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By R. Hawker, P. Singh, K. V. Jessu, P. C. Pinazzi, A. J. S. (Sam) Spearing

Rock bolts are highly important underground to prevent falls of ground and thus, ensure safety. In situ, the ground reinforcement is subjected to a combination of loads, such as shear, tensile, and/or bending loads. Studies have been conducted to evaluate the effect of either shear, tensile, or bending loads on the ground support. However, only a few studies have been done to evaluate the effect of combined load on the rock bolt performance. In situ, the order of loads acting on the bar cannot be predicted, and more than one load can act on the bar at the same time. Thus, a hybrid failure criterion was developed that covered all combined loading conditions. Fifty-eight un-grouted laboratory rock bolt tests were conducted in total under two load conditions: applying shear displacement to the rock bolt and then tensile load to failure, and applying tensile displacement to the rock bolt and then shear load to failure. From the test results, the failure criterion was developed based on regression analysis. A nonlinear relationship was determined for the loading condition variations. The failure criterion presented in this paper can be used as a guide in the rock bolt capacity design under all loading conditions.

Sep 8, 2020

By Don Suttie, Frank Roybal, John Wright

The Roybal Raise incorporates the simplicity and low cost of a short bald-headed raise while overcoming the usual impediments to driving a high baldheaded raise. The concept provides for speedy excavation and maximizing the use of the excavated opening, using the rock for structural support. The design is simple: two baldheaded raises are driven parallel to one another, interconnected by dogholes about 8 m (25 ft) apart. In this fashion, the raise can be driven safely and efficiently to 60 m (200 ft) or more. When the raise is complete, the excavation requires no timber for support or partitioning. Rather, the rock itself supports the construction. As a test, a two-compartment Roybal Raise was attempted at the Independence mine in the Willow Creek District of Alaska. One side was driven 2 x 2 m (6 x 6 ft), intended for a manway and equipment skip. The other was driven 1.5 x 1.5 m (5 x 5 ft) for a muck compartment. Both sides were driven at a 65° angle from horizontal and 1 x 1 m (4 x 4 ft) dogholes spanned the 4.6-m (15-ft) pillar between the two compartments. After topping out at 50 m (160 ft), the raise was found to meet all expectations of efficiency, low cost, and practical simplicity. Technique Preparing the Roybal Raise for driving involves no elaborate or costly site prep except assembling materials and providing for muck removal. Normally, the raise muck falls directly onto the sill or track and is picked up either by an overshot mucker or a front-end loader. Raise mining proceeds initially by taking up both compartments simultaneously to the first doghole. It progresses by alternating one side as a clear manway for access with the other side, the active side, as a muck compartment (Fig. 1A). This stage proceeds quickly for no mucking or staging is required to cycle the first three rounds. On the fifth round, in addition to the normal raise round, rib holes are winged out toward the adjacent raise, thus starting the dogholes. Finally, as the sixth raise rounds are drilled and shot, the first doghole is also completed from both sides. The second stage commences by establishing one side as a clear manway for access while the other side, used as a muck compartment, is prepared for active mining. Figure 1B illustrates this step in the succession of raising with the active side advancing to the second doghole level. During this stage, services are maintained through the manway side and equipment is stowed in the doghole during blasting. As the active side advances, muck may be allowed to fill the bottom portion of that side since it is unnecessary to clear it for access. The next stage of raising involves cleaning out the former muck compartment and preparing it for use as a manway. At the same time, the former manway is prepared for advance and use as a muck compartment (Fig. 1C). As in the previous step, the same doghole is used for access and equipment storage. The active side advances until the second doghole is completed, at which point equipment and access are moved to the new doghole. From there, the active side is driven past the second doghole 8 m (25 ft) more to the third doghole level. Again, half of the doghole and the next raise round are mined. The fourth stage involves switch ing back the manway side for the muck side (Fig. ID). The new muck side is driven to the third doghole where equipment storage and access are reestablished. From there, the active side is advanced to the fourth doghole. In the same fashion, the raise is advanced to the top, alternating the manway side with the active side, maintaining access through the inactive manway, and storing equipment in the uppermost doghole. The cycle time for driving each compartment, regardless of the raise height, is greatly improved over that for normal bald-headed raises of comparable height. By storing equipment in the upper-

