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Many states rely upon the Pennsylvania 1957 “Gas Well Pillar Study” to evaluate the coal barrier surrounding gas wells (Commonwealth of Pennsylvania, 1957). The study included 77 gas well failure cases that occurred in the Pittsburgh and Freeport coal seams over a 25-year span. At the time, coal was mined using the room-and-pillar mining method with full or partial pillar recovery, and square or rectangle pillars surrounding the gas wells were left to protect the wells. The study provided guidelines for pillar sizes under different overburden depths up to 700 ft. The 1957 study has also been used to determine gas well pillar sizes in longwall mines since longwall mining began in the 1970s. The original study was developed for room-and-pillar mining and could be applied to gas wells in longwall chain pillars under shallow cover. However, under deep cover, severe deformations in gas wells have occurred in longwall chain pillars. Presently, with a better understanding of coal pillar mechanics, new insight into subsidence movements induced by retreat mining, and advances in numerical modeling, it has become both critically important and feasible to evaluate the adequacy of the 1957 study for longwall gas well pillars. In this paper, the data from the 1957 study is analyzed from a new perspective by considering various factors, including overburden depth, failure location, failure time, pillar safety factor (SF), and floor pressure. The pillar SF and floor pressure are calculated by considering abutment pressure induced by full pillar recovery. A statistical analysis is performed to find correlations between various factors and helps identify the most significant factors for the stability of gas wells influenced by retreat mining. Through analyzing the data from the 1957 study, the guidelines for gas well pillars in the 1957 study are evaluated for their adequacy for room-and-pillar mining and their applicability to longwall mining. Numerical modeling is used to model the stability of gas wells by quantifying the mining-induced stresses in gas well casings. Results of this study indicate that the guidelines in the 1957 study may be appropriate for pillars protecting conventional gas wells in both room-and-pillar mining and longwall mining under overburden depths up to 700 ft but may not be sufficient for protective pillars under deep cover. The current evaluation of the 1957 study provides not only insights about potential gas well failures caused by retreat mining but also implications for what critical considerations should be considered to protect gas wells in longwall mining.

Jul 28, 2020

By Steve Kral

Borates are minerals that contain boron. Trace amounts exist in rocks, soil, water and people. Boron-containing ores are rare and U.S. Borax, a subsidiary of Rio Tinto Borax, controls one of the world’s two world-class borate deposits. Through its global systems of mines, refineries, ports, sales offices and distribution centers, the company supplies nearly 45 percent of the world’s demand for borates. Borax has been mining borates in California for more than a century. This year the company celebrated 131 years of continuous business in the Golden State and 76 years at its operations in Boron, the site of California’s largest openpit mine. It also has mines and refineries in Argentina, refineries and ship-ping facilities in Europe and technical staff in the United States, North and South America, Europe and Asia Pacific. So, with the 130±years of borate mining and processing experience behind it as well as its global marketing and distribution centers, there is very little that Borax does not know about borates.

Jan 1, 2003

By Ian Martin

A precious metals refinery’s switch to personal computer-based, three-dimensional piping design saved many hours in the design of a South African precious metals refinery. Bateman Minerals and Industrial provided engineering, procurement and construction management services for Impala Platinum Limited-Refineries’ new $60 million refinery in Springs, South Africa. This project is one of the largest platinum refineries in the world. Bateman evaluated a new design method during this project that involved developing a three-dimensional model for the project. The new method saved time by reducing the man-hours required to generate complete project documentation, including plans, sections, isometrics and material takeoffs. The new method also saved design and construction time by allowing designers to detect clashes before construction began.

