Search Documents

By James P. Hambleton, Sam A. Stanier

A perceived advantage of screw-type foundations is the ability infer aspects of foundation performance from quantities measured or observed during installation, especially the installation torque. A particular concept widely used in practice is to correlate installation torque to ultimate capacity. This notion has proven useful as a field verification technique despite the absence of validated models that relate key variables of interest, such as installation torque, axial (crowd) force, geometrical parameters, and soil strength. This paper considers previous work by the co-authors and collaborators on analytical, numerical, and physical modelling of screw piles to relate the quantities measured or controlled during installation (e.g., installation torque) to the ultimate capacity and soil strength. Attention is given to saturated clay as a particular soil type amenable to simplified analysis. An analytical model for a single-helix pile is considered as a means of directly relating the ultimate capacity and undrained shear strength to the installation torque, crowd force, plate pitch, plate diameter, shaft diameter, installation depth, and surface roughness. The connection between the installation variables and ultimate capacity—and the sensitivity to crowd force in particular, a quantity that is typically not measured during field installations—is also discussed. The theoretical predictions are compared against data obtained from small-scale laboratory experiments that suggest the installation torque relates to the remolded strength of the soil. INTRODUCTION Screw piles are deep foundations that are twisted into the ground through an applied torque. Advantages over driven piles or drilled foundations include the relative silence of the installation, with low ground vibrations, and the possibility of being easily decommissioned by reversing the direction of twisting. Screw piles are now routinely encountered as a flexible, low-cost solution for numerous applications (Figs. 1 and 2), and they are also being considered for applications in offshore energy production due to limitations being imposed with respect to decommissioning and underwater noise. Also known as “screw anchors,” “helical piles”, or “helical anchors,” screw piles consist of helices or helical plate elements attached to a central shaft. Figure 3a shows the components of a single-helix pile and key variables. The diameters of the shaft and helix are denoted by d and D, respectively, and p is the pitch of the helix. Variable H denotes depth of the helical plate, and T and N denote the torque and axial (crowd) force applied during installation. In typical applications, the pile includes multiple helical plates, and the shaft is composed of segments that allow for it to extend to large depths into the soil.

Jan 1, 2019

The Johnny Mercer lyrics 'You've got to accentuate the positive, Eliminate the negative, Latch on to the affirmative à' would best sum up the traditional approach to community relations in the mining industry. This '90s 'Public Relations spin' approach, usually backed up by scientific data, technical reports and graphs outlining risk probability and the impact potential on people and communities, is being challenged. Challenged by communities who have greater access to information, demand greater levels of transparency and corporate responsibility of large corporate operations and possess greater awareness of the communities they live in.   The growth of the environmental movement, of anti-globalisation, anti corporatism, apprehension of a large corporate's ability to deal with community issues, and a lack of faith in the abilities of regulators to regulate corporate activities, means our industry faces challenges on multiple fronts. It must now be able to address these from a personal/community perspective if it is to remain relevant within communities.   One of the keys to this is linking the internal activities and responsibilities to the externals concerns and demands for higher levels of operation and care.   This presentation draws on Corporate Public Affairs trends, functions and approaches and the application to External Affairs activities within Newmont Waihi Gold's operations in Waihi and regional exploration activities throughout the Hauraki Goldfields.   The approach presented works on the philosophy that communities don't necessarily have to like what we do, but should be able to identify and recognise the way in which we involve them in decision making, communicate our intentions and respond to issues.