Jan 1, 1984

By Erwin Riyanto, Roy William, Karl Llewellyn

The Deep Mill Level Zone (DMLZ) mine is currently one of the deepest block cave mines in the world. The rock mass is heavily veined with little to no joints and faults are usually healed cohesive structures leading to difficult cave mining conditions. The caving process is improved if the rock mass contains fractures with sufficient density that it will cave by gravity as undercutting progresses. Hydraulic fracturing (HF) has been used to create fractures around the cave to improve mining. A seismic monitoring system has been used in DMLZ since the start of mining. Therefore, the seismic activities before, during and after HF can be monitored. Shear wave splitting is a process used to study the impacts of HF on the rock mass. This process involves the measurement of travel times from splitting shear waves after seismic events and using this to define the anisotropy within the rock mass and subsequently fracture density. This paper sets out the methodology for carrying out the interpretation of the shear wave splitting process using seismic data from the fracked cave crown and abutments along with an overview of the benefits to cave mining as result.

Apr 26, 2022

By Donald J. Reining

The California Surface Mining and Reclamation Act (SMARA) is the nation's first legislation establishing a statewide mineral resource policy governing mining activities that recognizes regional needs and retains local autonomy. The Southern California Rock Products Association supported this proposed legislation. It was through our efforts that SMARA was passed in 1975. The local planning and zoning processes, which are so critical to the mining industry, have been significantly improved with implementation of SMARA. Recognition of the importance of the mining industry is now being developed by the State Mining and Geology Board and the California Division of Mines and Geology (CDMG).

Jan 1, 1984

By B. Ollila, L. Brown

As mining fronts converge in sill pillar extraction, the mine seismic hazard can be significantly altered and large seismic events have been known to occur. This study used common seismological tools to analyze the extraction of highly stressed sills from two deep Canadian mines with the objective of characterizing the rock mass failure process and relation to large seismic events. The approach treated a sill pillar as a mine-scale failure process, meaning the temporal and spatial analysis scales needed to exist on a similar scale to a significant part of the mine. The temporal analysis scale overlapped with the entire mining sequence, included several years of data to establish long term change in the characteristics of rock mass failure. The spatial analysis scale included the rock mass surrounding a large part of the convergent mining sequence. To accommodate the large spatial and temporal scales, the highest magnitude 2% of events in the dataset were analyzed. Similar results were shown for sill pillars in both mines. Changes in event location, time, magnitude, energy index and apparent volume were similar to expected behavior of rock failure. Indications of strain hardening and strain softening were observed in the sills. The hardening period was characterized by a high rate of small events, high energy index and low apparent volume, giving an indication of high stress and low rock yield. The softening phase was characterized by a decrease in the rate of small events concurrent with an increase in the rate of large events, low energy index and high apparent volume, indicative of release of stress and increase in deformation. Large magnitude seismicity was strongly related to the softening phase, with several Nuttli magnitude 3.0+ events occurring shortly after the transition from hardening to softening failure regimes. Sill failure was indicated by consistently low EI and low levels of seismicity and seismic hazard in the sill pillar.

Apr 26, 2022

By George Hufford

An investigation is made into the applicability of queueing theory to simulating the operation of a large open pit copper mine in the southwestern United States. Actual data from a working mine was used to construct curves for truck loading time, haulage and return time, and dumping times. Known results of investigations of queueing models (Koenigsberg - 1958, Gordon and Newell - 1967, Cabera and Maher - 1973) were used to simulate the actual operation. These did not give acceptable results so commonly used probability distributions were fitted to the actual data. A large computer program known as Q-GERT was used with the various parameters obtained from fitting the curves. Kolmogorov- Smirnov tests were run that showed that this was not satisfactory either. Finally, Q-GERT was used with the actual data from the mine. An appropriate correction factor is then found to apply to the exponential probability distributions tested previously and satisfactory results are obtained.

