Search Documents

By C. R. Fahnestock

One of the major problems for us in the earthmoving industry is the analysis of materials under the ground surface. Countless engineering and construction jobs would be simplified if there were an inexpensive and fast way to obtain information on problems such as: Depth and solidith of bedrock? Nature of the materials between bedrock and the surface? Adequate foundation for bridges and drainage structures? Location of supplies of materials to be used in construction? Investigation of tunnel sites? Characteristics of swampy areas and investigation of existing and potential slide areas? These questions are of paramount interest to highway contractors as they bid jobs and plan, equipment spreads to handle them at optimum efficiency. Such information also is invaluable to engineers in the design and construction of bridges, buildings, railroads, canals, and tunnels.

Jan 1, 1961

By H. Maleki

Roof falls continue to affect productivity and safety in U.S. coal mines in spite of significant increases in support utilization in recent decades. To minimize roof stability problems while controlling support effectiveness, the U.S. Bureau of Mines is conducting research on support and ground monitoring techniques. Practical implementation of this research is presented in this paper. Instruments to monitor rock mass deformation, support loads, and microseismic emissions have traditionally been used to assess roof stability. Controlled-source seismic surveys are being used as well. In this paper, measurement techniques are reviewed, and the effectiveness of deformation measurements is demonstrated. This is achieved by an analysis of deformation history from four case studies in room-and-pillar retreat mines. In spite of differences in geologic, geometric, and support conditions in these mines, roof behavior is shown to have been similar prior to failure. The rate of roof movement is suggested as a reliable indicator of roof stability.

Jan 1, 1993

By Musa D. Manzi, Raymond J. Durrheim, Richard T. Masethe

An investigation into the source mechanism of mining-induced seismic activity plays a vital role in understanding the various modes of failure observed in the underground deep-level South African mining environment. The seismic events data for this study was captured by the mine-wide seismic system operating at Kloof Gold Mine. This system comprises 40 4.5 Hz tri-axial geophones sampling at 6 kHz installed at locations that surround the stopes mining the Ventersdorp Contact Reef (VCR), Main Reef (MR) and Kloof Reef (KR). A set of 103,753 mining-related seismic events (-3.0≤ ML ≤2.7) that occurred during 2017 and 2018 was selected for this study. The mining depth of these seismic events ranges from 1600 – 4200 m; most located close to stopes mining the VCR ore body. The main criteria used to select a subset of events for detailed analysis were the number of stations that recorded the seismic event and the azimuthal distribution of the sensors.

Apr 26, 2022

By Bruce A. Kuyper

Routine core drilling at the Cove deposit failed to confirm gold-silver grades and length of intercepts observed in reverse circulation drilling. A drilling program was designed to ascertain whether the disparity was due to problems with reverse circulation drilling techniques, core drilling techniques, or the erratic nature of the gold-silver mineralization. Special sampling devices and core drilling methods were employed. Data obtained from core-reverse circulation twins showed that down-hole contamination during reverse circulation drilling accounted for much of the variation between reverse circulation and core drill results. Down-hole contamination occurred as a result of high ground-water inflows eroding friable vein material from hole walls.

Jan 1, 1991

By S. Šolar

The countries of Southeast Europe are rich in aggregates, but neither management nor supply are coordinated within or across this area. There are open issues in SEE on the local scale as well as on regional/national and transnational scales that will need to be addressed in order to meet societal expectations related not only to the security of aggregates supply for economy, but also those linked to environmental concerns and social issues. The Sustainable Aggregates Resource Management project (SARMa), an EU Southeast Europe (SEE) activity, has as its objectives the development of common approaches to sustainable aggregate resource management (SARM) and sustainable supply mix (SSM) planning in SEE. In this paper we describe the SARMa project structure and report results for Work Package 3 activities pertaining to best practices for environmental management, the reduction of illegal quarrying, and the promotion of recycling of quarry wastes, construction and demolition wastes and other materials.

Jan 1, 2011

By Mostafa Benzaazoua, Mariam El Adnani, My Ahmed Boumehdi, Rachid Hakkou, Salah Ouhamdouch, Abdelmalek Goumih

This study focuses on the environmental characterization and assessment of long-term neutral mine drainage (CND) potential from waste rock piles at the abandoned Erdouz mine in Morocco. The study involved metallographic analysis, static tests, and column tests. Results indicate that the waste rock is not an acid mine drainage generator but produces CND, mainly with sulfates exceeding Moroccan standards. The waste rock is relatively stable and could be reused after pretreatment.

