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By J. Hunter, E. Jackson

This paper describes work done by Placer Dome Technical Services Limited, a subsidiary of Barrick Gold, and Nautilus Minerals Inc. in support of the conceptual design of a subsea mining system. It describes an overall concept design plus specific studies into mechanical excavation at depth. The concept design includes one or more subsea excavators connected to a suction riser, which transports the cut material to a shipboard dewatering and offloading system. A multi-phase investigation was performed into the mechanical excavation of seafloor massive sulphides at depths of around 1600m. Rock samples were recovered and tested for rock properties and cutting behaviour. A small pick drum cutter was procured and tested on a representative concrete slab in a lab and tested again while submerged in a test tank. Finally the cutter was tested on a massive sulphide ore body at 1600m depth. The cutting performance results, e.g. pick forces and specific energies, should provide valuable input to the design of future full scale subsea mining systems.

Jan 1, 2007

By B. Solar Menéndez, M. B. Díaz Aguado, I. Á. Fernández, C. González Nicieza

The analysis of subsidence due to the opening of an underground void (mining, water exploitation or civil works hole) is a problem usually hard to solve. First of all, it requires a predictive model, in order to define both the displacement magnitude and area affected by subsidence. Such model should be validated with measurements of the actual movements sustained on the surface, in order to adjust it properly and enable influence of future behaviour in a reliable way. Two different kinds of problems might arise. On one side, it is necessary to control and measure surface movements in a very exhaustive way during a long period of time, beginning before underground works take place and finishing years after they are over. Furthermore, three factors bring in errors, some times of magnitudes higher than the displacement magnitudes measured. These include: the fact that reliable and long-term information cannot always be achieved; the precision of measuring devices; and the design of the topographical network itself. In addition, the predictive models more widely used only apply to certain excavation geometries, mainly to horizontal holes. In light of this background, the Group of Rock Engineering, of the University of Oviedo Mining Department, has developed a working methodology and a specific software tool, Subsidence 3D, to estimate ground displacements and strains. The program will allow for predictive models to be defined and also allows the treatment of data related with topographical marks and its comparative analysis with calculated results. The software has been programmed using Visual C++. Graphical outputs however are generated using AutoCAD 2000. This paper mainly refers to a practical situation, an underground coalmine, remarking the main difficulties arisen during the study of the available information and proposing how to solve them. A predictive model in subsidence 3D was established and validated. The actual behaviour of the ground was that in the model.

Jan 1, 2003

By N. B. Aughenbaugh

Subsidence due to abandoned coal mines has received copious attention recently. This is a result of many factors such as the enactment of new mining laws and the effect subsidence has on land use over the mines. Prediction of subsidence features and the time aspects over supercritical extraction (i.e., longwall and high extraction ratio pillaring) is relatively accurate. However, predicting when subsidence will occur and the surface features' size and shape above subcritical extraction of room and pillar mining is not yet possible. This paper will discuss the factors that influence the time aspects of subsidence in room and pillar mining.

Jan 1, 1983

By Axel Preusse

For the last 150 years, subsidence damage to the surface has been an unavoidable phenomenon associated with underground coal mining. In particular, the mechanization of mining methods in multiple seam mining and the concentration of mining activities in densely populated European metropolitan areas (e.g., Ruhr, Upper Silesian industrial region) have led to mining having a very strong influence on the earth?s surface. In both these regions, surface subsidence of more than 20m has been reported up to now in comparison to the original state. Underground coal mining in these regions strongly impairs all kinds of surface use, such as urban and industrial development, infrastructure (roads, waterways, and railways) and pipelines?without restricting the functionality of those objects to a greater extent. Demanding and, in some cases, globally unique engineering solutions have been developed and implemented for this purpose. The previously mentioned mining and industrial regions are still very strongly characterized by the (increasingly declining) coal industry and will remain dependent to a large extent and for an indefinite period on artificial drainage measures because subsidence that has already occurred is irreversible. This paper will primarily discuss the prediction of subsidence that is caused by intensive multiple seam mining and its influence on surface objects (e.g., underground pipelines). However, an approach for predicting ground uplifts due to rising mine water as a consequence of mine closures will also be described.

