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By James L. Hendrix, David Castillo

Cyanidation is one of the most common practices used in the extraction of gold and silver. One method of application is heap or dump leaching which entails the leaching of the gold or silver ore by spraying or dripping a cyanide lixiviant over the ore and collecting the effluent. The ore is placed on what is known as a leach pad system. A typical leach pad system consists of a foundation, a leakaqe detection system, a liner, and a cover layer (Strachan and van Zyl, 1988). There are many types of liners available for use. The type of liner depends upon what type leaching pad system us used. Generally, leaching pad systems can be categorized into two types: an expandable pad and a reusable pad. An expandable pad exposes the liner to the elements only in the initial stages of ore placement on the leach pad system. A reusable pad exposes the liner to the elements on a periodic basis. In addition to the exposure to the elements, the liner is also under the stress of the ore placed on it and the stress of the vehicular traffic across it. These stresses and exposure to the elements are the major causes of liner failures, which can appear as punctures, tears, cracks, and deterioration. Because of the possibility of the failure of the pads to contain cyanide-laden solutions the designs for liners of pads and ponds have become more and more stringent. Currently, though, there is some recognition that in some locales such stringent design criteria may not be required (Chatwin, 1989). Some soils have significant cyanide attenuation and degradation capacity. It has been found that soils containing carbon- aceous materia1 wi11 remove cyanide from solutions percolating through them (Chatwin, 1989). Of course metallurgists have long recognized the deleterious effect of carbonaceous material in the mill circuit. Sheridan, et a1 (1988) have shown that WAD cyanide is detected in the effluent of a 2 m column filled with ground carbonaceous ore only after it had been continuously washed with greater than 9 pore volumes of NaCN solution. It was decided to examine the potential of successfully attenuating cyanide by placing an organic material layer between a 1iner and the prepared soil base. One consideration for the selection of the organic material was cost. Sawmill wastes, ground agricultural wastes (such as corn cobs), and other organic wastes were considered. But the first waste to be tested was a product found at any metropolitan area, sewage sludge.

Jan 1, 1990

By T. Hollingsworth

The Boddington Gold Mine, located near Perth in Western Australia, has recently completed the construction of a new process plant. An overland conveyor system was installed to convey the ore from the primary crusher to the process plant. This paper will discuss the overland conveyor?s mechanical design including dynamic analysis and the selection of primary mechanical and electrical components.

Jan 1, 2010

By J. G. Mansanti

The metallurgical response of a deposit's various ore types usually has a strong impact on the flowsheet design of most mineral processing plants. This impacts the materials handling, equipment selection, capital and operating costs, and plant availability. Because of the rapid leaching characteristics of Chimney Creek ores a variation of the conventional gold plant, carbon columns and CIP was proposed. The proposal consisted of a washing stage which was installed between the typical leaching and CIP stages. The circuit was simulated in the lab and was modelled using a computer program to evaluate the metallurgical impact and the effect on the system's mass balances. Also, actual plant data was reviewed comparing the results that were achieved with the results that were expected.

