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By Richard E. Gray

Subsidence due to coal mining is poorly understood by non-specialists. This has led to numerous misconceptions and myths based on limited observations and lack of knowledge. The three most common are: 1. Mine maps are inaccurate. 2. Deep mines are not a problem. 3. If no subsidence has occurred for many years after mining, there is no risk of future subsidence. Maps are important during mining and most are carefully prepared. Future use to evaluate conditions at mine level often includes drilling to confirm what the map shows. Usually, little or no effort is made to tie the surface survey of the property to the mine survey, to conduct a well designed drilling program to confirm the mine map, or to drill test borings vertically. When a mine entry is encountered rather than a coal pillar, or vice versa, and conditions at mine level appear different than anticipated, the first reaction is the mine map is inaccurate. The idea of a safe depth from subsidence is often based on the false premise that mining results in sufficient breakup of the overlying rock strata that bulking compensates for the coal extracted. The safe depth idea first appeared in the literature about 1880 and remained prevalent well into this century. Sadly, it is still encountered. The modern understanding of fragmentation of the immediate mine roof with the overlying beds sagging down on the broken roof rock was first described in 1900. With full extraction mining, either longwall or retreat room and pillar, surface subsidence occurs regardless of the depth of the mine. Subsidence over longwall mines at depths of 2000 feet can be 90 percent of the mined seam thickness. Numerous studies of undermined sites conclude that mining occurred many years ago and since no subsidence has occurred, there is no risk of future movement. This is true if sufficient coal pillars have been left to support the overlying strata. However, every year subsidence occurs over mines that have been closed for 100 years or more. In a study of subsidence incidents over the Pittsburgh Coal, the senior authors found that 50 percent of the incidents occurred above mines that had been closed for at least 50 years and 10 percent over mines closed for at least 80 years.

Jan 1, 1996

Numerous underground coal mine ventilation seals have been installed in the United States of America prior to 2006 and after implementation of the Mine Improvement and New Emergency Response (MINER) Act. Seal engineering, design, placement, and construction is regulated in industry, but post-construction monitoring of seals is limited to visual inspection of the outby face and seal perimeter, convergence measurement, and atmospheric monitoring. To monitor seal integrity and to provide safe working conditions, a form of non-destructive testing (NDT) is necessary to accurately reflect the health of the seal by detecting post-construction changes, deterioration, or defects within in-situ seals in underground coal mines. Previous research from the National Institute of Safety and Health (NIOSH) has indicated the potential for utilizing ground penetrating radar (GPR) for assessing in-situ mine seals. This paper provides an update to the assessment of proposed NDT methods for seal evaluation using commercially available GPR technologies and systems. Full-scale free-standing seals and large-scale seal specimens were analyzed with an array of GPR units from various manufactures using multiple frequencies.

Feb 23, 2014

By A. Adu-Acheampong

Photogrammetry and laser scanning has been employed at a number of Newmont mine sites to mitigate risks associated with conventional structural mapping, determining the geometry of voids from old underground workings, and generating topography in areas of slope instability. Laser scanning has also been used to evaluate as-built pit slope configurations with respect to design assumptions, operational practices, and rock fall potential. Recently, remote sensing applications carried on an unmanned aerial vehicle (UAV) were used to generate base topography at some Newmont sites. UAV are generally more convenient and less expensive and can be utilized in areas where cloud cover prevents manned aerial photography missions. This paper discusses these applications, and provides commentary on their benefits and limitations based on recent experience.

