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By James S. Browning

Mica mining in the United States is confined largely to pegmatites and schists in a few well-defined areas. The largest region extends from central Virginia southward through western North and South Carolina, northern Georgia, and east-central Alabama. 1, 2, 3 Whereas in western North Carolina these pegmatite dikes are weathered to only a shallow depth, they are deeply weathered in the Carolina Piedmont and in Georgia and Alabama. Particularly in Georgia and Alabama, mica is found in the decomposed slates and schists adjacent to the pegmatites, and in deeply weathered granites. Most flake mica is obtained as the major marketable product by crushing and milling pegmatites.4 To a lesser extent, mica is produced as a byproduct of feldspars and spodumene.6 Past research by the Bureau of Mines has developed two methods for mica flotation. One method utilizes acid-cationic flotation for recovery of mica." This method requires thorough desliming of the ore with consequent fine mica losses. The other method utilizes an alkaline-anionic-cationic process for recovering fine size mica from pegmatite ores after desliming sufficiently to remove clay materials but not so drastically as to remove the fine mica. 8, 9, 10, 11, 12, 13 The latter process has also been successfully applied to a micaceous schist ore from California.14 This report summarizes the results of these research studies. Both of the flotation processes developed by the Bureau of Mines have been adopted by the mica industry and are being commercially utilized separately and in combination for flotation of mica from weathered pegmatite ores.

Jan 1, 1969

By Dan Eyde

Low levels of thallium were detected in the mine water drainages, and process water discharges of western mining and smelting operations. This required remediation under state regulatory standards, which allow discharges of no more than .0017 ppm thallium in mine water discharges. Influent streams containing thallium can be mitigated to state discharge standards after a single pass through the series of fluidized upflow columns. Test work to determine the optimal flow rates used pilot scale systems at two separate locations treating 5 - 25 gpm of effluent. The test system at the gold mine mimics the full-scale system, which will be based on the existing upflow carbon tanks that have been converted to zeolite columns. The system installed at ASARCO's East Helena smelter has a far more complex influent stream with a high loading of competing cations. Nevertheless the columns filled with CABSORB® are successfully mitigating the thallium contamination. CABSORB® ZS500RW is a product based on the sodium analog of the zeolite mineral chabazite named herschelite.

Jan 1, 1998

The purpose of this paper is to demonstrate how the Computational Fluid Dynamics (CFD) technique can be an attractive approach to evaluate the performance of face ventilation systems. To present the capability of the CFD for such a study and for design purposes, a series of simulations using CFD have been performed at the Department of Mining Engineering, University of Kentucky, for different face ventilation arrangements (e.g. different scrubber geometries, brattice (curtain) and continuous miners locations, airflow quantities, etc.). Results from these simulations are displayed as three dimensional graphs and discussed. Needs for the field validation of these results and refinements of design methodologies are also discussed.

Jan 1, 1998

By J-Y Chen

China was once deficient in nickel and almost totally reliant on imports for its domestic needs, supplies mainly coming from Canada since the ending of imports from the U.S.S.R. in early 1960's. However, the discovery of the huge nickel/copper sulphide deposit in Jin Chuan, Gansu Province of northwestern China in late 1950's and its development and construction through the 1960's and 19701s, have much improved China's domestic nickel position. In 1985. China's nickel production has exceeded 27.000 tons, compared with only 7,000 tons in 1977. Today, Jin Chuan Nonferrous Metals Company operates two underground mines and a small open- pit; owns China's largest reserves of nickel and platinum, and the second largest reserves of copper and cobalt; and has become the most important subsidiary of China National Nonferrous Metals Industry Corporation (CNNC) which was established in April 1983. The Jin Chuan nickel-copper mines are located in Jin Chang City, Gansu Province, 1,700 km west of Beijing in the People's Republic of China (Figure 1). It is believed that Jin Chuan mines have the second largest nickel reserves in the world, after Sudbury basin, Canada. The deposits are situated on the north slope of the Longshu Mountains, 50 km north of Jin Chang City, and border on the southmost edge of the Gobi Desert plateau. The deposits were discovered in 1958. The total strike length of mineralized zones was approximately 6.5 km long, which was divided into four mining areas by faults (Figure 2). The Longshu underground mine of No. 1 mining area began development in 1959, with full ore production capacity of 1,000 TPD. The open-pit, also in No. 1 mining area, which was brought into operation in 1966 with ore output of 5,500 TPD, was closed down in 1982. The East Extension of the open-pit was put into operation in 1983; present production capacity is about 2,200 TPD. Nickel production of Jin Chuan mines in recent years, and production capacity of each mining operation, are shown in Tables 1 and 2.