Jan 1, 1988

By Albert Hofstra, Joel Leventhal

The gray, dark gray and black colors of the sediments and the presence of pyrite in the Carlin, Jerritt Canyon, Horse Canyon, Betze, and Gold Acres sediment-hosted disseminated gold (SHDG) deposits indicate that these rocks are not oxidized with respect to carbon and iron sulfide. Both ore and non-ore host rocks generally are dark colored. Analyses for noncarbonate carbon (usually called organic carbon) in samples from SHDG deposits and related unmineralized rocks indicate that these rocks contain from a few tenths to a few percent carbon. We use the term noncarbonate carbon because, strictly speaking, organic carbon denotes carbon that is bound to hydrogen. However, the carbon present in SHDG deposits and related rocks has very little hydrogen chemically bound to it. Rocks with less than 2% organic carbon are usually gray in color. The dark colors in our samples are due to the relatively high temperatures that these rocks have experienced relative to organic matter maturation. We confirm the results of Nelson et al. (1982) that previous reports (for example, Radtke and Scheiner, 1970) were incorrect in reporting significant amounts of humic acids, extractable hydrocarbons (bitumen) or "carbonaceous" material. We believe these reports had problems with contamination or misdirected emphasis. Our samples consisted of unweathered rocks, collected mainly from mine cuts (benches, trenches, cores) and put into glass containers or wrapped in aluminum foil to avoid contamination. Only a few samples were collected from natural outcrops. We were careful to avoid samples in proximity to blast holes that were packed with ammonium nitrate and diesel fuel ("ANFO"). Contamination by ANFO may explain some of the previous reports of hydrocarbons, pyrobitumens, humic acids and anomalous nitrogen. When we were collecting samples, it was apparent that in addition to lithologic and color differences, the surface appearance of the rocks was distinguishable: "preg robbing" material that had a sooty surface; "graphitic" rock with a shiny surface; and more ordinary rocks that had a flat gray or black appearance. [Preg robbing is a term for ores that adsorb gold from the milling circuit; the graphitic material had not been x-rayed to actually identify graphite.] We hoped that laboratory study of these samples would show some fundamental differences that we could relate to ore genesis. Even though these sample types appeared different in the field, we could not distinguish any differences in thermal maturity (see below). Normal petroleum/organic geochemical laboratory procedures (solvent extraction, Rock-eval, pyrolysis-gas chromatography) failed to yield much information because the carbon was over-mature relative to oil and gas generation. Rock-eval results show less than 20 (± 20) mg of pyrolizable hydrocarbons per gram organic carbon (and an indeterminate Tmax) indicating that the organic matter in these deposits is burned-out relative to petroleum generation [with an H/C (atomic) ratio of less than 0.41. Because of the non-definitive results from standard organic geochemical methods, x-ray diffraction (XRD) and Raman spectroscopy were used to characterize the carbon. Prior to XRD, samples were treated with HCl and HF acids (1) to remove quartz that has a peak near 26° [20] at the position of the 002 peak of graphite and (2) to concentrate the carbon to a level detectable by XRD. The residue was put on a colodion mount and analyzed by XRD. The XRD analyses yielded a broad peak at 26° [20]. The shape of this peak indicates that the carbon is more thermally mature than anthracite rank coal but less mature than crystallized graphite. Based on XRD results from the literature (Landis, 1971) that are calibrated to metamorphic facies, results from our samples correspond to pumpellyite-actinolite to lowermost greenschist facies conditions, probably

Jan 1, 1990

By Anthony Peach, Lok Home

Introduction Raise boring is the most accepted form of mechanized hard rock boring in the mining industry. It appeared logical to take this mechanization one step further by introducing computers. Atlas Copco Jarva has produced a series of raise boring models that use an integrated computer. The company decided to use electronics and computerization, not for marketing purposes, but to make its equipment more cost-effective. Basis of Cost-Effective Design From the manufacturer's standpoint, it is possible for the equipment owner to reduce the cost of putting in raises by: • Replacing existing components with less expensive components that produce the same results; • Replacing existing components with more expensive components that make the equipment more productive; • Mechanizing equipment to reduce associated labor costs; and • Combining the above. Analysis of a standard raise boring machine (RBM) system showed that little could be done with less expensive components. It appeared, however, that the RBM could be more productive by transmitting more horsepower through the expensive drill string, while being precisely controlled by computers. An RBM system includes a basic machine, drill pipe, accessories, reamer, and cutters. The approximate percentage cost of various components on a standard system capable of boring 300 m (985 ft) long and 3-m-diam (10-ft-diam) aises in medium to hard rock is shown in Table 1. Also shown is the increased cost above standard of the Jarva computerized machine, and the productivity of both. Increased Productivity Penetration is important during the reaming cycle for more productive raise boring. This is possible by increasing the cutter load with constant rpm or increasing the rpm with constant cutter load. To increase thrust and maintain rpm requires increased capacity in the cylinders, drive train, main thrust bearings, drill string, electrical motors, and power units. To increase rpm and maintain cutter load requires only increased capacity in the electrical motors and power units. This is possible because the torque requirement remains constant for a constant thrust load. Only the horsepower increases, proportional to rpm. Since cutter costs are a big factor in raise boring, changes in machine performance must be analyzed to assess the effect on cutter performance. With a standard or typical carbide cutter, as used on raise boring machines, the effects of increased thrust or rpm are shown in Table 2. The assumption is made that the base data is the current rpm and thrust range where the cutters are now operated. It is also assumed one variable is held constant while the other increases. The result of this comparison, approximately, is that a 50% penetration increase can be achieved with little or no increase in cutter cost if rpm is increased 50% and cutter load is maintained constant. A similar 50% penetration increase can be achieved with a 45% increase in cutter cost, if the cutter load is increased by 20% and maintained constant. From an equipment standpoint, it is significantly less expensive to increase rpm 50% than it is to in-

