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By Ravi Shah, Augusto Lucarelli, Daniele Peila

"In mechanized tunneling the annular gap between the segmental lining and the surrounding soil caused by tunnel driving, must be backfilled almost instantaneously with an adequate grouting mortar. The objective of this research is to perform a fully three dimensional modeled parametric study using FLAC 3D and evaluate the effects of backfill grouting on the tunneling performance. The research focuses on comparisons between different injection materials and state-of-the-art Bi-Component grout and their effects on the settlements on the surface. The research consists of testing a regular situation of tunnel excavation using a shielded machine with face under pressure. The tunnel dimensions and the soil properties are selected as close as possible to the reality and based on Turin Metro case. 1 INTRODUCTION Excavation of tunnels in urban areas can induce ground movements, which have negative effects on existing structures. In such scenarios, shield tunneling has become a well-accepted construction method in various ground conditions. It is characterized by relatively complex interactions between the soil, the tunnel boring machine (TBM) itself, the tunnel lining and the tail void grout. The problem to control the settlement depends on the face pressure, ground properties and back filling procedure and material of the tail void. The face pressure acts against the front to guarantee the face stability. In case of EPB TBMs the stability of the tunnel face is ensured through the excavated soil itself, which is conditioned and is maintained in compressed state within the excavation chamber. When excavating with TBMs a tail void is created between ground and the lining (Fig.1) after the TBM excavation and ring assembly that must be backfilled instantaneously by injecting the backfill material through the TBM’s tail shield. The process is of primary importance as it reduces the surface settlements and creates an immediate link between the ground and lining, sealing against ground water and leakage, reducing the differential movements between segments and providing long-term stability. The most used backfilling materials are: Inert mixtures that do not contain cement instead sometimes they are replaced by fly ash or other substitutes. A typical design of an inert mortar consists of sand, fly ash, bentonite and water. Pea gravel, which is constituted of granular materials with grain size ranging from 8 to 12 mm. This mixture is highly recommended for tunnels being constructed in rock mass with little deformation rates.Cement mortar is composed of cement, water, aggregates and sometimes bentonite. Cement controls the principle mechanical property of the mix, which can reach high values of 15-20 MPa in 28 days. The aggregates contribute towards the shear strength and reduce the pumpablity of the mix (Thewes and Budach, 2009). The reduced active systems have a cement content of 50-100 kg/m3, whereas the active system the binder component derives full hydration with cement content of over 200 kg/m3 ."

Jan 1, 2016

By K. C. Nathsarma

An attempt was made to extract niobium oxide from ~98.5% Nb2O5 using solvent extraction processes. Nb2O5 is used as the feed material in carbothermic reduction processes aimed at producing high-homogeneity, superconductor-grade niobium on a laboratory scale. The Nb metal used for superconductor applications requires a residual resistivity ratio (RRR) > 300, which in turn needs a stringent purity of Nb and allows impurities (substitutional and interstitial) in ppm levels only. In this paper, solvent extraction of niobium was studied under various experimental conditions, such as effect of different extractants, concentration of methyl isobutyl ketone (MIBK) in the organic phase and concentration of various acids. The concentrate was digested with hydrofluoric acid, with ammonium fluoride (NH4F) as a stripping agent. The extraction of niobium from low hydrofluoric- (HF-) bearing solution was found to be low. Thus, various concentrations of hydrofluoric acid and sulfuric acid, as well as hydrofluoric acid and hydrochloric acid, were investigated towards obtaining a maximum amount of niobium in the filtrate and a minimum amount of niobium in the residue. A McCabe - Thiele plot for extraction of niobium from the aqueous phase, HF-bearing solution using HCl with 85% MIBK in kerosene has been constructed to determine the O:A ratio and the number of stages of the process.