Feb 27, 2013

By Nikolaus Schneider

"Abstract: The combination of failure in joints of diaphragm walls and their exposure to water pressure may have far reaching effects ranging from water leakage to the risk of catastrophic loss of stability for the retaining wall and civil structures behind it. Investigations of imperfect joints in diaphragm walls have led to the development and testing of a quality tool to monitor the joint integrity of diaphragm walls during construction. By applying independent mechanical sensors (“joint inspector”) to the steel frame of hydraulic or mechanical grabs, it is now possible to record the surface conditions of exposed primary joints during the construction of secondary panels. This allows for the implementation of corrective action during the construction process should joint quality not indicate a watertight connection to the adjacent panel. The joint inspector, used for different types of stop ends, was tested on a full scale test field at several construction sites. The implementation of this new quality tool drives a new quality standard for deep excavations in inner city areas.General introduction to diaphragm wallsDiaphragm walls are reinforced concrete elements constructed using bentonite slurry to temporarily support an open trench in the ground. They are used in two main fields of application in civil construction, as foundation elements for vertical and horizontal loads (barrettes) and as retaining walls for excavation pits.Particularly for deep excavation pits in inner city areas, diaphragm walls are used as temporary or permanent walls of retaining walls. Alternative retaining wall systems would be secant pile walls, sheet piles or soldier piles, but these have disadvantages in structural strength when compared to diaphragm walls. If the vertical load of existing buildings next to the excavation pit has to be accommodated, the most practical solution can be found using diaphragm walls supported by prestressed anchors, steel struts or slabs."

Jan 1, 2014

By Richard P. Reiff

"The Facility for Accelerated Service Testing (FAST) program has been involved in numerous rail wear tests since its inception in 1976. A number of specialized tools have been developed to aid in assessing specific performance parameters including gauge face wear, head height loss, metal flow, head area loss, hardness, and welded rail end batter. The layout of a test site, including position in curve, number of measurements per rail, and train operation must be properly controlled/monitored to provide valid wear comparisons.This paper will provide an overview of the above-mentioned tools and techniques. In addition, a summary of recent test results from FAST, including information on head hardened rail investigations, will be provided. A set of guidelines for establishing a revenue service field test site will also be provided to aid users in performing evaluations of their own.IntroductionBackground of Rail Wear Testing at FASTThe Facility for Accelerated Service Testing (FAST) located at the Transportation Test Center, (TIC), Pueblo, Colorado has been involved with testing of rail since program initiation in 1976. A huge data base of rail wear information has been gathered from FAST operations under a variety of rail metallurgies, lubrication conditions, and measurement techniques. Attempts at obtaining meaningful rail wear information from early (1976-1978) FAST rail wear data was hampered by two main factors: (I) measurement techniques were insufficiently accurate for the amounts of wear being experienced, and (2) the lubrication was not sufficiently controlled to obtain uniform conditions for a sufficient measurement time period.Subsequent test periods were operated with improved measurement techniques and controls that ensured statistically valid data. The policies and conditions that permit accurate rail wear assessment will be reviewed and outlined in this paper, along with some specific TIC and field examples that will allow the user to improve the accuracy of a field rail test on their own operating property."

Jan 1, 1988

By Peter A. Rona

The Mid-Atlantic Ridge in the central North Atlantic and the Gorda Ridge within the U.S. Exclusive Economic Zone off northern California and southern Oregon are yielding new discoveries of seafloor hydrothermal mineralization. The TAG hydrothermal field in the rift valley of the Mid-Atlantic Ridge near 26 degree N, 45 degree W has been a site of international collaborative research since the discovery there of extensive manganese deposits associated with low temperature hydrothermal activity in 1973 as part of the TAG (Trans-Atlantic Geotraverse Project). The first high-temperature hydrothermal activity, massive sulfide deposits and vent biota discovered in the Atlantic were found at the TAG hydrothermal field in 1985. Collaborative dive series with DSV ALVIN in 1990 and in 1991 with the two Russian MIR submersibles in the TAG field have found and sampled large inactive sulfide mounds in addition to the previously known active sulfide mound. The active sulfide mound on the floor of the rift valley is about 250 m in diameter and 40 m high with a concentric zonation of mineral types and flow regimes decreasing in temperature from 365 degree C black smokers at the center to white smokers and diffuse flow toward the margins. The recent dive series in coordination deep-towed instrument surveys have delineated a zone extending about 5 km along the lower east wall of the rift valley of inactive sulfide mounds up to a kilometer in diameter. MIR Mound in this zone consists of a central sulfide zone about 400 m in diameter and 50 m high surrounded by a halo of low-temperature deposits to 200 m wide. Inactive sulfide chimneys contain the first primary, free gold grains found at a hydrothermal site on a mid-ocean ridge (P.A. Rona, Y.A. Bogdanov, E.G. Gurvich, N.A. Rimski-Korsakov, A.M. Sagalevitch and M. D. Hannington, 199 1 EOS, Transactions, American Geophysical Union, 72:470-471 and Journal of Geophysical Research, submitted).

