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By G. S. Walker, W. van Bronswijk

The accurate determination of free cyanide and metal cyanide complexes is of increasing interest to Carbon-in-Pulp (CIP) gold extraction operations as cyanide consumption is an important economic factor in the processing of complex ores. Characteristically complex ores are high cyanide consumers and these ores usually contain a range of sulfide minerals e.g. covellite (CuS), digenite (Cu1,S), chalcocite (Cu, S), Pyrrhotite (Feci-x)S), marcasite (FeS2), arsenic and antimony sulfides and zinc sulfide. These minerals can consume significant quantities of cyanide, e.g. various copper(!) cyanide complexes such as CuCN, Cu(CN)2·, Cu(CN)/ and Cu(CN)/ can form, depending on the cyanide to copper ratio in solution. Measurement of free and complexed cyanide is thus a prerequisite for efficient cyanide dosage control. Free cyanide can be determined potentiometrically or amperometrically but the methods are prone to error and are laborious [1]. Metal cyanide complexes can be determined by reverse phase HPLC, however, the species ofa single cation (e.g. Cu(CN)i-, Cu(CN);2 and Cu(CN)/) elute as one species [2]. Additionally the high amount of suspended matter in CIP leach solutions tends to introduce errors. Raman spectroscopy has the potential to be used as an in­line or on-line method of analysis. Free cyanide and the cyanides of gold, silver, copper and iron have been studied in aqueous alkaline solutions with a view to developing such a method. Spectra were obtained with a Bruker RFSl00 FT-Raman spectrometer using a 1064 nm laser delivering 800 mW of power at the sample. Depending on the solution, 250, 1000 or 4000 scans at 4 cm-1 resolution were accumulated. The cyanide stretches observed were relatively narrow (10 15 cm-1 full width at half height) and well resolved (Figure 1 ).

Jan 1, 1995

By E. D. Attanasi, M. W. Bultman, J. H. DeYoung

The 1987 recovery in the US mining industry permitted modest increases in exploration expenditures that year (Fig. 1). Favorable market conditions apparently allowed the gains to be sus¬tained in 1988. There was great uncer¬tainty early in the year as to whether world and US economic growth would be a casualty of the October 1987 worldwide stock market crash. By nearly all measures, the performance of the US minerals industry was strong¬. A weak US dollar and the strong growth of worldwide capital spending resulted in in¬creased US exports of con¬sumer and producer durable items as well as strong domes¬tic demand for metals. In fact, 1988 US steel industry exports reached levels not attained since the mid-1970s. It was re¬ported that steel industry labor productivity is now roughly twice the 1981 level. Among metals with signifi¬cant average nominal price increases in 1988 over 1987 levels were copper (43%), alu¬minum (52%0), and zinc (44%). Even though domestic copper production has grown since 1984 by 30% in mining and 24% in refining, em¬ployment in mining and milling is 4% below the 1984 level. Domestic unit costs are reported in the range of $1.10 to $1.33/kg (50 to 60 cents per lb). The US base metals industry is proba¬bly in its best cash position in many years. However, there has not been a large increase in exploration expendi¬tures. This is due mostly to the percep¬tion that worldwide capacity can easily be increased. Industry reports do show that "low cost" copper producers have been buying reserves from weaker com¬panies. The 1987 Society of Economic Ge¬ologists (SEG) survey of exploration activity indicated that 95 cents out of every exploration dollar spent by US and Canadian firms was for base and precious metals (Economic Geology, January 1989). Press reports, though, make it clear that most of that spending was targeted for precious metals. US claim staking data (Fig. 2) rein¬forces this suspicion. The apparent lag in new claim filings in Alaska and phe¬nomenal growth in filings in the lower 48 states suggests that exploration is directed at relatively low risk targets. In the conterminous 48, more than 40% of the new claims were made in Nevada, indicating an emphasis on gold (although even Nevada had some base metals exploration). Even with a price decline during 1988, the difference between the gold price and average global "cash" production cost of $7.30/g ($227 per oz) still leaves room for an attractive return (Northern Miner, 1988). Exploration plans and results Metals Economics Group (Halifax) indicated in its 1988 exploration survey that exploration expenditures by US and South African firms would be at about 1987 levels. It also reported that Canadian and Australian firms were ex¬pected to reduce their exploration spend¬ing significantly. Firms in both coun¬tries were caught in changes in tax laws. In Canada, the Mining Ex¬ploration Depletion Allow¬ance (MEDA) once permitted generous tax write-offs to in¬dividuals investing in miner¬als exploration. It was to be replaced in January 1989 with the Canadian Exploration In¬centives Program (CEIP). Although structured and ad¬ministered differently than MEDA, CEIP can provide an equivalent or possibly greater financial incentive for min¬eral exploration, for junior mining companies. In 1987, it is estimated that junior com¬panies accounted for two¬-thirds of the off-property (or grass roots) exploration ex¬penditures in Canada. Australia will revoke the tax exemption for gold in 1990. Australian operators, therfore, were expected to concentrate efforts on speeding up pro¬duction during 1988 and 1989. In 1988, Chile and Mali announced special efforts to attract gold explora¬tion by foreign companies. The Cana¬dian government continues to express concern about the write-off (and drawdown) of base metal reserves. Falconbridge did announce a new initiative to identify additional base metal reserves in the Sudbury district. Discoveries Gold deposits dominated discoveries