Jun 1, 2010

By A Li, H Jinto, M Laxman

The behaviour of tailings under cyclic loading has an impact on the stability and deformation of tailings dams and a good understanding of the cyclic behaviour of the tailings under earthquakes is important for tailings engineers and tailings operators for the design and safe operation of tailings dams. This paper presents an investigation into the cyclic behaviour of tailings using both laboratory cyclic direct simple shear (DSS) testing and numerical modelling. The laboratory testing involved cyclic DSS tests on gold tailings and zinc-copper tailings under different loadings and loading frequencies. The gold tailings specimen tested at a higher loading frequency and a higher cyclic stress ratio experienced spontaneous liquefaction during cyclic shearing and the zinc-copper tailings specimen tested at a lower loading frequency and a similar cyclic stress ratio exhibited ductile behaviour and liquefied due to cyclic mobility. The liquefaction behaviour of the tailings was modelled using an advanced constitutive model (UBCSAND), which was developed specifically to model soil liquefaction and strain softening under cyclic loading. The constitutive soil model presents the nonlinear soil behaviour under dynamic loading using a hyperbolic stress-strain relation. Dynamic analyses were carried out using a finite difference program FLAC. The cyclic stress-induced excess pore water pressures measured in the laboratory were modelled using numerical simulations of the laboratory tests under different loading conditions. The results of the non-linear dynamic analyses demonstrated the capability of numerical modelling of cyclic shearing induced excess pore water pressure and the onset of the spontaneous liquefaction. The laboratory investigation and numerical modelling technique provided the key properties and parameters for the dynamic analyses to assess the stability and deformation of tailings dams under design earthquake events. More importantly, the laboratory tests and numerical modelling provided some insights into liquefaction behaviour of the tailings during earthquakes. CITATION:Li, A, Laxman, M and Jinto, H, 2018. Liquefaction behaviour of tailings under cyclic simple shear testing, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 250–262 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By Timothy C. Siegel

This report presents the results of a synthesis on the design and analysis of ground improvement for liquefaction mitigation. The synthesis included an industry survey concerning the practice of ground improvement for liquefaction mitigation. Participation in the survey was solicited by advertisements in several trade magazines and by e-mail for the DFI membership. The survey participants numbered 150. Their professional roles include consulting engineers, specialty contractors, design engineers, government engineers, and academicians. They represent a variety of geographical areas including North/Central/South America, United Kingdom, Middle East, Caribbean, Hawaii, Japan, India, Egypt, France, Australia and New Zealand. Upon completion of the survey, several professionals in the field of liquefaction and ground improvement were interviewed for them to elaborate on the survey results. The interviews are included in the Appendix of this report. Financial support for the project was provided by DFI and Dan Brown and Associates PC. The concept of the liquefaction mitigation synthesis was developed by DFI?s Ground Improvement Committee in recognition that: (a) The results of recent research and post-earthquake reconnaissance have challenged previously longheld beliefs about liquefaction and associated mitigation techniques, and; (b) The DFI membership and the engineering/construction industry are interested to know if and how engineers and designers are subsequently adjusting their practice in consideration of recent research and post-earthquake reconnaissance. For more detailed information on recent research and post-earthquake reconnaissance, presentations are available from the State-of-the-Art Forum: Liquefaction Consequences and Mitigation that was held in St. Louis in 2012. A commentary of the state-of-practice in ground improvement for liquefaction mitigation (prepared by DFI?s Ground Improvement Committee) is included in this issue of the DFI Journal. The author would like to thank the participants of the survey and especially Mr. Mike Jeffries, Dr. Les Youd, and Dr. Ikuo Towhata for their willingness to share their expertise in interviews. The author also acknowledges Mary Ellen Bruce of DFI, Billy Camp of S&ME, Inc., and Marty Taube of DGI Menard (and Chair of DFI?s Ground Improvement Committee) for their signifi cant contributions.