Jan 7, 1984

The Witwatersrand reefs provide excellent examples of chemical and structural control on gold distribution. All mined gold appears to coma from a carbon -gold association and/or Fe-S-Au association, and also from immediately above or below unconformity surfaces. A total raliance on the current syngenetic model for Witwatersrand gold does not appear to be justified from the accumulated data and may be responsible for missed opportunities during exploration: consideration of other models is suggested especially where they better fit the data. The stratabound natura of Witwatersrand gold 1& critical to mining, but is emphasized in syngenetic models to the virtual exclusion of many other important observations. By analogy with other deposit types, stratabound character is probably a poor guide to genesis.

Jan 1, 1988

By Katherine Hynard, Colin Eustace

Development quarterly mine plans is generally time-consuming and requires consideration for many operational constraints and competing objectives. With lengthy turnaround times, there is often limited opportunity to adjust the quarterly plan details to account for differences between actual state of the mine operation at the time of execution and expected state at the time that the plan was developed. Actual mining task completion times can vary significantly from the expected task completion times, due to many factors. In the absence of revision to account for differences between the planned and actual state, resource allocations and mining sequences, embodied in the quarterly mine plan may no longer be the best approach at the time of execution to achieve an efficient mining operation. Simulation and optimisation tools can be used to support rapid refinements for development and execution of weekly mine plans. When initialized with an operations data feed to establish the actual state of the mine operation, optimisation models can be used to facilitate both automation and revision of the quarterly plan to produce a weekly or daily plan for execution. This approach can remove much of the manual burden of revision if the existing quarterly plan no longer represents the best approach to meeting production objectives. Following initialisation with mining actuals, simulation models can provide a representation of the range of likely mine operations outcomes. The models can be used to accelerate the planning process by providing visibility of future performance and identifying likely operational issues. They can also be used to test the robustness of the plan with respect to performance variability and response to disturbances. Following identification of issues, simulation models can also be used for evaluating mitigation measures, through automated testing of alternative plans. Integration of mine data feeds with simulation and optimisation tools enables automated optimal responses to variations between the quarterly mine plan and actuals to be tested prior to release of and execution plan and implementation. The use of simulation and optimisation in weekly mine planning will be discussed in this paper with reference to surface mining examples.

