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By Robert Stefanko

13.1-SUBSIDENCE AND GROUND MOVEMENT ROBERT STEFANKO 13.1.1-SUBSIDENCE AND FAILURE This treatment of subsidence and ground movement will be confined to subsidence control for limiting surface damage by assessing the significant parameters affecting ground movements during mining to optimize mining techniques. The material will be equally applicable to evaporite mining as well as coal but will not deal with block caving or similar systems where failure is deliberately induced and surface protection is not necessary or provided. When an underground opening is established, the original equilibrium is disturbed with resultant stress concentrations. While many factors are involved in opening stability, the span (W) undoubtedly is one of the most important factors in failure. Assuming it is relatively small, the overlying rock strata can bridge across the opening and little if any movement or convergence of top and bottom will occur. However, as the span increases, a point is reached where the stress in the overlying rock strata exceeds some strength value of the rock, and the top breaks. If the opening span is limited to some subcritical value (-We) and/or is at great depth (D), a pseudo-arch will form, achielring stability before rupture occurs to the surface. The boundary of this arch is thought to approximate an ellipse in form with the major axis vertical and equal to four times W, although there has been little field research to substantiate this theory. However, if the width of this opening is increased at this horizon to some critical value (W,) or the same span is created in a shallower seam, the overlying strata ill progressively rupture to the surface and the characteristic subsidence trough is formed (Fig. 13-1) The area of the surface affected is much greater than the area of the seam extracted, depending on the "angle of draw" (a), which is the angle between a vertical line from the edge of the opening and another line extended to a point at which subsidence tails out to zero. This angle has been found to be about 35° in Europe but is rather academic, being a function of instrument precision in detecting subsidence. Since the subsidence effect is so small at any point beyond n 25° angle, this latter may be considered the practical limit of subsidence. Further- more, indications are that the angle of draw varies with depth and nature of the strata.' In a field study over a 1,000-ft-deep potash mine in New Mexico, the maximum angle of draw was found to be 51.5°.2 So far, only a single opening has been considered. However, the width of the excavation applies to any complex mining system of entries, rooms and longwalls as long as the seam has been fully extracted and the width represents the distance from one solid rib to another. It will be noted that the amount of vertical displacement varies from point to point on the surface (s), but the maximum subsidence for a given trough occurs at the center (S). This latter value may not he equal to the maximum possible subsidence (Sm) which occurs only if a critical or super- critical (+W,) width has been exceeded (Fig. 13-1). Substantial surface damage can result when subsidence occurs. Factors affecting the amount and type of ground movement are: thickness and properties of the seam, angle of draw, width of excavation, depth and type of overburden, inclinations of strata and surface, and the amount of support left in the gob. In Europe,

Jan 1, 1973

By J. G. Groppo

A series of performance studies have been conducted using counter-current column flotation to recover a marketable clean coal product from existing preparation plant fine waste streams. The test work was conducted at several preparation plant sites in Kentucky and Virginia and utilized a 0.15m (6 in.) I.D. column that was 5.79m (19 ft.) high. The refuse streams tested included both thickener feed and classifying cyclone overflow with a typical size distribution of 100 mesh X O. The percent solids of the column flotation feed varied from 1.5 to 15% while the ash content ranged from 30-60%. The concentrates produced contained 2-10% ash with BTU recoveries of nearly 90% using 0.12-1.25 kg/ton (0.25-2.5 lbs/ton) fuel oil and 0.12 kg/ton (0.25 lb/ton) MIBC. These results were consistent with or better than results obtained in preliminary laboratory scale column flotation evaluation. Test results from 7 different seams are discussed as well as scale-up relationships utilized to design a full scale installation presently in operation.

Jan 1, 1990

By C. A. Rowland

The rising costs for and the possibility for limited availability of electrical energy are emphasizing the continual conflict faced in the selection of comminution circuits used in preparing ores for concentration, namely; capital cost vs. operating cost. Frequently, the circuit with the lowest capital cost is not the most efficient in the use of electrical power and wear resistant materials. The simplest circuit in terms of flow, pieces of equipment and capital cost is the single stage autogenous or partial autogenous circuit used to grinding primary crusher discharge or run of mine ore to the desired product size. (Fig. 1) From this circuit, complexity increases to multi-stage crushing circuits preparing feed for multi-stage grinding circuits. Fig. 2 showing a three stage rod mill ball mill arrangement is an example of a complex grinding circuit. Stage concentration further complicates the flow. Multi-stage circuits being the most expensive to install, often give the greatest operating flexibility and offer the best possibilities for the most efficient use of available power and wear resistant materials. Within available grinding circuits, other comparisons such as high speed vs. low speed mills, grate discharge vs. overflow discharge, metal liners vs. rubber liners, high charge vs. low charge, etc. all add to the conflict