Jan 1, 1987

The last decade has seen the use of powerful computerized Mine-Wide Monitoring (MWM) systems for detecting hazardous conditions in underground coal mines. Recently, the U.S. Bureau of Mines and Jim Walter Resources, Inc. (JWR) expanded the scope of MWM system to include ground control. Single-point extensometers were installed in each of 30 intersections along a tailgate entry. These instruments monitored the rate of roof sag, a sensitive indicator of roof instability. Data were collected by the mine's own computerized MWM system. The paper describes the successful integration of ground control instruments into MWM, the data reduction procedures, and the identification of several hazardous areas.

Jan 1, 1994

By Joseph W. Mullan

The today status of air pollution control legislation and regulations can best be described as an exaggerated state of environmental limbo. The '70's began but one and one-half months ago yet it already has been very appropriately named "the decade of the environment." This certainly will be the decade for new legislation - new regulations and hopefully "Clean Air." Already Washington is faced with legislators playing "pollution politics" to the crowds. Students have redirected their efforts from Vietnam to the cleansing of the environment and everyone including the man on the street has become an environ¬mental expert. This is the decade we all face, but where are we today? Pollution is not a new problem. It has been with us for centuries and while much is left to be done, much has already been accomplished. I will try to make some comparisons of what I believe to be the good and bad points in the national air pollution control picture and hopefully will generate within each of you sufficient concern as to which comparisons are sound.

Jan 1, 1970

By Mark C. Russell, Charles T. Russell, Brooke Colburn, Parker Bailey, Desiree Bernhard, Kaito Durkee, Tristen Cutshall, Rob P. H. Urselmann

Hypersonic tunnel boring (HTB) uses directed, high velocity projectile impacts to remove rock. HTB is highly independent of rock strength and targets hard, abrasive rock and variable rock environments. This paper discusses history, theory and presents test (2×2 m and .75×.5 m tunnels) field trial results and technical and economic evaluation. The HTB tests are compared against the historic ‘project REAM’ and the concept against tunnel boring machines and drill & blast in design studies for full-scale 12 m and 4.5×5.5 m tunnels. The positive results indicate that under these conditions HTB can replace Drill & Blast and Tunnel Boring Machines.

Jun 13, 2021

By B. C. Lewis

The mining industry has experienced a general trend toward an increasing number of longwall operations, an increasing percentage of underground coal being mined by longwalls, and increasing productivity from the longwalls. Longwall operators have not yet reached a state of mining euphoria. Competitiveness both within the industry and from alternate fuel sources is forcing continued pursuit of higher productivities and lower costs. The following graphics present trends in the industry. Longwall mines, as defined for this presentation, are those reportedly having longwall installations in each of the respective years. Production from both the continuous miner and longwall units is included in the longwall mines. Non-Longwall mines are all other underground mines. Productivity calculations are based on total employee-hours associated with the operation.

Jan 1, 1990

By R. G. Reddy

Viscosities of Feo-SiO2 slags were calculated using the previously developed structural based model. An expression was derived using hole theory and the atomic pair model to relate the NO0 and temperature to the viscosity. The deduced equation n=4.9x10-9 T1/2 NO0 exp (E/RT) poise was successfully applied to predict the viscosity of FeO-SiO2 slags in the composition range of 0.1 < XSiO2 < 1 for several temperatures. The calculated data agrees well with the experimental viscosity data.

Jan 1, 1991

By V. P. Mehrotra

The effect of dissolved ions present in plant water on the flotation of phosphate ore from central Florida was investigated. Of the three most abundant ions, namely Ca++, Mg++ and SO4--, calcium ions were the most detrimental in the flotation of phosphate with sodium oleate collector. In one feed, a 10 ppm concentration of Ca++ ions reduced the BPL recovery from 86% to 46% whereas in the other a 40 ppm concentration lowered the recovery from 90% to 52%. The effect of Na2C03, NaHC03, Zeolite and EDTA to remove ca++ ions from water and hence improve apatite flotation was also studied.