Jan 1, 1989

By Mike O’Brien, Rob Croll

The Evolution of AngloGold -Incorporated in 1944 under the name of Vaal Reefs Exploration and Mining Company Limited -Name changed to AngloGold Limited in 1998 as the vehicle consolidating the gold interests of Anglo American Corporation -Diversification (geographic and orebody) through the sale of low-margin, deep level, short-life assets and the acquisition of higher margin, open-pit and shallow underground operations

Jan 1, 2003

By Andrew W. Jenike

There used to be a time when bins were designed for total volume and placed in any available place of the plant. Poke holes were provided and feed was maintained by manual prodding, lancing, hammering, and by various mechanical flow-profiting devices. Little thought was given to what occurred inside the bins and why materials did not flow. Indeed, such mental effort was hard to justify while low-cost manual labor was plentiful, quality standards low, and rates of feed moderate. The past fifteen years have seen a drastic change in these conditions. We all know that labor for hard manual work is becoming unavailable at any wage, level. Standards of product uniformity are continuously rising. This uniformity is just as important in a fine ore feed to ball mills as it is in a cattle feed or in a flour mix. Rates of feed now frequently exceed 2,000 tons per hour per feeder. At that rate there is no time for, lancing or prodding. An efficient storage, plant contains a known available volume of bulk solid, and feeds it at the required time, at the prescribed rate, and without degradation of the product. A storage bin may also perform other functions such as blending of different grades, degasification of aerated, powders, isolation of different gaseous media. A contact bed of particles flowing by gravity in counter-current with a gas or liquid may be used as a continuous reactor. Gas or liquid pressures can be simply contained by, a sufficient head of flowing solid.

Jan 1, 1968

By C. Richard Tinsley

Investment activity in the Pacific Rim of Fire has seen a phenomenal surge from epithermal gold exploration. Individual countries are attractive because of lower up-front minerals lease costs (United States, Canada), better geological prospects (Chile, Indonesia), or cheaper equities (Australia). Since the October 1987 stock market crash, large companies are shedding minority joint venture interests to focus on core businesses. Some vertical integration is evident in Japanese coal investments in the Pacific Rim. This article does not cover the aluminum industry oligopoly, which is multinational in character. Nor does it cover the many Canada to US minerals investments. It will be interesting to see if the new US-Canadian free trade treaty will reverse that investment flow. Cross-border investments The following examples should dispel any doubts about the significance of cross-border investment in the Pacific Rim. BHP, Australia's largest public company, has invested $US 4.5 billion in the JS for the following transactions 1984 $2 billion Utah Minerals 1984 $500 million Energy Resources 1985 $745 million Monsanto Oil 1987 $400 million 50.7% Hamilton Oil 1989 $378 million Pacific Resources Placer Dome, mainly through 76% owned Placer Pacific, has the following gold mine developments in hand including the date the project began, Placer Dome's ownership, project name, its location, and capital expenditures: • 1985, 53.1 %, Kidston, Queensland, $A 139 million; • 1989, 37.9%, Big Bell, Western Australia, $A135 million; • 1989, 60.6%, Misima, Papua New Guinea, $C252 million; • 1990,45.5%, Granny Smith, Western Australia, $A95 million; • 1991, 50%, La Coipa, Chile, $US276 million; and • 1991, 25.3%, Porgera, Papua New Guinea, $C1.1 billion. Australia's Western Mining Corp. (WMC), through a foray of off-market acquisitions in late 1987, acquired con¬trol of five Canadian gold companies for a $A488-million outlay ($C452 million) as follows:

Jan 1, 1990

By D. C. McDonald, P. R. Whincup, H. Duke

Due to grade, overburden depth and stability and the presence of groundwater it was considered impractical to recover gold contained in unconsolidated palaeochannel sediments by conventional mining, dredging or borehole mining techniques. A series of field experiments was conducted to determine the feasibility of recovery of gold by in situ leaching from sediments located at a depth of about 80 metres. The test wellfield site and plant are described together with field test procedures, results and wellfield rehabilitation procedures. Choice of sodium cyanide as leachant and laboratory testing are discussed in relation to groundwater and sediment chemistry and problems encountered in field tests.

