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By B. Mishra

This paper presents a rock mechanics investigation of the time-dependent behavior of the rock immediately surrounding the excavation in a hypothetical one-entry coal mine based on the geology of the Illinois coalfields Research in the area of time-dependency is almost nonexistent and, therefore, this research was performed to make inroads into this neglected research area. Numerical analysis of a typical one-entry coal mine in an Illinois basin was performed using the commercial finite difference program FLAC3D. The immediate roof of the coal entry was assumed to be a shale formation. Shale in other formations has shown a tendency to creep with time. Therefore, in this study the authors modeled the shale in the roof using time-dependent characteristics. The input properties were taken from laboratory creep tests performed on shale. Model runs were performed at different stages, mimicking the progressive excavation of the entry. The model results showed that stresses in the roof attained the limit of yielding. Using Mohr-Coulomb failure criteria, potential zones of failure were also predicted. The results showed that the current computational capacities are sufficient to explore this previously uncharted territory of ground control.

Mar 1, 2014

By M. D. Flavel, J. C. Motz, G. V. Jergensen

Introduction Compared to the gyratory crusher, the cone crusher is character¬ized by its higher speed and a flat crushing chamber design which is intended to give a high capacity and reduction ratio for materials suitable to this type of processing. The aim is to retain material longer in the crushing chamber to do more work on material as it is being processed. A concept of how a piece of stone might flow through a secondary crushing chamber is shown in Fig. 45. The number of times material will be nipped during crushing will depend on material size, friability, and the geometry of the crushing chamber as well as its speed and eccentric throw. Cone crushers are usually specified in terms of closed-side setting (CSS) and a given quantity of material passing a particular square-mesh screen size. A criterion of product passing closed-side setting is often available. This value will vary according to the particular crusher design and the details of its applica¬tion. Essentially, cone crushers can be classified into distinct types, depending on their duty. Crusher sizes for all duties are described by terms arising out of common industry usage, such as 3-ft, 7-ft, etc., which refer to the crushing-head (mantle) diameter. At present the range of sizes available varies from approximately 2 to 10 ft diam. Weights vary in the range of 5 to 200 tons, and connected horsepowers range from 10 through 700. There are so many variations that specifics should be obtained from machine manufacturers. The crushing chambers that are fitted to various machines are also often referred to by terms arising out of common usage, such as standard for secondary crushers, and short head for tertiary crush¬ers, which refer specifically to the Symons design. Also used are more specific but equally vague descriptions, such as coarse, intermedi¬ate, and fine chambers. Some manufacturers such as Allis-Chalmers with their Hydrocone crushers refer to the model number of the machine by the feed opening and the diameter of the mantle. For example, a Model 10-84 Hydrocone crusher has an 84-in. diam man¬tle, and is capable of accepting a 10-in. diam sphere at the feed point to the crushing chamber. Rexnord and Telsmith define crushing cavi¬ties in their capacity tables as feed openings at minimum recommended discharge settings (closed-side settings). Each practice offers guidelines which should be carefully defined for the specific crushing problem. The utilization of a cone crusher depends on how well it is controlled and the features of the circuit in which it operates. Normally, it will operate in the range of 75 to 85% of the peak capacity. It is likely that industry pressures will call for a standarized de¬ applied crushing power. Experience has shown that the crushing process is more controllable if certain reduction ratios are adhered to for each stage. Technically, this is defined as that size of feed (in. or mm) of which 80% will pass, divided by the size of the product (in. or mm) which 80% will pass. Secondary Crushers These are the cone crushers which accept suitable feed size material either prepared by a primary crusher or occurring naturally, and reduce it to a size suitable for marketing in one stage, or make feed for subsequent crushing or grinding stages. Secondary crushers have feed openings of 4 to 25 in. in the larger (7-ft) models down to a 2'/a to 4 in. in the smallest 24-in. models. Reduction ratios normally range between 3:1 and seldom more than 5:1. In the 7-ft models, the cone crusher typically makes a product all passing 2 in., but this is dependent on the machine design and properties of the material being treated. Secondary crushers most commonly operate in open circuit. They also are operated in closed circuit with a vibrating screen, depending upon product requirements and conditions where the reduction ratio does not cause excessive power draw and build-up of circulating load. Screening ahead of secondary crushers is generally recommended, especially where the feed contains more than 25% material smaller than the desired closed-side setting. Tertiary Crushers These are cone crushers that normally take secondary crusher product and reduce it to a marketable product or make it suitable for subsequent comminution steps. The reduction achieved is a func¬tion of the crusher design and the properties of the material to be treated. The reduction ratio is normally in the range between 1.5 and 2 to 1, and seldom more than 3 to 1. The tertiary crusher normally operates in closed circuit with a vibrating screen and makes a product smaller than all passing 'h or 5/8 in. Fine Crushers Sometimes these machines are called sand crushers and are called by various manufacturer brand names, such as Gyradisc, Hydrofine, V.F.C., and others. A cross section of a Symons Gyradisc crusher is shown in Fig. 46. Essentially, these crushers would be used in a fourth-stage crushing operation, but could be called on to reduce a screened feed size fraction from a secondary or primary crushing operation. This type of crusher normally receives feed no coarser than 1'h in. that is scalped of all over-sized material and operates in closed circuit with a vibrating screen. For average materials, typical product is '/e in. top size, although a -10 mesh product can be produced on those materials having suitable characteristics. The crusher is nor¬mally operated in a separate circuit from the main crushing plant because of the variations in output rates that are caused by varying physical properties in the feed. The reduction ratio is generally less than 2:1, and circulating loads are generally high. More interparticle crushing takes place in these machines than with conventional cone crushers and capacities can be more sensitive to changes in moisture content, feed size graduation, and other physical properties. Design Features For the various applications, crusher manufacturers normally have a range of crushers of different sizes and power ratings to select from.