Aug 1, 2013

By Martin Walker, Joseph Ang, Jongwon Lee, Alvin Bayudanto, Lilian Lorincz, Morteza Khorshidi, Wenyong Rong

This paper presents a case history of liquefaction susceptibility evaluation study for a major infrastructure project in the San José area. The subsurface material of the study area consists of Holocene alluvial deposits composed of interbedded and crosscut clays and silts, sands and gravels. The simplified approach for liquefaction triggering evaluation was carried out using both CPT data and SPT data representing site’s seismic capacity and the peak ground acceleration associated with a return period of 975 years at ground surface representing seismic demands. Site-specific cyclic stress ratio (CSR) profiles as seismic demand are also estimated from one-dimensional site response analysis. The simplified approach uses empirical depth stress reduction factors (rd) based on generic shear wave velocity profiles to account for the non-rigid response of the soil profile in estimating CSR. The CSR profiles of the simplified procedure were examined by completing site response analyses using site-specific soil profiles to represent site-specific seismic demands in the liquefaction triggering evaluation. The paper concludes with a comparison and discussion of the liquefaction evaluation examining results from CPT versus SPT data, and the comparison of CSR profiles from the simplified procedure versus site-specific response analysis.

Sep 8, 2021

By I. Ngoma, Marijke Fagan, Susan Harrison, Rebecca Chiume

"Heap bioleaching is an unsaturated hydrometallurgical extraction process which is commonly applied to the recovery of copper from low grade sulfide ores as well as for preparatory treatment of gold ores. The leaching reactions occur in the liquid phase, catalysed by iron and/or sulfur oxidising micro-organisms. Contact of the mineral grains with the leaching solution is consequently essential for metal recovery. Additionally, the liquid is responsible for the transport of the liberated metal out of the heap under gravitation-driven flow. However, the highly inhomogeneous structure of the heaps coupled with low irrigation rates cause the flow to vary between being gravitationally and capillary dominated, resulting in non-uniform wetting of the ore. In this study a 132 kg agglomerated ore ‘slice’ is used to examine the effect of liquid distribution on microbial colonisation and mineral recovery in a long term bioleach (> 500 days) when irrigation from a single drip emitter source is employed. The novel setup enabled sample collection from ports positioned along the length and height of the ore bed, so that 2D maps of the degree of wetting and microbial colonisation could be generated at different times in the leach. Lateral movement of the liquid increased with bed depth; the majority of flow was below the irrigation point while the top corner of the bed that was not irrigated remained the driest region of the heap throughout the experiment duration. The lowest cell numbers were also recorded in the driest regions. Specifically, cell numbers in the top corner of the bed, 400mm from the irrigation point, remained at undetectable levels until the 283rd day measurement, in line with typical heap operation durations. This indicates that slow colonisation of the heap in the regions between irrigation points may be a significant issue in heap optimisation."

Jan 1, 2014

By I. S. M. K. Ilankoon

In heap leaching the transport of the acid from the drippers to the surface of the ore particles is a major factor in the overall performance of a heap. This flow behavior is complex as the flow is unsaturated and occurs along a tortuous set of inter-particle channels and connections. Previous modeling of this system has used equations from oil and ground water flow to model these systems, but the applicability of these models with the larger particles found in typical heaps is suspect as these systems are not necessarily capillary dominated. In particular, as the characteristic particle size goes from below to above a few centimeters, the flow changes from capillary to gravity dominated. This means that typical heap leaching heaps cover this interesting, but complex, transitional fluid flow regime. In this paper a set of experimental studies of this flow, including PEPT (positron emission particle tracking) based tracer experiments, highly accurate liquid holdup measurements and axial dispersion experiments using salt tracers will be presented. In this study, flow through mono-dispersed particle beds was carried out. In particular, the hysteresis in the liquid holdup as the liquid flow rate into the particle bed is varied is investigated, since this hysteresis means that the relationship between flow rate and holdup is history dependent, an effect not included in models currently used to describe fluid flow in heaps. A theoretical model that describes this hysteresis will also be presented. Keywords: heap leaching, hydrometallurgy, modeling

Sep 1, 2012

By AIME AIME

IN many countries the lack of liquid petroleum supplies has centered interest upon the hydrogenation of coal and coal tars for the preparation of motor fuel. In the United States, hydrogenation has been of greater interest for grading up low-value petroleum fractions to the more valuable volatile fuels and for the preparation of a variety of premium products, including aviation gasolines, solvents, Diesel fuels, and lubricating oils. Chemically, the basic reason for this process is that, as shown in Table 1, the ratio of hydrogen to carbon (H/C ratio) in available raw materials is quite different from that characterizing the products sought.

