industry would be helpful to setting the stage for a constructive dialogue. It is appropriate to begin this review by mentioning that there is complete agreement among the research community that the major goals are: Improve health and safety Protect the environment Increase capital and labor productivity Increase resource recovery Since the basic functions of the academic, industrial and government sectors are different, we should expect that the research and development objectives and priorities, roles and responsibilities under each major goal will be different for each research group. The differences do not represent problem areas. However, problems will arise if the objectives are not properly interfaced at the appropriate time. The consequences of railing to understand the need for integrated programs will be the classic result, best described by the phrase --"a technical success but a commercial failure."

Jan 1, 1978

By Zhiguo Chang, QINGXIANG CAI, Ebelia Manda, IZHAR MITHAL JISKANI, XIANG LU, Wei Zhou, Saleem Raza Chalgri

The concept of mine safety is highlighted in the literature of sustainable mining but not extensively discussed. This study analyzes various aspects of underground and surface mine safety and emphasizes its importance in the context of sustainable mining. More specifically, this research attempts to find the relationship between mine hazards and demographic characteristics, examine and compare the perceptual difference among miners, and determine the impact of mine hazards on workplace safety and safety climate. Descriptive analysis, chi-square test, independent samples t test, and linear regression modeling were conducted to achieve study objectives. Results confirmed that mine hazards were significantly associated with age and experience. Miners perceived lower levels of management safety practices, followed by supervisor safety, coworker safety, and job safety. The analysis showed that underground miners reported lower safety scores than surface miners. There was a statistically significant difference between miners’ perception of safety climate (p < 0.05). The results showed that the higher prevalence of mine hazards predicts poor workplace safety and a low safety climate. The regression models revealed that mine hazards have a significant effect on workplace safety (p < 0.05) and safety climate (p < 0.05). In conclusion, the distinctive model of mine safety presented here contributes to the monitoring and design of comprehensive safety interventions and helps to better understand how certain factors interact on multiple levels to influence the overall safety of the industry. In this study, some suggestions are put forward to provide directions to develop a sustainable mine safety system.

Mar 27, 2020

By Isabel F. Barton, MarkD. Barton, Christian A. Rathkopf

Molybdenite is the world’s principal source of rhenium (Re), a critical element in multiple high-tech applications. However, the Re contents in molybdenite vary by orders of magnitude on scales ranging from single grains to whole deposits. In order to better understand the systematics of this variation and what geochemical factors control molybdenite Re concentration, and hence overall Re resources, we examine global patterns in molybdenite Re contents through a compilation of > 3000 measurements of Re in molybdenite from > 700 mainly ore-bearing moderate- to high-temperature hydrothermal systems of different types. Our results are similar to but expand on those of earlier studies. Rhenium concentration in molybdenite has a lognormal distribution and varies systematically with type of geologic system, intrusive lithology, and Mo grade. The lowest-Re molybdenite occurs in greisens (geometric mean 1 ppm ± a multiplicative standard deviation of 9), quartz vein-hosted W-Sn deposits (2 ± 5 ppm), unmineralized granites and granodiorites (12 ± 8 ppm), intrusion-related deposits (24 ± 8 ppm), and porphyry W-Sn deposits (16 ± 11 ppm). Rhenium is most enriched in molybdenites from volcanic sublimates (23,800 ± 5 ppm), with skarn Fe and Au (560 ± 5 ppm and 540 ± 3 ppm respectively) and porphyry Cu and Cu-Au deposits next (470 ± 4 and 430 ± 7 ppm respectively). Among porphyries, skarns, and quartz vein-hosted deposits, Re is most highly concentrated in molybdenites from Cu and Au systems and its concentration decreases systematically through Cu-Mo, Mo, Sn, and W deposits. In nearly all cases, molybdenites from systems associated with intermediate igneous rocks contain more Re than molybdenites from systems of the same type with more felsic rock associations. The disparity between Re contents of molybdenite in felsic and intermediate systems is largest for porphyries, quartz vein-hosted, and skarn deposits and is near zero for subeconomic or barren granite and granodiorite Mo systems; felsic intrusion-related deposits have slightly higher molybdenite Re than their equivalents associated with intermediate intrusions. In most systems, molybdenite Re content does not correlate with metal grade, but may have an inverse correlation with Au grade in intrusion-related deposits (based on a small number of data points) and does exhibit a strong inverse correlation with deposit Mo grade. Dilution of Re through larger amounts (higher deposit grades) of molybdenite explains about 40% of this correlation, but the relative enrichment of Re in molybdenite from low-Mo deposits must also reflect some selective enrichment of Re/Mo in porphyry Cu systems compared to porphyry Mo systems. We found no evidence for secular increase or other systematic temporal variation in molybdenite Re content. The data regarding the use of molybdenite Re content as a proxy for mantle influence are ambiguous. Nearly all observed empirical correlations can be traced back to differences in redox state and sulfide concentration, the two geochemical factors identified here and by previous experimental work as the controlling influences on Re mobility under hydrothermal conditions. Hydrothermal systems with reducing conditions (W- and Sn-rich) tend to have low molybdenite Re even though compiled whole-rock data indicate that their source rocks have as much or more Re as those of more oxidized systems (e.g., Cu-rich). Vapor-phase exsolution, crustal assimilation, and mixing with external fluids may all enrich molybdenite Re concentrations in individual deposits and deposit types, but their extent and importance in overall hydrothermal concentration of Re is uncertain. Thus, it appears that the available molybdenite Re resource in an ore deposit largely depends on how the deposit’s redox and sulfidation conditions have varied over time and space during the timespan of hydrothermal activity. Oxidized, high-sulfide conditions tend to concentrate Re in molybdenite, whereas reducing conditions tend to leave Re dispersed at low concentrations in the bulk rock.

By Chuang Sun, Feng Luo, Guo‑dong Li, Xue‑qing Li, Tuan He

The mining-induced failure of the coal seam floor is essential for water inrush. The mining disturbance to the floor, especially in the thick coal seam, is severe, and the water inrush risk is also higher than that in regular thick coal seam excavation. The superposition of many stresses, including in situ stress, mining-induced stress, and confined water pressure, must be considered in the prediction of the floor failure depth. This study adopted the elasticity analysis, FLAC3D numerical simulation, and on-site acoustic wave test comprehensively. The thick coal seam working face of the Zhong-Yu coal mine affected by confined water was selected as the engineering background to study the characteristics of the floor failure. Based on elastic foundation theory and the superposition principle, the mechanical model and the failure depth criterion of the floor were established, respectively. The distribution and evolution of mining-induced stress and the plastic zone in surrounding rock during the mining process are obtained by FLAC3D. In addition, the changes in the P-wave wave velocity in the floor before and after mining were compared and studied by the acoustic wave test method. The range of floor damage depth is determined on the basis of the above research.

Jun 8, 2022