Jan 1, 1977

By K. Saberyan

A technique is described for the solvent extraction of zirconium. In this method, zirconium has been extracted quantitatively from 0.005 M sodium salicylate solution at pH 2.5 - 3 using 0.01 M triphenylphosphine oxide dissolved in toluene as an extractant. Zirconium has also been recovered quantitatively from 0.2 M potassium thiocyanate solution, but extractions in nitric and hydrochloric acids (as media) were negligible. The resulting extracted metal ion has been stripped with sulfuric acid (0.5 M) and determined with inductively coupled plasma atomic emission spectrometry. This method has been applied successfully to achieve 95% recovery of zirconium from zircon concentrate.

Jan 1, 2010

An upgrade to Vale?s existing Clarabelle dual-pinion, semiautogenous (SAG) mill was completed by the power and automation technology company, ABB. The mill is used to reduce the size of the ore at the company?s nickel and copper mines in the Sudbury area. The project was completed on time and on budget with an excellent safety record. Located in Ontario about 400 km (250 miles) north of Toronto, Vale?s Sudbury operations are primarily underground nickel sulfide mines, with integrated mining, milling, smelting and refining operations. One of the characteristics of Clarabelle Mill is to accept nickel-copper ore from various sources and companies and to produce a nickel-copper concentrate and copper concentrate for further processing. The size of the ore is further reduced in SAG mills, rod mills and ball mills, where all milling is done wet.

Mar 1, 2014

"A fire design innovation of the concrete lining of the Ohio River Bridges East End Crossing Tunnel has been developed. As a result from a fire suppression and tunnel ventilation system, the project design Heat Release Rate (HRR) was able to be constrained from 300 MW to about 50 MW. With this reduced HRR, concrete lining without passive fire protection may be acceptable, if the tunnel concrete lining will not result in explosive spalling during the designed fire event. Concrete explosive spalling test was proposed to verify this assumption. Since no standard concrete fire explosive spalling testing procedure exists, a project specific testing procedure was developed and fire tests conducted. From fire test results, it is concluded that the proposed tunnel concrete lining, in conjunction with the proposed fire suppressing and ventilation system, will not experience explosive spalling and does not require a passive fire protection system. INTRODUCTION The Ohio River Bridge East End Crossing Tunnel is part of a Public Private Partnership project, which connects transportation network between Louisville, Kentucky and southern Indiana. Located in Louisville, Kentucky, the twin-tube highway tunnel provides northbound and southbound lanes of the Kentucky approach to a new bridge across the Ohio River. Tunnel lengths are approximately 1,675-ft and 1,685 for the northbound tube and the southbound tube, respectively. Connected by two cross-passages, both tubes have a roadway width of 40-ft, for 3-lane traffic, and a vertical clearance of 26.5-ft.The Tunnel was constructed by drill and blast method with shotcrete and rock dowels as initial ground supports. The final tunnel lining consists of 16 inches cast-in-place concrete lining and 20 inches invert slab, with a waterproofing system around the tunnel perimeter. Two (2) tunnel side drains and one (1) invert drain were provided for each tube. This paper describes the rational in assessing fire design requirements of the tunnel final concrete lining, to answer the question whether a passive fire protection system is needed or not."

Jan 1, 2016

By Judson H. Whitman

To evaluate intelligently and to market a source of rare earth raw material, it is necessary that the producer understand the requirements of the processor and the manner in which these requirements effect the value and salability of his product. This paper will be an attempt to aid in such an understanding. The majority of rare earth processors are primarily chemical companies, not mining or metallurgical companies, as the complexities of the processing procedures are' much more chemical in nature than metallurgical. The rare earths and the rare earth industry are normally divided into two groups - the ?light? or cerium group and the ?heavy? or yttrium group. They are so named because cerium and yttrium are the most common elements in 'heir respective groups and are so divided on the basis of mineralogical and chemical characteristics. The dividing line of the two groups is not rigidly fixed but usually is considered as being between samarium (atomic number 62) and europium (atomic number 63). Although the two groups are quite similar, processing procedures differ significantly, hence most processors tend to specialize in one group or the other. There is, however, a growing tendency toward participation in both groups.

Jan 1, 1960

By B. M. Davis

Characterizing exploration prospect potential has aspects that differ from those encountered during ore reserve estimation. One problem is determination of the ore reserve potential prior to acquisition of significant volumes of hard data. The evaluation is subjective and data are usually sparse and of uncertain quality. However, estimations of the ore reserve potential are commonly demanded by management before project funding will be approved. The estimations from several prospects, along with the uncertainties inherent to the estimation, are then used to compare and contrast the potential of several prospects, often with widely varying geologic models.