Jan 1, 1936

By Dr. R. W. Mead

There are two basic problems when one attempts to separate a solution of metal ions utilizing a chelation-solvent extraction cascade (commonly called liquid ion exchange). First, it is impossible to produce any great degree of separation unless the separation factor (also called selectivity, which is the ratio of the distribution coefficients) is very large. Second, the richest possible extracted product, using an infinite number of equilibrium stages, is at best only in equilibrium with the feed solution. These factors combined with equipment design considerations have led to a situation where only the most selective chelating agents are applicable to economic industrial operations. The authors know that distillation techniques are used routinely to separate compounds with nearly identical relative volatilities and that there should be a way of operating solvent extraction cascades in an analogous manner to obtain separations of metal ions. The advantage of this approach would be that solutions of metal ions of any desired purity could be obtained even if the separation factor was close to unity. This paper presents this idea and suggests some possible applications.

Jan 1, 1977

By Ralph W. M. Lai

The liquid membrane separation process was first patented in 1968 for separating hydrocarbons.(1-4) This stimulated many researchers to join in the area of separating organic compounds. l Since then, its applications have been extended to the removal of contaminants from waste water,(12-33) encapsulation of enzymes and/or microorganisms for reaction and/or separation, (24-28) oxygenation of blood (artificial lung),(19) removal of toxins from blood (artificial kidney)(26,20) and metal extraction.(31-63) This paper discusses the possible process schemes for using liquid membranes to separate and concentrate copper ion from its acidic leaching solution.

Jan 1, 1982

By S. Eckert, G. Gerbeth, K. Timmel, B. Willers, T. Wondrak, N. Shevchenko, M. Röder

The quality of the produced steel in the continuous casting process is significantly governed by the melt flow in the mold. However, direct flow measurements in liquid metals are still rather scarce. In order to investigate these flow phenomena, three experimental facilities operating with low melting liquid metals were installed at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The melt flow in the models is measured by the Ultrasonic Doppler Velocimetry (UDV) or the Contactless Inductive Flow Tomography (CIFT), multi-phase flows can be visualized by X-ray imaging. The obtained measurement results are primarily used for validation of numerical models. In this paper we will investigate the fluid flow in the mold and the behavior of the surface of the liquid metal using flow measurements by UDV and surface profile measurement by a laser scanner, respectively. Strong fluctuations and deviations of the free surface were observed in case of a static magnetic field

Jan 1, 2016

By N. B. Gray, I. F. Taylor

"Gas injection to promote chemical reactions or mixing is a feature of many metallurgical processes. Often the aim of gas injection is to bring about a chemical reaction between the gas and liquid but most of the past physical and mathematical modelling work has ignored the influence of such reactions. In the work reported here, cold model studies have been conducted in which gas reacts with the liquid into which it was injected. The rate of liquid mixing has been measured as an indication of the mechanical energy transfer. It has been found that gas generated chemically within the liquid is significantly less effective at promoting mixing than the equivalent volume of inert gas. The relative ineffectiveness of chemically produced gas is thought to be due to smaller bubble sizes in comparison to the inert gas case. Small bubbles characteristic of chemically generated gas move with low slip velocities relative to the liquid and lead to different turbulence generation mechanisms.IntroductionIn processes such as steelmaking, copper conversion, bath smelting and ladle steel finishing gas is injected into liquid metal where it reacts chemically or simply serves as a source of agitation. An understanding of fluid flow phenomena in such situations is an essential pre-requisite to the calculation of process intensity and the optimisation of vessel productivity. Traditional physical cold modelling approaches to prediction of liquid flow in such situations are now often augmented by the techniques of computational fluid dynamics. Even with the availability of numerical modelling techniques cold physical models continue to have an important role for validation because it is generally difficult to obtain quantitative data from high temperature processes.Almost all previous cold modelling work has been based on the injection of an inert gas into water or some other non-reactive liquid. Such models do not include the significant increase in gas volume inherent in some processes. For example the oxidation of carbon in steelmaking leads to a twofold increase in molar gas flux through the reaction:"

