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By Don Phelps, Christopher Tattersall, David McAllister

Located south of downtown Seattle, the Beacon Hill Station & Tunnels is the key section of the southern segment of Sound Transit’s proposed new LINK light rail system. This paper presents an overview of the design, which includes 4,300 ft of segmentally-lined bore twin tunnels and a deep mined station. With platforms located156 feet below grade, the station itself is only the second large-scale mined station in soil the US. Its complex geometry combined with variable soil conditions—sands, silt sand clays with slickensides—challenged the designer’s to come up with a SEM-based design that addresses the owner’s risk, cost and schedule concerns.

Jan 1, 2003

By B. T. Mirabile, D. Tang, Y. Luo, S. S. Peng, C. T. Holland

Knowledge of local coal mine roof geology is critical to the design of a safe and suitable mine structure. An automated drill control and data collection system has been designed for a J.H. Fletcher twin-head roof bolter. Drilling parameters collected during the drilling process can be used to interpret geologic features intercepted in the mine roof. The drill and data collection system have been tested in both laboratory and underground settings. Visualization of certain drilling data has shown good correlation with geology drilled. A quantitative prediction model was developed using drilling parameters examined with data visualization. The quantitative model was tested using laboratory drilling data.

Jan 1, 2004

By Leon J. Jacobs, Kyle R. Ott

This paper discusses design and construction aspects of the tunnel, shaft and station for the Weehawken Tunnel and Bergen line Avenue Station. The project consists of a 1,269 m (4,156 ft) long existing railroad tunnel, which will be enlarged and equipped with a two-track light rail system. The project also includes construction of a deep underground station, with a large shaft connecting the surface station to the below ground station for access and ventilation purposes. Vibration and noise from blasting is a critical community issue and blasting adjacent to two 230-kV duct banks located in the tunnel invert required special blasting procedures.

Jan 1, 2003

By J. A. Siekmeier

The thickness of the laminated beam modeled in this study is based on bridging potential and TDR measurements. The laminated beam stiffness is based on the effective stiffness of an equivalent transformed section. The maximum deflection of this near-surface laminated beam is compared with the maximum measured surface subsidence. The spreadsheet provides a rational technique to graphically display the character of the overburden and potentially allows prediction of a subsidence factor based on boring logs and the proposed mine plan. The U.S. Department of the Interior, Bureau of Mines (Bureau), utilizes a commercially available computer spreadsheet program in combination with a modified version of Bieniawski's Rock Mass Rating (RMR) system to characterize the geology overlying high extraction coal mines. The spreadsheet program calculates a RMR for each bed based on the lithology, thickness, and engineering properties, which are determined from boring logs and laboratory tests. Once the RMR is calculated the spreadsheet has two major functions. First, the spreadsheet calculates values used to graphically represent the character of each individual bed in the overburden. It calculates an in situ deformation modulus using an empirical rela¬tionship between the modulus and the RMR and then uses this effective modulus along with additional parameters that are based on mine geometry to calculate the bending stiffness and bridging potential for each bed. Second, the spreadsheet creates a transformed section that allows groups of beds to be modeled as an elastic beam. It then calculates a bridging potential for the entire rock mass. The bridging potential of the rock mass is a single value that takes into account both the geology of the overburden and the geometry of the mine. It seems reasonable that there would be a strong correlation between the bridging potential, the overburden response to high extraction mining, and the subsidence ratio. The results presented in this paper focus on the relationship between the bridging potential of individual beds and the deformation measured using Time Domain Reflectometry (TOR). Subsurface displacements measured over seven high extraction coal mines in southern Illinois were correlated with the bed stiffness and bridging potential profiles. Based on these correlations it was evident that the process of caving and subsidence over these high extraction mines involved momentary bridging by individual beds or groups of beds and the ultimate development of a laminated beam near the surface.

Jan 1, 1986

The "Gold" chapter of my adventures did not start with a rush. On May 14, 193 1, Thayer Lindsley wired me asking if I could examine the Pioneer mine in British Columbia right away. I replied, "Yes," but I had never heard of the Pioneer and, although many others were asking about gold during the Depression, none were doing anything about it. A little later another wire asked me to meet Gen. A.D. McRae in Vancouver in a couple of days. This was the start of 20 years of intermittent examinations for Lindsley. I took the train to Seattle and the night boat to Vancouver where I met Gen. McRae and his associate Victor Spencer. McRae had been one of the Canadian leaders during World War I and, for his services, he had been made a Canadian senator, a lifetime job. Col. Spencer was proprietor of a big store in Vancouver, and almost as distinguished. A seaplane was waiting for us in the harbor, to be piloted by Major McLaren, one of the leading Canadian flyers during the war. He flew us up the long fjord of Howe Sound and then on north along the route of the provincial-owned Pacific Great Eastern Railway past jagged snow-clad peaks to the village of Shalalth on Seton Lake. A rental car run by Curley Evans, a noted British Columbia character, was waiting for us in Shalalth and it took us for 50 miles over one of the steepest and crookedest roads I had ever seen. At the end of the road the Pioneer camp was set in a deep canyon in the Coast Range. Dave Sloan, another British Columbia character, was waiting for us and he immediately took me underground, at nine in the evening, to see the Pioneer ore. The ore body was then a small one but it was running over an ounce of gold per ton. The name Dave Sloan became synonymous with Pioneer. McRae and Spencer told me the history of Sloan arid the Pioneer on the way to the mine. The rich surface ore had first been discovered about 1879. It was then far inside the almost trackless wilderness of the beautiful