Jun 25, 2023

By A. Martikainen, H. Dougherty

"At the Kemi Mine, a recent expansion into the Surmaoja orebody required an increase in ventilation capacity. A new ventilation shaft was built with two main fans. The installation is near the entrance gate and only 1.7 kilometres from the nearest permanent dwelling. The main fans were first taken into use as exhaust fans in October 2014. Shortly after the fan installation, comments concerning fan noise were received from the neighbours. The first noise measurements were taken at the main fan installation site by Outokumpu personnel in March 2015. Due to higher than expected recorded values, during late June, 2015, a two-week environmental noise study was planned by the engineers and executed by a consultant specialized in noise measurement. The measurement results were analysed and compared to the requirements of the environmental permit and Outokumpu’s factory standards. While the measured values at the nearest dwelling were within the environmental permit limits, high noise values were recorded at the fan station. A second two-week study will be performed after construction of the main-fan heating station has been completed. Actions taken will depend on the outcome. INTRODUCTION The Kemi Mine is a part of the Outokumpu chain of integrated ferrochrome and stainless steel manufacturing in the Kemi-Tornio region in Finland. The mine itself is a large underground operation with a production capacity of 2.7 million tons of ore per annum. It is also the European Union’s only chrome mine, and at present (2015) the mine extracts 2.4 million tons of chrome ore per year. Safety, cost-effectiveness, and environmental friendliness are hallmarks of the Kemi Mine. Environmental impact produced by the operation of the mine is limited due to the insolubility of the oxide chromium ore, the gravity-based and chemical-free enriching process as well as the closed circulation system of the process water which serves both the whole mine and the enrichment process (Outokumpu, 2015). Importance of the environmental impact of the Kemi Mine is amplified by its closeness to the cities of Kemi and Keminmaa with the nearest habitants living less than 2 km away from the mine site. To show the cooperation with residents the Kemi mine organizes special “neighbour days” for the habitants of the areas closest to the mine. Also, information letters are sent to the neighbours, when changes that may affect the neighbours are being planned and executed."

Jan 1, 2016

By P. Conrad, S. Rosenthal

"Engineers remain in demand. Job opportunities in the United States still exceed the number of students graduating from college with degrees in Mining Engineering. Although enrollment is up for freshman studying Mining Engineering, many of those students will either change majors or not complete their degree, maintaining that deficit of available Mining Engineers. What can be done to ensure that enough Mining Engineers will graduate to fill the needs of the mining industry over the next ten to 20 years? The authors believe that this need can be met by recruiting students to Mining Engineering programs who are genuinely interested in working in the mining industry. With this in mind, Montana Tech conducted its first Mining Engineering camp in July 2014 to get junior and senior high school students interested in careers in the mining industry by showing them that Mining Engineering is both an exciting and rewarding career. This paper discusses What a Blast! The 2014 Montana Tech Mining Camp. INTRODUCTION The concept of summer camps for high school students is not new. For example, Missouri University of Science and Technology has offered their “Explosives Camp” for several years. A large percentage of attendees to these camps discover or confirm an interest in Mining Engineering and enroll in the school’s program. The Dean of the Montana Tech School of Mines and Engineering challenged department heads to develop and offer summer camps for prospective high school students to get a taste of engineering with the goal being to improve recruitment for each discipline. Mining Engineering embarked on the concept of a summer camp in 2013 with a concept to provide a week’s experience in Mining Engineering during the summer of 2014. What it takes to progress from concept to reality, with some of the learnings to be shared, follows."

Jan 1, 2015

By J. Kretschmann, P. Goerke-Mallet, C. Melchers

Mining always leaves a mark behind. Dealing with this legacy is not only a tremendous challenge in Germany, but internationally too. The Technical University Georg Agricola (THGA) in Bochum, Germany, has established a Research Center for Post-Mining. Researchers combine expertise from a variety of technical and nontechnical fields in their quest to shape the post-mining era that completes the mine life cycle. In this respect, the Research Center focuses on four research areas: Perpetual tasks and mine water management, Geomonitoring, Material sciences and site transition. With more than 200 years of successful partnership with the mining industry in Germany and abroad, THGA offers a perfect setting for fresh and sound ideas in order support mining’s social license to operate. The aim of the paper is to describe the Post-Mining Research Center along with exemplary research projects that are of interest to the mining industry globally and to foster technical communication and research networking.