Jan 1, 1992

By Andrea Lisjak Bradley

Clay shales are currently being assessed as possible host rock formations for the deep geological disposal of radioactive waste. However, one main concern is that the favourable long-term isolation properties of the intact rock mass could be negatively affected by the formation of an excavation damaged zone (EDZ) around the underground openings. The goal of this thesis was to develop and validate a mechanically-based model of the deformation and failure process of a clay shale, namely Opalinus Clay (OPA), with particular focus on the influence of anisotropy on the short-term response of circular tunnels. To achieve this goal, a hybrid continuum-discontinuum numerical approach was developed in combination with new field measurements from the Mont Terri underground research laboratory. The response of OPA during the excavation of a full-scale emplacement (FE) test tunnel was characterized by geodetic monitoring of wall displacements, radial extensometers and longitudinal inclinometers. The deformation measurements indicated strong directionality induced by the combined effect of in-situ stress field and bedding planes striking parallel to the tunnel axis, with the most severe deformation occurring in the direction approximately perpendicular to the material layering. Computer simulations were conducted using a newly-extended combined finite-discrete element method (FEM/DEM), a numerical technique which allows the explicit simulation of brittle fracturing and associated seismicity. The numerical experimentation firstly focused on the laboratory-scale analysis of failure processes (e.g., acoustic activity) in brittle rocks, and on the role of strength and modulus anisotropy in the failure behaviour of OPA in tension and compression. The fracturing behaviour of unsupported circular excavations in laminated rock masses was then analyzed under different in-situ stress conditions. Lastly, the proposed modelling methodology was applied to the aforementioned FE tunnel to obtain unique insights into the EDZ formation process around emplacement tunnels for nuclear waste. The calibrated numerical model suggested delamination along bedding planes and subsequent extensional fracturing as key mechanisms of the damage process potentially leading to buckling and spalling phenomena. Overall, the research findings are already having a direct impact on the preliminary design process of an underground repository for nuclear waste in Switzerland.

Jan 1, 2015

By R. J. Young, S. J. Tennant, A. D. Drummond

"Gibraltar Mines is located on the western slope of Granite Mountain, 230 air miles north of Vancouver, B.C. and 38 miles north of Williams Lake, B.C. There are four mineable zones within the copper-molybdenite deposit: Gibraltar East, Gibraltar West, Pollyanna and Granite Lake. Open-pit reserves are 358 million tons which average 0.37% Cu and 0.016% MoS2 at a 0.25% Cu cut-off. The Granite Mountain pluton is one of the several Jurassic-Cretaceous intrusions which outcrop along the east side of the Fraser River fault system between Williams Lake and Prince George, B.C. The original Granite Mountain quartz diorite has been metamorphosed by a cataclastic deformation which foliated the rock on a regional scale. Attendant to the development of the foliation, the rock was saussuritized such that the present mineralogy is compatible with that of the greenschist facies. The presence of garnet-bearing assemblages is explained by a restricted increase in water pressure. Pre-mineral intrusive phases within the saussuritized quartz diorite are: (1) leucocratic quartz diorite, (2) aplite and (3) quartz-feldspar porphyry. A late chloritized hornblende dacite dyke is post-mineral. Quartz-feldspar porphyry and leucocratic quartz diorite are locally present on the inner sides of the Gibraltar East, Pollyanna and Granite Lake pits. Their presence suggests a core around which occurs an elliptically shaped sulphide-bearing stockwork. The stockwork, which comprises four ages of vein development, is imposed on and partly controlled by the regional foliation of the samssuritized quartz diorite."

Jan 1, 1973

By Ulrich Kappus

The purpose of the project is to divert flood flows of North Potato Creek. The project is located in the southeast corner of Tennessee near Copperhill, approximately 160 kilometers north of Atlanta, Georgia. The project consists of: a 28-meter high dam, a 90-centimeter diameter outlet conduit; an emergency spillway; and a 4.0-meter diameter hard rock trans-basin diversion tunnel. This floodwater management system was part of Cities Service Company mine safety program for the Cherokee orebody which is partially located within the stream channel. The following paper describes the entire project development from feasibility studies to design and construction management.