Jan 1, 1985

By D. D. Potter

ABSTRACT OF ORAL PRESENTATION Extraordinary conditions are often encountered when designing large blasts for in situ mining methods and spatial or innovation techniques are sometimes required. Some of the considerations in designing these large blasts will be discussed with emphasis on those factors that concern powder factor, rock movement and fragmentation. Sources of basic data will be described, along with some of the methods for obtaining these data.

Jan 1, 1977

By Robert S. Neil, O&apos

The basic transportation planning process consists of: 1. Inventories and analyses of existing conditions. 2. Estimates of future growth. 3. Determination of future travel demand. 4. Testing alternative systems to satisfy future travel demand. The many modeling techniques used in the transportation planning process are well known, commonly accepted, and thoroughly described in readily available literature. This paper will concentrate on the fourth step of the planning process, specifically the development of alternative systems for testing, and will discuss some of the factors which should be considered during the development of alternative systems. There are many factors which require consideration and which have a bearing on the configuration of alternative test systems. These comments will be limited to the influence of geographic, demographic, geologic, and economic factors. Although addressed separately, the four are to a great extent related and have a significant effect on each other. The objective of examining these factors during the early phases of system planning is to assure that more detailed corridor studies will not be stymied by considerations which could have been anticipated and accommodated at an earlier time. It is particularly important that feasibility of construction be assured before test systems lead to corridor decisions and accompanying commitments to

Jan 1, 1974

By Charles J. Johnson

The United States is totally dependent on imports for all primary chromite and most ferrochrome supplies. Although the United States imports chromite and ferrochrome from a number of countries, the long-term future of chromite supplies appears to lie in southern Africa (Republic of South Africa and Zimbabwe) where 88 percent of known world reserves exist. Floreover, low mining costs and the availability of low-cost electricity for ferrochrome production gives South Africa a comparative advantage over most other chromite and ferrochrome-producing nations. A well-known problem faced by the United States is that when viewed from a longer-term perspective, the major sources of supply of metallurgical grade chromite and ferrochrome may be subject to disruption. The three countries that have caused the greatest concern have been the Republic of South Africa, the Soviet Union, and Zimbabwe. South Africa presents a particularly difficult problem because it may be subject to internal political unrest and/or U. N, economic sanctions. South Africa has increased its share of world chromium production from about 30 percent in 1968 to 62 percent in 1978.1