Jan 1, 2012

By R P. Callaghan

Underground production from the low grade copper orebodies at Mount Lyell in recent years has involved surface subsidence of open cut areas. Relevant structural and lithological features of the geological environment are described. The highly mechanised underground mining system involves sublevel caving and sublevel open stoping with associated hanging wall cave. Monitoring of subsidence and caving has been made by regular visual inspection and measurement of crack development, and by surface profile surveys. These simple techniques have proved adequate in assuring management that ground movement is proceeding normally and safely.

Jan 1, 1980

By Victor V. Nazimko

Long term stability of the pillars that have been remained after R&P extraction causes postponed subsidence. To prevent unforeseen subsidence and to diminish postponed subsidence 25-50% new method for its control has been developed by the author. It supposes to use drilling and blasting technology and other original approaches. New method has been fulfilled through the holes being drilled from the surface or from the active underground openings. Explosives had been charged into the holes and were blasted. This had increased bulking factor dramatically and prevented natural caving of the strata. Physical scale modeling corroborated efficiency of the new approach. The bulking factor has grown from 0.0623 to 0.1185 and surface subsidence has been diminished from 1.1 m to 0.2 m or 5.5 times.

Jan 1, 1996

Mining is taking place at increasing depths of cover on the Southern Coalfield beneath predominantly massive sandstone strata. Within the next twenty years, there will be longwall mining at depths greater than 600 m. As the Sydney Metropolitan area continues to expand and as coal mining approaches these urban areas subsidence will continue to become an increasinglY important aspect of coal mining research. Investigations, commenced in the mid 1960's, allow prediction of subsidence in the Southern Coalheld with reasonable confidence. The work is showing that the characteristics of thc subsidence troughs over the deeper mining at Appin differ from the characteristics of mine subsidence at less cover.The longwall mining at Appin Colliery has resulted in a maximum measured subsidenee of 730 mm. The maximum strains were small because of the large radii of curvature of the subsidence profiles. There was no damage to any of the buildings in the township of Appin.

Jan 1, 1982

By G. Krogman, C. Walla, B. Wood

The Gebo Mining District (District) is located in the Bighorn Basin of Wyoming. Commercial underground coal mining began in 1906 with the arrival of the railroad in Thermopolis, which is located approximately 11 miles to the south. Mining in the District ceased by the early 1970’s. In Fall of 1999, Lidstone and Associates, Inc. (LA) and their subcontractors were retained by the Wyoming Abandoned Mine Land Division (WyAML) to perform an inventory of over 500 abandoned mine sites across Wyoming. During the summer of 2000 field inventory, a 30-foot deep headcut (Figure 1) and sink-hole were noted in the West Fork of Sand Draw (WFSD), immediately west of the Town of Gebo. The headcut and sink-hole were located at the culvert outfall associated with a stream crossing of a relatively well traveled county road. Upon further investigation, it appeared that underground mine workings had been exposed at this location. This resulted in a condition whereby water would be conveyed directly into the mine workings during a runoff event. The exposed mine workings as well as stream capture created a very hazardous condition. The WyAML implemented mitigation measures in the summer of 2000 by constructing a temporary stream crossing upstream of the existing failed crossing. To address this hazardous situation as well as a number of other hazards identified in the District during the field inventory, the WyAML retained PHC Reclamation, Inc. (PHC). PHC was directed to perform a field investigation and develop a Reclamation Plan to address all existing abandoned mine hazards in the District. Federal, state, and private parties own lands within the District. Hazards identified during the investigation included an underground mine fire, open adits, open shafts, subsidence, drainage problems, and coal slack. A Report of Investigation (ROI) was submitted to various regulatory agencies that documented the existing conditions and conceptual reclamation plans to remediate the hazardous conditions. After review of the ROI by the US Department of Interior - Bureau of Land Management (BLM) an on-site meeting was conducted. BLM Cultural Resource personnel declined to approve a District reclamation project until a historical overview of the entire District was prepared. Due to the hazardous situation associated with the WFSD stream crossing, Hot Springs County Road and Bridge Department convinced various state and federal regulatory agencies to allow reclamation of the stream crossing to occur. A decision was made to allow reclamation on privately owned lands within the WFSD drainage. This decision limited the amount of channel that could be subjected to reclamation upstream of the crossing to privately owned lands. PHC contracted LA to perform a geologic, geomorphic, hydrologic, and hydraulic investigation of the drainage to assist in the development of a WFSD reclamation plan. LA’s investigation consisted of four parts: Delineate the extent of mine workings in the area; Identify all drainage structures that required mitigation; Survey a series of channel cross-sections and a longitudinal profile of the impacted channel; and, Develop basin hydrology to assist in the design of a stable reclaimed stream channel.