Jan 1, 1981

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 Morgan M. Sears, Mark Morris, Joseph Bright

In an effort to advance the science underlying modern coal pillar stability analysis, researchers at the National Institute for Occupational Safety and Health are currently involved in research aimed at better understanding the impact of an in-seam rock parting on the strength of coal pillars. The purpose of this study is to determine a suitable virtual mining height that could be applied using current pillar stability analysis tools. To accomplish this, the boundary element model LaModel was used to back analyze data collected on pillar performance in a room-and-pillar panel at the Maple Eagle Mine located in Southern West Virginia. In a previous work, data collected from borehole pressure cells (BPCs) and extensometers were taken from three instrumentation sites. Data collected from the back bleeders were used to measure the rear abutment stresses, and data collected from two instrumentation sites in the wraparound bleeder were used to measure the front and side abutment stresses as well as the peak strength and performance of the slabbed leave pillar. The utilization of two nearly identical instrumentation sites in the wrap-around bleeder provided much needed repeatability of the obtained measurements. In this study, the data collected from BPCs at the three instrumentation sites was calibrated to match the Bieniawski pillar stress gradient. To model the measured pillar behavior, the LaModel program was selected due to its capability of being directly comparable to the Analysis of Retreat Mining Pillar Stability (ARMPS) and Analysis of Coal Pillar Stability (ACPS) programs. The model was then calibrated to match the measured abutment extent and abutment stress. Finally, the model was validated by reducing the modeled mining height until the yielding of the slabbed leave pillars in the model matched what was measured in the field. The final calibrated mining heights show that a reduction of the shale parting thickness, not including any clay layers, of 52% is applicable. This research study provides the first known measurement of the ARMPS/ACPS “50% Rule” and its applicability to this panel of the Maple Eagle Mine. This finding provides a proof of concept and could have significant implications for future research.

Feb 1, 2024

By A. Dell’Era, E. Ciro, C. Lupi

The indium recovery via electrowinning from sulfate baths has recently gained significant attention as it does not present toxic emissions, hermetically sealed system requirements, human health, and environmental hazards. Following previous works related to the optimization process for AISI 316L and Ni cathode, it was observed significant importance of the metal supports on the input and output parameters of the indium electrowinning process from sulfate solutions. Thus, comparing input and output parameters in both cases seems very interesting. Particularly, regarding the input parameters, the attention has been focused on the electrolyte composition, current density, and temperature, while productivity, morphology, and structure have been considered regarding the output parameters. Considering the productivity as the optimal output, the findings for Ni cathode were better than that for AISI 316L in most of the selected conditions studied. In the case of morphology, indium grains appear rounded and dendritic on the AISI 316L, while those on the Ni cathode show stratified lamellar grains. Anyway, the indium deposit obtained on Ni cathode shows bigger grains independently from the used operative conditions with respect to that on AISI 316L. Regarding the structure, it is clearly tetragonal, but preferential orientation, crystallinity, and deformation of the structure strongly depend on the metal support.

Jun 14, 2023

By L. L. Chasko, D. W. Alexander

Los investigadores del National Institute for Occupational Safety and Health’s Office of Mine Safety and Health Research han evaluado los efectos que la malla de control de suelos podría tener en la distribución de polvo flotante de roca y carbón en minas de carbón. El creciente uso de mallas para controlar el desconchado o caída de material del techo y las vigas introduce superficies elevadas adicionales para recolectar el polvo de roca o de carbón. Es posible que el potencial para la propagación de explosión del polvo se incremente si el polvo flotante de carbón no es convertido en inerte de manera adecuada. Adicionalmente, la malla podría interferir con la recolección de muestras representativas de polvo cuando se usa el método de recipiente y brocha desarrollado por la U.S. Bureau of Mines y usada por la Mine Safety and Health Administration para muestreo de banda. Este estudia hace una estimación del polvo de roca o carbón adicional que pudiera acumularse en la malla y desarrolla un método para recolectar muestras de polvo representativas atrapado en las mallas.

Jan 1, 2014

By Franziska Günther, Helmut Mischo

The calculation of costs for an underground mine, as well as the planning of the equipment and materials to be used, is a complex and time-consuming process. The estimation depends on a multitude of parameters, and all mining processes are interconnected. A novel tool has been developed that enables automated calculation of underground mines and allows for the comparison of the effects of changing individual parameters. Previously, changing individual planning parameters often necessitated a complete recalculation of the mine. The newly developed calculation tool provides an innovative planning aid that allows for more efficient and accurate mine planning and cost estimation. The tool enables the user to implement continuously up-to-data costs and prices. This allows for more accurate planning data and results. The underlying concept of the calculation tool, its implementation at a planned quartz porphyry mine in Germany, and the verification of the tool at an existing underground mine will be presented.

