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By H. Sis, D. Dahlin, S. Chander, C. Summers

Bench-scale selective-flocculation tests were conducted on samples of Florida and Western phosphate process tailings. Physical, mineralogical, and surface characteristics were determined for both types of samples. The flocculation tests investigated dispersant and flocculant types and doses, pH, and slurry percent solids, while other parameters were held constant. Where selectivity was achieved, phosphate minerals remained dispersed, whereas silicate minerals flocculated and settled. In single-stage tests, flocculants having low to medium anionic character effectively upgraded products at moderately elevated pH. Multiple-stage tests, and tests in which flocculants of lower molecular weight were used as site-blockers, gave improved results.

Jan 1, 2002

By Larry G. Stolarczyk

This report deals with information regarding a new Medium Frequency (MF) Wireless Communication System for underground mines. This new telecommunication system works on low loss electromagnetic wave propagation modes which allow it to provide quality radio communications almost anywhere in a mine. Tests show the MF system can provide improved safety and managerial control, increased productivity, better organizational team-work and reduced maintenance cost; furthermore, MF's unique design allows for easy installation at a minimum cost. This paper covers the following: 1) MF design plan, 2) Overview of mine radio communications systems, 3) Preparations needed for designing an MF system, 4) MF equipment, 5) MF installation, 6) MF design considerations, 7) MF design specifications, and 8) Recommendations dealing with MF system. Experiments in four mines are illustrated to demonstrate the success and viability of the MF system. The mines range from small (500 tons/day) to large (67,000 tons/day) capacity and represent several different mining methods. The MF Wireless Communication System represents an advancement in mining communication and the groundwork for other advanced mine systems.

Jan 1, 1984

By Ching L. Wu, Joseph Penzien

An analytical procedure is presented for evaluating the stresses in linings of bored tunnels caused by kinematic soil-lining interaction. Three cases of interaction as produced by the following conditions are treated: (1) relaxation of in situ soil stresses near a lining following its installation; (2) overburden pressure at the soil surface; and (3) free-field soil response resulting from an earthquake. Non-dimensional formulas and graphs resulting from parametric studies are presented for practical tunnel design applications. The procedure is applied separately to a steel lining and a concrete lining for a site located at the lower end of Market Street in San Francisco through which a BART (Bay Area Rapid Transit)tunnel passes.

Jan 1, 1997

By P. Mark. Hawley

Development of Barrick Gold?s Pierina Gold Mine in north-central Peru requires construction of a waste dump for disposal of non-ore grade materials stripped from the open pit to expose the ore. The waste dump site is located near the open pit in a U-shaped valley that is underlain by thin colluvial and morainal soils with locally thick peats and glaciolacustrine deposits. Bedrock underlying the site consists of variably weathered volcanics. The site is subject to moderately high seasonal rainfall and significant seismicity. The geotechnical quality of the waste rock is highly variable, ranging from low quality, degradable, soil-like materials containing appreciable quantities of silt and clay, to high quality, hard, durable, blocky waste rock. A hybrid dump design concept was developed that requires in-pit segregation of high and low quality waste, and selective placement of materials in the dump to maximize stability and enhance internal and subsurface drainage. The design includes a rock drain beneath the dump along the axis of the valley and a series of connected finger drains. Extensive peripheral diversions and stormwater control measures to inhibit infiltration of precipitation are also included. This paper discusses the unique challenges presented by the site and waste materials, the design methodology and stability analyses, and planned monitoring systems.

May 1, 2002

By J. Kulas, J. Weaver, K. Hagley

An assessment of potential groundwater movement beneath the tailing impoundment at the Red Dog Mine was performed, and has indicated a unique aquifer situation within sub-permafrost groundwater at the site. The aquifer was shown to be isolated from both vertical recharge and a real discharge, and is characterized as a virtually no-flow system. The permafrost resulted in a deep aquifer with high tidal efficiency, meaning that variable surface loads are easily transmitted to the fluid. The tidal efficiency has been characterized through analysis of water level fluctuations that respond to earth tides, barometric pressure loads, and loading from the pond.