Nov 1, 2011

By Michael A. Trevits

A mine fire represents one of the most dangerous and challenging safety issues facing underground mine operators. Given the right circumstances, a mine fire can occur at any location in the active or abandoned mine workings, can quickly grow beyond control, and threaten the welfare and livelihood of the entire underground workforce. The National Institute for Occupational Safety and Health (NIOSH), in partnership with the Mine Safety and Health Administration (MSHA), has been conducting an in-depth program of research addressing mine fire prevention, early and reliable fire detection, and mine fire suppression technologies. One portion of this program is focused on understanding the characteristics of mine fire combustion products and flame spread through large scale deep-seated (firmly established) fire tests and use of computational fluid dynamics (CFD) modeling. In this study, two deep-seated fire tests were conducted; one fire consisted of coal material and the other utilized the two most abundant fuel sources found in a coal mine: coal and wooden cribbing blocks. The fires were burned to completion while the combustion products were collected and analyzed. In addition, an array of thermocouples was placed within the body of the material to measure flame spread rate. The coal fire test information was then used to develop a CFD model of the fire. This paper describes the fire tests, provides insight into characteristics of flame spread, and presents the CFD modeling work results.

Jan 1, 2009

By R. Bryce, T. J. Doughty, K. Stoll

Sulfate-impacted mine waters are under regulatory scrutiny to reduce total dissolved solids (TDS). There are several options to reduce TDS. One option is transforming the soluble sulfate into insoluble ettringite. The Water Company LLC (TWC) patented a process for sulfate removal through ettringite formation by reacting directly with metallic aluminum. Freeport-McMoRan (FMI) and TWC have collaborated to design, build and operate a 10-gallon-per-minute (gpm) ettringite pilot plant to establish reagent consumption, plant availability and full-scale design criteria. Using metallic aluminum as the primary aluminum source for ettringite precipitation eliminates the addition of other ions, resulting in significant demineralization. The pilot plant achieved greater than 98% water recovery, greater than 90% reagent efficiencies and maintained reactor sulfate levels below 250ppm. BACKGROUND Ettringite is a hydrated calcium, aluminum, sulfate mineral with the following formula: Sulfate-impacted mine waters are under regulatory scrutiny to reduce total dissolved solids (TDS). There are several options to reduce TDS. One option is transforming the soluble sulfate into insoluble ettringite. The Water Company LLC (TWC) patented a process for sulfate removal through ettringite formation by reacting directly with metallic aluminum. Freeport-McMoRan (FMI) and TWC have collaborated to design, build and operate a 10-gallon-per-minute (gpm) ettringite pilot plant to establish reagent consumption, plant availability and full-scale design criteria. Using metallic aluminum as the primary aluminum source for ettringite precipitation eliminates the addition of other ions, resulting in significant demineralization. The pilot plant achieved greater than 98% water recovery, greater than 90% reagent efficiencies and maintained reactor sulfate levels below 250ppm. BACKGROUND Ettringite is a hydrated calcium, aluminum, sulfate mineral with the following formula: Ca6Al2(SO4)3(OH)12•26H2O Ettringite readily precipitates in high pH water and by doing so, removes sulfate from impacted waters. The SAVMIN process, piloted in South Africa, is one method to produce ettringite. In this process, aluminum hydroxide is the aluminum source. The Cost Effective Sulfate Removal (CESR) process is similar to SAVMIN, but uses a proprietary aluminum source instead of aluminum hydroxide. Outotec and Veolia also have their own versions of the process using their specialized process equipment. TWC patented a version of ettringite precipitation using metallic aluminum as the aluminum source for ettringite formation. The benefit of using aluminum metal is that no additional ions are added to the process. At high pH, the raw aluminum corrodes in water causing hydrogen gas generation as the water is chemically reduced. This reaction is shown below:

Jan 1, 2019

By B. Pesic

Manganese is about twelfth in the list of the most abundant elements in the earth's crust (Reidies, 1981). More than 150 known minerals contain manganese as an essential constituent (Mellor, 1932). In general, ores containing at least 35%Mn are classified as manganese ores, ores with 10-35%Mn are called ferroginous manganese ores, and ores containing 5-10%Mn are known as manganiferrous ores. One very important class of manganiferrous ores are manganiferrous-silver ores. They occur in the oxidized portions of the silver deposits of the Western United States. Silver is very often associated with manganese oxides which in some ore deposits are dispersed through calcite, causing the black color of the host rock, which is known as black calcite. Black calcites can occur in carbonate rocks (10-1500oz Ag/ton) and in volcanic rocks (less than 1.0oz Ag/ton).