Jan 1, 1982

By C. O. Brawner

Geotechnical theory is reasonably well developed to evaluate the stability of rock slopes for surface mining projects. It is recognized widely that structural geology, groundwater pressures and seepage, and blasting are key factors that influence the stability of such slopes. However, our capabilities to model the structural geology, to determine rock strength along discontinuities and to model groundwater pressures and profiles are still very approximate. Plus, practical experience of the rock mechanics engineer is one of the most important inputs to the design of open pit mine slopes. To emphasize the use of practical experience, a number of case examples are reviewed here to illustrate key factors that must be evaluated. These case examples comprise a continuation of other examples presented in the Jackling lecture to the SME in 1986 by the author (Brawner, 1986). Example no. 1 In situations where the orientation of geologic discontinuities will not influence rock slope stability, extremely steep slopes can be developed, providing blasting and groundwater are controlled adequately. An excellent example of this condition is the Republic Pit of Cleveland Cliffs in Michigan. The rock slope in Fig. 1 isover400fthigh with a face angle of approximately 80". The rock is hard and massive, and blasting was carefully controlled. The original design of this slope was at45", a standard design angle at that time. The competency of the rock and the lack of critical geologic structure subsequently was recognized, and the much steeper slope angle was developed successfully. The rock proved to be so competent and the slope sufficiently stable that an underground crusher station was developed with entrance and exit tunnels excavated at the toe of the steep wall.

Jan 1, 1991

Nautilus Minerals and Neptune Minerals are betting that the next great metals rush will take place more than 1,500 m (5,000 ft) below the sea. Nautilus is the first company to commercially explore the ocean floor for gold and copper seafloor massive sulfide (SMS) deposits. Its main focus is the Solwara 1 Project, a polymetallic copper, gold, zinc, silver deposit that is under 1,600 m (5,200 ft) of water off the coast of Papua New Guinea in the western Pacific Oceans? Rim of Fire. Nautilus Minerals, in a joint venture with Placer Dome (now Barrick Gold), began its exploration of what would become the Solwara 1 area in 2005 with side scan sonar and dredge sampling. The dredge and grab sampling confirmed the grade tenor of earlier sampling by scientific research programs. The 45 dredge samples aver-aged 10.8 percent copper, 3.7 percent zinc, 224 g/t (6.5 oz/st) silver and 13.7 g/t (0.4 oz/st) gold. Nautilus has since staked out more than 300,000 km2 (115,800 sq miles) of tenement licenses and exploration applications in the waters off Papua New Guinea, Fiji, New Zealand, Tonga and the Solomon Islands. That is an area about the same size of the United Kingdom. Interest in Nautilus and its projects has grown tremendously since its inception. The company is now listed on the Toronto Stock Exchange. It has raised more than $300 million and spent more than $23 million on exploration. The company has gained the backing of mining majors such as Teck Cominco, Epion, Anglo American and Barrick Gold. It is positioned to become an emerging producer in 2010. Teck Cominco recently agreed to exercise share purchase warrants to acquire three million additional common shares of Nautilus at a price of US$15 million. This will take Teck Cominco?s shareholding to approximately 7.2 percent of the issued shares. Teck Cominco will conduct and manage a ship-based exploration program that will run in addition to the exploration that was already planned for 2008.