Jan 25, 2022

By W. C. Hirt

Deposits of ferromanganese crust containing cobalt and nickel occur on the seafloor in the Pacific Ocean near the Hawaiian Islands and Johnston Atoll. This paper describes developmental flotation metallurgy to separate crust from its associated substrate gangue. Important variables in ferromanganese crust flotation include reagent type, aeration rate, conditioning time and agitation intensity, pH, temperature, water type, and feed size distribution. Flotation in seawater of minus 600 ~m (-28 mesh) material assaying 6.2% Mn, 0.2% Co, and 0.13% Ni with diesel fuel-crude tall oil-sulfonate collectors produces concentrates assaying 15% Mn, 0.6% Co, and 0.3% Ni with recoveries of 89-95% while removing 62% of the feed weight.

Jan 1, 1990

By J. Gauntt

Calcium carbonate is one of the most widely used industrial minerals in applications like cement, lime, agriculture, power plant fluegas desulfurization (FGD) and construction aggregates. Most applications are generally high-volume and low value ($9/t or $10/st) or less free-on-board (f.o.b.) mine site) uses of this material. Specialty uses of ground calcium carbonate (GCC) are typically referred to as ?performance mineral? or ?extender and ?ller? applications. Primary specialty markets for GCC include paper and plastics as well as a number of construction applications including joint compounds, carpet backing, paint, and adhesives, caulks and sealants (ACS). Other important specialty applications for GCC include rubber, food and personal care products. A new and growing application for GCC is in nonwoven fabrics, where this mineral replaces a small percentage of the polymer. Typical specialty applications for GCC are color sensitive and require extremely white/bright materials. Although deposits of limestone are located in most states, high brightness resources are relatively rare and controlled by a limited group of suppliers.

By D. L. Boreck

With increasing land development, the potential of fatalities from abandoned mine shafts increases. To minimize potential liability, shaft closure should be a critical part of mined land reclamation. The Bureau of Mines is conducting research into using lightweight foam concrete in sealing abandoned coal mine shafts. A demonstration seal consisted of a 3m thick foam concrete plug to provide lateral stability inside the shaft. A high density concrete cap provided load-bearing capacity for a 100-year service life. The USBM has also completed research into changes in foam concrete when it is pumped or dropped from different heights. It is concluded from the research that foam concrete can undergo significant air loss with pumping or dropping. This foretells significant changes in the characteristics of the concrete as well as an increase in the weight and cost of the in-place concrete seal. When using foam concrete to seal abandoned mine shafts, care must be taken to minimize air loss during placement.

Jan 1, 1994

By W. Collingwood, K. V. Raj, S. Bandopadhyay

In the mining industry, computational fluid dynamics (CFD) modeling is used extensively to simulate air flow in underground mines. CFD modeling of pollutant transport in openpit mines is relatively new. Modeling the actual pit geometry of an openpit mine and the open domain is complex. The complexity is primarily due to the faceted geometry of an openpit mine with its numerous associated sharp features. Important issues that are not considered carefully at the geometry level are generally propagated to the subsequent processes. Several challenges and pitfalls are encountered in modeling pollutant transport in openpit mines. These challenges and pitfalls are related to the geometry, meshing, boundary conditions and turbulence modeling parameterization. An appropriate mesh selection is critical. A detailed discussion of the meshing of the domain of an openpit mine is presented in this paper. The selection of an appropriate turbulence model, such as kappa-epsilon (κ-ε), large eddy simulation (LES), Reynolds stress model (RSM), etc., to obtain the best possible solution is equally significant. This paper discusses the various challenges in modeling the pollutant transport process in an openpit and some of the approaches adopted to address these challenges.

Jan 1, 2013

By J. E. Murphy, L. A. Walters, F. H. Nehl, G. B. Atkinson

The US Bureau of Mines investigated the selective electrowinning of Ag and Au from cyanide solutions contaminated with Cu with the goal of decreasing the amount of Cu codeposited. Decreasing Cu codeposited will reduce refinery costs. Direct current was applied to the cell in pulsed and square wave voltages at 0.7 A h/150 mL of solution. Times tested for each cycle ranged from 1 to 10,000 msecs. Graphite, lead and stainless steel were evaluated as electrode materials. Square wave electrowinning at 70°C (158° F) gave the best separation of Ag and Au from Cu. Applying 2.5 V during the duty cycle, 0.0 V the rest of the period, a duty cycle of 10% to 30%, and a period of 100 msecs to 1000 msecs gave the following results: Ag concentrations decreased from 34 µg/mL to 0.1 µg/mL. Au concentrations decreased from 54 µg/mL to 0.2 µg/mL and Cu concentrations remained almost constant at 560 µg/mL.