Jan 1, 2000

"Editor’s note: Each year, Mining Engineering features an industrial minerals review. Several people put in a fair amount of time in developing the material for this issue, all the while doing their own jobs. Thank you to the industrial minerals annual review editor, to the Industrial Minerals and Aggregates Division technical committee chair and vice chairs, and to the authors of the individual commodity profiles.Jim Norman, member SME, of Tetra Tech, is the industrial minerals annual review editor.Vishal Gupta, member SME, of EP Minerals LLC, is chair of the Industrial Minerals &Aggregates Division’s Technical Committee.The technical committee vice chairs include:• Vishal Gupta, member SME, of EP Minerals LLC, Agricultural Materials.• Joe Garska, member SME, of Imerys, ceramics and refractory materials.• Stanley Krukowski, member SME, of the Oklahoma Geological Survey, chemical raw materials.• Russell Winn, member SME, of R.E. Janes Gravel Co., chemical raw materials.• Justin Zdunczyk, member SME, of Pike Industries, construction aggregates.• Jerry Gauntt, member SME, of Golder Associates, fillers and pigments.• Ebrhaim K. Tarshizi, member SME, of the Michigan Tech, sorbents, filters and process aids.• Daniel T. Eyde, member SME, of St. Cloud Mining, specialty minerals.Their help makes possible this July industrial minerals issue. On behalf of ME readers, the editors thank them.Virta, R.L. U.S. Geological Survey, National Minerals Information CenterFour companies - H.C. Spinks Clay Co., Inc., Imerys, Old Hickory Clay Co., and Unimin Corp. - mined ball clay in four states in 2013. On the basis of preliminary data, production was 1 Mt (1.1 million st) with an estimated value of $47 million. Production increased by 3 percent in tonnage from 973 kt (1.1 million st) with a value of $45.1 million in 2012. Tennessee was the leading producer state accounting for 64 percent of domestic production, followed by Texas, Mississippi and Kentucky. About 67 percent of total ball clay production was airfloat, 22 percent was crude or shredded and 11 percent was water-slurried.ConsumptionIn 2013, domestic ball clay producers sold clays to the following markets: ceramic floor and wall tile (44 percent); exports (21 percent); sanitaryware (18 percent); miscellaneous ceramics (9 percent); fillers, extenders, and binders, and unspecified uses (4 percent each), based on 2012 end use patterns and current markets. Other markets accounted for less than 1 percent of the remaining ball clay sales or use. Sales reported for the manufacture of fiberglass or most filler, extender, and binder applications were likely to have been mainly kaolin mined or purchased by the ball clay producers.PricesThe average value of domestically produced ball clay was approximately $47/t ($43/st) in 2013 compared with $46/t ($42/st) in 2012, on the basis of a preliminary survey of domestic ball clay producers. The unit values of exported and imported ball clay were $126/t ($114/ st) and $373/t ($338/st), respectively, in 2013, compared with $62/t ($56/st) and $314/t ($285/st), respectively, in 2012. Unit values for most large export shipments increased in 2013, and a larger number of low-tonnage, high-value export shipments were shipped in 2013 than in 2012, resulting in a doubling of the average export value. Two low-tonnage, high-value shipments in 2013 accounted for the increased value of imports."

Jan 1, 2014

By Lee W. Abramson, Kenneth P. Akins

The authors have accumulated published data on residual soil and rock tunnels in the United States and have compared it to transit tunneling experience in Atlanta, Georgia, and tunnels in other soil and rock conditions. Two 6.1 meter (20 foot) diameter shield driven, compressed air tunnels were constructed for the Metropolitan Atlanta Rapid Transit Authority (MARTA) connecting the Five Points Station (central hub) with the Peachtree Center Station (first station on the north line). Because of the historic multi-story structures above the tunnels and the variety of subsurface conditions, a comprehensive ground monitoring and observation program was conducted. Conclusions are drawn regarding residual soil and rock ground response due to tunneling. Comparisons are made to ground response due to tunneling in other soil and rock conditions.

Jan 1, 1983

By Michelle L. Ramos

INTRODUCTION The Ballard Siphon was built in 1935 and consists of two 91.4 cm (36-inch) diameter wood-stave pipes. These pipes convey sewer flowsunder the Ship Canal from northwest Seattle and the Ballard Regulator to the North Interceptor and the West Point Treatment plant. The siphons were constructed using open cut construction, are now buried in the sediment on the floor of the canal, and have severely limited ability to be dewatered, inspected, or cleaned. The existing siphon is 394.7 m (1,295 feet) long from the junction structure on the southern shoreline to the regulator structure on the north. The location of the Ballard Siphon is shown in Figures 1 and 2. The area around the Ballard Siphon has become more populated and developed since the siphon was built. Additionally, the Ballard Siphon is subject to high flows that are greater than the capacity of the pipelines. This has resulted in predict-able Combined Sewer Overflows(CSO?s) whenever a large, long duration rain event occurs. The aged pipeline of uncertain viability has become a critical piece of the sewer system infrastructure. Because of the age of the pipelines and their importance, a sonar survey was completed on both barrels of the Ballard Siphon in December of 2005. The sonar images appeared to indicate crown intrusion of the wood-stave pipes, which suggested that the pipes were in imminent danger of collapse. As a result, an Emergency Declaration was executed by King County and the Ballard Siphon Replacement Project was initiated. Staheli Trenchless Consultants was retained to perform feasibility studies to deter-mine the viability of using microtunneling and horizontal directional drilling (HDD) for replacement of the Ballard Siphon. For the evaluations, the preferred site location was determined to be at or near the site of the existing Ballard Siphon in order to minimize the ancillary sewer work which would accompany moving to a new site. To meet flow demands and hydraulic requirements, the replacement siphon needed a mini-mum equivalent diameter of 182.9 cm (72 inches). This could be accomplished with a number of different siphon diameters and configurations including, but not limited to, three 106.7 cm (42-inch) diameter pipelines, two 152.4 cm (60-inch) pipelines, or two 91.44 cm (36-inch) pipelines and a 121.9 cm (48-inch) pipeline.

