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By Xinming Chen, Huazhe Jiao, Qi Zhang, Yunfei Wang, Liuhua Yang

The effect of initial damage generated by weakly cemented interlayer surfaces on the physico-mechanical properties of layered cemented tailings backfill (LCTB) is considered for the interlayer inclination structure generated by multiple layered backfills in large-scale mining voids. Utilizing the theory of damage mechanics, the damage evolution and constitutive model of LCTB with interlayer inclination is constructed by considering the coupling of interlayer inclination effect and loading. Based on Mitchell’s mechanical model, we analyze the damage mechanism of the inclined cementation surface of LCTB, and derive the expression for the strength of LCTB considering interlayer inclination. The mechanical properties test of LCTB with different inclinations was carried out, and the results showed that the damage model of LCTB established was highly consistent with the experimental curves, which verified the correctness of the model. The initial inclination damage leads to the decrease of adhesive cohesion of cemented surface, and with the increase of inclination, the separation of layered surface, aggravation of misalignment, layered cemented surface is more prone to shear damage, and the mechanical properties of cemented tailings backfill in the lower part of layered surface are not effectively played, which reduces the overall performance of the material.

Nov 23, 2023

By D. Zim

Mining activity in South America is a growing enterprise. One of difficulties found in many areas of the South American continent, especially in north Chile and south Peru, is the shortage of water supply. In order to overcome this difficulty some mining companies proposed to transport the water from Pacific Ocean up to the mountains. This can be accomplished by the use of stainless steel pipelines, but this is a cost prohibitive solution and is also subject to severe pitting corrosion in a saline environment. The use of mild steel may be a lower cost solution than stainless steel as the material of construction for pipelines but it is subject to corrosion anyway. The corrosion in this case can be internal or external corrosion although cathodic protection as well preventive maintenance usually is enough to mitigate external corrosion without the need to shut down the pipeline. The same is not true about the prevention of internal corrosion. It is not practical, sometimes not even possible, shutdown a pipeline to carry out an inspection and fix sections where potential failures are detected. It is possible avoid corrosion caused by sea water within the mild steel pipelines by applying a proper chemical program designed to virtually eliminate dissolved oxygen in the water commonly called deaeration.1 This type of treatment obviously involves additional capital investment since it requires the construction of one deaerator with the first pumping station and additional equipment at each point where the water can come into contact with oxygen. Deaerators will increase operational costs and subsequent injection of chemicals will be required in the case of multiple degasification facilities thus increasing the consumption of chemicals. grams based on oxygen scavengers, the objective of the present study is to develop a new water treatment capable of preventing mild steel corrosion in aerated sea water. The new treatment must be able to prevent both generalized and localized (pitting) corrosion and overcome the necessity to construct and operate deaerators.

Feb 23, 2014

By Joseph P. Sobanski, Michael P. Bruen

The North Branch tunnel segment of the Tunnel and Reservoir Plan Mainstream System consists of 14,075 m (45,885 ft) of 9.2 m (30.2 ft) finished diameter and985 m (3,232 ft) of 2.5 m (8.25 ft) finished diameter concrete lined rock tunnels. The TBM mining and concrete lining methods used in completing this $166million project differed from “typical” TARP construction methods in that a two-stage concrete lining was placed and the lining was initially placed concurrently with TBM mining as a two pass system in the same tunnel segment. For the main tunnel (9.85 m diameter), TBM mining averaged 24 m/day (79 ft/day), excluding downtime associated with two main bearing changes, and the concrete lining placement, averaged 117 m/day (380 ft/day) and 53 m/day (174 ft/day) for the invert and arch segments, respectively.