Jan 1, 2008

By Matthew Grzelak, Gulsah Erinc, David R. Chapman

"The third phase of the Bagram Drainage System project at Bagram Air Force Base in Afghanistan included construction of a shallow, 540-m long, 1.8-m inside diameter drainage tunnel. The tunnel penetrated mostly stiff to hard clayey and silty soils. The contractor’s Value Engineering Change Proposal (VECP) to use pipe-jacking with a microtunnel boring machine (MTBM) instead of the specified two-pass Earth Pressure Balance method was evaluated and supported using hand calculations. Contractor support was provided throughout the project by providing design reviews and instrumentation monitoring during construction. This paper compares the value-engineering proposal to the specified method and describes the construction conditions encountered. INTRODUCTION As part of a larger improvement project at the Bagram Air Force Base in Afghanistan, a shallow, 540-m long, 1.8-m inside diameter drainage tunnel was constructed to provide additional capacity for Coyote Creek to pass below several critical structures, including taxiways and the main runway, for mitigation of recurring flooding (see Figures 1 and 2). Overburden over the tunnel crown ranged from about 3 m to 5.5 m. An existing cast-in-place twin barrel concrete culvert runs approximately parallel to the new tunnel and is within about 8 m at its closest point. The contractor’s Value Engineering Change Proposal (VECP) to the specified two-pass Earth Pressure Balance (EPB) method (steel ribs and lagging or steel liner plate with a carrier pipe later grouted in-place) called for installation of the required drainage pipe by pipe-jacking (one-pass installation) using a slurry microtunnel boring machine (MTBM). The critical nature of the operations at the air base resulted in significant construction coordination challenges and a greater than usual need to avoid excessive settlements. Substantial restrictions were placed on drilling of investigative borings and installing instrumentation near runways and taxiways due to drill mast height. The prime contractor was SERKA TAAHHUT INSAAT A. S. (SERKA), the microtunneling subcontractor was Ludwig Pfeiffer Microtunnel GmbH & Co.KG (Pfeiffer), the jacking pipe designer was Gollwitzer Pipe and Shaft Technology GmbH (Gollwitzer), and the contractor’s tunnel engineer was Lachel & Associates, Inc. (Lachel). Lachel provided contractor support throughout the project including preparation of a VECP/Design Summary (including interpretation of existing and new geotechnical information), design reviews for jacking pipe, estimating settlement of an existing drainage structure above the new tunnel, and instrumentation planning, monitoring, and analysis during construction."

Jan 1, 2016

By T. M. Hanna

The results of using a simple analytical solution and a relatively complex numerical model to estimate ground-water inflow to an open pit mine are compared. The analytical solution assumes lateral, radial flow to a fully penetrating pit in an idealized confined aquifer, whereas the numerical model simulates fully three-dimensional flow to a partially penetrating pit from a water table aquifer. The latter is obviously a more realistic simulation of the problem, but the former method is significantly easier to use, Comparison of the results obtained with the two methods for some typical hydrogeologic conditions encountered in mining yields ratios between them in the range of 0.15 to 0.60. These values can be used as a coefficient in the Pit Flow analytical solution to produce reasonable estimates of in-flow even when there are significant differences from the idealized conditions implicit in its application.

Jan 1, 1992

By G. Wang, L. R. Moore, Y. Xiong, J. Gu

"Quartz is the second most abundant mineral in the earth’s crust. Not only does quartz have many valuable industrial applications, it is also one of the most concentrated gangue minerals encountered in the processing of other minerals. Minerals such as hematite, apatite, calcite, feldspar, barite, and many more. Numerous applications of industrial minerals are sensitive to the hardness and abrasiveness encountered with quartz minerals, while other applications may lead to processing challenges for the end user. Therefore, process and chemistry optimization must be applied to ensure optimal grade is obtained for these valued industrial minerals. Extensive studies have been conducted in processing various industrial minerals, thus achieving a range of quality specifications, which entailed the application of ArrMaz’s CustoFloat and CustAmine collectors towards the separation of quartz from other minerals. INTRODUCTION Industrial minerals often have the misfortune of the gangue mineral being very similar in surface charge, and coordination properties, to that of the mineral of interest. An example is seen in phosphate beneficiation, when dolomite can be a gangue minerals (Table 1). Therefore, the development of processing reagents are quite complicated. Some minerals, like clays, may be washed away. However, most require the manipulation of the pH, in efforts to fine tune the system to the narrow difference in isoelectric points of the different minerals, as well as the knowledge, and resources that are necessary to exploit the differences to yield and an optimal grade/recovery. In some cases, the application of a depressant may be required, such as the phosphoric acid commonly applied to achieve the optimal balance of grade/recovery for phosphate from a mineral with elevated concentrations of dolomite (Wang, 2016), or the application of hydrofluoric acid to assist in producing feldspar product from a mineral rich in quartz (Heyes, 2012).ArrMaz's CustoFloat and CustAmine product lines have successfully been applied to the processing of industrial minerals for more than 50 years. Applications include, but not limited to phosphate, sand (glass, foundry & high purity quartz), clays (feldspar, kaolin, etc.), and many carbonaceous and sulfate minerals. The successes of these 50 years are largely due to ArrMaz's ability to tailor make the processing chemistries to fit the ever changing and declining mineral feed grade and variations in water quality (Moore, 2015; Moore, 2016). This technical knowledge of mineral processing is strongly complimented by the intimate service programs in place at many of the beneficiation plants."