Jan 1, 2002

By Harry Schnabel

A 6200 m² cement deep soil mixed (CDSM) wall was constructed for an addition to the Museum of Fine Arts in Boston, Massachusetts. The addition was located along the east side of the existing museum within an existing courtyard and in the area of a recently demolished structure. The basement for the new addition extended up to 9.1 m below the floor slabs of the adjacent buildings. The adjacent buildings are supported on a variety of foundations including; shallow spread footings on alluvial sand deposits, low capacity piles bearing in the alluvial sands and Boston blue clay, and caissons bearing on the alluvial sands and clay. Groundwater was less than one meter below the top of the CDSM wall. The new addition was founded on shallow foundations in the desiccated crust of the Boston Blue Clay. The CDSM wall was selected as the most economical means to control deep seated ground movements, limit movements of adjacent structures, and inhibit groundwater flow into the excavation. Braces and a continuous wale were used to support the CDSM wall where it was located adjacent to structures. Tiebacks were used where there were no structures. Other geotechnical construction at the site included: ? Jet grouting (JG) to improve the ground and provide an impervious subgrade layer at the west end of the addition, ? Concrete pier underpinning was used to support an existing structure on the west end of the site, and ? A secant pile wall using alternating drilled shafts and jet grout columns was used for earth support and a barrier to groundwater flow to allow for the installation of a storage tank at the south end of the site. Inclinometers, total station surveying, vibrating wire strain gauges on the braces and wales and load cells on the tiebacks were used to monitor performance of the excavation support system. The excavation support system performed better than required limiting lateral movements of the adjacent structures to less than 13 mm and vertical settlement to less than 8 mm. No settlements or movement were detected during the construction of the wall. Lateral movement of the CDSM wall was typically below 15 mm with the maximum movement occurring near subgrade.

Jan 1, 2011

By G. F. Kuncir

The analysis described herein evaluates the Bureau of Mines Program for Advancing Mining Technology - Oil Shale in terms of the economic benefits which may be derived for the Nation as a result of its successful research and development efforts. On the basis of postulated oil shale production scenarios, benefit-cost ratio indicators are computed for the program elements as they apply to surface, underground, and modified in situ oil shale mining systems. Eight value indicators are used to measure the Program's beneficial impact on the future oil shale industry in relation to planned research and development costs. These are: capital cost savings, operating cost savings, labor savings environmental quality maintenance cost reduction, reduction in production costs, byproduct production benefits, total production benefits, and additions to recoverable reserves. Program costs are aggregated from 1974 through 1987 and major benefits are accrued from 1982 through 2040. Both cost and benefit streams are discounted to mid-1975 present value.

Jan 1, 1977

By John Feddock

A recent increase in energy demand has resulted in the rapid growth of coal consumption in the People?s Republic of China (PRC), which is the largest coal producer and consumer in the world. Reportedly, the safety issues in Chinese coal mines have been improving, but the number of fatalities and serious injuries continues to be alarmingly high. The number of fatalities from catastrophic accidents have prompted researchers to review the Chinese mine safety situation and to look for potential solutions. Marshall Miller & Associates, Inc. (MM&A), along with various collaborators, has investigated these issues as part of its work on various projects in the PRC and has discussed the concerns with relevant Chinese officials. Preliminary investigations by MM&A of coal mine accidents during 2001?2006 in the PRC indicate that 65%-78% of the total fatalities were the result of gas explosions and roof falls in underground mines. Even though the drainage of methane has been practiced for decades, current practices do not always produce satisfactory results due to technical constraints and equipment limitations. Based on prior experience of in-seam degasification at the Daning Coal Mine located in Shanxi province, MM&A believes that in-seam directional drilling technology can be a viable solution to degas the low-permeability Chinese coal deposits. This paper 1) reviews current Chinese coal mine safety conditions, 2) analyzes the advantages/disadvantages of current degasification practices in China, and 3) presents the pre-mining degasification practices for the longwall panel at the Daning Coal Mine.