Jan 1, 1999

By P. Rusin

A new bacterium, Thiobacillus cuprinus, can extract copper from chalcopyrite as rapidly as T. ferrooxidans. On solution with and without nutrient amendments and bacterial growth media were supplemented with T. ferrooxidans or T. cuprinus in shake flask studies. Both species extracted -42% of the copper using growth media. In one case, T. cuprinus solubilized approximately twice as much copper as T. ferrooxidans utilizing a seeded On solution. Thiobacillus prosperus also oxidizes chalcopyrite and tolerates high chloride concentrations. These sulfide-oxidizing bacteria are representatives of the mixed microbial community found in sulfide dumps. Rates of biological copper extraction from sulfide ores, using the native microbes, have been significantly enhanced by amending On solution with PGM.

Jan 1, 1994

By William H. Pelton

The presence of high-grade massive sulphides near York Harbour, Newfoundland has been known since the turn of the century. In the early 1900's a small, massive-sulphide deposit was worked by conventional hand methods and yielded about 100, 000 tons of high grade copper-zinc ore. Since that time, a number of mining companies have held options on the property and an exploration adit was driven along the fourth level of the original mine. Underground drilling revealed several additional massive sulphide lenses in the range of 10, 000 to 60, 000 tons (Fig. 1). The problem facing Long Lac Mineral Exploration Ltd. when they undertook an option on the property in 1969, was to outline any possible extensions to the known sulphide lenses which were outside the reach of underground drills and to search for new ore deposits which might double the known reserves into a feasible project for development. GEOLOGY AND PHYSICAL PROPERTIES: The geology is typical of many massive sulphide deposits within volcanic rocks in the Canadian Shield. The sulphide pods appear to occur along a complex andesite-basalt contact. Identification of the two volcanic types is difficult since they are almost the same colour. The most direct means of identification is by the slight difference in their magnetic susceptibilities. Pyrite, chalcopyrite and sphalerite are the main minerals in the sul¬phide lenses. The ore is massive, differing in density from the host rock by at least 1.0 gm/cc. There is little pyrrhotite or magnetite associated with the sulphides, so there is no appreciable difference in magnetic susceptibility between the sulphides and the basalt. Also, there is no alteration halo around

Jan 1, 1971

By Sandy Worden

Coal mining companies in Australia are managing the high-consequence risks across their operations more effectively by using an interactive online risk management system known as Riskgate Developed by the Minerals Industry Safety and Health Centre (MISHC) at the University of Queensland, Australia, Riskgate contains detailed information about 11 high-consequence risk areas (called topics in the system) for opencut and underground coal mines (Table 1). The existing topics are: fires; strata control for underground mining; ground control for opencut mining; tires; isolation; collisions; explosions and explosives; manual tasks; and trips, slips and falls. Every Riskgate topic is focused on coal industry activities (mining, processing, transport and storage). The scope includes mine sites, lease areas and mine infrastructure (mobile, fixed plant, field equipment, buildings, road and rail transport), and all aspects of the mine life cycle from design through to decommissioning. The topics uniformly recognize that a loss of control can result in injury or fatality, equipment damage, production loss, reputation loss and environmental damage. However, the priority focus for Riskgate is the safety of mine personnel.

Jul 1, 2013

By B. E. MacNab

During the past several years, Raymond Kaiser Engineers has prepared numerous studies concerning the technical and economic feasibility of coal exporting facilities in the western United States. Perhaps the most striking conclusion to be drawn from these efforts is that many people underestimate the complexity of the highly competitive, dynamic coal marketing system which includes coal loading terminals as an essential but relatively low-cost link in the energy production and delivery chain. The title of this paper, "The Status of Western United States Coal Ports - An Economic Assessment," should not delude anyone into thinking that the future of western U.S. coal- exporting ports has now congealed into a well- defined economic plan. As this paper will demonstrate, the situation is complex and more dynamic than ever and promises to remain so into the late 1980's.

Jan 1, 1982

By Hongwei Wang, PEIPEI CAO, Yongping Wu, JIANQIANG JIAO

In the fully mechanized top caving mining of steeply inclined, extra-thick seams with variable angles, the mechanisms of roof rock movement, failure, caving and filling are highly complex. This is due to the varying angle of coal seam in different areas, which makes rock–equipment stability control challenging. In this paper, the surrounding rock deformation and failure mechanisms, bearing structure of the overburden, and working characteristics of the supports are elucidated. The principle and key technologies of rock–equipment stability control are presented and applied to control the overburden of the regional failure and realize safe and efficient mining of the working face.