Jan 1, 1986

By N. Merriam

This report describes Koppelman's work to develop the K-Fuel® Series C Process used to dry and stabilize Powder River Basin coal. It also contains summaries of the results of bench-scale and pilot plant tests conducted to prove the Series C Process. The process is being used by the KFx-Thermo Ecotek partnership for a 500,000 ton per year commercial plant that has been constructed near Gillette, Wyoming. The plant is presently undergoing shakedown.

Jan 1, 1997

By R. L. Derick

The Orchard Valley Mine, a large underground coal mine located in western Colorado, experienced a major mine fire during an idled Sunday on June 1, 1986. This mine had extensive problems with spontaneous combustion near the coal outcrop. Spontaneous combustion has been determined to be the probable cause of that fire. Preparing for a mine emergency was an on-going task. Once the emergency occurred, much of the preparation work was implemented and aided in controlling the situation. Later, the successes and shortfalls that arose from that emergency were analyzed for future course of action. This paper summarizes the activity that led up to the major fire, the handling of that emergency, the lessons learned, and the changes implemented.

Jan 1, 1993

By C. Leal

Modern production has as goal to reach high and uniform quality in their products. To success with this, it is essential to have a good knowledge of the different variables involved in the process. Investigation or analysis of a process or system has as references the measurements of the variables. These measurements are presented normally in form of data. These data are measured in intervals over time. The aim with measurement of the data in a process is to obtain information about the state of it in order to have it under control. Other goal is to know how the results are affected by the process variables to improve upon product quality, redunding manufacturing cost, better pollution control etc.

Jan 1, 1994

By D. R. East

Recent experiences within certain sectors of the international mining industry suggest an underestimation of the environmental risk associated with the design of mine waste management facilities. These experiences show that the technical and managerial challenge of responsible mine waste management is not always fully appreciated. Unfortunately, the image of the mining industry's environmental performance is negatively impacted by a relatively few number of failures. This negative view overrides the many positive contributions made by the majority of mining companies. The fact that these failures continue to occur to this day in both developed and developing countries is indeed remarkable, and indicates a degree of risk-taking approaching unacceptable levels. The design requirements for tailing storage facilities are, in many cases, more demanding than those of conventional water dams, because seepage of fluids which contain dissolved metals may pose a greater threat than the mere loss of water.

Jan 1, 1999

By John Greenhalgh, Benoit De Rivaz

"1.INTRODUCTIONThis paper is based on the Lee Tunnel project, which is part of the Thames Water’s Tideway Project.The client Thames Water has employed a Joint Venture of Morgan Sindall/Vinci Grand Projets and Bachy Soletanche to undertake the design and construction of the project under the management of CH2M Hill at a value in excess of £635 million ($990 million). The 3 main elements of the tunnel project are the permanent lining to the shafts, the precast segmental lining, and the secondary tunnel lining. All 3 are reinforced with different types of Dramix steel wire fibers and each element will be described in this paper. This paper will explain the basic structural design of FRC (Fiber reinforced concrete) based on the post cracking residual strength and will describe all the steps of this project, the testing program realized to support innovative design and the main technical learning point. 2.BASIC CONCEPT OF STRUCTURAL DESIGN OF FRCStructural design of FRC elements is based on the post-cracking residual strength provided by fiberreinforcement. Other cases, like early age crack-control or fire resistance, are considered non-structural use of FRC. For structural use, a minimum mechanical performance of FRC must be guaranteed. Fibers can be used to improve the behavior at SLS (Service Limit State) since they can reduce crack spacing and crack width, thereby improving durability and they can be used to improve the behavior at ULS (Ultimate Limit State) where they can partially or totally substitute conventional reinforcement in most conditions. In the design process, the definition of the performance expected from the material is a key factor and the mix-design of the material has to be optimized for the required structural performance.2.1 Testing Method In order to ascertain the structural requirements requested for the FRC segments, preliminary testing on samples will be required and the effectiveness of the proposed solution will also be assured by the testing of full scale specimens. Structural design of FRC elements is based on the post-cracking residual strength provided by fiber reinforcement. For structural use, a minimum mechanical performance of FRC must be guaranteed. Nominal values of the material properties can be determined by performing a 3-point bending test on a notched beam according to EN14651 (figure 1) or by performing the ASTM C1609 beam test:"