Jan 1, 1995

By Rob Thomas

It is generally agreed that standing support should be installed in roadways that will for various reasons, be holed through with a longwall. Considering the magnitude of the associated abutment loading in conjunction with the need to ensure that the material used is cuttable, some form of cementitious support is often used.

By E. E. Caba

Copper smelter flue dusts containing arsenic are hazardous materials requiring environmentally accept-able disposal, preferably with re-source recovery under the RCRA and CRCLA regulations. However, the known resource recovery processes entail capital and operating costs greater than can be justified by the revenue of the recovered metal. Consequently, the smelting industry is tending to forego resource recovery in favor of encapsulation and storage in a certified class I hazardous waste site, or in a dedicated facility located at the source Superfund site. Order of magnitude costs for this option with portland cement encapsulation are estimated at $100 per ton, not including transportation. Industrial adoption of a new resource recovery process re-quires that its cost, including capital amortization, exceed the cost of encapsulation and storage only by the amount of the offsetting revenue from sale of metal. The lime-roast/ammoniacal leaching process is expected to meet this goal.

Jan 1, 1992

By S. A. McGhee

ASARCO Incorporated embarked on a modernization and expansion program to improve overall operating efficiencies and to more effectively develop the large mineral reserve at the Ray Complex Open-Pit Mining operation located near Kearny, Arizona. Major elements of this Ray Modernization and Concentrator Expansion Project included engineering and construction of a 54,400 MTPD (60,000 STPD) In-Pit Crusher and Overland Conveying System. and a 24,200 MTPD (30,000 STPD) Copper SAG Concentrator and Tailings Disposal System. Detailed engineering, procurement, and construction management were initiated in November 1989 under contract with Bechtel Corporation. Field construction commenced in May 1990 leading to mechanical completion and start-up during February 1992.

Jan 1, 1993

By J. A. Marts

Reservoir properties including porosity and permeability distributions in longwall coal mine gobs have direct application to modeling the flow patterns and gas distributions in the gobs. Proper assessment of these distributions is required to assess gob gas hazards such as spontaneous combustion and explosive methane mixtures and to optimize gob gas venthole operation and nitrogen inertization. Determining the reservoir properties is difficult given that the gob is inaccessible and direct measurements cannot be easily taken. Several techniques have been used by previous researchers and will be discussed. This paper will present the methodology used to model the gob compaction by simulating the sequential extraction of coal. Two Western US coal mines were used for case studies. By determining volumetric strain, the porosity and permeability distributions in the gob can be calculated. The geo-mechanical model predicts an axisymmetric volumetric strain distribution with a steeper slope near the start-up room and a shallower slope near the active face.

Feb 23, 2014

By Robert L. (Original by) Llewellyn

Many of the problems that occur in the preparation plant originate from practices in the mine. Impurities in raw coal can be in the seam itself or from extraneous material taken in mining from the roof or bottom. In the case of underground mines, the choice of mining equipment will affect the size consist and the amount of extraneous material included with the coal. Also, governmental regulations concerning the degree of rock dusting, gobbing underground, and cleanup have increased the dirt in raw coal. Sulfur dioxide emission standards, on the other hand, are pressuring the coal industry to clean coal more thoroughly. Coal supplied for coking purposes is nearly all upgraded by washing, while for the largest market, electric power generation, a high proportion is shipped as a raw product with processing, in whole or in part, only necessary when excess impurities are mined with the coal. This chapter will deal primarily with plants that process or wash coal to some extent (Fig. 1) and only incidentally with mines shipping raw run-of-mine coal crushed to a top size of, usually, 51 to 102 mm (2 to 4 in.), with little, if any, other treatment.