By I. H. Warren

The high temperature lubricant molybdenite, MoS2, is usually produced by a complex sequence of processes involving mineral dressing of molybdenite concentrates followed by leaching with hydrofluoric acid to remove abrasive impurities such as silica (1). Many attempts have been made, mostly by techniques involving, direct fusion of molybdenum compounds with sulphur, to produce synthetic molybdenite. However, apart from some experiments of geochemical interest (2) in which aqueous solutions of sodium sulphomolybdate, Nat MoS4, were decomposed under pressure at temperatures between 300°C and 700°C, no attempts to produce the mineral by hydrometallurgical procedures have been reported. Since molybdenite is nominally a compound of tetravalent molybdenum with sulphur, and the most common state of molybdenum is +6, production of molybdenite is likely to involve reduction and sulphidization. The present study, therefore, describes the reduction, with hydrogen and carbon monoxide, of molybdenum in the hexavalent state in alkaline aqueous solutions containing sulphide ion. In these

Jan 1, 1972

By F. W. Schweitzer

The trend toward development of large low grade ore bodies has accelerated in recent years. It has been estimated within the copper industry that "porphyry" type deposits will provide the bulk of copper production during the next 30 years. It is further estimated that in these deposits the average ore grade by the year 2000 will be 0.25% copper (1). Many of the new porphyry copper discoveries are of such extremely low grade that they are particularly sensitive to small fluctuations in cost variables and copper prices. Because haulage constitutes a major item of surface mining expense, the capability to transport large tonnages of material at increasingly lower unit costs is vital to the profitable operation of many of these mines. High capacity conveyor belts appear to have considerable promise in this area. The heaviest use of high tonnage conveyors has been in the brown coal industry in Germany. In the past 20 years several such installations have proven successful. In addition to the German installations, several other successful systems have been put into operation. Some examples are: The Oroville Dam project in the United States; the tar sand operation in Northwest Canada; the pre-mine stripping and mining of the Twin Buttes Mine in the United States; the Kursk Magnetite 'dine in the U.S.S.R.; and the Nchanga Copper Mine in Zambia. Most of the systems mentioned are handling alluvial material consisting mainly of fines. The noteworthy point regarding these installations is their high continuous capacity. One of the largest lignite mines in the world is at Fortuna, Germany, where over 15,700 tons (15,250mt) per hour of overburden is transported on an 87 inch (221cm) wide belt running, at over 1000 feet (305m) per minute.(2). Another example is a 20,000 ton (18,150mt) per hour system for loading iron ore into barges on the Great Lakes (3).

Jan 1, 1976

By S. K. Kawatra

Many mineral oxide and multi-component oxide (basalt) specimens break down into powders upon expo-sure to sodium vapor at elevated temperatures for extended times. This paper examines several possible mechanisms of oxide breakage by sodium vapor, both experimentally and from a thermodynamic viewpoint. The oxides for which reduction by sodium was thermo-dynamically favorable all exhibited some degree of fragmentation. The oxides which were not favorable for reduction by sodium did not exhibit fragmentation, with the exception of rutile, a titanium oxide. The rutile fragmentation was caused by the reduction of iron that was in solid solution in the rutile crystal structure.