Jan 1, 2016

By T. C. Bibb

Longwalls using shearers in seam heights of less than 1.2 m (48 inches) are relatively rare in the U.S. Westmoreland Coal Company is currently operating a shearer-equipped longwall at a cutting height of 1.17 m (46 inches) in its Bullitt Mine. This face has averaged 2795 metric tons/day of operation since its startup on April 3, 1984. Longwall productivity in thin seams is substantially impacted by equipment reliability and availability of useable working room for travel and access. This paper addresses the design criteria used in selecting this face equipment, with the goal of maximizing these two parameters. Equipment discussed includes shearers. face conveyor, shields, stageloader, and emulsion system.

Jan 1, 1985

By Omar A. Muhtadi

Brohm Mining Corporation, in conjunction with Geobiotics, Inc. has nearly completed a pilot heap biooxidation test on sulfidic ore from the Gilt Edge Mine near Rapid City, South Dakota. Some results from the pilot testing have shown the correlation between the extent of biooxidation and the increase in cyanide gold recovery seen in the laboratory. Bench scale testing showed approximately a 1: 1 correspondence between percent biooxidation and percentage increase in gold recovery. The economics of large scale biooxidation were also evaluated in terms of increased gold recovery versus the time and cost of biooxidation. In the pilot test, the rate of biooxidation became limited by the acid water neutralization system. Later in the test, measures were taken to overcome this problem. Results from bench scale column bioleach testing showed that the Gilt Edge sulfide ore is quite amenable to biooxidation with a substantial increase in gold recovery with just partial biooxidation. Direct cyanide gold recovery of 51 % on ore crushed to -3/8" was enhanced to 82-85% after oxidation of37% of the sulfide as measured by iron. Laboratory experiments also showed that the slow rate of biooxidation of this ore could be accelerated by removal of metal sulfate build up from the leach liquor. The combination of these normally non-toxic metals became inhibitory to biooxidation if not removed by the neutralization circuit.

Jan 1, 1995

By L. C. Atkinson

A three-dimensional finite element Ground-water flow code has been developed that incorporates saturated/unsaturated, two-regime flow (i.e., both Darcian and non-Darcian) and solves for the seepage face at a surface of outflow. This code is capable of more realistically predicting ground-water inflows to an open-pit mine under the throttling effects of non-Darcian flow. The height of the seepage face on highwalls and the shape of the phreatic surface in the vicinity of the pit that it calculates can also produce more probable estimates of pore pressures for analysis of slope stability.

Jan 1, 1992

By A. K. Bakshi

Slurry rheology affects autogenous grinding performance by changing the rock's breakage characteristics. In this study pilot scale batch autogenous grinding was carried out to observe the effect of viscosity on the breakage characteristics of the rocks (the media), and on the overall specific energy consumption. Clay/fines content, and temperature of the initial charge, were varied to alter the viscosity of the slurry. Results showed that at higher slurry viscosity, rocks became more difficult to break, resulting in an overall increase in the specific energy consumption of the mill. Also, it was observed that viscosity had a significant effect on the amount of critical size material present in the grinding circuit, where the critical size material is the material which is too large to be effectively ground in the mill, and too fine to act as grinding media.

Jan 1, 1996

By Lawrence A. Roe

This paper describes research and development efforts leading to a wet process for the beneficiation of Western talc ores in which the values are primarily present as soft, platy talc mineral. The mineralogy of the ore, as it relates to the logic of utilizing an uncomplicated, attrition-scrubbing sedimentation process is described. Bench-scale laboratory testwork and a pilot-plant test program are described. The pilot-plant program included production of several tons of products. The thickened talc slurries were very difficult to dewater prior to the drying step. Dewatering difficulties were overcome by use of a high-speed centrifuge. The centrifuge cake was dried either by tray, flash or spray drying. The successful use of one high-grade talc product as titanium dioxide extender in paper is discussed. The talc product has extremely low abrasion values, an important characteristic for minerals used in paper manufacture. It is concluded that this wet process for soft talc ores is capable of producing high-purity talc products for paint, paper, cosmetics and other industrial uses re-quiring very pure soft talc.

