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By Thomas W. Camm

A WINDOWS-based object-oriented expert system for prefeasibility evaluation of hard rock mines is being developed at the Western Field Operations Center (WFOC) of the Bureau of Mines. Designed for use with the Bureau's Cost Estimating System (CES), this expert system assists an evaluator in choosing an underground mining method, and the related design parameters. The system provides the engineering and design guidelines necessary for an evaluator to perform a prefeasibility type cost estimate.

Jan 1, 1992

By M. S. Klima, A. P. Pinkerton

Solid-bowl (decanter) centrifuges are used extensively to dewater slurries in a wide range of industries. However, the application of decanters as classification devices is not as common. In this study, the performance of a continuous, pilot-scale, solid-bowl centrifuge was evaluated when classifying an ultrafine coal slurry containing nearly 60% material less than 10µm. The current study examined the effects of operating conditions on centrifuge performance. The test conditions included centrifuge bowl and scroll speeds, volumetric feed rates, solids concentration, and pond depth. Centrifuge performance was evaluated using partition curves, along with product yields and solids concentrations.

Jan 1, 2000

By Dong-mei Zhang, Feng Zhang, Hong-Wei Huang, Qiang Huang, Bin Ye

"1. INTRODUCTION Nowadays, many cities around the world have constructed metro tunnels to alleviate transportation pressure from rapid urbanization. In soft soil areas, metro tunnels are usually constructed by shield-tunneling method due to its high efficiency and little disturbance to environment. However, the tunnels may show significant post-construction settlement after several years of operation. Take Shanghai Metro line 2 for example, the maximum longitudinal settlement reached 160mm after ten years of operation, shown in Figure 1. When analyzing varying factors that contribute to the long-term settlement of tunnels, the effect of cyclic loading from train vibration is rarely taken into consideration for most researches only focus on the influence of leakage problems in the tunnel while neglecting train vibration induced leakage and resulting settlement. It’s true that metro tunnels from shield-tunneling method are prone to have leakage problems due to the special structural configuration. Furthermore, trains move hundreds of times inside the tunnel every day, which inevitably will cause accumulation and dissipation of excess pore pressure. When the excess pore pressure dissipates, tunnel settlement induced by train vibration occurs(Deng F H, 2007). Although researchers (Zheng et al., 2005; Wongsaroj et al., 2007; Mair, 2008; Shin et al., 2012; Zhang et al., 2012, 2015) conducted extensive numerical analysis on the relationship between tunnel settlement and relative permeability of tunnel to surrounding soil by treating tunnels as permeable media, their attention was only paid to the tunnel settlement from reduction of hydrostatic pressure in the ground, rather than from the dissipation of excess pore pressure generated by train vibration. Therefore, the influence of train vibration on the long-term settlements of metro tunnels is still not clear."

Jan 1, 2016

By V. Karra

Based on extensive investigations on the effect of design variables on process performance, during 1982-85, Nordberg developed a 1000 hp cone crusher, with the objective of boosting crushing productivity in existing plants. The 2390 fits on the same foundation as the 7' SHD Symons cone, but is designed to give two times the capacity of the 7'. The economies of scale involved give the customer substantial cost savings. In this paper process performance of the Nordberg 2390 relative to the 7' SHD Symons cone, while crushing the same ore, will be presented. Also, implications of such a crusher scale-up to associated cost savings will be addressed.

Jan 1, 1988

By David L. Moffatt, Leon Peters

A unique electromagnetic pulse sounding system for the detection and identification of geological and man-made anomalies which represent hazards in hard rock rapid tunneling operations is described. The main features of the system including a periodic video-type pulse interrogating signal and a probe structure that permits operational modes which either "see" or are "blind" to homogeneous-type targets are reviewed. The results of experimental pulse measurements on targets buried in the overburden and in a limestone medium are presented. Since the electrical properties of limestone are not radically different from those of a hard rock medium, conclusions based on these data should be valid for a hard rock media also.

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 R. Harris, M. Misra

Column flotation technology has a demonstrated potential for recovering clean coal from high-ash waste fines. The effect of different variables such as air flow rate, frother addition, depressant addition, percent solids and particle size on the quality of separation are discussed. Results indicate that air flow rate and depressant addition are the important variables which control the selectivity in the flotation of fine coal in a column cell. Separation efficiency achieved with column cells is significantly better than that with conventional flotation cells. Under appropriate experimental conditions with a deep column, more than 80 percent coal can be recovered in the concentrate containing 10 percent ash from waste fines containing over 60 percent ash.