Jan 1, 2007

By John C. Niedzielski, A. Frances Ackerman

The existing US-70 Bridge over the Gila River at Bylas, Arizona is planned to be replaced due to its current poor condition. The replacement bridge is planned to be a 15-span, 1,904-foot (580 meter) long bridge, the third-longest bridge in the state highway system. Within the Gila River floodplain, granular alluvial soil is underlain by cohesive lacustrine soil; bedrock was expected due to nearby terrain but not encountered within the geotechnical exploration depth of 166.5 feet (51 meters) or less. Based on the anticipated loading conditions, design scour depths and the soil conditions, the full structural loads are carried by large diameter drilled shafts; therefore accurately determining the axial capacity of the proposed drilled shafts has important practical and safety implications. The conventional methods for axial capacity determination may be overly conservative to use for design in the site’s layered granular and hard clay soils. An Osterberg cell load test was performed to obtain detailed information on the load transfer from the drilled shaft in side friction and base resistance to allow optimization of the bridge foundation design. The fullscale field test played a significant role in the design of the project’s deep foundations, notably, by incorporating the specific subsoil properties and consequently, an exact prediction of the load-settlement behavior under loading. This paper provides the results of the geotechnical site investigations, drilled shaft load testing procedures, and shaft load distribution from the load test results. Comparisons were developed between predicted axial capacities of drilled shafts using several design methodologies and the axial capacity measured from static load testing. The load test results showed that underestimation of the axial capacity is evident using conventional methodologies. The exact prediction of the load-settlement behavior under loading combined with a site-specific design approach, resulted in a substantial reduction of foundation costs due to reduced drilled shaft dimensions.

Jan 1, 2017

This report is the 24th in a series summarizing research on coal and related investigations3 by the Bureau of Mines. The coal programs of the Bureau of Mines include a wide range of theoretical and applied studies--such as fundamental studies of coal structure and properties, the development and evaluation of new mining techniques, and work toward more effective processing and utilization of coal. The scope of these programs is indicated, in topical outline, by the table of contents. These investigations are integrated into a broad but coordinated effort to develop information on coal that will benefit the coal mining industry and the coal consumer while promoting the wise conservation and utilization of our national coal resources. Any attempt to summarize in one volume the progress in all of the program areas indicated must necessarily be limited to a brief review of developments, without detailed reporting of the data. However, while the brief discussion in each section will present only the highlights of the Bureau's work during the year, details of many of the operations or investigations described here can be found in the publications cited throughout the text. Other work, reported here for the first time, will be covered in greater detail in later publications.

Jan 1, 1962

IN the underground department of a mine, we may fairly say that "good management is based upon three elementals: first, sound engineering; second, proper coordination and efficiency of every human unit; third, economy in the purchase and consumption: of supplies.This paper is practically an analysis of the second element; which stands out prominently as the most important in the winning of successful results. The human units are divided into officers and men. The officers intermesh. One man takes responsibility where another throws it down; incessantly new conditions are arising where they may be doubtful of their powers; and always, on account of the three shifts, varying methods of work are coming into conflict. This very often results in disorganization. What is most necessary to guard against this is an esprit de corps, which would influence officers to stifle personal feelings for the general welfare of the department, To secure co-operation and loyalty of the staff, the writer recommends for the mines of the field a system of profit-sharing. Distributed on a salary basis, together with liberal holidays (not less than three weeks in each year) on full pay...

Jan 1, 1912

By Steve Dillingham

Today, a typical blaster is likely to wear many hats, including, but not limited to, supervisor, risk manager, safety coordinator, explosives engineer, communicator, as well as professional decision maker. Simply put, a blaster in the new millennium is an all encompassing blast site manager. As you know, accidents on the blast site can range from blast crew injuries to blasting incidents resulting from vibration, flyrock, misfires, etc. Not surprising, the incidents can quite often be traced back to direct preventable human action on the blast site. They can, however, frequently be avoided, if responsibly identified early and managed properly by an efficient blast site manager. Your company cannot afford to simply employ blasters; good blast site managers are necessary to produce the safest results possible.

