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By D. D. Harbuck, G. K. Green

The Bokan Mountain area on Prince of Wales Island, AK, contains vast quantities of heavy rare earth minerals. To lessen the US dependence on foreign sources, the US Bureau of Mines (USBM) investigated yttrium recovery from this ore. By sulfating the ore at 250 ° C for 1 hr at an H2S04:ore ratio of 1:1 and then water leaching the sulfated material for 1 hr at 20% solids and 25ºC, over 74% of the yttrium, cerium, and lanthanum were solubilized. Solvent extraction (SX), using a synergistic combination of OPAP and DEHPA, selectively loaded 100% of the yttrium. Yttrium was stripped directly as a solid using a 2M, 35 ° C NaOH liquor. When the OPAP/DEHPA mixture was tested in a continuous SX circuit, yttrium loading and stripping were 100% and 96%, respectively. The organic showed excellent recyclability properties with minimal solvent loss.

Jan 1, 1996

By D. W. Fuerstenau, P. C. Kapur

A model equation is presented for breakage of single particles as a function of the impact energy. The model takes explicit cognizance of the distribution of feed particles in their resistance to breakage as well as of the weakening of particles under repeated impacts. With the proposed formulation, it is possible to simulate the size spectra of progeny particles, interrelate quantitatively the so-called ‘t’ family of curves, derive an energy-size reduction relationship, compute the primary, energy-free breakage distribution function, and predict the optimum level of impact energy for a given size reduction task. Published data on single-particle impact grinding are in agreement with the model.

Jan 1, 1995

By P. Mousset-Jones, F. Calizaya

Ultrasonic anemometry is a relatively new method of measuring the air velocity in underground excavations and is not widely used. The method has been mainly used for surface applications, such as meteorology and fluid flow measurement. Several instruments were looked at to determine their applicability for continuous underground monitoring systems. The units fall into two main categories: variable distance units and fined distance units. The method relies on the acceleration and deceleration of ultrasonic pulses transmitted through a moving airstream. This study presents some of the results of the testing of variable and fixed distance ultrasonic anemometers in a wind tunnel and a mine drift.

Jan 1, 1995

By Yuusaku Tominaga, Sukumar Bandopadhyay

A power-series trend curve of elapsed time was estimated by using time series data of measured concentrations of carbon monoxide in the Taiheiyo coal mine, Hokkaido, Japan. The difference between the moving average concentration data and the estimated data from the trend curve showed linear correlation when plotted on a normal probability paper and a correlation coefficient value of 0.99. It is concluded that the estimate of carbon monoxide concentration using moving average values of concentrations compares very well with the results obtained from the trend curve within the three-sigma (standard deviation) range of the distribution. Thus, it is believed the results can be used to monitor and detect abnormal ventilation conditions in a ventilation network such as the occurrence of spontaneous combustion at an early stage.

Jan 1, 2002

By Dave Rogstad

The DART NC-1B Tunnel Project consists of two 5,100 m TBM excavated tunnels, a principal underground station, a partially completed future station, a surface station, and eight associated ventilation shafts and exit tunnels. This paper presents a case history of the project's construction, and will focus on six topics that give this project a unique and unusual history; the TBM excavation, two major differing site conditions, roadheader excavation, polyfiber reinforced shotcrete lining, the NATM design geometry, and a design/build type of contract.

Jan 1, 1995

By Jan Wolski, Jack Barry

Ventilation ductlines with a single fan or with a series of fans are analyzed. The duct friction loss factors are discussed. Numerical solutions, presented in the paper, applies to any fan number and locations along a duct line. The findings are compared with formulas available in the technical literature. Values of the air leakage factors are presented in the SI, technical metric, and US unit systems. A method is shown of how to determine the leak- age factor for a given ductline. Optimum solutions for the sample duct lines with two and five fans in series are discussed and presented in a graphical form. Performance of fans in series is discussed in conjunction with both friction pressure loss and leak- age.