Jan 1, 1989

By John Oskam

In 1873 Barton tines Corporation mining Garnets for Abrasives. From providing bulk Garnet Concentrate the technology has advanced to the sizing and classification of micron sized particles utilizing a Barton process. Processing of Garnet involves extensive quality control at all steps, first to insure product purity and secondly to insure the correct size range. Barton Mines produces about 30 different sizes of Garnet products to lead the world in the manufacture of technical abrasive Garnet. This paper will examine the present technology of Garnet Abrasive Manufacture and the specification to which the sizes are produced as well as some of the markets served.

Jan 1, 1980

By Klaus Beckmann

Gentlemen : My object reads "Longwall Rapid Advance of Coal Mining in the Federal Republic of Germany". It is true that the percentage of coal obtained in your country from longwall faces, with at present 1.2, is still rather low, but it increased considerably since 1966 with 0.4 %. The coal mines of the Federal Republic of Germany ever used longwall as the classical method of coal getting. All attempts to introduce bord and pillar mining did not lead to any wider application of this method. The principal reasons, for this appear to have been: - the deeper depth of our workings, - the wish to keep working losses as low as possible and to utilize the deposits opened up by deep and therefore expensive shafts to the furthest possible degree, - the dense sequence of seams and the mutual influencing of the working points, - the high number of disturbances in the geologically much stressed deposits, - and the necessary considerations to the protection of the densely built-upon surface.

Jan 1, 1970

By R. Cohen-Alloro

Classical apparatus for granulometric separation generally have limited applications which are found either in the level of the size of separation or in that of the accuracy and the efficiency of the separation or in that of the rate of feed. In industrial practice, the classification of the products of coarse dimensions generally poses no problems. On the contrary, the separation of fine particles presents some difficulties, however the apparatus is used (mechanical classifiers, curved screens and sieves, hydrocyclones, etc...). These difficulties are due to hprfections of separation, rather high cost prices, and sometimes large amounts of recycled materials.

Jan 1, 1970

By A. L. Mula

Pasaremos revista brevemente a 10s fundamentos de 10s ciclones, considerando un ciclón típico. Los datos gráficos disponibles en la literatura han sido convertidos en ecuaciones matemáticas por conveniencia. Se suministran los procedirnientos preliminares para seleccionar y diseñar tanto los ciclones como las bombas, y se facilita con algún detalle un ejernplo de cálculo para un hipotético circuito de molienda. En general, debe consultarse a 1os proveedores de ciclones y bombas para determinar un disefio definitivo. Algunos suministradores de ciclones emplean normalmente computadores digitales para el diseño definitivo con objeto de asegurar una gran precision.

Jan 1, 1982

By Thomas D. Henderson

Este capítulo presenta- un "caso histórico" de los pasos a dar para estimar IDS castes de capital y operativos para un concentrador típico de cobre porfirico de ± 9;070 toneladas métricas de producción diaria. El concentrador que se describe es hipotético, pero está basado en la experiencia propia y es, en efecto, una composición de varios proyectos reales. Las cifras utilizadas son ilustrativas solamente y no representan los castes reales de ningún lavadero en particular. Estas cifras son, sin embargo, representativas de los castes tipicos de molienda en un punto en el tiempo y son to suficientemente precisas coma para iIustrar los procedimientos de estimación de castes descriIos en este capítulo, No es posible publicar cifras reales y corrientes de los castes del lavadero y, en cualquier caso, las cifras de Ios castes reales pierden rápidamente su significación en Ia actual situación económica con los rápidos incrementos de las diversas partidas que configuran los castes. El trabajo está dividido en tres partes: (1) orden de la magnitud estimada, (2) estimación def estudio de viabilidad, y (3) comparación entre los castes estimados y los castes rea¬les. Con vistas a este trabajo supondremas que una mina tiene una propiedad minera explorada mediante perforación con testigos que refleja un yacimiento, ampliamente definido, como de unas 45,3 millones de toneladas métricas con una ley del d,6°/ de sulfuro de cobre, Esta compañia desea obtener primero una estimación del orden de magnitud de los costes (canto de los costes operativos como del capital) para determinar si la pertenencia garantiza más perforación y desmuestre de testigos. Suponiendo que esta evaluación económica obtenida utiIizando Ia orden de Ia magnitud de Ios costes sea favorable, sera a continuación requerido un estudio de viabilidad más preciso de los castes de capital y operativos. Seguidamente of recemas una descripción de los diferentes pasos dadospara desarrollar ]as costes del orden de primera magnitud y a continuación para los castes del estudio de viabilidad.