Jan 1, 1978

By Elaine R. Goetz

The eastern and southeastern regions of Ohio are part of Appalachian coal country, with a documented 1,300 miles of streams impacted by acid mine drainage. Since 1995, partnerships of local watershed groups, government agencies, private industries and universities have focused on the remediation of the affected waterways. The partnerships have spent $2.4 million annually in constructing and operating treatment systems such as wetlands, anoxic limestone drains, successive alkalinity production systems, steel slag leach beds, and lime dosers. These systems have been partially successful, and water quality has improved in the region, but no treatment has yet met the ultimate objectives of low cost, continual remediation. Our research group has investigated an alternative system for acid mine drainage treatment: electrolysis combined with pH adjustment to selectively precipitate recoverable, saleable metal products to offset the cost of treatment. We utilized a $0.2 million pilot facility constructed by the Wayne National Forest, in Nelsonville, Ohio, to process approximately 40 L/min of mine drainage from surrounding seeps. The pilot facility has multipurpose tanks that can be adapted to process acid mine drainage with different characteristics, such as high or low aluminum content or high or low carbonate concentrations. Sodium hydroxide was used for pH adjustment. Results indicate that saleable product can be generated with this treatment technology. In an initial, not optimized trial, one seep yielded 4.7 kg of dried 69 % iron oxide product from 10 hours of pilot facility operation, treating 23,000 L with electricity costs of $4.68. Dissolved iron concentrations in the water were reduced from 242 ± 18 mg/L to 2.8 ± 2.0 mg/L (99.0 % removal) while the initial acidity of 443 mg/L as CaCO3 was neutralized to an alkalinity of 160 mg/L as CaCO3. Iron oxide can be sold as pigment for an average of $1.47 per kg in the United States. Currently, approximately 80 % of all pigment used in the United States is imported, and there is incentive to purchase domestically recovered pigment. If the iron oxide from the pilot facility could be sold as pigment for $1.47 per kg, 43 % of the operating cost (raw materials, electricity and construction costs) of treatment could be offset by the sale of the product. Considering the cost offset, the electrolysis process shows potential as a sustainable low cost alternative for treating acid mine drainage.

Aug 1, 2013

By Anthony Edey

This report describes work performed and results obtained for the technical and economic feasibility study of oil production by mining methods. The characteristics of oil fields which would make them amenable to mining techniques were identified. An inventory of known U.S. oil fields that offer this potential was collated. This was further divided into fields having potential for underground and surface mining systems development. Several candidate fields that fit particular underground and surface mining system types were then selected. Conceptual mining systems were designed for the selected fields. Five underground and four surface methods were chosen. Costs of oil production were estimated for these selections. The impact of oil mining an the environment was also considered.

Jan 1, 1978

By A. S. Knight

THE breaking and handling of ore is obviously the most important consideration when the layout of a new mine is contemplated. The problem must be attacked with due regard to the claim area of the property, the dip of the orebody, the anticipated percentage of payability, the width of the reef, and the amount of dislocation anticipated by dykes, faults, or sills. Among these, as far as East Geduld is concerned, the three most important items are: Area. 2,640.5 claims. Average dip 12° (from flat to 35°) Average channel width 36 inches. We are fortunate on the Witwatersrand in 'chat there is usually sufficient information available from surrounding properties to determine, within narrow limits, the factors mentioned above. With this information avail-able, the choice of layout is not limited, and it will be found that on the Witwatersrand each group has developed its own technique to suit its individual requirements. On East Geduld, the layout of the property for handling ore is known as the endless-rope haulage system. Following is a brief description of the general principles followed.

Jan 1, 1942

Factors leading to the necessity for some individual testwork in solving most specific hydraulic transportation problems are listed and a description is given of a method used in determining critical flow conditions. An outline is given of the basic theory of the purpose of the testwork, and a means of applying test results for varied pipeline diamet.er and material conditions follows. Engineering and economic factors are applied to the solution of a specific hydraulic transportation problem and the use of the test results in plant practice is illustrated. The advantages of connecting pumps in series in centralised pumping stations rather than individually along the pipeline are stressed. Some notes are added on the future possibilities and economies of post pump injection of solids into high pressure pipelines.THE HYDRAULIC TRANSPORTATION OF SANDSAs well as all the classical variables involved in a pipeline installation, one must consider, when solids are to be transported, the effects of such variables as:(i) Proportion of solids in the pulp.(ii) The average specific gravity of the pulp.(iii) Specific gravity of the solid material.(iv) Solid particle average sizing and possibly shape.(v) Solids particle grading.(vi) Pipeline diameter for effects other than classically hydraulic.(vii) Pipeline material.(viii) Fluid viscosity.(ix) Pump characteristics.(x) Abrasive or corrosive properties of the pulp.Not surprisingly, the application of published data to the hydraulic transportation of a specific material is difficult if not well nigh impossible. Most hydraulic transportation investigations also involve economic and site factors vary...