Jan 1, 1990

Power plants that utilize conventional wet flue-gas desulfurization methods produce enormous amounts of flue-gas scrubber sludge. A typical 400 MW power station that burns a high sulfur coal produces 170,000 tons of wet flue-gas scrubber sludge per year. This scrubber sludge is currently landfilled at an enormous cost to utility companies. This material could be used as a raw material for industries that use gypsum, such as the wallboard and plaster industries. However, before it can be used as feedstock for these industries, some of the impurities such as unreacted limestone and silicates must be removed from the scrubber sludge. Froth flotation has tremendous potential for separating these impurities from scrubber sludge. In order to select an optimum flotation process, it is necessary to characterize the surface properties of the major components in the scrubber sludge, which consist of calcium sulfite, calcium sulfate, calcium carbonate (limestone), and silica. In this study zeta potential measurements were used to determine the surface charge of the components in scrubber sludge, with the goal of optimizing a froth flotation process to produce a marketable gypsum product for the wallboard and plaster industries.

Jan 1, 1996

By William J. Miles

The markets and applications of Wyoming bentonite deposits are primarily determined by the functional properties of a bentonite ore which results from the unique mineralogy and chemistry of each deposit. Commercial bentonite products contain sodium montmorillonite as the major mineral component, with minor concentrations of accessory minerals such as quartz, opal (silica hydrate), mica, feldspar, gypsum and zeolites. The chemical composition of the sodium montmorillonite influences the functional properties of the bentonite in significant ways. The type and concentration of various accessory minerals also influence the acceptability of the bentonite in each market.

Jan 1, 1995

By A. M. Raichur

Flocculation of fine coal is usually accomplished with the addition of commercially available organic flocculants. Recently it has been shown that biopolymers derived from microorganisms can be used to flocculate coal. The biopolymers flocculate coal efficiently and render the coal surface hydrophobic. The increase in hydrophobicity can be utilized either to separate the coal flocs from mineral matter. It can also be used for reducing the moisture content of fine coal. In this regard, flocculation and settling tests of fine coal with biopolymers and synthetic flocculants was undertaken and the results are discussed here. Also, a transport model was developed for the time-dependent settling tests for fine coal.

Jan 1, 1996

The Functional Performance Equation for ball milling circuits provides plant staff with a new means to improve circuit performance. However, successful execution of a plant project, with verifiable circuit processing performance improvements, requires a significant number of accompanying steps beyond the equation alone. In order to identify and articulate all these steps, a study with plant staff from two milling operations and a grinding media supplier was undertaken. ?Task analysis? of improving plant grinding performance was carried out. This analysis called for the development of a number of system components, and ultimately yielded a ?Plant Grinding Circuit Processing Performance Management/Improvement System.?

Feb 23, 2014

By Howard N. Egan

EASTERN COAL CORPORATION is located in the heart of the Appalachian Mountain area of extreme Eastern Kentucky, The mountains are of sedimentary origin, and have been deeply eroded by streams as the area has been thrust up during geologic time. There are many seams of coal interspersed between beds of shale and sandstone. While some of the seams are thin, there are a number that can be economically mined. We are mining the Pond Creek, or No. 2 Gas Seam, at a rate in excess of 6,000 tons per day. Our central preparation plant utilizes tromp baths for the plus 3/8" size and Rheolaveur for the minus 3/8" portion. No provision was made to recover the fine coal, which was included with the plant effluent pumped to a 12 acre refuse pond. The pond is impounded behind the coarse refuse dump. This pond rose 15 feet last year. Obviously, no pond could stand many years at this rate. Limited pond space in this rugged area of steep hills and narrow valleys dictated a revised disposal method. Our first thought was that it would be necessary to dry the fine refuse sufficiently to permit inclusion with the coarse refuse, which is hauled uphill by monitor and then trucked to final disposal.

Jan 1, 1967

By Arthur W. Ruff

Estimated reserves of high-grade iron ore at Serra dos Carajás total 16 billion metric tons and have an average grade of 66.7 percent iron, 2.2 percent combined silica and alumina, and 0.05 percent phosphorous on a dry basis. Hematite is predominant and no significant sulfur or other deleterious elements are present. Figure 1 illustrates the comparative magnitude of the Carajás reserves. Serra dos Carajás is located in northern Brazil, about 550 kilometers southwest of Belém, Pará. It is six degrees south of the equator between the Xingu and Tocantins Rivers. Both rivers flow northward toward the Amazon River. The greater part of the area is covered by thick jungle, and the most practical means of access is by air. Figures 2 and 3 show the location of Serra dos Carajás. Figure 4 shows the distribution of the major iron-ore deposits.