Jan 1, 2018

By Richard D. Doepker, Cathy A. Summers

Part 1: Physical Characteristics The physical and mineralogical characteristics of samples from five sources in the Western United States were determined using size analyses, microscopic studies, and point counts. These results were combined with leachability assays and the chemistry of leachates obtained during slurry tests to predict sample dissolution characteristics during column leaching tests. Part 2: Dissolution Characteristics Two columns of each sample were leached over a period of 3 years with synthetic rain. Residence times were between 2 and 11 weeks. The samples were subjected to daily and seasonal temperature fluctuations and wet-dry and freeze-thaw cycles. During the latter part of this study, a biocide leachant (sodium benzoate) was substituted for synthetic rain to assess the degree of dissolution caused by biological oxidation. It was found that the presence or absence of barite or carbonate minerals can be used to predict the leaching behavior of the column material.

Jan 1, 1995

Laboratory techniques have been developed at the Julius Kruttschnitt Mineral Research Centre which relate comminution energy to size reduction. These relationships have been applied in the mathematical modelling of autogenous and semi-autogenous mills. Since their development in 1987 these models have been successfully used in many wide ranging design and optimization studies. A description of the basic structure of the models is presented with particular reference to ore characterization. Two case studies are presented which illustrate their effectiveness in evaluating and predicting the effects of circuit changes.

Jan 1, 1992

By Robert A. Jankowski, Charles Babbit, Natesa I. Jayaraman

The Bureau of Mines, together with Foster Miller Inc., has developed a compact, high pressure scrubber system for continuous miners. Powered by water energy alone, it can move up to 1.4 m3/s (3,000 cfm) of air and scrub a significant amount of the dust in the air. Full- scale model and underground trials showed excellent performance. Operated at 8.3 x 10[3] kPa (1,200 psi) and 38 L/m (10 gpm), the scrubber has reduced operator and return dust concentrations by more than 50 pct. This paper describes the full-scale model development, system fabrication and underground evaluations of this novel and inexpensive scrubber.

Jan 1, 1989

By J. P. Brady

A major spontaneous combustion incident occurred in the sealed goaf of the SL3 Panel; Southland Colliery in 2003 resulting in the loss of a longwall and sealing of the mine. The most important issue for the new owners, Yancoal Australia Pty. Ltd, was to effectively manage the atmosphere in the fire affected sealed area. This atmosphere comprised of flammable gases, the products of combustion and excessive levels of oxygen due to pressure differentials across the panel isolation seals with a potential ignition source associated with the residual spontaneous combustion event. The challenges were met in the first instance by the erection of pressure balance chambers with limited success. The problem was not solved until the pressure chambers were pressurized using a Floxal Nitrogen Plant supplied by Air Liquide Australia. Given the success of this approach on a small scale, a higher capacity Air Liquide Floxal Unit was acquired to manage spontaneous combustion at the recommencement of longwall mining operations. This provided the ability to pressurize pressure chambers that were installed in the Maingate Seals behind the face of the adjacent Longwall Block effectively preventing the ingress of oxygen and permitting the goaf to self inert in a reasonable time period. This paper summarizes a new proactive method of mitigating the risks associated with active and sealed goaves. Proactive management of these areas using low flow nitrogen into pressure chambers to maintain a positive pressure has eliminated typical reliance in explosion proof or explosion resistance seals as the primary control.