Jan 1, 1959

By G. Nash

Despite further declines in production for some producers, 1986 proved to be a landmark year for the asbestos industry. The key event was the adoption of The Asbestos Convention by the Inter- national Labour Organization (ILO) and its 150 member countries. The document, entitled "Safety in the Use of Asbestos", reaffirms the international consensus on the "controlled-use" approach to chrysotile asbestos regulation. The decision of the ILO has come at a critical point in time. It represents a major turning point and provides an important building block for the long term future of the asbestos industry.

Jan 1, 1987

By Willie M. NeSmith

Conventional augered, cast-in-place (ACIP) piles were introduced into the New York City area as a result of the damage to existing structures caused by pile driving operations. ACIP piles are often specified where deep foundations are to be installed adjacent to transit facilities, sensitive underground utilities or in close proximity to existing structures. However, loss-of-ground issues associated with the installation of ACIP piles have prevented the wide-scale use of these systems. Beginning in 2002, Berkel & Company Contractors, Inc. began using its augered, cast-in-place displacement (ACIPD) system in the New York City area. Like conventional ACIP piles, this system produces almost no vibration. Also, as almost no material is brought to the surface, there is no opportunity for loss of ground. This paper presents a description of Berkel's displacement pile system and a brief discussion of six projects in the New York City area that have been executed with this system over the past two years.

Jan 1, 2004

By Sherwin F. Kelly

THE geophysical scene shifts and alters, the emphasis changes, and new possibilities loom, but the tendency is always towards widening the field and deepening the analytical penetration. Seismic methods have had their heyday, the torsion balance is being displaced by the gravimeter, electrical methods are showing deeper penetration, soil analysis is the newest tool, and gamma-ray logging appears on the horizon. One of the striking features of re- cent geophysical work in the oil fields has been the marked decrease in the number of seismic crews employed. Although the percentage of company crews is believed to have increased appreciably. the sum total has fallen sharply, as shown by the figures for the Gulf Coast area. About two years ago probably over 100 seismic parties were operating there, whereas now there are only about 35. This decrease may be partly due to the low prices of petroleum with a consequent reluctance to spend money to increase crude-oil re- serves but more probably to the fact that reflection and refraction shooting have been carried on so extensively that they have been applied to a large pro- portion of the areas in which they may reasonably be expected to succeed. Some of the earlier enthusiasm, particularly over reflection prospecting, may have erred on the side of over- optimism; some of the present curtailment may be due to over pessimism; but in the opinion of various observers seismic work at the present rate seems to be at it- optimum. It nevertheless remains pre-eminent as a technique for detailing structures in areas where good reflections can be obtained and is the only method that will give accurate depth to definite beds. Results may be poor in certain areas but many regions still remain wherein it can be applied, so that plenty of structural mapping remains to be done by the reflection seismic method.

Jan 1, 1940

By Alex Chapman, Cam Thomas, Bryan Karney

"During the early summer of 1989, Ontario Hydro removed a concrete portion of the North Channel Dam at Crystal Falls Generating Station by blasting and excavating in marine conditions. Because of the severity of underwater blasting and because the site was in close proximity to the replacement dam, there was concern that hydraulic shock waves generated by the detonation could damage either the new dam or its control structures. This paper examines the data associated with the hydraulic shock waves generated by underwater blasting, and studies the effectiveness of an air curtain in reducing the peak pressures. In previous trials using the air curtain technique, a rule-of-thumb factor was used to estimate that only 10% of the original pressure pulse would propagate across the air curtain. However, this value had little basis in theory. A theoretical formulation of the problem by Karney in 1989 indicated a provisional value of 0.18 for this factor, but was heavily dependent on confirmation from in-field testing. Data provided by Ontario Hydro from an actual blasting procedure indicate that a more conservative value of 0.32 may be more appropriate. Thus.although the air curtain did provide considerable reduction of peak pressures, the data at Crystal Falls indicates its performance was below the anticipated level. However, due to problems with the instrumentation and some inconsistencies in the resulting data. it is recommended that this value be further refined as additional data become available."