Jan 1, 1982

By Richard W. Patton

With the advent of the Clean Air Act and the installation of flue gas desulfurization (FGD) equipment (scrubbers) on coal fired power plants, the management of solid wastes has taken on added importance. Aside from the large amounts of fly ash and bottom ash usually generated, large quantities of liquids in the form of scrubber sludge are also produced. These wastes must be disposed of within the constraints of land and water quality regulations. This paper describes the practices adopted by the electric utility industry in denting with this problem, including methods of generation and treatment, quantities and characteristics of the materials, and transportation and disposal practices. The paper also briefly describes final product characteristics and several applications for commercial utilization and land reclamation.

Jan 1, 1983

By Rasik H. Raythatha

Calcium carbonate is perhaps the most widely used mineral in the world. With total consumption of all calcium carbonate exceeding over 25 million tom per year, within this class of filler, a relatively smaller segment of precipitated calcium carbonates (PCC) is often misunderstood as a commodity product and bundled in the same category as ground calcium carbonate. However, each material has a distinctly digerent role and characteristics. Precipitated calcium carbonates are used to influence specific performance in a specific application whereas ground calcium carbonate is used primarily to reduce cost in many applications. In this paper, attempts are made to demonstrate the role of nano-fine-PCC in improving shear-thinning characteristics of common and specialized sealants and automotive underbody coating and how such "nano-particle" cal- cium carbonate properties can be exploited to process PVC plastics while reducing overall cost. We also review the role of precipitated calcium carbonate as "nano" material and why it must be viewed as a specialty additive.

Jan 1, 2003

By Hans G. Kok

At this time in the history of engineering and construction, cost indexes give weekly evidence of the sharply rising costs of labor and materials. Paralleling the rise in construction costs are the costs of plant maintenance. Automation of the modern industrial plant has permitted a substantial reduction in the total number of employees required for plant operation. Of this reduced total, however, up to one-half of the employees may be engaged in plant maintenance. Management's decision to risk investment capital for a pro- posed plant or improvement is increasingly dependent upon the engineer's ingenuity in designing plant systems and structures which will require a minimum of materials and labor for manufacture, installation, and operation and which will be maintenance-free to a maximum degree. This paper concerns itself with the structural elements of bulk material handling systems in which the foregoing factors influenced the design to a considerable extent.