Jan 1, 1986

By M. Javier

"Mining makes civilization possible. It also creates socio-environmental liabilities forcing us to ask how much more of this mining can our planet support. It is clear that the future of mining differs from mining in the future. The laws of nature are being compromised by mining. This paper studies the problems at the core of the mining business which need to be addressed. What kind of mining will serve our existence with nature on this planet? What kind of mining perspectives are we able to formulate without having negative effects for future generations? Is mining technologically sustainable? The values of predictions, imagination, and creativity must be integrated to define what mining should be. Those values should be in the technologies necessary to restoring equilibrium of nature (Geomimic) as well as in complete extraction of metals, better utilization of the mineral reserves, and design the usage of metals to recycle. The purpose of this research is to examine many views and perspectives for future generations and to accelerate the pace of innovation of having mining without socio-environmental liabilities by design and by understanding nature. KEYWORDS: Geomimic, Sustainability, Waste mine Design, Management by Loss. INTRODUCTION The future of mining is being stifled by many antiquated and stagnant attitudes and policies by the industry and society as a whole. The time is now or never for real action and education against these attitudes and to upgrade them to meet the current needs of this planet if we are to survive. Doing this will prove that we understand and respect nature for us and our posterity. It will also show a positive assessment that the mining process can be reversed before the point of no return. And that is to say, only if reversibility is still an option. It may not be anymore but it’s worth a try. We need to use our imagination and engineering know-how to come up with new proposals to change the core of mining. It would entail re-engineering. There is a profound difference between the future of mining and mining in the future. The future of mining is the continuation and persistence of past practices in the industry and expecting new results. Mining in the future requires a paradigm shift for extraction through modern thinking about mining as it pertains nature. The new paradigm for mining in the future would restore equilibrium with nature. Always keep in mind the connection of mining to nature. What is the future of nature? To predict mining in the future we need to use past experiences in mining and our knowledge of modern science and engineering to formulate a prototype that will enhance mining while maintaining equilibrium with nature. Mining and protecting nature are not mutually exclusive. This new prototype has nothing to do with the level of bonding or insurance that the mining industry can legally provide. The goal of this paper is to contribute some new ideas to help transform the mining industry based on the laws of nature and its limitations. Using this new prototype we will develop the following 1. Extraction of minerals Reserves-Dimensions-Technologies 2. Usage of mineral resources-Manufacture’s products designed to be reused and recycled 3. Nature- Equilibrium (physical, chemical and biological)"

Jan 1, 2016

Terminology. The term potash originated in "pot ashes" produced by burning wood to ashes in iron pots and then leaching out the soluble salts, chiefly potassium carbonate, from the residue. In modern usage potash is a generic term for various potassium salts used in agriculture and industry. More specifically, it denotes the oxide of potassium, K2O, and the content of potassium in ores and products is stated as weight percent of K2O present. Its salts are commonly referred to as muriate of potash, sulfate of potash, etc. The presence of an adequate supply of available potassium in the soil promotes the health and improves the quality of the plant. insures greater efficiency in photosynthesis, increases resistance to certain diseases, offsets the effect of an oversupply of nitrogen, and helps the plant to utilize soil moisture more advantageously. ("Soils and Men," U.S. Dept. of Agriculture Yearbook 1938.) Occurrence. Potassium ranks seventh among the elements in abundance. It is estimated to constitute some 2.6% of the lithosphere and is found in soluble forms in the oceans, lakes, rivers, and subsurface waters. It is also an important constituent of plant and animal life. Commercially significant accumulations of potassium salts occur in underground deposits formed in past geologic times by evaporation of ancient bodies of saltwater, inland drainage basins, and shallow sea lagoons. The potash content of such waters was the end result of weathering and leaching of insoluble potash-bearing aluminosilicates, such as feldspars, micas, leucitcs, and others. The concentrations of potassium salts in the natural brines of some lakes in the arid and semiarid regions of the continents are also important as sources of potash; the brines of the Dead Sea in Asia Minor, the Great Salt Lake in Utah, and Searles Lake in California typify such concentrations. Every continent has major potash deposits as listed in Table 1 adopted from Cawley.1