Jan 1, 2001

By T. J. Serenko

The epithermal deposit is hosted by Tertiary volcanic rocks that lie between mid-Miocene normal faults of the Northern Nevada Rift. Petrographic, laser-ablation and metallurgical observations suggested that the gold occurs in two principal forms: native (and electrum) and disseminated in arsenopyrite. It was proposed that gold is distributed between two parageneses with distinct mineralogical associations. Detailed downhole geochemical study supported the observations. Concentrations of Au, Ag, As, Sb and Se were determined from drill core and reverse-circulation cutting composites and contoured on cross-sections. Gold was indeed shown to have a bimodal distribution with the two parts separated spatially and perhaps temporally, implying that two separate genetic processes acted to concentrate gold at Mule Canyon

Aug 1, 1995

By S. Bellec, P. Champagne, J. Châteauneuf, A. Berton, S. Fortier

"The start-up of new plants, extending from the commissioning of equipment to the production ramp-up, is a critical period where the processing circuit operation must be done in a structured and well controlled way to enable the gradual, safe and rapid achievement of production targets. The magnitude of the many risks associated with this pivotal period is accentuated in the actual context of low commodity prices. However, the implementation of a method that analyzes risks associated with a start-up, their probability of occurrence and their impacts leads to the identification of a series of preventive actions that can be applied in order to reduce potential negative impacts.Soutex has been involved in numerous start-ups over the last few years and has developed a structured methodology to assess this crucial period, maximize the pre-start-up preparation, ensure a smoother and safer ramp-up period and minimize the time needed before reaching commercial production.This paper describes a method to identify preventive actions to apply in order to reduce risks related to a plant start-up. Then, the various steps of the method are demonstrated using the industrial case study of the Canadian Malartic gold plant situated in Abitibi, Québec. The specific preventive actions, during start-up, the organisational measures and the ramp-up plan are detailed as they were effectively achieved. Finally, the post start-up actions are presented as well as some key results illustrating the achievement of their prior defined objectives.IntroductionPlanning a new plant or new circuit start-up in a mine installation involves various risks, both at the economical and safety levels. Unprepared staff and equipment can lead to safety issues that could threaten plant staff as well as the environment. Moreover, a poorly prepared start-up could often lead to equipment break-down, production stoppages and delays, leading to important economic impacts, delaying commercial production and therefore affecting directly the profitability of mining projects.It is common in the industry to have structured commissioning procedures for major equipment taken separately. Technical personnel from the equipment manufacturing company would usually come on site in order to perform the pre-operation verification, dry runs and the first hours of operations. This kind of assistance is usually focussed on one piece of equipment and neglects the interactions between the various equipment of the production chain. The commissioning phase is usually maintenance oriented and the information given by the manufacturing representative seldomly flows through the operation staff (in the case of this paper, the denomination “staff” refers to both managing and operating employees). The global process is usually not taken into consideration by the technical personnel sent on-site by the manufacturer during the commissioning phase. Many papers can be found describing the commissioning of new equipment focussing on the technology (Côté and Adante (2009), Wells et al (2007)) but without dealing with its integration process in the complete production chain."

Jan 1, 2016

By K. Lang

A case study is provided that highlights the successful use of high efficiency electrical submersible pumps (ESPs) adapted from the oil and gas industry for a large scale, open pit mine dewatering operation. In this case, the mine is Goldcorp?s Peñasquito Mine, Peñasco and Chile Colorado open pit development areas in Zacatecas, Mexico. At the time of publication (July 2012), there were 18 vertical bedrock dewatering wells producing an average flow rate of 350 liters per second (lps) from the Peñasco and Chile Colorado development areas. Average pumping rate per well was 18 lps, with a maximum of 44 lps. The depth of wells varies from 330 m to 500m, and includes both in-pit and perimeter (ex-pit) pumping centers. A network of 50 piezometers was used to monitor the response of groundwater levels to pumping. Since dewatering operations were initiated in 2007, groundwater elevations decreased overall, from approximately 1950 m above sea level (masl) to around 1625 masl, for a total of 340 m of drawdown. The pit floor elevation was approximately 1655 masl. All of the producing wells were constructed with 16-inch boreholes, completed with 10-inch diameter blank casing and louvered screen sections and equipped with ESPs. The application of ESPs has proven to be highly effective in the case of Peñasquito?s dewatering operations. Noted advantages include the following: ? Small diameter pump allows use of smaller diameter boreholes (16 inches) and casing / screens (10 inches) reducing well drilling and construction costs ? Greater application range for flow rate and total dynamic head ? Variable speed drive systems for greater energy efficiency and flow rate optimization ? Integration of downhole instrumentation into the motor and pump assembly The advantages and benefits of using high efficiency ESPs revolutionized the dewatering program at Peñasquito open pit mine as evidenced by the number of deep vertical well installations and high dewatering flow rates and total dynamic head requirements.