Feb 1, 2025

By John W. Wilson

Every operation connected with the working of a deep-level mine has, to a greater or lesser extent, a direct bearing on the costs of production, and hence, profitability of the mine. If adequate mine planning is not done in the early stages in the life of a mine, considerable expenditure can result from the cost of maintaining mine service tunnels, production delays in stopes caused by poor strata control, distortion of fittings in hoisting shafts, rockbursts and so on. In fact, the optimum profitability of a deep-level, hard-rock mine can only be achieved if the layout of the shaft systems, ore passes, tunnels, stoping areas and other underground excavations are designed to withstand or accommodate the rock stress conditions that will be created by mining operations. In South Africa where the deepest mines in the world are located, access to the underground workings of most deep-level gold mines is via vertical shaft systems and a network of tunnels connecting the shaft systems to the stoping areas. In current practice, there are two basic methods of extracting the gold-bearing reef,* namely, the scattered stoping method and the longwall stoping method. The choice of the stoping method is governed largely by the anticipated gold distribution and payability of the reef in the area, the geological conditions, the degree and complexity of faulting and dyke intrusions, the depth at which the gold-bearing reef is to be mined and the inclination and width of the reef. The longwall system was first introduced at the East 717 Rand Proprietary Mines Limited in 1942 in an effort to combat the rockburst hazard which appeared to increase with increase in depth. This mining method became standard practice on that mine for stoping operations 700 ft. below the surface. Since that date, several deep mines on the Central Rand, East Rand and West Wits gold mining areas have adopted this method.

Jan 1, 1977

By K. KAKLIS, O. SAUBI, Z. Agioutantis, R. JAMISOLA

Three-point bending (TPB) tests were conducted on prismatic Nestos marble (Greece) specimens. The specimens were instrumented with piezoelectric sensors, and comprehensive recordings of acoustic emission (AE) signals were obtained. Machine learning in the form of artificial neural networks (ANNs) was then applied in an effort to investigate whether specimen load evolution can be predicted as a function of AE signals. A number of ANN models were developed, and the optimum model was selected based on the highest coefficient of determination (CoD) value as well as the lowest root mean square error (RMSE) value that was calculated for each model. The best performing ANN model exhibits accuracy above 99% with an RMSE value below 4%. It can be concluded that ANNs can potentially be applied to predict rock behavior under load especially when such loads lead to failure.

Sep 7, 2022

By Yuting Xue

Classification of rock and coal is one preliminary problem for fully automated or intelligent mining. It assists in automated rib stability analysis and enables the shearer to adjust the drums without human intervention. This paper studies the classification of rock from coal on rib images using machine learning techniques. A database of rock and coal images was created by filtering photographs taken by NIOSH researchers during site visits. Machine learning was conducted on patches, smaller images randomly extracted from each rock or coal image. After training, the classifier was validated with the testing dataset and achieved an accuracy score of 0.9.

Jan 13, 2022

By L. M. English

A basic model was developed to help assess methane control needs for the longwall mining of coal in gassy areas. Rather than depending on reservoir and rock mechanical theories, it uses an empirically determined gas emission rate as an input, and it operates on the assumption that, within a specific region and zone, gas emissions will be relatively equivalent for uniform incremental volumes of gob created by mining. The computer program divides longwall panels into segments, keeps track of the face advance and generates emission rates and volumes for both the entire panel and for individual zones within the panel by summing values for all undermined segments. This model can aid in the determina¬tion of the number, size and location of vertical wells or other methane-control applications that are needed for gob gas control.