Jan 1, 1995

By I. M. Ahmed, R. S. Hassan, M. I. Aly

Extraction and separation of La, Sm and Dy ions from acidic sulfate-phosphate solutions was investigated using a cation exchange extractant, bis(2,4,4-trimethylpentyl) phosphinic acid, CYANEX 272, in kerosene. The influence of shaking time, equilibrium pH, extractant, sulfate and phosphate ion concentrations, diluent type and temperature was studied. The extraction was found to be pH-dependent, and increasing the phosphate ion concentration inhibited the extraction which was found to be endothermic. The stoichiometry of the extracted metal species was found to be MOH.H2OHSO4H2A.A2. Aliphatic diluents were found to enhance the extraction compared to aromatic diluents. The results showed that there was a separation mode between the metal ions when varying the hydrogen ion and sulfate ion concentrations, under the used experimental conditions. The investigated process was used for the recovery of La, Sm and Dy from the acid solution resulting from the leaching of low-grade monazite.

By R. Herrera-Urbina

Measurements of the electrophoretic mobility of bastnaesite in aqueous solutions of sodium nitrate reveal that the isoelectric point (iep) of this cerium fluocarbonate occurs at about pH 9.3. These results also indicate that the pH affects significantly the electrophoretic mobility of bastnaesite, which becomes more positive as the pH decreases and more negative as the pH increases from the iep. Computations of solid-solution equilibria for the bastnaesite-H2O system closed to the atmosphere as a function of pH indicate that cerium fluoride precipitates in acidic solutions, whereas cerium hydroxide precipitates in alkaline solutions. When the initial amount of bastnaesite is fixed at 0.05 wt.% (the solids concentration used for electrokinetic experiments), these computations reveal that bastnaesite is the only solid phase in the pH range from 5.75 to 8.55, it coexists with CeF3(s) between pH 5.22 and pH 5.74, and with Ce(OH)3(s) between pH 8.56 and pH 10.12. Cerium fluoride and cerium hydroxide are the only solid phase below pH 5.2 and above pH 10.2, respectively. According to these computations, the dissolution-precipitation processes that occur when bastnaesite is equilibrated in aqueous solutions at different pH values determine the solid phases present in the system. In turn, these processes must affect the electrokinetic potential at the solid-solution interface, and they must be considered for explaining electrokinetic measurements as a function of pH when bastnaesite is the original solid phase in aqueous suspensions.

By J. B. Hiskey

Of the halogens, the gold iodide complexes are the most stable in aqueous solutions. A series of experiments were performed to investigate the kinetics and mechanism of the leaching reaction between gold and iodide. Using a rotation disk technique, the effects of rotation speed, iodide and iodine concentration, temperature, pH and in the presence of different electrolytes were measured. Oxygen and hydrogen peroxide were also examined as oxidants in the iodide system. The first order reaction rate was found with respect to 13 and half order reaction rate with respect to 1-. The comparison of gold leaching between iodide and cyanide is also presented, in which a rate constant of about 2.6x10-9 mol/cm2? sec for 10-2 M I- and 5x10-3 M I2 was obtained. This value is close to that -for typical cyanidation. Cyclic voltammetry experiments were also performed to examine the electrochemical nature of the reaction which will be presented in part II of this study.

Jan 1, 1990

By John Durkin

A system based on seismic techniques has been developed to detect and locate men trapped underground following a mine disaster. Both theoretical and field studies have been used to generate models to predict the performance of the system. For a strong source, it is almost certain that the miner's signal will be detected if the geophone array can be positioned over a likely area of entrapment. After signal processing, it is highly likely that the location of the miner can be determined within an accuracy of 100 ft (30.5 m). The system is presently operational in a state of readiness in the event of a mine disaster.

Jan 1, 1980

By R. W. Waytulonis

New exhaust control techniques and devices may be necessary to meet future diesel particulate matter emission standards in underground coal mines. This paper reviews conventional work practices and devices used to control diesel exhaust emissions, and new techniques being tested by the Bureau of Mines. Discussions will center on important work practices and on the function and efficiency of exhaust after-treatment devices. An industry/government cooperative research project to develop and test an exhaust after-treatment system for part 36 equipment is also discussed.