By L. W. Berry

Drill and blast planning is critical to successful mine production, both in timing and in results. However, typical planning, reporting, and information exchange usually involves large quantities of data collated in a discordant set of spreadsheets, databases, and reports. Collecting, analyzing, modeling, and distributing all data necessary for efficient drill and blast operations is time consuming and cumbersome. MineSight Axis Drill and Blast provides an extensible core of functions, seamlessly integrated with other MineSight software tools, to make sense of this information. The benefits of improving the management of drilling and blasting processes are immense and result in improved fragmentation at a lower cost, improved shovel and truck productivity, and enhanced ore processing.

Jan 1, 2011

By Paul D. Dupree

Introduction Trapper mine is a dip-line strip coal mine, located about 10 km (6 miles) southwest of Craig, CO. The mine provides the Craig Generating Station, operated by Colorado-Ute, with about 2 Mt (2.3 million st) of coal annually. The Trapper mine is situated on a hillside that climbs in elevation from 2 to 2.5 km (6500 to 7400 ft) at average grade of 15%. The coal seams dip at about 16% down-grade and they outcrop near the top of the hillside. They exceed maximum stripping depth in 1 to 1.7 km (3500 to 5500 ft) of pit length. Stripping in the three existing pits is performed with three Page 752 23 m3 (30 cu yd) walking draglines. Two of the pits are currently being cast blasted. Until the active cut, the Derringer pit was cast blasted only where the lower mined seam exceeded stripping capabilities and the pit was a single seam operation. Now, a 9-m (30-ft) interburden bench has been incorporated into the stripping plan. This bench protects the first seam of coal from shear when the overburden is cast blasted. The cast blasted section of the 1.6 km (53,000 ft) long pit has been increased from the 457 m (1500 ft) casted previ¬ously to 1 km (3500 ft). High speed films show the coal losses due to shear of the blast are minimal. The pit width in Derringer pit is 61 m (200 ft). This is necessary for efficient spoil side stripping of a relatively thin interburden in the two-seam section of the pit. The Enfield pit is entirely cast blasted. The single seam pit is 46 m (150 ft) wide, 1.1 km (3600 ft) long, and varies from 15 and 46 m (50 and 150 ft) in overburden depth. The overburden strata at the mine consists of medium-hard layers of sandstone, shale, and

Jan 1, 1987

By J. S. Peterson

Occupational noise-induced hearing loss (NIHL) has been recognized by the National Occupational Research Agenda (NORA) as the most common job-related disease in the United States. Roughly 30 million workers are exposed to excessive noise levels or toxins that are potentially hazardous to their hearing. The National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR)is investigating noise controls to reduce operator overexposures caused by haul trucks used in underground metal/non-metal mines. To identify the most significant contributors to the overall sound level, Source Path Contribution (SPC) analysis was conducted. Noise dosimetry and time-motion analysis were also conducted to quantify operator noise exposure. SPC analysis determined that, under high idle conditions, a source near a hydraulic pump mounted to the rear of the engine and the engine cooling fan were the major noise sources. The time-motion/dosimetry analysis showed that the operators accumulated more than 90% of their noise exposures while they were hauling ore to the dump site and traveling back to the load site unloaded.