Jan 1, 1988

By David B. McWhorter, John D. Nelson

INTRODUCTION The quantity of seepage that will be released from a tailings impoundment depends not only on the characteristics of the seepage control system, but also on the properties of the foundation soil or rock beneath the impoundment and the nature of the groundwater in the area. The interaction between various elements of the seepage control system and the influence the various characteristics of the site and impoundment have on seepage are the subject of this paper. The results of analyses are presented herein to indicate the nature and magnitude of the effect that the various factors will have on seep¬age losses. Analyses were conducted for a uranium mill tailings impoundment located in an area characteristic of many found in the western United States or Canada. A typical seepage control system consists of placement of either a clay or synthetic liner beneath the impoundment. In some cases an underdrain system may be placed on top of the liner to collect drainage from the tailings. The parameters that were varied in the analyses included those pertaining to the liner, underdrains and foundation strata. In general, it is shown that the seepage losses will vary in a complex manner depending on the interaction of the elements of the site and the seepage control system. As may be expected, the liner and underdrain systems have the most pronounced effect on controlling seepage. This paper deals with the quantity of seepage released from an impoundment However, the impact that seepage losses from an impoundment will have on the surrounding environment will depend on the rate at which contaminants will enter the groundwater and the nature of the groundwater flow itself. Consequently, when considering these results with regard to environmental impact they must be interpreted along with considerations of geochemical factors. MECHANICS OF SEEPAGE The mechanics of seepage and methods of analysis that were used will be discussed briefly herein. For a more detailed discussion the reader is referred elsewhere (McWhorter and Nelson, 1978, 1979, 1980). A general column through the impoundment was considered to be as shown in Fig. 1.

Jan 1, 1980

By Yuting Xue, Danqing Gao, Brijes Mishra

Heterogeneity and discontinuity significantly affect rock strength. For accurate stability prediction, intact rock behavior is imperatively included in rock mass behavior. However, past research largely used arbitrary scaling approaches to produce rock strength. This paper considers a stochastic approach in order to determine the strength of a rock. Based on the laboratory data, a MATLAB® with extreme value stochastic model generates a database for each physico-mechanical property. Then FLAC® simulates laboratory-sized rock specimens. The grids developed in the numerical model can in turn develop random material properties in MATLAB®, which researchers then applied to the final FLAC® model. Model runs simulate the approach performed in the laboratory. The results from the model indicate that a stochastic approach produces strengths that are lower than a deterministic approach. Failure modes for each specimen are different, similar to observations in the laboratory. In addition, random density also influences the failure mode, highlighting the importance of stochastic analysis in rocks.

By G. B. Amicucci

A Denver Autometrics Particle Size Monitor, PSM-400, was installed at Golden Sunlight Mines, Inc. in October 1988. The PSM-400 measures the grind product's particle size and percent solids. The particle size is used to control grind size by automatically adjusting mill feed rate. The PSM's continuous response to ore changes has improved grind product uniformity and mill throughput. Metallurgical testing has shown the PSM's accuracy to be +/-1 % + 150 µm (100 mesh).

Jan 1, 1991

By Steve Kral

Amax Coal Industries Inc.'s Delta Mine is a medium-sized. high-sulfur coal producer that has lived up to the challenges posed by nearly six decades of a highly competitive domestic coal market. The mine now faces one of its biggest challenges - the same one staring at the dozens of other high-sulfur producers in the Midwest - the Clean Air Act Amendments of 1990. The 59-year-old mine, located in the coal fields of southern Illinois, has remained one of the state's oldest continuously operating mines by rolling with the ups and downs of the coal market and by incorporating new technologies and innovative productivity improvements into its operation.