Jan 1, 1990

By C. G. Anderson

The treatment of materials for the recovery of the precious metals imposes many processing and environmental challenges. Sunshine Mining and Refining Company has developed hydrometallurgical technology for recovery of values from refractory precious metal materials. At Sunshine, the industrial focus of these processes has been for the direct recovery of silver without cyanidation. However, recent work has indicated that these technologies can provide a means for treating complex, refractory gold concentrates. This will be the focus of this paper. The practice of pretreating ores and concentrates to make them more amenable to cyanidation is becoming more common. Several pretreatment options for sulfide concentrates containing gold include roasting, bio-leaching, direct pressure oxidation and nitrogen species catalyzed pressure oxidation. The industrial use of nitrogen species catalyzed pressure oxidation has been limited to the Sunshine refinery where its focus has been for the treatment of silver concentrates. Much of the reluctance, outside of Sunshine, to use this type of technology may be based on the perception that high costs are associated with using nitrogen species (e.g. nitric acid, sodium nitrite) to leach. Also, the use of nitrogen species catalyzed pressure oxidation on an industrial scale is unfamiliar to most metallurgical professionals. A summary of pressure leaching processes which utilize nitrogen species as a catalyst is presented in Tables 1 and 2.

Jan 1, 1996

By T. C. Vogt

Earlier we described the uranium mineralogy of an areally broad sampling of Crownpoint ore, including the characterization of organic carbonaceous material associated with the uranium mineral. (1) We also reported on the leaching behavior of Crownpoint ores with a mild alkaline leaching system, oxygen (02)-sodium bicarbonate (NaHC03). (2) There was a wide range of leaching responses, with samples from some areas leaching at a slow rate with low uranium recovery. Evidence indicates that in these samples the organic material is intimately associated with the uranium mineral and shields it to some extent from contact by the leachate. (1,2) One method to obtain faster leach rates and higher recoveries is to use a chemically severe leaching system such as sodium hypochlorite (NaOCI) as an oxidant. (3) The use of sulfuric acid (H2SO4) and an oxidant for leaching ore in surface milling operations is widely practiced to effect high recovery of uranium (U308) from the ore. (4,5,6) The U308 is mobilized as the disulfate complex, U02(S04)224-, or possibly, the trisulfate complex, U02(S04)34-, is the soluble species. (7) Sulfuric acid leachate formulations were used in the first in-situ leaching operation in the Shirley Basin in Wyoming. (8) More recently H2S04 formulations have been used in the Rocky Mountain Energy field tests in the Powder River Basin (Bear Creek) and in the Teapot forma¬tion at Nine Mile Lake site near Casper. (9,10) Laboratory studies related to the use of H2SO4 for in-situ leaching have been reported (11-17) and Yan has .reported packed column leach studies on Crownpoint ore using H2504 and oxidant. (18)

Jan 1, 1981

By Todd S. Webster, Matthew J. Pierce, Brad D. Krumel

With the Working Shafts and Starter Tunnel under way, it became apparent this 4.7-mile, 19-foot diameter wet weather tunnel was going to live up to its name. The shaft’s pre-excavation grouting was completed, and ground water inflows were slowing project progress. As the tunnel drive was approaching 50% complete a cooperative effort was underway between the owner, engineer, and contractor to raise the base of the Retrieval Shaft by 65 feet to avoid ground water infiltration construction challenges. The tunnel alignment needed to be raised in kind. The project was behind schedule and rethinking the cast-in-place adit work was next on the agenda due to the very wet environment in the tunnel. The race was on to finish the project within the owner’s time constraints while completing multiple redesign aspects of the tunnel alignment and associated adit construction. This paper will evaluate original design criteria and actual in-route design modifications and change management to meet the owner’s just-in-time schedule needs.

Dec 1, 2022

By T. W. Martin

The use of conveyors in large, open pit mines and their drawbacks are discussed. Technological developments such as long distance conveyors capable of handling large rocks are explored. The development and testing by the Bureau of Mines of a prototype crib and cable conveyor for handling large rocks are discussed, and possible modifications of the concept for a production model are examined.

Jan 1, 1984