Jan 1, 2012

By Satoshi Honda, Mitsuru Shimizu, Tatsuji Nagao, Motoaki Kurisu, Hirokazu Izumi, Toshinori Takahashi, Hiroyuki Itoi

"1. INTRODUCTION Grade separation of roads and railway tracks is an effective method for solving traffic-related issues in cities. However, in urban areas where the existing traffic infrastructure is already overcrowded, construction of new roads often faces problems especially in the proximity of existing structures. This paper summarizes the construction plan and results of new road tunnel construction in the proximity of the piers of elevated tracks on the Tokaido Shinkansen railway.2. SUMMARY OF CONSTRUCTION AND ISSUES Auxiliary Route No. 26 as specified in the Tokyo urban plan is a project by the Tokyo Metropolitan Government, covering the construction of a new road with a total length of 22.3 km currently on the way to completion. In Shinagawa Ward, Tokyo, Auxiliary Route No. 26 is designed to cross the railway tracks of the Yokosuka Line and the Tokaido Shinkansen Line, so for this project, the East Japan Railway Company (JR East) was commissioned to design and build a road crossing under the railway tracks (Sumiyoshi Underpass). Figures 1 through 3 show a sketch of the Sumiyoshi Underpass. The Sumiyoshi Underpass was planned as a two-lane tunnel for vehicles, which was to cross under the railway tracks of the Yokosuka Line and the Tokaido Shinkansen Line at an angle of 70 degrees. The structure concerned is a single-story single-span box culvert structure with the following dimensions: 11.5 m wide, 7.7 m high and 31.6 m long. The Tokaido Shinkansen Line tracks were constructed on a girder-type elevated bridge built in the 1960s, and the foundation piles of the piers (P7 and P8) in the proximity of this crossing box culvert of RC structure were constructed using an earth drill method. The crossing structure for this project is located extremely close to the piers of the Tokaido Shinkansen railway tracks, with a minimal separation of 0.4 m, and the most significant issue of this project was construction in a manner that would not obstruct the normal operations of the Tokaido Shinkansen (Figure 4). Initially, we considered installing a temporary earth retaining structure in the proximity of the piers, cutting the ground and building an RC box, but concluded that it would be very difficult to apply this method because of probable excessive displacements in the Shinkansen railway piers. That is why we decided on the use of a non-open cut method in order to minimize the impact on the piers."

Jan 1, 2016

By A. J. Wainwright

The Coffee Creek lode gold discoveries are located in the White Gold district (Dawson Range), west-central Yukon, 130 km south of Dawson City and 30 km south of the Golden Saddle gold deposit (Figure 1). Extensive structurally-controlled gold mineralization has been discovered during the 2010 and 2011 exploration drilling campaigns, highlighting this part of the Dawson Range as a significant emerging gold district. [ ] In this contribution we review the geological framework and describe the mineralization styles and metal signatures observed to date on the Coffee project. The main Coffee area is underlain by a 15 km by 4 km geochemical footprint, characterized by discrete linear gold-in-soil anomalies that correspond to various mineralized corridors. Of several mineralized areas tested in the past two drill seasons by diamond core and reverse-circulation (RC) drilling, we focus on the Supremo, Double Double, Latte and Kona zones; areas with the most information obtained from drilling thus far (Table 1; Figure 2).

Jan 1, 2012

By G. M. Wilemon

The U.S. Bureau of Mines has conducted preliminary investigations on the leaching of phosphate ores obtained from deposits in the western United States using sulfuric acid (H2SO4) in the presence of methanol. Phosphate extractions in excess of 80 pct were obtained on an ore sample from Pocatello, ID. Initial leaching studies using the ore as received yielded extraction levels of approximately 35 pct. However, when the sample was ground for as little as 5 min in a rod mill, in methanol, then treated with HzS04, 82 pct extraction was achieved. The R2O3-P2O5 (R2O3 = Al2O3 + Fe2O3) ratio of the starting material was 0.11. Solubilized products after leaching exhibited an R2O3-P2O5 ratio of 0.02, which is well within desired limits. These results illustrate the potential of acid-alcohol leaching for recovering phosphate values from marginal-grade ores and as an alternative to methods involving current beneficiation techniques that yield lower phosphate recoveries.

Jan 1, 1992

By K. F. Bailey

Naturally occurring asbestos in aggregate and other mineral deposits, and the release of asbestos fibers into the ambient environment, is a public health concern. Determining the presence of asbestos in an ore body also presents a considerable sampling and analytical challenge. Improper and inaccurate identification of asbestos can result in unwarranted public and worker panic leading to significant costs to mine operators both in terms of dollars and company image. Some companies have been forced out of business simply because they had the non-asbestiform, prismatic variety of one of the six asbestos minerals. In the late 70’s, asbestos was found as a contaminate in a trap rock quarry in Rockville, Maryland. This discovery led to a massive overreaction by federal, state and local governments. In 1986, the Occupational Safety and Health Administration (OSHA) promulgated a final rule that regulated the common non-asbestiform mineral habits of actinolite, tremolite, and anthophyllite as if they were asbestos. The rule was reversed after a six-year struggle. Recently, the Libby, Montana, W. R. Grace vermiculite - asbestos, as well as the California chrysotile in serpentinite, and the New Jersey Southdown quarry – asbestos events have rekindled the entire issue of naturally occurring asbestos. It is time to get this concern addressed with sound science so that real asbestos is properly identified and controlled.