Mar 2, 2022

By Patrick Shea

Old mine workings are found throughout the Western United Sates on lands administered by the U.S. Bureau of Land Management, U.S. Forest Service and private lands. Some of these mine workings date back to the late 1800s. There may be as many as 100,000 sites on lands administered by the National Park Service, U.S. Forest Service and Bureau of Land Management. The U.S. Department of the Interior has worked with the U.S. Geological Survey, the U.S. Forest Service, the U.S. Environmental Protection Agency, and western state governments to identify and prioritize these sites on Bureau of Land Management, National Park Service and U.S. Forest Service administered lands. This presentation will discuss the accomplishments we have made to date to clean up inactive and abandoned mine sites, focusing primarily on lands administered by the Bureau of Land Management.

Jan 1, 2000

By R. V. Ramani, R. Natarajan, A. Bhattacherjee

Industries in general, and mining in particular, have become safer than ever before. However, there is a need to increase the search for the causes of mining work-related injuries and to contribute to their reduction, as required, through job redesign, work procedures and worker training. Mine accident and hazard control must be practiced in a manner consistent with the overall objectives of the mine management, which include the optimum allocation and effective utilization of the resources. The purposes of this paper are to: • present a set of analytical tools to analyze injury experience data. • apply these tools on a case study example, • discuss the results of the case study, and • identify the application limitations and the future research needs.

Jan 1, 1993

By Harold G. Arthur

INTRODUCTION Stillwater Tunnel construction is scheduled to start in the spring of 1973. The tunnel will be the site of an extensive program in rapid excavation research. This paper presents a progress report regarding our plans and relates the tentative decisions which have been made on how to carry out the research effort. The details are subject to revision as more input is obtained from other Government agencies interested in tunnel construction and from experts in industry and educational institutions. The objective of the research program is to bring about faster, less costly tunnel construction. This objective will be pursued through the development, improvement, and evaluation of various construction systems and investigative techniques. The need for this kind of program was recognized by the National Research Council, in its authoritative report "Rapid Excavation - Significance, Needs, Opportunities." (1) The Council advocated a federally funded $200 million, 10-year program to help meet the $69 billion market it expects in underground excavation between 1970 and 1990. The significance of tunnel construction to Reclamation is made clear by statistics of its tunneling experience and outlook. Reclamation has constructed 174 water conveyance tunnels totaling over 190 miles, Six tunnels are presently under construction which have a combined length of about 27 miles. There are on the books nine authorized, but unfunded tunnel projects totaling another 70 miles in length. Many more miles of tunnels are included in programs in various stages of investigation.

Jan 1, 1997

By T. J. Batchler

"INTRODUCTION A variety of standing supports are being applied in underground coal mining operations to assist in providing stable mine entries. Standing support performance requirements depend on the nature of the ground deformation behavior, and therefore require a good understanding of the interaction between the support and ground to achieve an optimum roof support system. Mining operations often employ standing support strategies that are unique to their mine. A support system that functions successfully in one situation could fail in another situation. It is important that the design and installation of the standing support systems provide the highest probability of preventing roof falls. Considerable research and development has been conducted by support manufacturers to develop standing support technologies for the mining industry. The National Institute for Occupational Safety and Health (NIOSH) researchers, with the cooperation of various support manufacturers, have developed a testing protocol that evaluates performance characteristics of these standing support systems.. Using this protocol, each of these support systems has gone through rigorous safety performance testing under controlled loading conditions in NIOSH’s Mine Roof Simulator (MRS). It is important to understand the unique performance characteristics of each type of standing support. This information allows mine operators to determine if the support system is compatible with the conditions in the mine and to compare each support system and determine if that support will provide equivalent or improved support capability. This paper provides a comprehensive summary of support performance to facilitate this objective. SUPPORT DESIGN CRITERIA AND THE GROUND REACTION CURVE Standing roof support systems are designed to prevent unplanned roof falls. The selection of the standing support is based on the interaction of the support with the surrounding rock mass, and its function is to assist the primary support system in maintaining the integrity of the immediate roof. The standing support works to control the immediate roof structure by resisting deformation that contribute to delamination of the bedded layers and displacements that lead to separation of the bolted zone from stable roof structures above the bolted horizon (Barczak, 2005). Standing supports should be installed early enough and develop sufficient capacity to bring deformation of the ground into equilibrium before a critical deformation is reached that leads to a detached block condition, at which point the standing support will be required to carry the entire dead weight of the detached rock mass to prevent a roof fall from occurring (Mucho, 1999). The ground reaction curve (GRC) can be used to assist in determining the compatibility and design requirements for a support system. It is important to understand the significance of the ground reaction relative to the support design requirements. The ultimate objective is to match the support behavior to the ground response and create equilibrium (stability) of the rock mass. This equilibrium is accomplished when the support loading intersects the ground reaction curve (Figure 1). Essentially, the ground reaction concept implies that the convergence in the mine entry is controlled by the magnitude of the support resistance. However, as a passive support, the standing support develops its loading through convergence. As such, the support needs to maintain its load capacity through the associated deformation of the ground and resulting entry convergence until the equilibrium condition is reached. This requirement causes factors such as the support stiffness, peak capacity, yielding characteristics, and stability to be fundamental to proper support design and application. NIOSH contributes to providing this understanding through full-scale performance testing of support products in the Mine Roof Simulator."