Feb 27, 2013

By Charles L. Allie

Since Reserve Mining Co. began commercial operations at Silver Bay, MN, some 25 years ago, major improvements in taconite processing technology have become available. In addition, significant new government standards have been imposed on industrial operations. By implementing a $370-million modernization program, Reserve was able to accomplish two major company objectives: the quality of concentrates produced from the Peter Mitchell mine has improved, and the operation meets both present and foreseeable environmental standards. Process modifications at Reserve were designed to: •Reduce the pellet silica content from 9% to 5%; •Increase the pellet iron content from 62.5% to 65.8%; •Implement a tailings disposal system utilizing "best available technology" water quality controls; and •Reduce air emissions by installing "best available technology" air emission controls. By adding dry cobbing, fine screening, and flotation to the concentrating process, pellet silica content has been reduced; the process reclaims and reuses all process waters; all tailings are stored in a zero discharge tailings basin; and all air emission standards are being met. Initial Beneficiation at Silver Bay Reserve's Peter Mitchell mine at Babbitt, MN, is on the eastern end of the Biwabik iron formation. The open-pit mine is approximately 16 km long, 0.8 km wide, and presently has a maximum depth of about 50 m. Principal constituents of the ore body are magnetite, quartz, and iron-magnesium silicates. The company's large commercial plant began operating at Silver Bay, 75 rail km from the mine, in 1955. Facilities have historically had the capacity to process 31.5 Mt/a of taconite, containing an average 24% magnetic iron, into 11 Mt/a of iron ore pellets. Reserve's initial beneficiation process-which existed up to early 1979-consisted of two crushing stages at the Babbitt mine site, two additional crushing and screening stages at Silver Bay, grinding in a conventional rod-ball¬regrind mill circuit, size classification with cyclones, and concentration with magnetic and hydraulic separators. Concentrate produced by that circuit assayed 65% iron and 8.5% silica, with a screen analysis of 94% -44 µm, and a surface area of 9300 cm2/cm3. Pellets produced from this concentrate assayed 62.5% iron and 9% silica (dry basis). Construction began in 1977 to modify Reserve's operation. Process modifications were designed from pilot scale operations that had been operated and researched by Reserve for more than 10 years. There were two design restraints imposed on the process: economic constraints that Reserve continue to use much of the existing processes and structures in the new operation; and a substantial number of government-imposed permit constraints. In effect, the tailings process was designed first and then a concentrating process was developed that would "fit" the tailings disposal system. Operation of the modified process began in June 1980. Crushing Remains Unchanged No changes in process flow were made at either the Babbitt mine and crushing plant or at the Silver Bay fine crusher. Gyratory crushers reduce run-of-mine taconite to -90 mm-diam at the mine. Taconite is then transported to Silver Bay by intra-plant railroad. There are 10 fine crushing lines. Each consists of a double deck screen, followed by a heavy duty short head crusher, a second double deck screen, and second short head crusher. All screen undersize material bypasses the crushing lines, resulting in an open circuit crushing process. Fine crusher product is approximately 98% - 20 mm, 80% -12 mm, and 50% -10 mm in diameter. Each fine crusher line processes about 400 t/h of crude taconite. Cobbing Provides Aggregate for Tailings Dams The first major process change was the addition of dry cobbing, a dry magnetic separation step between the fine crusher and concentrator. Dry cobbing serves two major purposes in the new process. Its principal function is to provide large volumes of dry coarse aggregate for use in construction of tailings dams. This process rejects about 20% of the fine crusher product as tailings with a size analysis of 98% -20 mm and 50% - 10 mm. These tailings are free draining and have high frictional shear strengths-two key requirements for dam building aggregates. Fine crusher product is conveyed to a new dry cobbing building. Here crushed ore is discharged into one of two 30-minute capacity surge bins. Crushed ore is withdrawn by 12 constant speed conveyor belts; each discharges 500 t of crushed taconite into a dry cobbing machine. Each machine consists of a 3-m-long riffle splitter and two vari-