Jan 1, 1972

By Gary E. McIntosh

This paper will discuss a U.S. Bureau of Mines project designed to assess and predict the impacts which surface coal mining will have on the regional shallow groundwater systems in the Powder River Basin. The primary objective will be met through the accomplishment of the following: (1) The design and establishment of a regional network for monitoring of shallow groundwater systems in the Basin. (2) Monitoring of the direction and rate of flow, water quality, and aquifer characteristics of the shallow groundwater systems. (3) Development of a regional groundwater simulation model with appurtenant subroutines to determine local effects.

Jan 1, 1978

By T. F. Torries

Identifying high value areas of unmined coal when large quantities of coal are available relative to annual markets is difficult because of the uncertainty of when the coal is to be mined. A GIS based methodology developed to value reserve coal in a producing coal region for the purpose of ad valorem taxation also identifies high value areas for mining investment. The methodology is unique in that it accounts for most mining, environmental, and market factors to determine when specific properties are to be mined. The methodology and data base are useful for directing regional exploration and acquisition activities toward most favorable areas.

Jan 1, 1999

By R. Merkl

Since the 1940s, decanter centrifuges have become more important for increasingly complex solid-liquid or solid-liquid-liquid separation processes. Sometimes processed industrial or metalliferous minerals are abrasive or are treated with corrosive chemical agents. Traditional mining applications include the processing of coal, gravel and other products, where low-speed decanters, as well as screen bowl decanters and filters, dominate. These have been increasingly replaced by high-speed decanters during the last decade. Decanter centrifuges also started to play a key role in applications such as drilling muds, processing carbonates and separating SX crud in copper platinum ore concentrations of nickel and gold. Communication between machine producers and mineral processing engineers is vital for the right choice of materials and the design of the right decanter centrifuge for the individual process.

Feb 1, 2012

By J. R. Iwinski

Escanaba, Michigan, is located on the South¬ern shore of the Upper Peninsula on a sheltered area of Lake Michigan called Little Bay de Noquet. The Chicago and North Western Transportation Company has operated a rail-to-ship ore transfer facility at this location for well over 100-years. It is the only terminal of its type on Take Michigan and thus can offer a longer navigation season to lower lake markets than other upper lake ports. It all started in 1864 when the Peninsula Railroad of Michigan, now a part of the C&NW, completed a 100 km rail line from Little Bay de Noquet to the Jackson Mines at Negnauee, Michigan. During that first year of operation approximately 31 000t of ore were loaded onto ships at Escanaba from what was then called the Merchants Dock. By 1871 demand had already exceeded capacity and it was necessary to build a larger dock, which in turn was replaced with a still larger pocket dock in 1903. There are no plans or records available to indicate how the ore was handled from rail to ship prior to the construction of the pocket dock.

Jan 1, 1981

By G. E. Viens

The electric arc furnace has characteristics which make it attractive for a number of metallurgical applications. Some of these characteristics are: high thermal efficiency, the possibility of attaining very high temperatures, low off-gas volume compared to fuel-fired furnaces, no impurities are introduced by the heat source, and impurities in only minor amounts are introduced by the electrodes. It also has disadvantages, the chief ones being the relatively high cost of electrical energy compared to fossil-fuel energy and the fact that, when oxide ores are smelted using carbon as reductant, the off-gases emitted are rich in carbon monoxide. As in many other pyrometallurgical processes, fumes and dust are emitted from melting or smelting operations. In many installations, some or all of the off-gases are flared, thereby wasting their energy and contributing to atmospheric pollution. During the last eight years, a shaft-electric furnace has been under development at the Mines Branch, Department of Energy, Mines and Resources, Ottawa, Canada. This project was initiated to try to overcome, or at least minimize, the disadvantages of the electric furnace. Experience on other projects, prior to the beginning of this program, had indicated that preparation of the charge materials, for example by sizing raw ore, sintering concentrates and crushing and sizing the sinter, or agglomerating concentrates into uniform-sized pellets, could make a substantial contribution towards achieving success in arc-furnace smelting projects; This entire

Jan 1, 1971