Jan 1, 2017

By Manoj Khandelwal, Bright Akuinor Tsidi, Newton Amegbey, Daniel Mireku-Gyimah

This study emphasizes the importance of understanding the factors that influence the throwing of flyrock in mining operations, a significant hazard to both workers and nearby structures. Moreover, it highlights how blasting engineers, when estimating flyrock occurrences and their travel distance, typically rely on input parameters such as powder factor (PF), hole length (HL), subdrill (SD), spacing (S), hole diameter (D), burden (B) and stemming length (ST), while overlooking crucial factors like velocity of detonation (VOD) and charge per bank cubic meter (CPBCM). Through analysis using support vector machine (SVM) modeling in MATLAB, the study underscores the impact of including or excluding VOD and CPBCM on flyrock throw distance.

Jul 1, 2024

By Jerry W. Danni, John E. Hardaway

Corporations today must comply with an ever growing number of complex and increasingly stringent environmental laws and regulations. An environmental audit program is an effective means in which to uniformly and systematically assess compliance, and to assure management that environmental liabilities are being minimized. This paper describes the design and implementation of Homestake Mining Company's environmental audit program, which has as its primary focus the objective verification of compliance with external requirements and internal good management practices. Major elements of the audit program discussed in the paper include: pre-audit preparation; on-site audit activities; and the post-audit report.

Jan 1, 1992

By R. M. Hernandez

The Bureau of Land Management (BLM) constructed four passive biochemical reactor systems (BCRs) to treat mining influenced water (MIW) in the Bunker Hill Superfund area near Coeur D?Alene, Idaho between 2002 and 2003. Initially, the BCRs operated very effectively. However, in the past couple of years, the zinc removal effectiveness of the four BLM BCRs has declined [1]. The central objective of this study was to characterize the microbial communities and substrate present within the BLM BCRs and to use these factors to propose strategies to promote sustained sulfate reduction levels. Microbial communities were characterized by quantifying total bacteria and sulfate reducing species. Substrate was characterized by quantifying the percent organic, acid soluble organic, acid insoluble organic, and bioavailable material within the BCR. The results suggest the depletion of bioavailable organic substrates is the primary cause of the decline in zinc removal and not the microbial community structure. The ability to assess the amount of bioavailable organic substrate and microbial community is important to the understanding of the sulfate reducing capacity of the BLM BCRs and developing strategies to facilitate performance enhancement of the current BLM BCRs. The characterization of organic substrate and microbial community structure are also important to improving design of future passive treatment systems for mining influenced waters.