Jan 1, 1996

By George Holderer

THE Enos Coal Mining Co. owns an area underlaid by coal, of approximately 5000 acres. This property is situated 9 miles from Oakland City, in the southern part of Indiana. The mine has been in operation 5 years, during which time some 350 acres have been stripped, and stripping is now proceeding at the rate of about 100 acres per year. TOPOGRAPHY These coal lands consist of gently-rolling agricultural fields which in times past were farmed for wheat. There is no timber and but very little brush to contend with. The overburden varies from 10 to 60 ft. in depth. A thin bed of slate overlies the coal, followed by limestone, which varies from 3 to 15 ft.; this, in turn, is followed by sandstone, slate, shale and clay. There is a very wide variation in the thickness of all of these beds. The coal has an average thickness of 5 ft., and is a good grade of high-volatile bituminous. MINING OPERATIONS Briefly, the sequence of operations is: drilling holes with churn drills; blasting with L. 0. X.; stripping overburden to, uncover coal and, finally taking up the coal, which is sent to a tipple for cleaning and sizing. In order to show what is being accomplished by the use of L. 0. X., results will be shown from May to November, 1926, inclusive, and compared to the same period in 1925. No work was done in No. 1 pit during May, 1925, hence all figures are unduly low for this month.

Jan 2, 1927

By George Holderer

THE Enos Coal Mining Co. owns an area underlaid by coal, of approximately 5000 acres. This property is situated 9 miles from Oakland City, in the southern part of Indiana. The mine has been in operation 5 years, during which time some 350 acres have been stripped, and stripping is now proceeding at the rate of about 100 acres per year. TOPOGRAPHY These coal lands consist of gently-rolling agricultural fields which in times past were farmed for wheat. There is no timber and but very little brush to contend with. The overburden varies from 10 to 60 ft. in depth. A thin bed of slate overlies the coal, followed by limestone, which varies from 3 to 15 ft.; this, in turn, is followed by sandstone, slate, shale and clay. There is a very wide variation in the thickness of all of these beds. The coal has an average thickness of 5 ft., and is a good grade of high-volatile bituminous. MINING OPERATIONS Briefly, the sequence of operations is: drilling holes with churn drills; blasting with L. 0. X.; stripping overburden to uncover coal and, finally taking up the coal, which is sent to a tipple for cleaning and sizing. In order to show what is being accomplished by the use of L. 0. X., results will be shown from May to November, 1926, inclusive, and compared to the same period in 1925. No work was done in No. 1 pit during May, 1925, hence all figures are unduly low for this month. Drilling There are in use 8 No. 44 Loomis clipper drills, caterpillar traction with gasoline engines; recently these were equipped with extra heavy stems, measuring 26 ft. overall and 4 ½ in. dia., to increase the speed of drilling. In addition, 4 No. 1 ½ G non-traction drills have been acquired, and are used to save the time of the larger drills when recleaning is necessary.

