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By W. Zitz

Incorporation of heat exchangers into drilled shaft foundations is a novel approach to both improve the energy efficiency of building heat pump systems and provide necessary structural support using the same construction materials. In an effort to quantify the structural and heat exchange performance of deep foundations used as ground-source heat pumps, two instrumented test foundations were constructed as part of a new construction project in Denver, CO. They will be integrated into the conventional ground-source heat pump system for the building. This paper focuses on the lessons learned from the construction process for these energy foundations.

Jan 1, 2011

By B. Briggs

Over the past 15 years, the tunneling industry has pushed towards a higher degree of mechanization in nearly every phase of construction. The overall objective of the mechanization was to increase production and the level of safety in tunnel operations. However, the overall complexity of some systems have been a hindrance to a seamless transition to the newer technologies as increased maintenance requirements and re-training of skilled workers has altered the benefit curve for some innovations.

Jan 1, 2010

By W. Robert Power

Dimension stone includes a wide variety of natural materials that are put to an equally wide variety of uses. It is possible to classify dimension stone according to the end use to which the stone is put or according to the lithology of the stone. Both schemes are used by the United States Bureau of Mines in the annual Minerals Yearbook. The 1969 Yearbook lists 15 specific uses and has additional miscellaneous catagories. The same Yearbook lists five specific rock types or lithologies, and also includes a miscellaneous category. In a short presentation it would hardly be possible to list and define all these categories, much less discuss the evaluation of deposits with regard to all possible combinations. Besides, I am only slightly familiar with some of the uses and their requirements. I have therefore chosen to limit my remarks to some special problems in evaluating dimension stone that is to be cut and finished to specific sizes, tolerances, and finishes for use in buildings and some monuments. This use class is called cut stone in the Minerals Yearbook. In terms of dollar value it is the largest single use category. In 1969 the dollar value of cut stone was $29,122,000 which is more than twice the value of the next largest category. For those of you who are interested in other use applications of dimension stone I suggest that you start with recent articles by Bowles (1960), Currier (1960), and Barton (1968).

Jan 1, 1972

By C. E. Ekburg

Gold Quarry is a sediment-hosted, epithermal disseminated gold deposit located along the Carlin Trend. Gold, hosted by allochthonous Ordovician siltstones and cherts, is localized at the intersection of structures sympathetic to the major Good Hope and Gold Quarry faults. The magnitude of Gold Quarry was discovered in 1979 by surface exploration and by percussion holes drilled near the Maggie Creek orebody. Four years of development drilling delineated an open pit mineable gold deposit that contains 130 Mt (144 million st) of ore at an average 1.68 g/t (0.049 oz per st) of gold and includes a high-grade core of 46 Mt (51 million st) that average 2.64 g/t (0.077 oz per st) gold. Milling of the higher-grade portion began in 1985.

Jan 1, 1987

By Dipl. -Ing. H. -J. Sager

The ‘Westerschelde Tunnel’ underpasses the estuary of the Schelde in the Netherlands. The tunnel will consist of two tubes which are driven by two hydroshields (slurry shields). The tunnels will each have a length of approx. 6.6km and a bore-diameter of 11.33 m. Demanding ground conditions had to be considered during the design of the shield machines. Loose sands, extensive clay formations and high ground water pressures of up to 6.5 bar will be encountered during the tunnel drive. The tunnelling activities will start in the middle of 1999 and are scheduled to end by the end of 2001.

Jan 1, 1999

By Mark Leggett, Kevin Roberts

The need to modernise and increase the safety provision of older road tunnels raises challenges in maintaining the operation of the tunnel during such improvement works. The Mersey Kingsway twin road tunnels located in Liverpool UK, constructed in the late 1960s, have had three new cross passages constructed to allow emergency evacuation from one tunnel to the other tunnel and provide safer access for emergency services. The 3200m long road tunnels are lined with an unusual reinforced concrete steel-faced segmental lining with a paint finish. Construction of the cross passages occurred during night possessions with the tunnels returned to normal operation during the daytime. Constructed through water bearing sandstone and lined with precast concrete segments, the passages required advance ground treatment and support works. This paper presents the historical background to the Mersey Tunnels and describes the procurement strategy, design and construction approach adopted for these important safety improvements.