Jan 1, 2006

By Dr. Peter J. Conroy

The current study is part of the U.S. Department of Energy's (DOE) on-going subsidence research program. The long-term objective of the DOE program is to develop analytical methods of subsidence prediction applicable over a broad range of geologic and mining conditions encountered in the United States. The DOE currently has several contracts in progress to develop a sound data base that can be used in the development of predictive models. Dames & Moore is currently under contract to the DOE to collect and analyze detailed subsidence and hydrologic data from a coal mine employing longwall mining methods in the Eastern Coal Province. Work under Contract No. DE-AC22-80PC 30335 began in October of 1980 and will continue through September of 1984. This paper summarizes the work that has been completed through September of 1981 and presents the results that have been achieved during this period. Technical difficulties encountered during both the installation and monitoring phases are discussed, and recommendations for future work are presented.

Jan 1, 1982

By Yoginder P. Chugh

Subsidence may be observed above partial extraction shallow room-and-pillar mines where the coal seam(s) is associated with weak and thick claystone in the floor. This paper presents results of subsidence studies at such a mine. During the 26-month study period, a time dependent subsidence causing a maximum vertical movement of 50 mn was observed. After a subsidence rate of 6.0-6.5 m/month for the first two months after development of mine workings, the rate decreased to 0.8-0.9 mm/month after 17 months. However, presumably due to settlement of barrier pillars, it increased therafter to 1.7 mm/month for the next 9 months. Angle of draw, based on zero subsidence, was calculated to be about 29 degrees. Maximum tensile strain and compressive strain values observed were 0.040 pct and 0.039 pct respectively. A hypothesis was fomlated to correlate surface subsidence movements with observed underground movments. The data collected to date fits reasonably well within the formulated hypothesis.

Jan 1, 1989

By C. A. Johnson, K. F. Unrug

The identification of the major subsidence areas in the Eastern Kentucky Coal Field has been made to distinguish the subsidence phenomena on the basis of geographical location. Further, this identification process is based upon selected critical geological, topographical, and mining features in the coal fields. The proposed identification of the regions is derived from a comparison of the subsidence potential in a particular area. The most likely severe subsidence areas are compared to those with the probable low subsidence severity. The combination of certain geological and mining parameters involved allows for the derivation of a classification of the subsidence potential.

Jan 1, 1986

By Jurgen te Kook

State-of-the-art for subsidence calculation are stochastical models. Although these models were successfully used all over the world they have their limitations due to the fact that they are not based on mechanical laws. For example the models did not take the rock mass structure and the rock mass characteristics into account. Therefore in a research program the skills of geomechanical numerical models for subsidence calculation were investigated. A case study shows that numerical models which are in principle based on the elastic theory are suitable for subsidence prediction. Due to the principles of these models the results are not sufficient in the case of multiple seam extraction. More extended geomechanical numerical models like FLAC and UDEC were investigated in further steps of the research work. Up to now large area geomechanical models require unrealistic long calculation times if the level of detail is similar to that of small scale calculations. Due to this it was necessary to implement a simplified description of the rock mass structure and characteristics. Different case studies show that this approach is successfull for subsidence calculation by numerical geomechanical models even for multiple seam extraction.

Jan 1, 2008

By Ian Misich

Surface subsidence resulting from "total extraction" of coal in the Collie Basin first occured in 1987 when Western Collieries Ltd trialed the Wongawilli mining method. Because very little quantitative subsidence data existed for the weak, Permian sediments, a research program was set up prior to the extraction of the first panel. The objective of the study was to be able to predict subsidence characteristics and effects prior to mining future total extraction panels. Attempts at predicting subsidence began using existing subsidence models from other coal mining regions, however, as more site information became available, it became clear that it was necessary to develop a separate, site specific predictive model for the Collie Coal Basin. Analysis of extensive field monitoring data for both surface and subsurface subsidence has produced a series of empirical models which can predict the shape of surface subsidence troughs and corresponding tills, and strains for rectangular panels and describe the sequences of ground movement from the mine root through to the ground surface. The fact that both subsurface and surface subsidence characteristics have tied in well, gives greater confidence for predictions made from these models