Jan 1, 2002

By J. Brent Hiskey

Thiourea is a reagent capable of complexing gold and silver. With the proper oxidant, thiourea can effectively dissolve metallic gold and silver. A thiourea leaching system possesses potential advantages over conventional cyanidation including acidic solutions instead of alkaline, cationic complexes in contrast to metal-cyanide anoionic complexes, and faster leaching rates with acidic solutions of thiourea. Generally, the rate of metal dissolution in thiourea solution is fastest when ferric ion is employed as an oxidant. Acidic thiourea solutions for certain applications could offer a nontoxic and noncorrosive option for processing gold and silver. This paper provides information regarding the fundamental chemistry of the acidic thiourea system, and reviews the dissolution of both silver and gold in acidic solutions of thiourea. The recovery of gold and silver from acidic thiourea solution is discussed.

Jan 1, 1981

By Andrew K. Simpson

What will this deal do to the company’s stock price? This question arises when a publicly traded mining company is presented with a new mine project, or business combination. The standard tool for addressing this question is to use discounted cash flow analysis, or net asset value(NAV), which is discounted cash flow net of liabilities. Cash flow-based analysis is invaluable for assessing project costs and other impacts on debt service capacity and internal rates of return. But cash flow analysis and NAV do not work very well for stock price analysis.

Jan 1, 2000

By Ed Cope

The newly discovered South Arturo deposit is a Carlin-type, breccia-hosted, oxide gold deposit located on the Dee Mine property at the north end of the Carlin Trend in Nevada. The Dee Gold Mine was discovered in 1981 by Dee Delamar, a Cordex geologist. The property was put into production by Rayrock Mines in 1984. During its 16-year mine life, the Dee Mine produced about 18.6 t (600,000 oz) of gold from oxide ore at an average production rate of about 1.24 to 1.55 t/a (40,000 to 50,000 oz/year). In October 1997, Bar-rick Gold Exploration acquired the right to earn a 60-percent interest in the Dee property from Dee Gold Mines through an exploration farm-out agreement. Barrick Gold Exploration began exploration activities on the property in 1998 and vested in its 60 percent operating interest in 2004. However, the discovery hole at South Arturo was not drilled until July 2005 from atop the historic mine dumps located 300 m (985 ft) south of the Dee openpit. The discovery hole (BD-72) encountered a cumulative 75.6 m (248 ft) of oxide mineralization grading 1.9 g/t (0.055 oz/st) gold beneath 260 m (855 ft) of dump material and post mineral Tertiary Carlin Formation volcanic and sedimentary rocks. Oxidation within the deposit extends to depths greater than 610 m (2,000 ft). The deposit has passed the prefeasibility test and is presently in the feasibility stage. Exploration is on-going to enhance or enlarge the known deposit. The current resource for the deposit stands at 40.4 t (1.3 million oz) of gold. The South Arturo discovery is an example of an historic mining property yielding a new discovery through the diligent application of area selection criteria of the model type and persevering when early results were generally negative. Barrick?s original exploration pro-grams on the property were focused on the discovery of deep, high-grade sulfide deposits that would likely be mined by underground methods. As it turns out, South Arturo is mostly oxidized and will be amenable to mining by openpit methods

Jan 1, 2008

By R. C. Ford, W. L. Niccoli, J. B. Finley

All mining operations are superimposed on natural hydrologic systems. As a result, mining operations are influenced by natural hydrologic processes and require water management systems to successfully conduct mining activities. Managing water and mining-related solutions is a critical task at all stages of the mine life because of the time-dependent nature of natural and mining-related flows. Effective operation of the mining water management system requires a “systems” approach that integrates the time-dependent effects of all water and mine solution handling components. This paper discusses the concept and application of dynamic systems modeling to address the time dependent nature of mining water management systems.