Jan 1, 1997

By J. Patrick Powers, Joel Miller, Arthur B. Corwin

A combination of a slurry trench with dewatering successfully controlled groundwater for a large sloped excavation immediately adjacent to the Arkansas River. The Murray Hydro Electric Project required excavation through sand and gravel to bedrock, 85 feet below high water in the River. The perimeter system of deep wells pumping up to 25,000 GPM (1,600 1/sec) lowered the water level to 15 feet (4.6 m) above bedrock. A short soil/bentonite slurry trench near the toe of the slope cut off the residual head. The method cut six weeks from the critical path. Design of the slopes and the dewatering system demanded high safety factors because of risk to existing Lock and Dam No. 7. A localized pocket of soft organic clay was supported by a rock filled bolster. A major flood event was successfully withstood. The method can be applied to large civil excavations and open pit mines.

Jan 1, 1989

By J. C. May, G. M. Elliott, J. J. Brady

Increased clearance was required in two railroad tunnels that were built about the time of the Civil War. Clearance infringements, whether they be excavation tights or caused by ice accumulation, reduce tunnel serviceability. Achieving increased clearance often means disturbing the ground and old ground support structures. Access and transportation needs dictate how and when the work can be carried out, and strongly influence the design approach and the methods used by the contractor to execute the work. This paper explores the pertinent considerations of the owner, the designer, the field inspection team, and the contractor in bringing this project to a successful conclusion.

Jan 1, 1997

By Joachim H. Schubert, David G. Hulbert, Ian K. Craig, Roger G. D. Henning

This paper presents a stabilizing controller for flotation plants which uses a quasi-multivariable technique. The controller monitors all the levels in the plant, and by anticipating interactions between various parts of the plant, is able to stabilize the plant far more successfully than the normal plant control. Once stabilizing control has been achieved, optimization of the process becomes easier and more sustainable. An estimate of the improvement in metallurgical performance is made and a singular value analysis was conducted to verify that the multivariable algorithm will theoretically control better than a collection of individual PID loops. Metallurgical results are presented to show that the improvements are attainable in practice. Control by the Mintek algorithm was alternated with normal plant control, to show that the improvements are statistically significant.

Jan 1, 1995

By Jerry W. Danni, R. Craig Ford, Kermit C. Benke, Jim B. Finley, Donald D. Runnells

Steady-state water balance models have historically been used in the management of acid drainage at mine sites. Such systems could be more realistically described by non-steady-state conditions. In addition, the evaluation of alternatives for closure and management of acid drainage must consider non-steady-state conditions. Dynamic systems modeling is a method for simulating water management systems, offering flexibility in: (1) simulating either steady-state or non-steady-state conditions, (2) allowing "what-if' scenario testing. and (3) optimization of operation and closure alternatives. A case study is given for acidic drainage management during closure at a heap leach facility that demonstrates the utility of dynamic systems models.

Jan 1, 2000

Laboratory techniques have been developed at the Julius Kruttschnitt Mineral Research Centre which relate comminution energy to size reduction. These relationships have been applied in the mathematical modelling of autogenous and semi-autogenous mills. Since their development in 1987 these models have been successfully used in many wide ranging design and optimization studies. A description of the basic structure of the models is presented with particular reference to ore characterization. Two case studies are presented which illustrate their effectiveness in evaluating and predicting the effects of circuit changes.

Jan 1, 1992

By Veliko Kertikov

Complicated processes of heat exchange and evaporation, leading to changes in the temperature and humidity of the ventilating air flow, take place during the driving of headings. In the case when virgin rock temperature is high, the increase in air temperature and humidity is significant. This causes a deterioration of climatic conditions in the headings. Procedures for predicting the changes in air temperature and humidity are discussed, together with appropriate calculations and computer programmes. Predicted results for example scenarios are used as a background for the selection of approaches and means to improve the climatic conditions in a dead-end heading using auxiliary ventilation.

Jan 1, 1997

By S. Barkhoudarian, R. R. Gupta, R. F. Steinberg

A study of the feasibility of using acoustic signals to detect discontinuities ahead of excavation has shown that reflecting interfaces in a homogeneous rock can be easily identified. Moreover, discontinuity interfaces in a very complex field site (where the rock face was weathered, was full of jointed rocks, and had a destressed zone running along the mine walls) could be identified with a reasonable level of confidence, using a cross-correlation technique for signal processing. The results of this study go a long way toward proving the feasibility of the technique. However, further development work is needed to optimize an operating system in a hard rock environment where boring machines are used for excavation.