Jan 1, 1969

By Vincente M. Jr. Lim, Brain W. Lawrence

Underground mining operating costs consist pri¬marily of direct costs such as labor, supervision, ma¬terials, and supplies, plus indirect costs. The material and supply costs vary substantially between mines but commonly range from 35 to 60% of the total direct costs. As part of the preparation of accurate operating cost estimates for a project, information must be as¬sembled to select the material and supply items and to determine the quantities of these items that will be required. Cost data then can be incorporated with the estimated material and supply requirements to determine the total material and supply costs for the project. Estimated quantities will vary considerably between mining projects depending upon factors such as the type of material being mined, the mining method, the equip¬ment selected, drilling and blasting techniques, mucking and haulage methods, ground support requirements, number of men employed, etc. Valuable information often can be obtained from suppliers and manufacturers, including data on current operating practices for similar projects, recommenda¬tions for the specific project, and preliminary cost quota¬tions. However, quotations obtained for estimates are generally higher than the prices paid at the time of purchase. Mines operating in the area, or those mining under similar conditions, also can provide essential design information, but it often is difficult to obtain cost information from the operators. Estimated costs for the most common major items of underground materials and supplies are presented in the accompanying tables. They represent current costs or cost ranges and are intended to be used only as a guide when preparing budgetary estimates for materials and supplies. Cost data were obtained mainly from suppliers and manufacturers, with up to three quotations being ob¬tained for each item whenever possible. In most cases, as noted in the table footnotes, prices were based on quantities representing normal requirements for me¬dium-size mine operations. Every attempt was made to assure accuracy. However, the cost for most items, especially those with multiple sources, can deviate sig¬nificantly for various reasons such as geographical loca¬tion, current market conditions, quantities ordered, size of the customer (which could influence the ultimate quantities purchased), and the ability of the purchasing department. It is also for these reasons that the actual amount individual mines are now paying for specific items may vary from the estimated cost in the tables. The cost for specific sizes of items that do not appear in the tables often can be factored from the data pre¬sented. Costs for many items can be converted easily to a unit that sometimes is more basic, but not as com¬monly used, such as from a length to a weight unit. Other items not listed, such as repair parts for equip¬ment, will involve contact with suppliers to determine specific recommended requirements and to obtain costs for these items as related to each individual project. Costs are expressed in terms of US dollars as of 1978 unless otherwise specified. All measurements, sizes, and weights are expressed in conventional units (i.e. feet, inches, pounds) ; applicable metric conversion fac¬tors follow each table. Costs are represented for drill steel and bits; mining explosives; blasting caps; blasting supplies; ground sup¬port items; ventilation equipment; utility pipe, utility hose, and accessories; mine track and accessories; tires for underground equipment; lubricants and fuels; and miscellaneous supplies.

Jan 1, 1982

Compagnie Minière Espérance mines a primary gold orebody in an openpit. The ore is processed through crushing, primary gravity concentration, grinding and secondary gravity separation, generating tailings with remaining fine gold. Analysis of the material in the pond has indicated a residual gold grade sufficient to justify a chemical treatment process to recover the gold. However, direct cyanidation would require a prohibitively large installation for the site, which is located in a remote rainforest environment. It was decided to test the feasibility of preconcentration using flotation. As lab tests proved up the technical feasibility of the flotation process, an on-site pilot operation was carried out to assess the continuous circuit performances, define the best configuration and obtain enough data for industrial circuit sizing. Data collected during the pilot campaign was used for calibrating a process simulator built with the USIM? PAC software. The simulator validated the feasibility of upgrading the existing plant, including the reprocessing of tailings to obtain an acceptable fine gold recovery from a small amount of concentrate.

Jan 1, 2010

By Steven Tubbs

Steven Tubbs From mine to farm is a long journey for Florida's phosphate, but it is an important one to the American farmer who uses phosphate fertilizers to replenish the soil and produce the crops which eventually wind up on the American dinner table. In this phosphate-food connection, transportation plays a vital life-giving role, a role that is unique because of the large quantities of phosphate produced and the mineral's location in relation to its markets. Florida Leads World Florida is the world's largest phosphate producer, supplying 80% of the nation's and a third of the world's annual total. About 95% of Florida's phosphate goes into agricultural chemicals, with 90% going into fertilizers. Phosphate production is primarily concentrated in west central Florida, with the exception of mining and processing in north Florida by Occidental Chemical Co. The phosphate rock is beneficiated at the mine sites and then is transported out of Florida in a raw state, or to one of the industry's 18 chemical complexes where it is processed further. In 1981, Florida produced more than 42 Mt (46 million st) of phosphate rock-a 1% decrease from 1980. The industry also produced more than 12 Mt (13 million st) of phosphate chemical products in 1981 and transported them to both domestic and foreign customers. This year, the state's phosphate production and shipments are substantially lower than recent annual levels because of a depressed worldwide phosphate market. With production down slightly in 1981, shipments declined and company inventories increased dramatically. Phosphate-related shipments through the port of Tampa alone fell 20%. As a result, in 1982, phosphate operations cut production to reduce inventories. According to the Fertilizer Institute, during the fiscal year ending June 30, 1982, phosphate rock production fell 18%; phosphate rock shipments, 28%; finished fertilizer production, 30%; finished fertilizer shipments, 25%; and phosphate rock exports declined by 20%. Despite depressed conditions, Florida phosphate production and shipments are expected to increase in the near future with more rock being processed into fertilizer products. Phosphate is one of Florida's major industries. The US Bureau of Mines estimates it contributed $3 billion to the state's economy in 1981 and an additional $1.4 billion to the US economy. In addition, phosphate exports contributed to

Jan 10, 1982

By W. F. Mullen

Within the scope of this discussion, artificial dimension stone is defined as any manufactured product used as a substitute for natural dimension stone. The history of the development of these substitute materials is reviewed briefly, representative characteristics of each product are listed, several analyses of their market position are presented, and suggestions are made for recapturing markets lost to these products and preventing additional inroads.