Jan 1, 2000

By K. L. Whitehead, R. A. Jankowski, N. I. Jayaraman

Most continuous miner sections utilizing flooded-bed scrubbers also use blowing face ventilation. Blowing ventilation, however, interferes with dust capture and minimizes scrubber effectiveness. To enhance the efficiency of the scrubber system and reduce dust concentrations, the Bureau of Mines tested various combinations of operating parameters. Experiments for system efficiency took place in a full- scale model mine at 3.05 m roof height. In general, higher values for scrubber and face airflows resulted in lower dust concentrations. In addition, optimum dust controls would include a face ventilation to scrubber airflow ratio of one. When the airflow ratio was either less than or greater than one, the dust levels in the return and at the operator locations increased. No single dust control technique was the most effective one at all locations due to mutual interaction among techniques.

Jan 1, 1992

By Robert A. Irvine

Traditionally, cost effective gains in the capacity of material handling systems were a result of increases in equipment size. In general, the use of maximum capacity components in a system optimizes the production "costs per ton." The trend-"Bigger is Better" will continue in material handling equipment. Since it is rare for plant operators to lament an over abundance of screening capacity, one can safely predict that vibrating screens will follow this trend. Large Vibrating Screens - The Challenge Large vibrating screens represent a unique challenge for Manufacturers, Plant Designers, and Plant Operators. The inherent mode of operation for vibrating screens is self-destructive. More often than Manufacturers admit, Designers plan for, or Operators staff for, a vibrating screen succeeds and self-destructs. This is a problem. It can magnify with larger vibrating screens.

Jan 1, 1983

By J. S. Lewis

Beneficiation and physical and chemical processing of non-terrestrial materials borrow strongly from terrestrial experience, but also involve the necessity of handling literally un-Earthly feedstocks, reagents, and environmental conditions. The present state of scientific and engineering understanding of the processing of non-terrestrial minerals, gases and hydrocarbons is reviewed with the production of rocket propellants, life-support fluids, structural metals, and refractories as the goal.

Jan 1, 1992

By R. E. J. Putman

Rising demand, artificial market conditions, increased overseas competition, and a fluctuating international situation have brought ever increasing pressures to bear on the nonferrous metals industries, and particularly in the United States, Although capacity is being expanded by the construction of new plants and the development of new ore deposits, increasing attention is being focused on the possibilities of improving the performance of the existing installations and of getting the most out of the new equipment now installed. At first sight the task appears formidable. Based on raw materials which are nonhomogeneous, and possessing characteristics which are hard to quantify, even the processes by which the values in the ores are concentrated and extracted are in many cases not fully understood. The necessary analytical equipment and transducers demanded by these industries have also been slow in development and their earlier absence has hampered the application of modern control technology, This is reflected in plants which have been designed for ease of manual rather than automatic control, and in which the application of control techniques at first sight appears economically prohibitive. However, in any industry progress often comes only in small steps, It may be that by the wise choice of limited objectives and perhaps only partial solutions, substantial improvements in plant performance can be implemented now, and with only a modest investment. If modern control equipment is chosen of the type which can be reprogrammed, advantage can be taken later of more sophisticated solutions as the technology of the industry advances. This task of improving plant performance can and must be commenced even though our knowledge is incomplete. The experience of a related mineral consuming industry, with similar problems in the past, can be encouraging.

Jan 1, 1967

By P. K. Kankar, Manoj Khandelwal, Ramesht Shukla

One of the utmost severe mining catastrophes in underground hard rock mines is rock burst phenomena. It can lead to damage to mine openings and equipment as well as trigger accidents or even threat to life as well. Due to this, a number of researchers are forced to study some easy-to-use alternative methods to predict the rock burst occurrence. Nevertheless, due to the extremely multifaceted relation between mechanical, geological and geometric factors of the mines, the conventional prediction methods are not able to produce accurate results. With the expansion of machine learning methods, a revolution in the rock burst occurrence has become imaginable. In present study, three machine learning methods, namely XGBoost, decision tree and support vector machine, are utilized to predict the occurrence of rock burst in various underground projects. A total of 134 rock burst events were gathered together from various published literatures comprising maximum tangential stress (MTS), elastic energy index (EEI), uniaxial compressive strength and uniaxial tensile stress (UTS) that have been used to develop various machine learning models. The performance of machine learning methods is evaluated based on the accuracy, sensitivity and specificity of the rock burst prediction.

Mar 17, 2021