Jan 1, 1992

By Kray Luxbacher, Mario Karfakis, Erik Westman, Peter Swanson

Three-dimensional velocity tomograms were generated to image the stress redistribution around an underground coal longwall panel to produce a better understanding of the mechanisms that lead to ground failure, especially rockbursts. Mining-induced microseismic events provided passive sources for the three-dimensional velocity tomography. Surface-mounted geophones monitored microseismic activity for 18 days. Eighteen tomograms were generated and high-velocity regions correlated with high abutment stresses predicted by numerical modeling. Additionally, the high-velocity regions were observed to redistribute as the longwall face retreated, indicating that velocity tomography may be an appropriate technology for monitoring stress redistribution in underground mines.

By Robert J. Timko

In early June 1986, an underground fire of unknown origin erupted in one of several entries of a coal mine located in southwestern Colorado. For a time, mine personnel aggressively fought the fire. However, control of the fire was later lost. To prevent further damage and reduce the possibility of an explosion, all portals and shafts to the mine were sealed. The mine operator requested the U.S. Bureau of Mines' assistance in obtaining and analyzing mine fire gases taken from sampling ports placed through the mine seals, as well as down boreholes drilled after the fire. This report recounts activities within the first 2 years of the mine being sealed. It includes a description of gases analyzed and mine atmosphere status equations generated from the analyzed gases. The gases were analyzed by chromatography and included standard atmospheric gases as well as higher hydrocarbons that are found in postfire atmospheres. Nine equations were used to evaluate what was occurring within the sealed mine. Following a description of the rationale behind each equation, the 2-year trend is briefly analyzed.

Jan 1, 2010

By F. P. Hassani, H. B. Poorooshasb

"A kinematically admissible velocity field is applied to study the arching phenomenon in a cohesionless granular backfill placed between two rough vertical inflexible walls. The study is different from the previous works which are almost entirely based on statically admissible stress fields. It is shown that the development of arches is strongly influenced by the previous loading history of the backfill which controls the nature of the constitutive laws that govern the mode of stress deformation of the backfill. This preliminary study employs simple models in order to show the potential use of such an approach in evaluating and understanding mine backfill behaviour in the underground excavation. The pressure exerted on the floor supporting the backfill is also studied in some detail.INTRODUCTIONAlthough the importance of the design of mine backfill has been discussed extensively by a number of authors, i.e. Hassani et al. (1985), such theories have not as yet been incorporated in design criteria for underground mine backfilling operation . One factor that such theories must incorporate is the so-called arching action .The phenomenon of arching has been the subject of study by many researchers in the field of civil engineering and mining engineering. Among these scholars the works of Terzaghi (1943), Krynine (1945), Lusher and Hoeg (1964) and Handy (1985) are noteworthy. All these authors use a statically admissible stress field as a starting point to develop their theories. The approach taken by the authors of the present paper is completely different because they employ a kinematicallyadmissible velocity field. It is their belief that the arching phenomenon is closely linked to the interlocking of grains as manifested by the degree of dilatation of the granular mass when subjected to a shearing process.This paper is written in the following sequence. To define the interlocking quantitatively it is necessary to state the constitutive law governing the stress deformation characateristics of the granular mass. This is done in the next section as the law proposed by Poorooshasb and Pietruszazck (1985, 1986) is stated and simplified to suit the present analysis. Next the mode of formation of an arch in a simple system consisting of a mass of backfill sandwiched between two vertical rough walls of infinite extent is examined. The velocity field obtained from the above example is used to obtain solutions to two more complicated situations. The first situation assumes that the backfill is supported, in addition to the vertical rough walls, by a Winkler foundation at its base. The second situation assumes that the Winkler foundation has been replaced by a horizontal beam of uniform section and simply supported at its extremities. The findings of the study are summarized and their practical implications discussed in the concluding remarks."

Jan 1, 1989