Jan 1, 2010

By Stryker Magnuson

While probe drills are not strictly necessary for all projects, the incorporation and use of probe drills and pre-grouting adds capability and insurance to boring operations. Water ingress and unstable ground can be resolved before becoming a problem and resulting in costly delays through the use of enhanced, 360-degree probe drilling setups. To do this, proper design of the array of drill ports in the shield, matched to the possible ground conditions, is critical. For ground with exceptional water and instabilities expected, additional probing locations are low-cost additions that can lower risk and increase efficiency. In this paper we will look at recent and ongoing projects including the Lower Meramec Tunnel and Jefferson Barracks Phase 2. We will detail the design of those probe drill arrangements, and our overall recommendations for probing/grouting systems that best suit challenging ground conditions and keep projects running smoothly.

Jun 13, 2023

By Fulian He, Jianhang Chen, Dongdong Chen, Shoubao Zhang

"The Wangjialing Coal Mine is the main colliery of the China Coal Huajin Energy Limited Liability Company. The average thickness of the coal seam in District 201 is 6.21 m. Fully mechanized longwall mining was used in this district. The ventilation roadway of panel 20102 was influenced by the retreat mining of the adjacent panel 20104. Therefore, large deformation and severe roof falls occurred in this roadway, seriously influencing the safety production of this coal mine. To support the roadway, cable truss was proposed to strengthen the reinforcement of this ventilation roadway. First, numerical simulation was used to optimize the reinforcement parameters, including the cable installation angle, cable length, and eccentric distance. Based on numerical simulation results, in-situ tests were conducted in the ventilation roadway of panel 20102 with the cable truss technology. In-situ monitoring results showed that the roof-to-floor convergence and the convergence of roadway on two sides were within the safety range. Furthermore, no apparent separations occurred in the roof. These indicate that based on the designed parameters, the cable truss system can effectively maintain the roadway stability under the severe influence of the adjacent longwall mining.INTRODUCTIONCable bolts are flexible tendons composed of multi steel wires, which are wound into a strand (Chen, Hagan, and Saydam, 2018). They were initially introduced in the hard rock mining industry in the 1960s. Later, they found rapid application in coal mines to maintain the stability of excavations (Wang et al., 2015).The standard cable bolt is composed of seven steel wires with a diameter of 15.2 mm. Laboratory and in-situ tests showed that there is a low bonding capacity between the standard cable bolt and the grout (Craig and Holden, 2014; Chen, Hagan, and Saydam, 2018). Then, modified cable bolts are developed based on the standard cable bolts. They are improved by changing the surface geometry of standard cable bolts, such as birdcaged cable bolts (Hutchins et al., 1990) or nutcaged cable bolts (Hyett et al., 1993). Further tests proved that modified cable bolts have better mechanical interlock and friction between the cable bolt and grout, leading to larger load transfer capacity of cable bolts.Although cable bolts have been used for many years, failure of the cable bolting system still occurs. A common failure mode is the damage of surrounding confining medium while the cable bolt is still hanging in the roof, which is caused by the bond failure of the cable/grout interface (Hutchinson and Diederichs, 1996). To prevent the cable bolting system from failing, the cable truss system is more widely used in mining engineering."

Jan 1, 2019

By A. Mukherjee

This paper presents an analytical technique for prediction of the damaged rock zone (DRZ) around a circular drift subjected to an anisotropic stress field (analytical solution exists only for the case of hydrostatic stress field). The method can readily be adapted to micro or personal computers. Stress concentrations around the drift are calculated at the centers of small rock elements, using the analytical solutions for a hole in an infinite plate. Potential failure of a rock element is assumed to be governed by the Coulomb failure criterion. When the failure condition is exceeded for an element, the excess shear stress is transferred to the neighboring elements. Progressive failure is allowed to occur until convergence is obtained. The final configuration of the damaged rock zone so obtained can be used to assess rock support requirements, as well as modified modulus and permeability of the DRZ.

Jan 1, 1988