Jan 1, 1927

By E. Keskinkilic

"Electrical steels are used in motors, power generators, and transformers for electrical applications owing to their superior magnetic properties. These properties are attributed to the presence of a significant amount of silicon in the steel composition. Silicon steels are mainly grouped into two categories: grain-oriented (GO) and non-grain-oriented (NGO). The Si content of silicon steels is generally between about 0.50% and 6.5%. Therefore, silicon steels are further classified as low-, medium-, and high- Si steels. In this paper, liquid steel processing practices for certain silicon steel grades are outlined by considering a steelmaking company that integrates a basic oxygen furnace (BOF), a ladle furnace (LF), and an RHtype degassing unit (RH). Possible problems are identified, suggestions are discussed, and conclusions are drawn on the basis of real plant data. IntroductionSilicon steels are widely used in motors, power generators, and transformers for electrical applications owing to their superior magnetic properties. They are mainly grouped into grain-oriented (GO) and non-grain-oriented (NGO) silicon steel grades. However, the differences in the properties and thermomechanical production of GO and NGO grades are outside the scope of this paper. In this study, liquid steel processing of certain silicon steels will be discussed. In the integrated iron and steelmaking process, converters are the primary steelmaking units that are used mainly for decarburization and removal of phosphorus, and for obtaining liquid steel with a specific chemical composition and suitable temperature for secondary steelmaking operations. Ladle furnaces are a type of ladle metallurgy station consisting of electrical and/or chemical heating facilities for adjusting the liquid steel temperature during alloying. Various types of vacuum units are used for decarburization and removal of nitrogen, hydrogen, and sulphur, depending on the metallurgical conditions of the vacuum units. In this study, an actual steel-production company is considered in which the primary steelmaking operation uses a basic oxygen furnace (BOF) converter with N2/Ar bottom blowing, and the secondary steelmaking operations involve (1) a ladle furnace (LF) heated by three graphite electrodes and equipped with Ar and N2 top/bottom mixing facilities, and (2) an RHtype (circulation) vacuum degassing unit equipped with a top-blowing attachment for oxygen blowing and an Ar-purging system from an up-leg snorkel."

Jan 1, 2018

By Stanley Griff, William Herrera, William O. Seals

"The Navy initiated liquid propellant research in the early 1940's. The first promising Navy liquid propellant, Otto Fuel II, was developd in the early 1950 as a potential torpedo fuel. Later, the Navy developed a HAN based liquid propellant designated NOS-365, a hydroxylammonium nitrate, isopropylammonium nitrate and water formulation. A large gas volume generated by this propellant produced a large wake behind the torpedo. As one can readily understand, this negated the useof the propellant for this application. Recognizing the large gas volume as a desirable propulsion system for guns, the Navy embarked upon a gun propellant proqam. Utilizing a bulk loaded gun sysytem, the program failed when the gun was destroyed by the propellant detonating."

Jan 1, 1990

By M. M. Papic, G. M. Kimber

"Hat Creek coal was treated by the liquid solvent extraction process in a continuous plant at the U.K. National Coal Board Coal Research Establishment.Extraction levels of over 80 per cent dry-mineral-matter-free (dmmf) coal were achieved.Total light oil yield was around 47 per cent of the dmmf coal. The light oil was shown to be a good feedstock for secondary refining into gasoline, jet fuel and diesel fuel.In spite of the high mineral matter content of the coal the solid residue was successfully removed from the coal extract by filtration.IntroductionBritish Columbia Hydro (BCH) and the National Coal Board of Great Britain (NCB) undertook a joint project to test the Hat Creek coal from British Columbia in the NCB's coal liquefaction process designed to produce transport fuels and feedstocks for the chemical industry by the liquid solvent extraction of coal(1), In this process most of the coal is dissolved in an aromatic solvent and the residual solids consisting of mineral matter and undissolved coal are removed by filtration. The resultant coal extract solution is fed to a hydrocracker for conversion to light liquid products and a fraction suitable for recycling as solvent. The light liquid products can be converted to gasoline and diesel fuel in a secondary refining stage.The dissolution of the coal is effected by heat-treating a slurry at a temperature in the region of 400°C which causes some bonds in the coal to rupture with the formation of radicals(2,3). These radicals are stabilized by hydrogen transfer from the hydroaromatic groups in the solvent, resulting in a reduction in the molecular weight of the coal. In the absence of donor groups the radicals combine to form an insoluble high molecular weight product(4). From studies of the kinetics of these reactions it has been shown that the formation and stabilization of the radicals is rapid at temperatures around 400°C(2,3). The dissolution of the depolymerizing coal is, however, relatively slow and the need to ensure complete dissolution in order to achieve a high extraction restricts the selection of digestion time(5). Further, it is important that digests do not contain depolymerizing coal as it may re-form under the applied stress in the filter cake inhibiting flow through the bed and resulting in low filtration rates(6).Thus, in practice relatively long digestion times are generally required in order to ensure complete dissolution of the depolymerizing coal, while it is also important to avoid depletion of the hydrogen donor groups in the solvent which would lower the rate of hydrogen donation to the coal and thus reduce the extraction yield and adversely affect the filtration(7). Clearly it is desirable to optimize the digestion time and temperature with regard to the extraction yield and filtration properties.The precise control of the distribution of products from the hydro-cracker is important for the composition of the recycle process solvent. The principal functions of the solvent are to provide a source of donatable hydrogen and a vehicle for the dissolution of the depolymerizing coal. Hydrogen transfer from the solvent, achieved by the conversion of hydroaromatic to aromatic groups, stabilizes the radicals formed by thermal cleavage of some of the bonds in the coal resulting in a progressive reduction in the size of the coal molecules(8,9) and dissolution in the solvent. The combination of radicals would result in the formation of insoluble material and a reduced extraction yield of the coal(4). Thus to achieve a high extraction yield the solvent should contain sufficient hydrogen donor groups to prevent extensive radical combination. The composition of the solvent should also be controlled to allow dissolution of the depolymerizing coal and to prevent precipitation of this material during the subsequent processing of the coal digest and extract solution. The formation of a precipitate not only reduces the extraction yield of the coal and adve"