Jan 1, 1993

By John T. MacWaters, George H. Milly

INTRODUCTION This paper describes operational procedures and instrumentation which were developed to implement a patented method of detecting and locating uranium ore bodies. All equipment was designed for accurate and reliable use under difficult field conditions. Data resulting from these developments, some of which are incorporated in a companion paper for this conference*, have contributed to our understanding, of the nature and significance of naturally-occurring radon exposures. Further applications of these techniques may prove useful in studying anthropogenic radon in evaluating the significance of variability in radon flux, or in taking proper account of the contribution of natural radon to ambient radon concentrations, particularly in mineralized regions. OPERATIONAL PROCEDURES The uranium search technique employed by GEOMET begins with a [reconnaissance mode], which utilizes a series of ambient air filter samples taken from a moving or standing vehicle to detect anamalous concentrations of radon. These samples are normally taken at night under stable (temperature inversion) or neutral atmospheric conditions, to avoid the rapid dispersion of the radon clouds typical of daytime turbulent conditions. Radon daughters formed by the decay of radon quickly attach to ambient aerosol particles and are captured on the surface of a membrane filter during a five-minute sampling period. The filter is placed in a portable alpha scintillation counter, and a five-minute count is started at a preset time after the completion of the sampling period. This count is followed immediately by a second five-minute count to enable determination of the cloud age, based on consideration of the relative half-lives of the initial radon daughters. With the use of tables computed from the mathematics of the uranium decay process, and with the measured radon background accounted for, the first and second counts are used to estimate the time which has elapsed since the pure radon initially emanated from the earth's surface. This cloud age, combined with wind speed and direction measurements made at the beginning and end of each sample, as well as with an understanding of the effects of local terrain features on wind trajectory, provides an estimate of the Probable location of the source. In practice the reconnaissance mode involves one vehicle with a single operator to take the five-minute samples, moving or standing, along any available roads or trails in the area to be covered. Under the usual nighttime stable conditions the cool air flows downslope and downvalley, and the operator will pay special attention to locations along the axes and confluences of the natural downflow patterns. These facilitate sampling of large air drainage areas. Successful detection of sources of radon based on high concentrations of radon daughters, and substantiated by evidence of "fresh" clouds, are frequently made on the basis of a relatively few samples taken judiciously by an experienced operator during a reconnaissance. At this point he has a choice: he can continue to cover the designated reconnaissance area, leaving the localization of any anomalous radon detections to await the ranking of detections by priority, or he can continue with localization of the detected source, either alone or by radioing for another vehicle to assist in triangulation operations. Localization of a source involves skillful and experienced use of the continuously collected data on concentration, age, and wind speed and direction, together with knowledge of the terrain from observation and contour maps, and exploitation of the available roads. Since age ratios are dependent solely on proximity of the source and wind speed, decreasing [cloud ages] based on statistically significant increasing age ratios represent the most useful. information in localization. The [magnitude of the concentration] of radon daughter products is also useful; however, it may vary widely for a variety of reasons during sampling for a localization, thus making this a secondary parameter for localization. Large values of concentration are of course useful; typical results for successful detection of a strong anomaly would yield alpha counts ranging from 10 to 25 times background values. These counts are convertible to ambient radon concentrations by appropriate consideration of the decay process. Successful localizations of radon sources using this procedure with ambient atmospheric measurements normally will narrow a source location to within an area ranging in size from less than a quarter of a square mile to at most a square mile, and frequently give information on the probable shape of the source (in plan view) on the earth's surface. Judicious use of this procedure could undoubtedly provide finer localization, but the coarser results just described are adequate for this Phase of GEOMET's uranium exploration procedures.

Jan 1, 1981

Effective ground control in the gate entries, particularly in the tailgate travelways, is essential for safe longwall mining. Longwall pillars maintain gate entry stability and carry abutment loads. To answer the need for effective longwall pillar design, an empirical method called Analysis of Longwall Pillar Stability (ALPS) was proposed several years ago. Some recent research at the Bureau of Mines has focused on the refinement and verification of the ALPS method. ALPS was originally developed from field studies in which multiple stressmeters were installed in longwall pillars and monitored during mining. Several new field studies have now been incorporated into the ALPS data base. The field measurements have' been used to verify formulas for predicting abutment strength and pillar loads, and to develop an expression for the distribution of the abutment load.

Jan 1, 1989

By M. Menéndez

Enhanced gravity separation appears to be one of the most promising methods for processing all types of <200-µm coal feeds and tailings. Systems based on this technology are reviewed, and the results of investigations based on C900 Multi-Gravity Separator tests conducted to assess the treatment of <200-µm, extremely difficult-to-wash coal settling pond tailings are presented. Multi-Gravity Separator processing tests of ultra-fine tailings with a high clay particle size content (22.6% <10 µm and 60.1% <40 µm) and a 69.56% ash content show that this material can be effectively treated after desliming (<10 µm) of clay-size particles to produce a coal with a 20.6% ash at a separator combustible material recovery of 69.3%. Desliming is shown to be critical in reducing coal ash content and combustible material recovery. Similar improvements are anticipated in the recovery and separation pro-cesses for other enhanced gravity separation systems from the desliming of feeds. Although not a conventional form of treating Multi-Gravity Separator data, the existence of well-defined polynomial relationships based on the product of drum shake amplitude and shake frequency relative to product coal recovery, product ash content and yields at varying wash water flows is demonstrated. Low-amplitude and intermediate- to high-frequency bed agitation are shown to produce optimum ash reduction results.