Jan 1, 2003

By Robin P. Gardner

The mechanistic approach to comminution consisting of incorporating particulate breakage functions into a suitable population balance equation has been developed by a number of researchers over the past decade or so. (1) To date this approach has been developed and demonstrated primarily for batch-operated, laboratory or small-scale ball mills. However, since industrial mills are mostly quite large and operated in the continuous mode; suitable population balance models and methods for obtaining the necessary breakage and other model parameters must be developed. This paper describes and investigates a radioisotope tracer technique for this purpose, Population balance models previously developed(2,3) are adapted for this study.

Jan 1, 1974

By S. P. Winkelmann

The expansion in gold production in the Carlin 'Trend over the last few years has been one of staggering proportion. To increase gold production while minimizing capital requirements and providing for the safe and efficient mining and processing of ores has required a tremendous effort by the Mine Engineering group at Newmont Gold. This paper discusses the organizational changes implemented to effectively deal with a full range of engineering problems and how the Newmont Gold Mine Engineering group dealt with these problems. Specially developed computer software and their applications will be explained. Improvements in the techniques used in converting geologic resources into reserves, and in scheduling the mining of multiple pits to feed multiple processing facilities, as well as ore control procedures are presented. Current mine engineering practices are discussed.

Jan 1, 1990

By Dennis C. Parker

The Porters Creek clay is mined for its absorbent properties. The formation is part of the Upper Mississippi embayment and is recognized in Alabama, Mississippi, Tennessee, Kentucky, Illinois, and southeast Missouri. Major minerals in order of abundance are Montmorillonite, Quartz, Illite, Kaolinite, and Chlorite. Mining consists of open pit operation utilizing track loaders or scraper. The clay is dried or hardened in rotary kilns and crushed to size by roll crushers. The clay granules are sized and air classified prior to storage for shipment or packaging. Granules are sold for pet absorbents, oil absorbents, anti-skid material, fertilizer, and pesticide carriers.

Jan 1, 1979

By E. Poeck, R. Garvey, U. Ozbay, K. Zhang

"A coal bump is characterized by the sudden failure of one or more pillars and an associated release of kinetic energy. Although the geologic conditions surrounding coal bumps are often similar, their occurrence and magnitude are difficult to predict. This paper presents the development of an approach to assess the potential for coal bumps in room and pillar mines through the use of energy concepts and special consideration of the interface properties between the coal and overlying rock. Back analyses were performed on the widespread collapse of a room and pillar mine with an associated 3.9 local magnitude seismic event. Pillar and mine-scale models were constructed using the distinct element method to simulate the mining stages leading up to the collapse. A variety of loading conditions, material properties, and interface properties were evaluated for their effect on unstable failure of single pillars, and the mine-scale model was used to study the evolution of failure during progressive mining. The extent of unstable failure was quantified in these models by calculating the total kinetic energy released during each mining stage. Through the parametric analysis of single pillar models, it was found that softening parameters in either the coal or the coal/rock interface can individually facilitate unstable failure of pillars, but the combination of the two in a single model produced a much higher release of energy during failure. The results of the mine-scale model further illustrated the trend as the combination of softening parameters in the coal and coal/rock interface produced a series of failures which most accurately reflected the collapse event at the mine. The method of room and pillar stability analysis demonstrated in this study effectively explores the potential for large coal bumps. INTRODUCTION The analysis of coal pillar behavior is challenging because natural variability in geologic conditions requires estimation of material strengths and predicted loads for a given mining situation. Large width-to-height (w/h) ratio pillars and deep overburden present an additional challenge, as the failure behavior of such pillars is more complex and may involve unstable, sudden collapse. Empirical methods have improved the success of coal pillar design for a wide range of conditions, but for deep cover and squat pillar geometries, less accuracy has been achieved in predicting pillar performance (Mark 2000). As with any empirical approach, more back analysis and the consideration of new variables may help improve understanding and accuracy of future designs. This paper presents a study of pillar stability through the back analysis of the Crandall Canyon Mine collapse, which occurred in August of 2007. Pillar-scale models are utilized for the calibration of material properties and assessment of potential instability under varying conditions, and mine-scale models are constructed in an attempt to reproduce widespread failure and correlate with observations at the mine. Special consideration is given to the properties of the coal and the coal/rock interface, and kinetic energy is calculated throughout the course of the simulations to gauge the level of instability when pillar failure occurs. Models were constructed using the Universal Distinct Element Code (UDEC) (Itasca, 2014)."