Jan 1, 1985

By A. Delgado-Jiménez, O. J. Restrepo-Baena, G. Aristazabal

"Mining industry as a source of raw material is essential to society however, it lacks of good reputation due to the type of management historically applied to many of its social and environmental impacts. It is argued that this situation has hampered the obtaining of social license to operate of a lot of mining projects around the world. The last considerations are very common in Latin American countries. As a result, the mining sector has understood that the viability of the business long term is associated with more profit for the shareholders but also with activities that improve the livelihoods of local communities, enhance the capabilities of local governments and preserve the ecosystems around the projects. Nevertheless, recent studios have shown that most of the current advances to incorporate sustainability concepts in mining have been mainly focused on control and the prevention of environmental and social impacts of extractive activities. Thus, contributing to the development of territories around mining projects constitutes a fundamental aspect of the business competitiveness through reducing cost and risks of stopping projects, innovating new ways of relationship with stakeholders, improving the level of reputation of the industry as well as its position in the market. However, this contribution requires formal strategies and models that enable companies understand the different resources in the territories where their mining activities are developed and those resource transformations, in order to establish the best way to articulate the project with the territory, pursuing an effective contribution to its development, truly sustainable over time even after the mine closure. CONTEXT Currently in the world but especially in developing countries such as Latin Americans, different stakeholders are increasingly vigilant of how mining companies carry out their activities in terms of socio-economic and environmental management of territories, not only for its impact on the livelihoods of the communities that inhabit them, but also because many demanders of raw materials -both countries and companies- have set sustainability standards as a prerequisite to establishing business relationships with mining companies, such as the recently declared Sustainable Development Goals by 2030 (UN, 2015). Accordingly, decide underinvest or not to invest in sustainability issues carries risks for mining companies. However, invest much in the wrong way may involve the same risks. Managers are concerned to ensure profits, and therefore they decide carefully how to invest in the areas of production, R & D or marketing. Likewise, they should think strategically about investing in initiatives related to sustainability. This if they really want that those investments in fact help to improve the competitiveness of the company. The mining industry benefits from natural capital that extracts, so it should implement strategies that lead to remunerate such benefit to the territories (Almaguer, 2007). One option is through the transformation of natural capital in other types of non-existent capital or poorly developed in their areas of influence. In this way, the value generated by the extraction of underground resources is shared and additionally contributing to improving the quality of life of the communities. Historically, mining industry has been into several problems to achieve this, which represents one of the aspects that has most influenced the current reputation of mining industry in some regions of Latin America. Many communities, local governments and civil society organizations continue to associate this activity with the destruction of the social fabric and ecosystems in the territories, and their opposition against companies working in the areas has led to affect the operational continuity of many projects (Hamann, 2003; Prno and Scott, 2012; Slack, 2012)."

Jan 1, 2017

By Gerald A. Zicg

The Sheep Creek project area lies between 15 and 20 miles north of White Sulphur Springs in west central Montana, on the southern flanks of the Little Belt Mountains. The Sheep Creek project is a joint venture in which Cominco American Resources, Inc., has a 50% operating interest and BHP-Utah International, Inc., has a 50% participatory interest. The property consists of over 40,000 acres of leased fee land and lode claims. Modern exploration of the Sheep Creek area began in 1973 and 1974, when Homestake Mining Co. examined the extensive Sheep Creek gossans with soil sampling, trenching, and drilling. Cominco American Inc. began exploration in the area in 1976. Between 1978 and 1985, Anaconda Copper Co., Exxon Minerals Co., and Freeport also conducted exploration programs in the area. In 1985, Cominco completed consolidation of the district, gained BHP-Utah International, Inc., as a joint venture partner, and the joint venture drilled the first significant copper mineralization on the property. Of six bodies of copper mineralization so far located, the best defined are an upper copper zone, which includes a probable resource of 4.5 million metric tonnes grading 2.5% Cu and 0.1 % Co, and a lower copper zone which includes a possible resource of 4.5 million metric tonnes grading 4% Cu. Exploration drilling of the property is in progress.

Jan 1, 1991

By Mehmet Guney

Acceptable working environments in production areas and service openings of Mindola Mine on the Zambian Copperbelt are currently maintained with an air volume of 1000 cu m/s and 5500 kW of installed refrigeration plant. It is planned to open up additional deeper areas of the mine for future production. Temperature problems, due to the increased heat generation from various underground sources are recognized as potential hinderances to efficient production. Findings of research work indicate that the present total heat output of 58,000 kW will inevitably increase by the second five-year period of the deepening program to 52,900 kW and by the fifth five-year period to 63,200 k\V. Estimated WB and DB temperatures, representing the total heat generation in stope faces and development headings during these same periods are predicted to increase to 53.8/40.2 °C and 35.5/42.1 °C respectively. It is assessed that the nominal refrigeration capacity needs to be progressively increased to 9,000 k\V This paper deals with the thermal problems in Mindola Mine, current heat output calculations, future prediction of temperature and heat load in various working areas of the mine with the application of computer programs and interpretation of data in order to find the effective solution for long-term planning of ventilation and air-conditioning.