Jan 1, 2007

By Nelson R. Shaffer

Secondary minerals, amorphous materials, and biologic entities that form on building stone can cause aesthetically unflattering changes in color and may even result in stone decay. Techniques to determine causes of such changes generally have entailed destructive sampling and often required chemical, thin section, X-ray, or other relatively slow, expensive measurements. We have found that a rapid leach of in-place stone using small volumes (50-100 ml) of very pure distilled, deionized water provides recovery of sufficient dissolved material to help diagnose stone anomalies. Water is sprayed onto the stone and collected in a nonwetting plastic pan. Ion chromatograph analysis of waters thus collected from more than 160 sites showed wide variations in concentration of anions F, Cl, NO3, and SO4. Anion analyses were made in minutes for less than $20 per sample. Cations Ca, Mg, Fe, and Sr also were detected, and analyses might be used to determine mineral sources using equilibrium computer models. Solid particles filtered from the samples can be examined microscopically to provide further information about atmospheric agents affecting the stone. The collected water can even be evaporated to precipitate dissolved minerals. Chloride values in samples rinsed from stone ran as high as up to 17,000 ppm, nitrate to 100 ppm, and sulfate to 1,000 ppm. Limited data also indicate that measurable amounts of fluoride were found in some of the rinse waters. Chlorides were most abundant in areas where the stone has become dimpled or spalled. Nitrates were generally higher near ground level, and sulfate tended to be more abundant in samples taken from higher sites or from sheltered sites. Dark-stained limestone tended to yield less soluble material than clean-looking stone. Leachable elements were higher in samples from urban areas. Most of our data are from limestone buildings, but the technique works on other types of dimension stone, man-made construction materials, and even natural outcrops of rocks. Longitudinal studies show that soluble materials vary through time and are affected by climate. This rapid, in situ leach technique, although still being perfected, shows great promise in the diagnosis of stone alteration and in the evaluation of stone treatments because it is completely nondestructive.

Jan 1, 1999

By Alfred W. Hefferan

A longwall face conveyor system serves the primary function as all material handling systems; i.e., to transport material between the source and its destination. However, the conveyor system must provide many other functions as opposed to the traditional belt conveyor system. In this paper, we will attempt to contrast the longwall face conveyor system with a belt conveyor system. In addition, the unique problems encountered along with the solutions to these problems will be covered. Table 1 lists the characteristics required of each conveyor system. The table demonstrates the contrast in the two systems. Both must be designed specifically to encounter its unique problems. The balance of this paper will explain how the longwall face conveyor is designed to address its requirements.

Jan 1, 2000

By Hingant Pierre

The Hurtières Tunnel was built in 1995 with drill and blast method, in metamorphic schist. It is located between Lyon and Torino on the A 43 motorway in the French Alps. During the construction, a geological hazard was encountered, which caused a massive ground collapse. The tunnel was filled up with 3,000 m3of glacial materials. Geological investigations realized after the accident showed that a narrow glacial valley was present at this location the water table was 40 m above the tunnel level. The paper will describe the collapse and the remedial methods which were implemented to proceed through the failure area. These included drainage works,2,000 m3 grouting and 6,200 ml jet grouting columns.

Jan 1, 1999

By Ing. H. Kellerwessel, Ing. M. Esna-Ashari

This paper refers to the new crushing and grinding process, invented by Professor Schonert (Ref. 1), Clausthal, Germany. The process is known as high pressure particle bed comminution or interparticle crushing. Several papers already describe fundamentals of the process, the equipment used, results of lab size and large scale tests and the first results of commercial operations (Ref. 2 to 7). Of course, we will treat the topic from the perspective of a downstream gold ore upgrading or leaching process. Some recently executed testwork indicates that the process provides special advantages in this field. To describe the process generally, in view of the already existing publications.

Jan 1, 1998

By I. R. McGowan, J. Tilk, J. I. Hershman, R. L. Lewis

The White Pine Mine is a large underground copper mine located in the Upper Peninsula of Michigan. A numerical ground water flow model of the White Pine Mine was constructed to evaluate potential engineering controls that would reduce the rate of mine-water discharge after closure. Of the passive controls evaluated, the placement of bulkheads within the mine workings was predicted to offer the greatest benefit, reducing the rate of discharge by as much as 35%.

Jan 1, 1998

By R. L. Lewis

The White Pine Mine is a large underground copper mine located in the Upper Peninsula of Michigan. A numerical ground water flow model of the White Pine Mine was constructed to evaluate potential engineering controls that would reduce the rate of mine-water discharge after closure. Of the passive controls evaluated, the placement of bulkheads within the mine workings was predicted to offer the greatest benefit, reducing the rate of discharge by as much as 35%.

Jan 1, 1997