Jan 1, 2016

By C. O. Brawner

A recent advance in slope dewatering-depressurization and stabilization is the use of vacuum assist horizontal drainage. (Brawner and Pakalnis) Horizontal drains have been used for several decades to reduce water pressures in slopes to improve stability. The benefit from vacuum assist arises from an increased hydraulic gradient caused by an induced negative atmospheric pressure. A research program included a laboratory model whereby the effects of vacuum drainage were evaluated. Three case studies are described where the technique has been successful. The first is in a rock slope where flows increased from 0.1 1/min. under gravity drainage up to 1.2 1/min, upon vacuum. The second study involves installation of 17 drains placed at a slightly downward gradient to intercept and de- pressurize aquifers under a major tar sand deposit in Canada. The third study was on a large open pit copper mine in British Columbia where flow increased about 30 per cent.

Jan 1, 1984

By M. Sears, G. S. Esterhuizen, Z. Khademian

According to the 2010-2019 Mine Safety and Health Administration (MSHA) accident report database, 91% of reported ground control accidents in U.S. longwall mines were caused by roof instability. Gateroads are subject to significant changes in loading conditions from the development to the longwall abutment loading phases. When combined with thinly bedded shale roof, found in many U.S. longwall coal mines, the design of efficient roof support becomes challenging. In previous work, the Bonded Block Method (BBM) modeling of roof by UDEC was validated against field extensometer measurements in a longwall gateroad entry roof at a 180-m depth of cover. The BBM was shown as capable of capturing delamination and buckling of shale roof, one of the main roof instability mechanisms in longwall mines. This paper presents the recent findings on the roof-support interaction using BBM models of the same longwall entry. The effects of cable bolts, roof bolt density, and strap support on potential roof instability are studied. These types of studies are difficult and costly to conduct in an operating mine. Results show how the contribution of bolts, straps, and cable bolts can be quantified using the BBM models. The study demonstrates the potential for BBM numerical models to help understand the complex roof and support system interactions and to assist with optimizing gateroad support systems.

Feb 1, 2023

By Peter B. Dowden, David T. Cass

A shield on a tunneling machine has two basic purposes. Firstly to provide temporary support in unstable ground, maintaining the integrity of the bore and protecting the operators, and secondly, in conjunction with other sealing devices, to prevent the ingress of water. In any specific tunnel, unstable ground and water may or may not occur together. Further, there are a number of different ground behaviors that may be termed unstable and these must be defined in order to determine the most suitable type of machine. Beyond the shield itself, the cutterhead and the mucking system design are critical in successfully traversing difficult geology. In any but the shortest tunnels, variations in the geological conditions and the requirement of an acceptable advance rate can impose increasing degrees of sophistication in the machine design. In this paper we will review current designs of shielded type machines and their application, and discuss new developments which blend hard and soft ground tunneling technology. We will also indicate that in some conditions, although first impressions seem to favor a shielded machine, in fact an open gripper TBM may be the wisest choice.

Jan 1, 1991

By Mo Wanqiang

Equivalent-pressure ventilation is a method of balancing the air pressure between a productive face and its gob to extinguish fires and prevent the infiltration of toxic gases, so that the production of the face can be maintained. The method was successfully applied in Coal Mine No. 1 of Hebi Coal Mining Administration in north-central China. In this article, a practical application of the equivalent-pressure method to prevent carbon monoxide from entering an active longwall face adjacent to a fire breeding area is described, and four steps to achieve equivalent-pressure are discussed. The reliability of using this method and measures to maintain the equivalent-pressure are analyzed. It was observed that this method could maintain high production level while no sacrificing safety at the longwall face.

Jan 1, 1984

By John Newby, Ulf Gwildis, Ken Massé, Guillaume Roux

How to connect an effluent conveyance tunnel to riser shaft and diffuser arms of an outfall system is dictated by the ground conditions, which ideally include rock or soil strata of low permeability. Where such favorable conditions are beyond reach, both the complexity of designing and the risk of constructing this crucial system connection increase disproportionally. This paper describes the considerations that went into the approach of connecting a 5-m-diameter TBM drive with the in-river riser shaft of the Annacis Island WWTP New Outfall System in the highly permeable Fraser River sands at hydrostatic pressures exceeding 3 bar.