Jan 1, 1997

By J. Paraszczak

Water-powered jackleg rock drills, introduced recently in South African mines, are reported to be more efficient, faster and more comfortable to operate than conventional pneumatic drills. Comparative testing of these drill types was performed in Quebec. Based on the test results and on time studies performed in the mines, water-powered drilling was reviewed. The review considered the drilling rates achieved, the infrastructure needed, side effects and health and safety considerations. This study shows that the application of water-powered drills may, under specific conditions, help increase the footage drilled and may improve the working environment. Examples of such applications are presented in the conclusions.

Jan 1, 1997

By Bruno Mattle, Max John

For tunnels with low overburden, the shotcrete lining is the main element of ground support, which is why shotcrete behavior is of prime importance. Following its application, shotcrete not only gains strength and stiffness with time but—if loaded at an early stage—it is also subject to creep which in turn leads to stress relaxation. For two-dimensional FE calculations, a computational modulus of elasticity of shotcrete is to be used. Based on parameter studies it was found that the modulus of elasticity of shotcrete depends on both shotcrete mix and ground behavior. While the Young’s Modulus used for young shotcrete may range from 1,000 to 7,000 MPa, the Young’s Modulus used for hardened shotcrete is best represented by a value of 15,000 MPa.

Jan 1, 2003

By A. M. Tunstall

Blasting is commonly viewed separately from mechanical handling and crushing. This view is misleading because the degree of fragmentation achieved by blasting can have a significant effect on the efficiency of these processes and, hence, on the overall cost of the mining operation. In this paper, aspects of blasting and crushing and their interaction are examined. A case study is also presented that dramatically illustrates the influence of blast fragmentation on subsequent processing and on the financial implications involved.

Jan 1, 1998

By J. Mastoris

The determination of the surface area that may be impacted by underground mining is an important consideration in subsidence engineering. A number of parameters have been utilized to identify this influence area, most notably the angles of draw and break. This paper discusses the implications of selecting an appropriate "damage angle" for defining a potential damage area due to mining, within which surface structures may be impacted. Furthermore, the influence of both mining and geological factors (i.e., mining width, depth and overburden lithology) on this angle is examined using the Surface Deformation Prediction System (SDPS) software. Finally, recommendations are given for applying these concepts in subsidence control.

Jan 1, 1995

By J. E. Gebhardt, L. Piga, G. Schena

The possibility of beneficiating a low-grade alunite ore from the Tuscany region of Italy was examined. Flocculation and flotation techniques were investigated to separate alunite and kaolinite from the ore, which also contained feldspar and quartz. Flotation was performed at pH 6.5 with oleic acid as collector and sodium silicate as dispersant. A concentrate containing 12% alunite with a recovery of about 65% and a concentrate containing 28% alunite with a recovery of 84% were achieved from the -38-µm feed samples containing 5.0% and 12.9% alunite, respectively. Poor recovery of alunite was achieved by flocculation methods.

Jan 1, 1999

By J. T. Ryan, Griffin. Wayne H.

This paper shows that if a drift has a brattice which is sufficiently leaky, changes in the operating point of the fan depend solely on the volumetric efficiency within the drift. Under this high leakage condition, an increase in the length of the drift causes very little shift in the fan operating point. For less leaky brattices, the operating point depends on both the fan characteristic curve and the volumetric efficiency. It is shown that for the fan curve and drift parameters used in this paper the fan operating point in a drift with a volumetric efficiency of 50% is essentially the same as a drift which has a zero efficiency. In this region of efficiency, an increase of 300% in the length of the drift causes only a 3% increase in fan operating pressure.

Jan 1, 1993

One of the most challenging and ambitious dump rehabilitation projects in South Africa’s mining industry is being carried out at Greenside Colliery’s smoldering coal dump, which lies adjacent to the N 12 Johannesburg-Witbank highway. Greenside Colliery is the largest coal mine in the Gold Fields Group. It began operation in 1946, the year in which the burning dump had its origins. Today, Gold Fields plans to spend R16 million (about $USS8 million) to encapsulate the dump, bringing it into compliance with South Africa’s Mining Environmental Management Programme, according to Martin Hamer, engineering manager of the Greenside Colliery. The improved environmental management approach will result in reduced sulfur dioxide gas, smoke and dust emisson into the air and an enhanced aesthetic appearance of the dump from the N 12 highway. The objectives of the project are to place and compact coal discard to within the National Institute of Coal Research specifications in order to prevent spontaneous combustion, and to preserve as an asset the coal portion of the discard.

Jan 1, 1994