Jan 1, 1973

By Salvatore Fancello, Ferruccio Cribari, Amerigo Tanzi, Mauro D’Angelo, Massimo Lodico, Alessandro Bertero, Eliano Romani, Tommaso Gondolini, Fabio Giannelli

"The new metro line “C” entails the construction and rehabilitation of 24 stations and 21,5 km of metro line, 13 of which carried out underground; the new metro line will improve the transportation system of a congested city such as Rome.The new line “C” of San Giovanni metro station will be constructed adjacent to the existing line “A” of San Giovanni station; the new metro line “C” is deeper than line “A” and will underpass the existing station. The underpass project envisages an Artificial Ground Freezing in order to excavate two new tunnels, while keeping trains running in the safest possible condition.In order to allow trains to regularly run to and from the existing station’s line “A”, a temporary structure for rail support, during excavation of the under-crossing tunnels, was installed and a real-time monitoring system was devised in order to control both soil temperature during freezing activities and the existing station’s behavior. The monitoring system has been one of the key to the success of the project.The excavation of tunnels under the water table, with a hydraulic head of over 10 m in not homogeneous soils having different mechanical properties and permeability and below existing sensitive structures, involves special ground freezing sequences and methods, as well as peculiar drilling systems and operations, such as TDDT (Trevi Directional Drilling Technology).THE NEW “C” LINE OF ROME’S METROThe world’s most complex and extraordinary Metro System is currently being built in the heart of Rome. Its underground route stretches underneath the most important monuments, churches and historical buildings.Rome’s Metro Line C is the longest urban underground railway in Italy and it is the first line in Rome to extend further east to the Great Ring Road, thus bridging the gap between the farthest suburbs and the Historical Centre. It is an original project, carried out mostly underground at a depth of 25/30 metres below road level."

Jan 1, 2016

By R. G. Reddy

Solid state reduction of roast movat chromite ore with carbon was carried out as a function of C/FeO ratio and temperature in the range 800°C to 900°C by thermogravimetry analysis (TGA). A two stage mechanism, (1) the reduction of FeO present in Roast Movat with carbon monoxide; and (2) the regeneration of CO by the oxidation of carbon with CO2 was proposed. The rate controlling step is the carbon oxidation reaction. A kinetic equation, that of random nucleation, was proposed. The activation energy for the reduction was determined to be 55800 J/mole and is compared to those activation energies determined for other chromite ores.

Jan 1, 1998

By F. W. Petersen

Slurry reactors are being used extensively throughout the chemical, biochemical and mineral processing industries. This paper describes the interaction between fine ore particles and granular porous adsorbents such as activated carbon and ion-exchange resins in a stirred tank reactor. Gold and silver cyanides were used as adsorbates to detect changes in the mass transfer characteristics of the adsorbents, which were ashed to determine the loading of ore particles. A simple kinetic model incorporating film diffusion, intrapanicle diffusion ~d the adsorption equilibrium, was used to interpret kinetic data and to estimate the effect of slurry conditions on the diffusion parameters. It was observed that the equilibrium loading of fines in the adsorbents was independent of their concentration in the slurry. Furthermore, the presence of these panicles inside an adsorbent decreases the effective diffusion of gold or silver cyanides into the adsorbent matrix. When fine suspended solids are present in the reactor, a decrease in the effective availability of the superficial surface of the pre-saturated adsorbent panicles for mass transfer from the liquid phase was observed. This newly defined surface availability factor was dependent on the concentration, panicle size, and the zeta potential of the fine particles in suspension.

Jan 1, 1993

By S. K. Kawatra

It is common in coal-cleaning operations to produce a fine waste stream which contains a considerable amount of coal, but which is not economical to recover both because it is mixed with large amounts of difficult-to-remove clay slimes, and because the fines are often heavily oxidized. Conventional froth flotation machines cannot produce an acceptable product from such material in a single stage of flotation, and even flotation columns often have difficulty cleaning this type of feed. A new type of flotation column was designed specifically to deal with these problems, and was installed and tested in a coal-cleaning plant in Ohio. The feed coal contained 39.8% ash as fine clay, and 2.83% total sulfur, and was 80% passing 176 micrometers. The coal was a thickener product which had oxidized for some time, and was very difficult to float. However, using the new column it was possible to recover up to 85% of the calorific value in a product containing less than 11% ash, and up to 60% of the calorific value in a product of less that 8% ash. The bulk of the pyritic sulfur was rejected from the coal as well. Multistage flotation tests showed that the flotation column was able, in a single stage, to produce the best froth flotation product that it was possible to recover from this coal.