Jan 1, 1992

By Miklos D. G. Salamon

If all stratifications are horizontal, the computation of surface deformation induced by coal mining involves the prediction of roof and floor convergence and then the transfer of the effects of this relative displacement to the surface through the use of the appropriate influence functions. A laminated model, in the form of a quasi- continuum, provides a simple means of computing the approximate convergence distribution and leads to the Gaussian distribution as the influence function. The ideas presented in this paper represent a subtle but fundamental generalization of the influence function Method. It is postulated that the influence of a small area of extraction is proportional to the roof and floor convergence and not to the thickness extracted. This difference in definition removes many conceptual difficulties associated with the influence function method. To demonstrate the utility of the model, the surface disturbances induced by the extraction of a parallel sided long panel are derived. Formulae giving subsidence, tilt, horizontal displacement and strain are given.

Jan 1, 1989

By Keith A. Heasley, Timotlly M. Barton

Historically, the surface subsidence over underground coal mines has been predicted using empirical profile or influence functions which have little or no connection to the actual mechanics of the subsidence- Without a mechanistic basis, establishing the exact site-specific parameters to use in these empirical methods has been problematic. A practical subsidence predictive method based on mechanics has the appealing capability of allowing the determination of site-specific parameters from fundamental properties of the overburden with minimal field calibration work. This paper presents a case study where a mechanics-based, boundary-element program is used to calculate the surface subsidence associated with several panels of a Northern Appalachian longwall coal mine. The program used in this case study is called LAMODEL, and it incorporates a frictionless, laminated overburden into a general purpose displacement-discontinuity code primarily designed for calculating the stresses and displacements in coal mines or other thin seam or vein type deposits. In this paper. the program is used to calculate both the underground convergence and the resulting surface subsidence at three longwalls. The subsidence results from the model are compared with field measurements and analyzed The results from the case study in this paper demonstrate that the laminated model with calibrated properties can easily provide fairly accurate subsidence predictions and is fairly flexible for fitting measured subsidence. However, additional subsidence predictive case studies are recommended in order to ultimately evaluate the potential of the laminated overburden model for practical subsidence prediction

Underground Mine Drainage may be conveniently divided into two operations:(a) Collecting and transporting drainage water to the pump eastern.(b) Elevating water to the surfacc by pumping.This short paper describes a system which automatically performs operation "a" and which has been developed on the South mine at Broken Hill, under the supervision of the mine foreman, Mr. F. McDonell. Operation "a" does not come under the heading of "subsidiary mine" drainage.SUMMARY(1) All drainage waters are collected by gravity flow into sumps.(2) Automatic control boxes operate syphons which transfer water from level to level to pump cisterns or to feed water service.EQUIPMENTSyphon Control Boar - Constructed of 10 ft. x 2 ft. oregon timber, suitably bolted together and equipped with a Bailey's cistern valve, with copper ball float control, and 12 in. pipcs and fittings forming a syphon (Fig. 1). One of these boxes is placed on each level at the shaft.The valve and float are so arranged that when the float is up (ie, box full) the valve will be fully open, and when the float is down (ie, box empty) the valve is closed. The vertical range between the cxtreme positions can be altercd by lengthening orshortening the adjustable arm of the float. The ideal valve is one...

Jan 1, 1927

By Evan Just

DIRECT subsidies for mine production in this country began as an outgrowth of wartime 'price regulation. The price-fixing authorities realized that the volume of production to be required from domestic copper, lead, and zinc mines would invoke costs of production considerably higher than the established ceiling prices. Accordingly, beginning Feb. 1, 1942 the Premium Price Plan was set up, which undertook to pay premiums to mines for production in excess of quota, of 5¢ per lb of copper and 2Y4¢ per lb of zinc or lead. Quotas, except for small mines, were initially established at the average rate of production in 1941, but were later reduced arbitrarily on an individual basis. Subsequently, additional "B" premiums were set for lead and zinc of 2Y40 per lb and a further "C" zinc premium of 2%¢. Additional copper premiums were negotiated on an individual basis, mainly with small mines. Quotas under each of these successive categories were the production obtained at the next lower premium level. In other words, under ceiling prices of 12¢ for copper, 6,14¢ for lead, and 83¢ for zinc, it was possible for high-cost operations to receive prices plus premiums of 17¢ or more for copper, 12¢ for lead, and 16% 0 for zinc on a portion of their production. On the other hand, some of the larger operators received only slight premiums and in at least one instance none at all. The average price plus premium for copper was 12.25¢ in 1942 and rose to 13.65¢ in 1945. That for lead was 6.99¢ in 1942 and 8.73¢ in 1945, and for zinc it was 9.06¢ in 1942 and 11.200 in 1945.