Jun 23, 2024

By Paul Lenchuk

The concrete block industry can trace its beginnings to the early 18th century when most of the experimental work was being carried out in England. In America, the concrete masonry industry got started shortly after the Civil War and has had sometimes a spectacular, but always a steady growth since then. From a few hundred thousand concrete masonry units made in the late 19th century, the industry today produces approximately 3.3 billion concrete masonry units making it the largest industry in the United States for masonry wall materials. There were 3500 concrete masonry plants manufacturing these units after World War II. This nwnber decreased to 1500 by 1970 although the production of concrete masonry units increased by over 100% in the last 25 years. One of the reasons for this increase in production by less than half of the plants which once existed, is the tremendous strides made in automation of production machinery. The concrete masonry plant of today is probably one of the most automated small businesses in existence. Within a few years it will be possible to push a button and the entire manufacturing process will begin with no human hands touching the units until they are laid up in a wall at the manufacturing plant and are trans-ported to the job site. No other concrete product has reached this state of manufacturing sophistication and it is one of the reasons why the price of a concrete masonry unit is not much different than it was 2S years ago. Because of automation, it is safe to say that concrete masonry will remain a highly competitive building material for many years to come. The problems that beset the continued use of this material are not related to the cost of manufacturing and delivering the product. What are some of the problems as well as some of the opportunities and is the golden age of opportunity knocking rather than a wolf in disguise? The use of concrete masonry has grown each year because a larger unit was provided at less cost than other competitive materials. Concrete masonry has had severe competition from the clay products industry as well as masons who laid the product in the wall and who resisted concrete masonry for many years. Even today

Jan 1, 1971

By E. R. DeMen

In late 1965 General Mills announced the availability of a new liquid ion exchange reagent, LIX®-64, for the recovery of copper from various solutions, such as dump leach liquors. Acceptance of this material by the copper industry has been gratifying. A number of pilot plants have been operated, and at this writing there are four commercial plants either in operation or under construction. The properties and operating characteristics of this reagent have been described in previous papers.1,2 LIX-64 is quite effective and selective for copper extractions although partially limited in pH ranges, losing extraction efficiency as the acidity of the feed solution increases to below pH 1.0. Also, the LIX-64 content in the kerosine carrier was limited to about 10 volume percent (except for special cases) because of rapidly decreasing phase disengagement rates above this content. This in turn led to large plant capital costs, as the organic flow rates had to be in- creased (rather than LIX-64 content) to extract the copper from high content liquors. This was true in all circuits where the feed copper content ran above 2.0 g/l copper. A reagent was needed which would extract copper from more acidic liquors (or higher copper content liquors) and which exhibited improved phase disengagement characteristics with reagent contents up to 30 volume percent. General Mills is pleased to announce the availability in commercial quantities of a new and improved reagent, L+-64~. This reagent broadens the pH range in which copper can be extracted, and exhibits superior phase disengagement characteristics. The improvement in the reagent has been noted in laboratory circuits, as well as pilot plant runs and commercial operations.

Jan 1, 1970

By X. X. Shao

Dewatering of ultra-fine clean coal slurry to a low moisture level of20 percent is difficult using the conventional techniques. A novel approach, which utilized mixing of fibrous waste material, such as paper, carpet and wood, with coal slurry prior to dewatering was developed. It was found that addition of about 10 Kg/t of carpet fibers or 5 Kg/t of raw paper pulp lowered the filter cake moisture from 22.5 to 18 percent. The compressive strength of the filter cake improved from 0 to 4.5 Kglcm2 and impact resistance from 0 to 4. The experimental data indicated that the handling character of the dewatered fine coal was improved significantly.

Jan 1, 1998

By R. M. Kakwani

The filtration and dewatering results of -32 mesh Pittsburgh seam coal are discussed with reference to the microscopic structure parameters, i.e., particle segregation in the cake and particle and pore size distributions at different layers. At low solid concentration of 0.33 kg coal/kg water, a non-uniform cake structure is observed in which the particle and pore sizes increase from the top to bottom layers in the filter cake. An increase in the solid concentration in slurry produces more uniform cake structure and higher filtration and dewatering rates. Air bubble entrapment in the coal filter cakes is also discussed.

Jan 1, 1984

By R. C. Bunge

A magnetogravimetric separation is the consequence of two competing forces with opposing directions, i.e., magnetic buoyancy and gravitation (or centrifugal force). While magnetic buoyancy is a function of particle volume, gravitational force depends on particle mass, thus permitting a separation according to specific gravity. Since magnetic buoyancy is not a phenomenon of common knowledge, this chapter is meant to briefly introduce the theory of magnetogravimetric separations. A particle that is suspended in a magnetic fluid which is exposed to an inhomogeneous magnetic field experiences a repulsive force -the so called magnetic buoyancy. In order to illustrate this effect, an analogy with the more familiar hydrostatic buoyancy is drawn. Hydrostatic buoyancy occurs due to unsymmetrical pressure distribution 'above' and 'below' a suspended particle (fig. 1).

Jan 1, 1990