Jan 12, 1980

By Don M. Coulter

"INTRODUCTION The Lookout Mountain coal deposits were examined by J.L. Stratton, an engineer of the Bureau of Mines in April and May 1943. The area investigated includes that part of southern Lookout Mountain in townships 4 to 8, south, ranges-9 to 11 east, and contains approximately 140 square miles in DeKalb and Cherokee Counties in northeastern Alabama (fig. 1.)Six coal seams having a minable thickness of 18 or more inches are represented in the area. The third seam, known locally as the Hill seam, has been correlated with the Upper Cliff No.1 seam and is referred to as such throughout this report. The preliminary investigation indicated that the Upper Cliff No. 1 seam is a low-volatile, high-grade coking coal. The work done on this project was confined principally to determining the amount and grade of coal in this seam.The only existing maps of mines in the area were one of the Lookout Fuel Co. at Lahusage, Ala. (fig. 2), and one of the Lookout Mountain Iron Co. at Battelle, Ala. (fig. 3), Consequently, to gain some knowledge of the grade and tonnage mined, surveys of the other mines were necessary. Many of them were caved, and many were filled with water, necessitating considerable preliminary work."

Feb 1, 1947

By Marco Fellin, Van E. Komurka

Significant cost and construction benefits were obtained from performing a bi-directional static load test prior to construction on the Russell Street Bridge Replacement project in Missoula, Montana. The project utilized 24 drilled shafts to support two three-span bridges across the Clark Fork River. A bi-directional static load test (“BDSLT”) was performed on a large-diameter production shaft to demonstrate construction methods and confirm design assumptions. Subsurface conditions consisted of gravel with sand to a depth of 20 feet (6.1 m), underlain by gravel with sand, silt, cobbles, and occasional boulders. The test shaft had a nominal diameter of 5.9 feet (1.8 m), and an embedded length of 75.5 feet (23.0 m). The geotechnical engineer of record and the BDSLT test engineer collaborated to optimize the BDSLT jack assembly location within the test shaft, determine appropriate instrumentation locations, and plan the test protocol. The maximum applied test load was 10,707 kips (47.6 kN). Significant benefits were obtained from performing the BDSLT test, including 1) reducing each production shaft’s length by using a higher LRFD resistance factor allowed by having performed the testing, 2) using test-determined unit shaft resistances to evaluate and accept two production shafts that may have otherwise required remediation, and 3) providing the Montana Department of Transportation (and other designers) with increased presumptive unit resistance values in the gravel/cobble/boulder deposits. PROJECT DESCRIPTION The project was constructed in Missoula, Montana for the Montana Department of Transportation (“MDT”). The original bridge was approximately 60 years old, and consisted of a two-lane, 420-foot-long (128-m), four-span, riveted steel plate girder design spanning the Clark Fork River. The bridge was due for replacement owing to its deteriorated state, and the need for increased traffic volume capability afforded by a four-lane structure. HDR was the structural engineer. The preferred bridge alternate was a 459-foot- long (140-m), three-span, welded steel plate girder design. The new bridge was designed to meet current standards in accordance with MDT bridge design and AASHTO LRFD criteria. The new bridge was constructed in phases to keep traffic open during construction.

Jan 1, 2019

By S. J. Schatzel, J. D. Addis, V. Gangrade, L. L. Chasko, C. A. Hollerich

A ventilation study using tracer gas was conducted at a western US coal mine. The objective of the study was to evaluate the movement of longwall face air exchanges between the face and worked-out area and to document the presence or absence of face airflow pathways between these locations. The mine operator uses a bleederless longwall ventilation system with a back return and a blowing mine ventilation system. The study was conducted on an active panel and included both underground and surface monitoring sites. The study used sulfur hexafluoride (SF6) released as a slug on the longwall face and in the front of the gob inby the face. The velocity of the tracer gas movement in the gob was 0.019 m/s (3.7 fpm). The rate of movement for the overall tracer gas slug averaged about 0.0091 m/s (1.8 fpm). A separate tracer gas test initiated with the release of SF6 into the legs of the first shield showed the existence of more than one pathway of face air in the general direction from the headgate towards the tailgate corner. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob. A more detailed characterization of longwall system air and gas movement allows a mine to better assess its ventilation design for controlling gas on the face and in the gob.

Remediation of Mine Seepage at Batu Hijau

Sep 13, 2010