Jan 1, 1981

By Mohamed Gamal, Bill Zietlow

"In oil fields that have been depleted with conventional surface oil wells but still contain significant reserves, an extraction alternative that has been constructed recently consists of a drilling gallery below the oil-bearing formation at the bottom of a 1,200-ft deep shaft where upward sloping wells are being drilled to allow oil collection by gravity. The gallery is 92-ft diameter with a flat ceiling supported by rock bolts and shotcrete structurally connected to the shaft liner, which doubles as a large tension support element. A special excavation sequence was implemented for the gallery to maximize arching in the stress above the large diameter gallery. The gallery was located in competent sandstone, constructed with sequential excavation methods, and designed with a 3D finite element model. Special consideration was given to optimizing the gallery location to take advantage of the geology for construction and support while giving good positioning to the well drilling equipment. BACKGROUND Brierley Associates was contracted to provide both design and construction management services for an approximately 1,165-ft deep, 18-ft excavated diameter vertical shaft that opens to a 92-ft diameter flat roof gallery. The geotechnical data for the site was based on information available from literature and from data obtained during core drilling and from in-situ testing in a 1250-ft deep borehole. Wire line coring was conducted using a HQ, 10-ft long core barrel with a mud-rotary drilling method through sedimentary bedrock. The geometry of the shaft and the bottom gallery is shown in Figure 1(a). GEOLOGIC SETTING AND STRUCTURAL GEOLOGY The stratigraphy at the site includes a series of interbedded marine limestone, shale, claystone, siltstone, sandstone, and chert units. Limestone and shale are the predominant lithologies in the upper approximately 675 ft, while the lower portion contains five distinct sandstone units and more abundant shale, claystone, siltstone, and coal than the upper zone. A cherty sandstone at a depth of 1,130 below ground surface (bgs) was encountered. At a depth of about 1,000 ft to 1,116 ft bgs, a non-marine sandstone unit was encountered. This sandstone is the hydrocarbon bearing layer. Joints and fractures observed in the limestone had dips ranging from 0 to 90 deg. from horizontal with joint and fracture surfaces that ranged from planar to irregular and smooth to rough. Several, near vertical shear planes with slickensides were observed with surfaces that were generally smooth and planar. RQD values for the limestone ranged from 0 to 100 percent but in general were good to excellent."

Jan 1, 2016

By E. Yan, M. Mankosa, G. Luttrell

"During the past decade, column flotation cells have become widely accepted for upgrading ultrafine sulfide ores. However, the use of columns has been widely relegated to cleaner circuits due to their comparatively high selectivity derived from the use of wash water dispersed over a deep froth. High tonnage rates and low feed grades make using column technology in roughing and scavenger stages challenging due to the resulting size of the needed equipment. To specifically address this challenge, a new high-intensity flotation system known as the StackCell™ was developed. This technology makes use of a novel pre-aeration method coupled with froth washing to simultaneously provide improved flotation kinetics and selectivity. The novel aeration system provides efficient bubble-particle contacting thereby shortening the residence time required for particle collection. This article reviews the technical design features of this new flotation technology and presents recent data from in-plant pilot testing in a copper-sulfide application. INTRODUCTION Column flotation cells have become very popular in the minerals processing industry for cleaner circuits due to their ability to produce a high-grade froth concentrate via the use of froth washing (Luttrell et al., 1999; Kohmuench et al., 2004). The use of wash water minimizes the nonselective recovery of ultrafine impurities that are normally entrained into the froth product from conventional flotation machines. On the other hand, the unique design of a column cell typically requires a large tank volume. Column cells must be tall to ensure that the pulp residence time is long enough to offset their inherently slow flotation kinetics and to minimize internal mixing that is detrimental to overall cell performance. The tall design minimizes the total floor space required for the column installation, but substantially increases the foundation load. The large size of the column tank can also create issues during fabrication, transportation and installation. To address these concerns, the engineering team at Eriez Manufacturing developed a next-generation flotation technology called the StackCell?. This high-intensity flotation machine was designed to provide column-like separation performance within a very compact volumetric footprint. This article describes the key working features of this new technology and provides data from recent pilot-scale tests conducted in gold and copper-sulfide applications"

Jan 1, 2016

Powder River Basin (PRB) mines were originally built to serve power plants designed specifically for their coal. Sulfur was the major concern, with BTU and sodium limiting the market for some. The Clean Air Act has extended the PRB market into plants converting from other coals. These new customers are more sensitive to constituents affecting boiler and precipitator performance. At the same time, the prospect of deregulation is forcing power companies to control cost more stringently than ever. Jacobs Ranch Mine has responded to the changing marketplace with an expanded coal quality and customer service program.

Jan 1, 1998

By V. B. Achanti

This paper deals with the effect of various bit geometric parameters on failure characteristics of rock material. Improvement of rock cutting efficiency of continuous mining machines has been an interesting research topic for the last few decades. In the current study, an automated rotary rock cutting simulator, duplicating a continuous miner, was utilized to study these parameters in the laboratory. Improvement of bit performance in terms of its life, cutting efficiency, dust production and energy consumption has drawn wide spread attention over the years. Research shows that optimizing bit parameters can result in efficient fragmentation of rock. Indiana limestone rock material was utilized in this study while bit tip angle, bit tip size, bit spacing, depth of cut and cutting velocity of rotary drum were varied to investigate the failure characteristics. The cutting pressure, penetrating pressure and the depth of cut were monitored on the simulator during the cutting process. Air borne dust and settled dust were measured for each experiment. Then, the specific airborne dust and specific energy were determined for the each type of bit. Triaxial tests were carried out to correlate the failure angle of the rock in static case to dynamic cutting process failure. The physical and mechanical properties of the rock were also determined in order to assess their influence on the wear characteristics of each bit.

Jan 1, 1998