Jan 1, 2009

"The mining industry suffers from a number of incorrect perceptions, one of which is that it is an outdated industry that has not changed for hundreds of years. But the truth of the matter is that mining is a vibrant, highly complex industry that not only employs highly skilled and educated professionals but is also often on the cutting edge of technology. It is an industry with projects that are ever-evolving and among the most challenging engineering feats in the world.Take for instance the U.S. 53 Highway Relocation project in Virginia, MN. While more of a civil engineering job than a traditional mining project, it is still a complex engineering challenge taking place in a mining environment that has called on the skills of eight state agencies, three federal agencies, a host of contractors and many consultants, including many from the local mining industry in the Iron Range of Minnesota.In 1960, the Minnesota Department of Transportation (MnDOT) constructed U.S, Highway 53 on a private easement owned by US Steel that cut across a massive taconite deposit. MnDOT constructed the highway with the agreement that if the highway needed to be moved to access the taconite deposit before 1987, US Steel would foot the bill. And if the move was required after 1987, the responsibility would fall to MnDOT. In 2010, MnDOT received the notice that the highway would have to move as property owner United Taconite planned to access the ore, setting in motion one of the greatest engineering challenges, and the highest risk project, in the history of the states’ transportation department.Pat Huston, U.S. Highway 53 Relocation project manager, opened the 90th SME Minnesota Section Conference in Duluth, MN on April 19 with a presentation about the project that includes 5 km (3.2 miles) of fourlane highway and a new 345-m (1,132-ft) bridge that will be the tallest in Minnesota when it is completed later this year.“This project was not business as usual,” Huston told the packed crowd. “Highway 53 connects Canada and the Iron Range to Duluth and Lake Superior. It is an important highway.”During his presentation he spoke about many topics that were familiar to the more than 1,100 mining professionals who attended the conference. In his keynote speech,"

Jan 6, 2017

By John B. Gustavson

This paper describes a case history of geochemical prospecting. An area of known mineralization was available for an orientation survey which led to the selection of elements and criteria for a reconnaissance survey in the area offsetting the known mineralization. Certain anomalies were found which were then made subject of confirmation sampling and of rock geochemical investigations. Inasmuch as the geochemical prospecting technique specifically led to a detailed area which now serves as a target for drilling and other exploration efforts, the geochemical prospecting part of the program is considered successfully concluded and, therefore, reported on here. Whether the target area will turn out to host the deposit or not is, of course, of utmost importance to the Company, but is of less importance to this paper. We will describe the concepts, the planning, the execution, the analysis and the interpretation of this typical geochemical prospecting case. A number of people on the staff of International Oil & Gas, Inc. have participated in this prospect, as have students from Southeast Missouri State University and their professor, Gary M. Lowell. In addition, the Missouri Geological Survey has been most helpful with records and letters on the century-old prospecting and mining in the general area. Many valuable discussions have also been held with geologists from the industry who, from time to time, have visited the area, examined the property and reviewed the status of the project. The support and interest from all these parties has made it possible to pursue and expand this exploration concept from one of being just "more of the same kind" to the most chal-1enging and exciting with which this author has ever been involved, namely the prospect for tin porphyry deposits in the mid-continent United States.

Jan 1, 1977

By Robin Dill, Wei Song, Andrew Perham, Leo Martin

"AECOM completed a subsurface exploration program for an 18-foot diameter, approximately 4-mile long rock tunnel project in Hartford, CT. The tunnel crosses the regional geologic trend through the middle of a sedimentary basin, passing through four separate rock formations, including two volcanic flows. Faulting is prevalent, with at least 15 faults encountered during the site investigation. Severe artesian flows were also experienced in several of the borings, requiring highly specialized drilling equipment. Sixty-two borings and associated testing were performed to characterize the structural geology, hydrogeology, rock properties and ground conditions. A phased program was carefully planned and implemented with participation of geotechnical and geologic specialists, with thoughtful evaluation along the way to react to the ground conditions encountered, and make appropriate refinements. This paper will discuss the subsurface program details; the integrated efforts used to effectively characterize the ground; and will summarize the final characterization presented in the GBR. PROJECT DESCRIPTION The South Tunnel Conveyance and Storage Tunnel project is part of the Metropolitan District (MDC’s) Long Term Control Plan to address discharges to various water bodies throughout the greater Hartford area. This program includes a main conveyance and storage tunnel; a tunnel boring machine (TBM) launch shaft and retrieval shaft; adit tunnels with associated drop shafts and connection structures; consolidation conduits and manholes; and a tunnel pump station (TPS) at the downstream end of the main conveyance tunnel. AECOM is serving as prime designer for the MDC on this project. The main conveyance tunnel (hereinafter referred to as the “South Tunnel”) will be a deep rock tunnel with an invert depth of approximately 180 feet at its downstream end and approximately 218 feet at the TBM retrieval shaft. The tunnel will have a finished diameter of 18 feet. The tunnel will rise in grade at a slope of 0.1 percent to its upstream end. Total invert depth along the deep tunnel alignment ranges from about 180 ft. to as high as 320 feet. The total length of the tunnel will be 21,754 feet. The South Tunnel will be constructed using a shielded TBM and fully lined with pre-cast concrete segments."