Jan 1, 1985

By F. L. Jackson

The large scale transportation and storage of sulphur in the liquid state is a relatively new development, but is really only a logical extension of old mining and processing techniques, It is not known who the first person was to win a relatively pure sulphur from ore by melting, but this method was commercially used at least two hundred years ago in Sicily and is still in use today. The Frasch process of mining was invented over sixty years ago, and the development and improvement of-liquid sulphur pumping and handling techniques has paralleled the growth in the Frasch mining industry. During the last fifty years, improvements in the technology of using sulphur have included the premelting of sulphur prior to its being burned for acid production or conversion into CS2 and other compounds. Yet, until fairly recent times, sulphur produced as liquid has been solidified into large blocks at the producing point, broken down by blasting or with mechanical equipment, and shipped in bulk form as a solid.

Jan 1, 1962

By L. S. Fountain

A national survey, 1978-1980, found 180,973 waste impoundments used by industrial mining, municipal and other interests. Possibly 27,000 contain hazardous materials. The potential hazard of leaks polluting water supplies is a growing concern. An electrical technique was developed to efficiently and speedily detect and locate leaks in geomembrane-lined liquid impoundments without emptying the contents. A potential applied between the liquid and earth causes electric current to flow through leaks in the insulating geomembrane material to ground. The cur- rent density around the leak is used to detect and locate the leak. Field tests show single and multiple leaks 2.54 cm in diameter or less can be detected and located to within less than 30 cm.

Jan 1, 1986

Protect mine rescuers from heat-induced stress that drastically cuts their endurance and saps their strength. Approach To prevent exhaustion caused by thermal stress, a rescuer can wear a liquid-cooled hood and vest which absorbs heat, thereby reducing the heat-induced strain on the rescuer's heart and circulatory system. How It Works Liquid coolant is continuously circulated through a self-contained system in which the coolant is chilled by a heat sink on the wearer's belt. The coolant, which is a mixture of alcohol and water, is pumped from the heat sink to bladders inside the hood and vest where it absorbs body heat. After absorbing heat In the hood and vest areas, the coolant returns to the heat sink where it is rechilled by passing through a tube coiled around a steel can containing a block of ice. To adjust the temperature of coolant leaving the heat sink unit, a valve can be operated by the wearer, causing part of the flow to bypass the coil. A small pump and a rechargeable battery are also part of the assembly.

Jan 1, 1979