Jan 1, 2002

By Carson Rife, Michael L. Clark

INTRODUCTION Zortman Mining Inc. is a wholly owned subsidiary of Pegasus Gold Corporation of Spokane, Washington. Pegasus has been producing gold and silver from the Zortman and Landusky mines since 1979. The Zortman and Landusky mines are two distinct open pit mines located approximately 6 kilometers apart in the Little Rockies Mining District of north central Montana. The two mines use large-tonnage, low- grade heap leaching techniques to efficiently process the gold and silver ore. PROJECT DESCRIPTION The Little Rockies rise abruptly 914 metres from the surrounding plains to about 1829 metres above sea level. The topography is quite steep, making efficient leach pad construction a major challenge. The climate is semi-arid with moderate summers and occasionally severe winters. Freezing temperatures usually arrive in late October or early November, influencing the effectiveness of leaching operations. GEOLOGY AND MINERALOGY The geology of the Little Rocky Mountains consists of steeply dipping sedimentary ridges forming an elliptical dome surrounding a core of intruding syenite porphyry. Within the syenite porphyry are well fractured and mineralized shear zones where the existing reserves and open pits are located. The ore is presently divided into oxidized, mixed, and sulfide. Only the oxides and mixed zones that are of ore grade are placed on the leach pads. The syenite porphyry host rock enables effective leaching of gold and silver to depths of 61 metres, having a major impact on leach pad construction costs. MINING All mining since 1979 has been by contractor. This enabled initial mining to commence without capital investment in equipment. Through competitive negotiations, Pegasus has been able to keep contract mining costs at levels very close to what would be experienced if Pegasus had purchased equipment initially. Contracts are negotiated yearly and are based on a unit price and haul distance for ore and waste. Haul distances have ranged from as little as 457 metres to as much as 3,050 metres. At present, Pegasus is developing a 27,000,000-tonne leach pad at the Landusky project that is adjacent to the minine area. This design feature will reduce the mining cost by 20 percent over the life of the mine. In 1987, over 5,900,000 tonnes of ore and 3,200,000 tonnes of waste will be mined at the Landusky project. Through 1986, 13,763,000 tonnes of ore have been mined at a waste-to-ore strip ratio of 0.60:l at the Zortman project, and 13,005,000 tonnes of ore at a waste-to-ore strip ratio of 0.79:l have been mined at the Landusky project. Current mining reserves are 32,769,000 tonnes of ore at a waste- to-ore strip ratio of 0.59:l. Through efficiencies of large-scale heap leaching, Pegasus has been able to lower the mining cutoff from 0.34 grams per tonne gold to 0.27 grams per tonne gold. This has reduced the mining cost per tonne of ore h percent through a reduction in strip ratio of 14 percent. Beginning in 1984, all pits were designed based on computer-generated "floating cone" pits. The geologic models were developed by Pegasus staff with a series of economic models evaluated. The resulting computer-generated pits were used as a guideline in designing the mine plans, including haul roads for final calculation of tons and grade. Input to the floating cone models consisted of mining cost, processing cost, cutoff grade (0.34 grams gold per tonne), recovery (67 percent) and gold price. Due to the gold being deposited primarily on the fractures of the syenite host rock, no crushing of ore is needed prior to leaching. This characteristic of the ore is a key in being able to profitably mine and process gold ore at an average grade of 0.69 grams of gold per tonne. Strict blasting control is also a key in success of the leaching operation. A system of splitting ore and waste in blast patterns has been devised to reduce dilution. Also, drill hole spacings are varied from 3m x 3m in breccia ore to 4m x 4m in syenite ore to 5m x 5m in waste. Drill holes

Jan 1, 1987

By Joseph L. Margin

From a stubborn start to record setting performances in little over a year, that is the story of the English Running Tunnel Boring Machines. The program to transfer technical information on these highly advanced machines from builder to user will be discussed as a vital link to this accomplishment. Some interesting features of these machines will be covered as well as a recounting of the various conditions that were encountered during these drives and how they were resolved.

Jan 1, 1991

By James A. Madonna

Information gathered while studying geological parameters that govern fine gold deposition in the a1luvial environment can be applied to the technological development and selection of fine gold recovery systems. It is recognized that substantial gold losses occur in the minus 1.5 mn (minus 12 mesh) fraction using conventional sluicing systems. Within the past two decades much attention has been given the design and efficiency of these thick bed concentrators. Studies and comparisons drew information from several foreign and domestic placer operations. These studies concentrated on: 1) the physical and chemical properties of alluvial gold 2) the parameters that control fine gold deposition 3) the geometrical form, components and general working structure of conventional sluicing systems 4) the physical properties which contribute to the overall efficiency of a sluice system 5) the comparison of three major styles of conventional sluicing systems. A dramatic improvement regarding fine gold recovery and water quality was observed when using modern multiple-channel sluicing systems in place of conventional single-channel sluicing systems.

Jan 1, 1988