Jan 1, 1982

By R. A. Ynchausti

In January 1993, Pyramid Resources began implementation of a supervisory expert control system at a U.S Cu concentrator. The objective of this control system was to improve plant profitability through unit operation optimization and integration. This paper documents the key aspects of the project, including: economic and associated benefits, system architecture, concepts of implementation, process control strategies, practical aspects of implementation and conclusions. The implementation of expert control at this concentrator has resulted in an estimated benefit of $50,500 per day. This is a net result of improved tonnage, reduced reagent consumption, improved concentrate grade and reduced energy per ton produced.

Jan 1, 1995

By Peter N. Calder

The selection of a slope angle for an open pit in rock has often been made without the benefit of a comprehensive engineering study. This is largely due to the fact that the hardware and procedures necessary for such a study have not been available. Recently this situation has been reversed. The application of borehole television and terrestrial photogrammetric devices has made possible the accurate determination of rock joint structure, on which stability calculations can be based. Another important aspect is the evolution of practical methods of conducting in-situ rock joint strength tests.

Jan 1, 1971

By R. J. Visintainer, J. M. Furlan

"Due to the time-consuming nature of froth testing in a laboratory environment, practical limitations require the development of a method of applying a single set of performance test data (Visintainer and Whitlock, 2012) obtained for a single froth pump at a given speed to a range of froth pump speeds and sizes, % air content and liquid viscosities. Head, efficiency and flow all vary as functions of both liquid viscosity and air content. As such, it is necessary to develop a technique that can be used to interpolate from existing test data in order to predict froth performance for pumps of various sizes running at variable speeds. Details of the technique developed in order to achieve this goal, as well as the insights gained from analysis of the resulting regressions, are discussed. Additionally, comparisons are made between the performance predictions of this test-derived method and those of the Hydraulic Institute standard for the effects of liquid viscosity on centrifugal pump performance (ANSI, 2010).IntroductionPump performance data (Visintainer and Whitlock, 2012) has been collected for a froth pump using an experimental loop outfitted with an array of pressure transducers, mass flow meters, an inverted U-loop, magnetic flow meter and an assortment of other instrumentation. Experiments were performed on pure water, water and air, pure corn syrup, and corn syrup and air. Data was obtained for % air contents of 0-30% and viscosities of 1- 15,000 cSt at eight specific valve positions (eight different flows as a percentage of best efficiency flow points) and the viscosity was changed by allowing the system temperature to increase during testing. The test pump is a 710-mm diameter impeller, GIW HVF, open shrouded, vented design that has its discharge axis oriented at 45° upward from the horizontal. A schematic diagram of the froth pump test loop can be seen in Fig. 1."

Jan 1, 2015

By K. Neumann

"INTRODUCTION For many automation and safety tasks in open cut and underground scenarios it is crucial to have highly reliable distance measurements at hand. These measurements can for instance be used to obtain the exact position of a machine in one-, two- or even three dimensions. Research and development has shown interest in the ultra-wide-band technology (UWB) in recent years. While for this technology short range, high speed data transfer is the current main research focus, the technology can also be used for highly accurate ranging applications. Due to the use of a very wide frequency band, it is robust against disturbances of many types (e.g. EMC, rain, dust etc.) and is therefore attractive for the use in mining applications. The wide frequency band also offers benefits for ranging applications. Especially in environments with strong multipath problems such as in underground mines it is possible to focus on the dominant signal propagation path, thus increasing the reliability of the measurements. [1] State-of-the-art UWB ranging equipment claims precision within the range of a couple of centimeters and working ranges of more than hundred meters. At the Institute for Mining and Metallurgical Machinery (IMR) at RWTH Aachen University in Germany a modern UWB system was examined in several laboratory and real life tests to examine the feasibility of UWB bases ranging equipment in mining applications. UWB TECHNOLOGY The term ultra-wide-band denotes radio systems that use an ultra-wide frequency band. A common definition for UWB radio systems is that it needs to work on a frequency bandwidth of more than 500 MHz or a bandwidth equal to 20% or more of the center frequency [1]. Due to the ultra-wide frequency bandwidth UWB systems overlap the frequency spectrum of narrow band radio technologies like Wi-Fi, Bluetooth and other mobile communication systems which use a defined carrier frequency onto which information is modulated on (e.g. by using frequency or phase modulation). In order to not conflict with these other radio applications, it needs to be ascertained that the transmission power of a UWB system on a given frequency is so low that narrow band systems are not affected by it. As opposed to this only a small fraction of the UWB system’s bandwidth is affected by the narrow band system. The unaffected remaining bandwidth is sufficient to reconstruct the original signal, even if additional noise is present. Figure 1 shows the power spectral densities of popular radio standards [6], [7], [8]. A significant driver of research and development of UWB systems has been wireless high bandwidth communication. Using an ultra-wide frequency band is highly desirable here, as the channel capacity is dependent on the bandwidth. So far systems have been realized especially for short distances (e.g. wireless USB or Wireless HDMI) but beyond that, communication systems for long distances (several kilometers) are possible [2]. Advances in semiconductor technology led to a reduction in power dissipation of such systems. This enabled higher integration levels which in turn facilitated smaller solution sizes for space constrained applications [3]. Nowadays, UWB is also used for high-precision ranging applications [4], [5]."