Jan 1, 1948

By Edward Thomas

Yucca Mountain Overview The U.S. Department of Energy?s Yucca Mountain Project is a geologic repository project designed to receive, handle, package, transport, and emplace spent nuclear fuel and high level radioactive waste. The planned repository would be located in Yucca Mountain on the western edge of the Nevada Test Site, about 90 miles northwest of Las Vegas, Nevada, and would include both surface and subsurface areas. Yucca Mountain rock formations consist of successive layers of volcanic rocks (called tuffs) approximately 14 to 11.5 million years old, formed by eruptions of volcanic calderas to the north. With the volcanic rock the potential for methane emission is not an issue and the subsurface repository is a non-gassy (methane) classification. This paper will provide a summary of the development ventilation system design that provides fresh air for subsurface construction activities, and the emplacement ventilation system design that removes heat generated by the waste packages. The subsurface layout, illustrated in Figure 1, contains 108 emplacement drifts, one Performance Confirmation(PC) observation drift, nine intake/exhaust shafts, and three access ramps. The existing Yucca Mountain facilities, shown in bold lines in Figure 1, include a 7.8 km long, 7.62 m (25 ft) diameter U shaped tunnel that is formed by the North and South Ramps at both ends of the Exploratory Studies Facility (ESF) drift and a 1.5 km long, 5.0 m (16.4 ft) diameter Enhanced Characterization of the Repository Block drift (ECRB) that were constructed from 1994 through 1998. These drifts were used for site characterization activities and have been incorporated into the subsurface repository configuration. The unexcavated perimeter access main and exhaust main drifts are typically 7.62 m (25 ft) diameter TBM excavations and the emplacement drifts are 5.5 m (18 ft) diameter TBM excavations. The turnouts leading into the emplacement drifts are to be excavated by either mechanical, or drill and blast methods and serve as the launch chambers for the emplacement drift TBM excavations.

By D. Bour, C. Nyikos, R. Curtice

Fire in a coal mine can be disastrous on many levels. In most cases, when a fire is detected, mining operations cease and all personnel are evacuated. Underground coal-mine fires are difficult to extinguish, can burn for a long time, and often result in an extended period of lost production. In a worst-case scenario, the mine is permanently sealed and abandoned, resulting in lost jobs, lost natural resources, and possible devastation of the local economy. In some cases, seals placed within the mine to isolate the fire could eliminate the need for sealing the entire mine and the subsequent extended delay in returning the mine to full operation. Previous attempts to place remote seals to extinguish mine fires in active mines have been largely unsuccessful. The West Elk mine experienced an underground fire in early 2000. The fire could not be accessed and extinguished from the active mine workings. A method of constructing seals remotely by drilling boreholes into the affected area was needed to help isolate and extinguish the fire. This paper describes the process by which remote seals were constructed that successfully isolated the fire and provided a means of extinguishing the fire by flooding the area with water. The period of lost production in the West Elk mine was considerably shorter than is typical in similar situations.

Jan 1, 2002

By D. C. Oldroyd

Western Coalfield?s Tandsi Mine, has difficult support conditions and a history of roof falls, resulting in mining roadway widths and depths being restricted for safety reasons. Rock Mechanics Technology Ltd was contracted to improve the support system to allow the introduction of mechanised room and pillar mining. The introduction of a ?world best practice? bolting system resulted in major improvement in roof stability, allowing mining restrictions to be lifted and Tandsi to become one of the first two Indian mines to introduce a mechanised continuous miner system. The first year?s production was some six times previous levels. Because of the improvement in the support system, RMT was also able to design a partial de-pillaring system suitable for the Tandsi continuous miner districts together with the introduction of monitoring procedures and guidelines to maintain safe roof support conditions. In situ monitoring of pillar and roof behaviour was undertaken as the first pillars were extracted to confirm the design. De-pillaring operations have also proved highly productive, and to date there has been no associated support related major injury or dangerous occurrence. The success of this project demonstrates the potential for mechanised room and pillar mining in India.

Jan 1, 2006