Jan 1, 1959

In April 2012, work started on one of the most ambitious construction projects of Austria?s ÖBB-Infrastruktur AG ? the New Semmering Base Tunnel. Scheduled for completion in 2024, the 27.3 km (17 mile) tunnel through the Semmering range will cut the journey time on the south railway connecting Lower Austria and Styria. Before con-struction can begin at the entrance portal and tunnel bores, the work concentrates on the above ground sections with the clearance and excavation of the entrance ramp site. The slope is currently being excavated by the Baubeteiligungsge-sellschaft m.b.H. BBG-GRAZ. The cut face is shored up with shotcrete and permanent self-drilling anchors produced by Minova MAI, an economical bolting solution for softer rock formations. After completing the surface construction work, the twin-bore, single-track tunnel will be cut through the Semmering by conventional and continuous excavation beginning in 2015. Once completed, the New Semmering Base Tunnel will be one of the longest rail tunnels in Austria. It will act as a vital link on the route crossing Europe?s heartland from Northern Germany to Italy, which currently has to climb the steep Semmering pass between Gloggnitz and Mürzzuschlag on a historic mountain railway recognized as one of the UNESCO World Heritage sites. The old route imposes considerable limitations on heavy freight trans-port, and passenger trains have to slow down to a speed of around 50 kph (31 mph). The New Semmering Base Tunnel will bypass this bottleneck and cut 30 minutes off the journey time between Vienna and Graz. It represents a particular advantage for freight traffic, since the new route?s minimal incline of 8.4 percent removes all obstacles for even heavy freight trains.

Jan 1, 2013

By Meng Wang

"In this study, multiple methods that include geological surveying, laboratory studies, and numerical modeling have been used to study the deformation characteristics of a “deep inclined rock roadway with weak planes” (DIRRWP). Failure of the DIRRWP was found to be triggered initially by the shearing of the rock near the weak plane. The movement of the failed rock resulted in reduced confinement of the deeper rocks, and causing the failure of the supporting units and the severe deformation of the surrounding rocks. Hence, it is concluded that DIRRWP stability is affected predominantly by rocks near the weak plane. Corresponding control strategies for DIRRWP deformation were proposed: (1) greater support intensity is necessary to maintain the stability of the whole DIRRWP; (2) additional support is needed for rocks near the weak plane to reduce the potential of failure; (3) to increase the bearing capacity of the floor strata, as the floor needs to be supported; and (4) a supplementary support technique should be considered for cases of large deformation. The case study presented here indicates that the proposed control strategies can significantly reduce the potential of failure in rocks near the weak plane, thus preventing severe deformation of the DIRRWP.INTRODUCTIONAs shallow seams are mined out, the cover depths in most Chinese coalmines have become increasingly greater. Deep cover in a coalmine is considered to occur when the cover depth exceeds 800 m (Sun, Chen, and Miao, 2018). The loading and failure behavior of rocks in a deep cover setting are quite different from those in a shallow cover setting owing to the increase in in-situ stress, temperature, and hyperosmosis (Lobanova, 2008; Zhang et al., 2013). For instance, experience shows that bulking and dilating deformation in deep roadways is much greater than that which occurs in shallow roadways (Hou and Yang, 2018; Zhang et al., 2016). In addition, anisotropic behavior and thickness deviation of coal measure rocks, combined with the appearance of weak planes (e.g., faults, joints, and coal cleats) in coal and/or rocks, can significantly affect the stability of an underground roadway (Ghazvinian et al., 2013; Sun, Chen, and Miao, 2018). The presence of weak planes can significantly complicate displacement and stress transmission in nearby rocks. Additionally, tensile, compressive, and/or shearing failure in rocks near weak planes can be easily caused by high in-situ stresses in deep roadways; such failures may lead to further severe deformation of the surrounding rocks, resulting in roof falls and rib spalling (Kamata and Mashimo 2001; Wu, Ohnishi, and Nishiyama, 2004). A typical failure of the so-called “deep inclined rock roadway with weak planes” (DIRRWP) is shown in Figure 1. Severe deformation can be found near the weak plane. In this study, a plane or thin layer of rock/coal parting that can significantly reduce the strength of the surrounding rocks—and thus affect roadway stability—is defined as the weak plane."

Jan 1, 2019