Jan 1, 1994

By Edgar O. McAlister

Associated with cordilleran intrusives of intemediate to acidic composition, gold/silver ores are generally found in the intruded host rocks which are adjacent to these intrusives. Generally precious metal deposits lie further from the intrusives than allied base metal deposits. For vented intrusives, the associated volcanics may constitute the intruded rock and form the host for precious metal accumulation. Potential field methods, particularly magnetics, can help to define unseen boundaries of intrusive systems and thus can point to generalized prospecting targets. Other clues arise from the intrusive system type, its emplacement fracturing, the host rock type and local magnetic changes caused by mineralization processes.

Jan 1, 1984

By H. J. Hutson

BRS, Inc. has utilized Carlson's Natural RegradeTM software to design the reclamation and stabilization of abandoned open pit uranium mine spoils, AML Project 16N, located in the Gas Hills Uranium District in central Wyoming. This work was completed for the State of Wyoming's Abandoned Mine Land Program (AML) on preSMCRA (Surface Mining Reclamation and Control Act) sites for which no reclamation obligation existed. The project successfully stabilized an eroding spoil dump, enhanced the local view shed, created habitat diversity and provided a significant source of fill material for open pit highwall hazard mitigation efforts. Additionally, the project served to evaluate innovative reclamation design methods, engineering software and grade control technology. This project was nominated for a National Association of Abandoned Mine Land Programs award by the State of Wyoming. The results of this project will be presented as a case history of the Natural RegradeTM approach to surface mine reclamation. Based on the successful application of this new mine reclamation technology on the AML 16N Project, reclamation designs for spoils associated with planned underground uranium mine operations at the Velvet Mine in the Lisbon Valley Uranium District of Utah for Uranium One USA, Inc have been prepared and will be presented. Critical elements will be the encapsulation of unsuitable materials, long term hydrologic stability, and sequencing and staging of ore and mine waste for final reclamation surface construction. The goal of the Uranium One Velvet Project will be to apply best available technology to reclamation planning and fully integrate the reclamation design with the mine planning. Benefits of the approach should include improved public and regulatory perception of the project, facilitate mine permit approvals and the eventual timely release of reclamation bonds, as it is anticipated the stable landform created through this process will result in more rapid stabilization of the site to pre-mine geomorphic conditions. NATURAL REGRADETM CASE STUDY AML Project 16N, D-9 and K Pit Reclamation Project, is located in an intensely disturbed area of the West Gas Hills Uranium Mining District in Fremont County, Wyoming. The overall design calls for the placement of approximately 7 million cubic yards of backfill materials in the D9 and K Pits, imported from adjacent mine spoils including the Central Spoils, and from local highwall excavation. Figure 1 shows the location of the Central Spoils excavation area, as well as the D9 and K Pits fill area. The entire project is located on public lands administered by the Bureau of Land Management, Lander, Wyoming District Office. No access controls are in place at the abandoned mine sites. The public lands are administered under a multiple use land policy including grazing of range land, public recreation, active mining and exploration, and oil and gas. The project site is located along Fremont County Road No. 5, which is a moderately well traveled road. Reclamation of the numerous and large abandoned open pits in the Gas Hills Uranium District has reduced the risk of death or injury to the public. Site History and Background The Gas Hills Uranium District was mined by multiple companies during the period from 1955 to 1981. The uranium was hosted in the Wind River formation, a sequence of soft sedimentary layers of interbedded sandstone, clayey shales, and conglomerates. Uranium was precipitated out of ground water in classic roll front deposits, which are found from very near surface to depths greater than 400 feet. Prior to the enactment of the Surface Mining Control and Reclamation Act of 1977 (SMCRA), very little reclamation work was performed when mines were abandoned or closed. The State of Wyoming Abandoned Mine Lands Program has worked to mitigate hazards associated with large open pits, control migration of unsuitable materials and restore watershed functionality of lands in the district. Additional reclamation is being performed by mining companies on bonded lands. Figure 2, Gas Hills Uranium District aerial photograph, shows the extent of the mining disturbance in the district. [ ] Project Hazards and Concerns The purpose of AML Project 16N is to mitigate hazardous conditions and risk to the public associated with open pit highwalls and toxic, acid forming, and /or radioactive mine waste materials. The D9 and K Pits are contiguous open pits characterized by an 8,800 foot long hazardous highwall that averages over 200 feet tall. In addition to the physical hazard presented by the highwall, the project addresses

Jan 1, 2009