Jan 1, 2015

By W. M. Ma, Daniel W. H. Su, K. Centofanti, Yi Luo, W. L. Zhong, Syd S. Peng

7.1 INTRODUCTION Subsidence measurements include surveys of surface and sub- surface movements and measurements and monitoring of surface structural damages. In this chapter the most commonly employed methods are discussed. 7.2 MEASUREMENT OF SURFACE MOVEMENT Surface movements involve two basic components, subsidence and displacement. The other five components (i.e., slope, curvature, strain, twisting, and shearing) are derived from the two basic components. Since all measurements are geometrical, they can be measured by common surveying techniques. 7.2.1 MONUMENTS The first step is to select the types of monuments or surveying stations. Various types of monuments have been employed. The simplest one is a paint mark on the pavement or concrete slab, although this should be discouraged because it is easily affected by artificial or environmental factors. Others use steel or wooden rods, 2 to 3 in. in diameter or square by 2 to 5 ft long, driven all the way down, flush with the ground. Both types of-monuments have no provision for frozen ground heave and both are tampered with easily. A more elaborate type is shown in Fig. 7.1 (O&apos;Rourke et al., 1982). A rebar or iron pipe, 2 in. in diameter by 6 ft long is driven down to nearly flush with ground surface. The top 4-ft section of the hole around the pipe is enlarged to 1 ft in diameter and grouted with concrete. The most sophisticated type of monument is shown in Fig. 7.2 (Conroy and Gyannaty, 1983a). It consists of two hollow steel pipes. The inner I-in. pipe, 10 ft. long is enclosed by a 2-in. pipe at the upper 5-ft. interval. The gap between pipes is filled with foam to isolate the inner pipe from external environmental effects. The bottom of the inner pipe can either remain open or be sealed with a cap, depending on whether the ground is dry or wet. 7.2.2 MONUMENT ARRANGEMENT AND SURVEY LINES The monuments are installed strategically to form survey lines. Three basic types of monument arrangements are shown in Fig. 7.3. Figs. 7.3a and 7.3b are for single and multiple panels respectively; Fig. 7.3~ is mainly for research purposes with multiple survey lines both in longitudinal and transverse directions. This is extremely useful for defining the distributions of ground deformation, as shown in Figs. 2.10 and 2.11. Basically there are two types of survey lines: the whole basin survey line which extends across the panel width or length (e.g., lines R, R, in Fig. 7.3 a&b), and the half basin survey line which covers approximately half of the panel width or length (e.g., lines R, F in Fig. 7.3 &b). Survey lines are generally straight and linear. They should be located on the major crosssections of the subsidence basin. Survey lines must extend beyond the edge of the opening for a sufficient distance so that the edges of the subsidence basin can be determined accurately. The minimum distance from the edge of the opening must be [ ] where h = mining depth, [ ] = angle of draw, and [ ] = 5 to 7 times monument spacing for whole basin surveys, or 8 to 10 times the monument spacing for half basin surveys. There must be at least two controlling monuments at each end of each survey line. Controlling monuments must be located beyond the influence of underground mining. The spacing of the monuments ranges from 15 to 200 ft. The UK National Coal Board (NCB, 1975) recommended a spacing equivalent to 0.20 of the mining depth. Peng and Geng (1982) recommended that the maximum monument spacing be dependent on mining depths as follows:

Jan 1, 1992