Jan 1, 2016

By Florence Munter

This paper provides a discussion of the various federal and state laws governing water quality as related to mining operations. The specific laws addressed are the Clean Water Act, and the Arizona Mined Land Reclamation Act. Topics that will be addressed are mine water and process water discharges, storm water discharges, pollution prevention, dredge and fill, spill prevention control and countermeasure plan, and surface water protection. Proposed changes to the laws and regulations will be discussed. Compliance strategies will be suggested to prevent potential noncompliance and enforcement.

Jan 1, 1996

By James Veri, Andrew H. Stern, Gerald N. Torbert

When mining coal, the occurrence of high methane liberation rates can often overwhelm the existing ventilation capabilities of the working place and result in elevated levels of methane gas. These “gas-off/stand-by condition" events often limit the production of the section and increase the potential opportunity for the occurrence of an ignition. This paper investigates the potential effectiveness of using a continuous miner equipped with an integral dust scrubber which was modified to provide high flow rates to reduce these events during active coal mining. Work was undertaken to quantify various adaptations of the mining system, by simulating site parameters in the controlled environment of an instrumented "full-scale" test facility. Monitoring (in real-time) of velocities and gas concentrations at many fixed points was also undertaken in an attempt to learn the effective limits of the system at high release volumes of gas.

Jan 1, 1997

By Dimitrios Litsas, Michael Kavvadas, Panagiotis Sitarenios

"The paper discusses the results of 3D finite element analyses to investigate the effect of face support pressure and soil permeability on face stability conditions in EPB tunnelling. Two main types of face behavior are identified: Undrained conditions ahead of the tunnel face, typically occurring in soils with permeability less than about k=5·10-7m/s, are shown to be favourable for face stability; analyses show that an applied face pressure comparable with the initial hydrostatic pore pressure is sufficient for adequate face stability, even for soils of relatively low strength. Drained or partially conditions, typically occurring in soils with permeability higher than about k=5·10-6m/s, show that face stability is strongly dependent on the horizontal effective stress of the muck in the excavation chamber; the presence of even a small effective stress in the muck is very beneficial for face stability conditions and can be a possible explanation of successful EPB tunnelling through relatively permeable soils. INTRODUCTION Face stability is probably the most important aspect in urban tunnelling. Usually, Earth Pressure Balance (EPB) machines are utilized, to ensure that a reasonable amount of face pressure is exerted on the advancing excavation face, reducing ground loss and preventing potential instability of the face core, thus controlling the amount of disturbance caused by tunnel excavation to surface structures. However, the ideal amount of face pressure depends on several factors (ground and groundwater conditions, tunnel size and depth, muck conditioning, etc.) which are difficult to include in analytical calculations. For many years, conventional empirical or analytical methods (e.g. Anagnostou & Kovari 1996) were the only available tools for quantifying face stability and selecting the required face pressure. In the last few years, however, numerical analyses have gained power over conventional methods, allowing more accurate designs and providing useful information about the anticipated ground deformations due to tunnelling. Numerical analyses have also been used in assessing safety against face instability using face extrusion (horizontal face displacement) calculations (e.g. Prountzopoulos 2012)."

Jan 1, 2016