Jan 1, 1976

By D. W. Fuerstenau

The flotation behavior of quartz in the presence of alkyl ammonium acetates as a. function of alkyl chain length has been interpreted in terms of hemi-micelle formation at the solid-liquid interface. The van der Waals cohesive free energy that is responsible for hemi-micelle formation has been found from these results to be 1.02 kT per CH group. This 2 is in excellent agreement with literature values obtained from research on the properties of micelles in bulk systems.

Jan 1, 1964

By Robert W. Bruhn

The prediction of damage to a structure that is to be undermined is generally a two step process. First, the expected ground movements (the displacements, slopes, curvatures, and strains) are estimated using available (often empirical) predictive methods or survey data from a site of comparable geology, topography, and mining geometry. Second, the prospects for damage to the structure are assessed by comparing the expected ground movements to tolerable limits, some of which appear in the technical literature as damage criteria. The inverse problem of relating observed building damage to causative ground movements involves essentially the same elements. In either case, the usefulness of published damage criteria to subsidence problems may be limited in all but the most elementary cases. This paper considers several cases where structural behavior and site specific details had to be taken into account in assessing the relationship between damage and ground movements.

Jan 1, 1986

By Gunnar Nord

Shifting ground conditions when tunnelling often call for different methods of attacking the tunnel face. In order to overcome problems with local unstable soft ground in a hard rock tunnelling project the Boodex method offers a cost effective alternative. Boodex and variants of it is a combination of two well-known techniques, drilling with Boomer rig using Odex gear. It will give a steel lined hole ready for grouting and the steel pipe has a load bearing capacity that means that a spiling effect is achieved. In this paper the method and some applications will be described with possibilities and limitations.

Jan 1, 2003

By Dave Southworth

After Abe Lee discovered gold (in April 1860) near the site of present-day Leadville, Colorado, he and is group staked nearly all of California Gulch with "speculative claims." They did so in an effort to grab any property that might be potentially profitable. But the plan did not work. New prospectors demanded a miners' meeting, from which arose the official "Bylaws of California Mining District, California Gulch, Arkansas River." These bylaws, adopted on May 12, 1860, established provisions as to the number, size and type of claims that could be filed. Fair laws invited more newcomers. By mid-summer, 5,000 people with tents and wagons were scattered from one end of the gulch to the other.Among the earliest arrivals to the region that spring were Horace Austin Warner Tabor and his wife, Augusta. H.A.W. Tabor, who was to become a pillar in the development of Leadville, arrived at California Gulch during a food shortage. He sacrificed his oxen so that hungry miners could eat. By doing so, he immediately became the friend of many. Augusta established a little store where she sold her baked goods and provided meals. Like most of the men, Horace prospected the surrounding hills. He only did so, however, for a short time. California Gulch yielded more than $5 million in gold during the next five years. By 1866, however, the placer gold was gone and most of the miners had packed up and left. Charles J. Mullen and Cooper Smith, who were grubstaked by a Philadelphian named J. Marshall Paul, found a new, rich lode at the Printer Boy Mine in 1868. It was the first underground gold mine in the Leadville area and marked the transition from surface mining to underground hard rock mining. Its discovery created a new but modest flurry of activity. Heavy black sand covered the region and made gold mining difficult. In 1875 William Stevens and Alvinus Wood decided to have the sand assayed. They discovered that it contained 15 ounces per ton of silver and was rich in carbonate. Stevens and Wood kept their find a secret for nearly two years. When the word spread in late 1877, the silver boom was on. In 1878 prospectors, merchants and others trickled into town from all directions. Dr. David H. Dougan closed his office. in Alma, crossed Mosquito Pass and set up shop in Leadville. Nobody seemed to need a doctor, however, and Dougan sat in his office for 28 days without a customer. On the 29th day he received word that there had been a mining accident and he was needed immediately. -That was the begin¬ning of his illustrious career in Leadville. Dougan was a successful physician, became mayor in 1881 and was later president of the Carbonate National Bank. Leadville was a simple community of log structures in 1878. By June of the following year, however, it had blossomed considerably. According to Cass Carpenter, as of May 1,1879, Leadville had "...19 hotels, 41 lodging houses, 82 drinking saloons, 38 restaurants, 13 wholesale liquor houses, 10 lumber yards, 7 smelting and reduction works, 2 sampling works for testing ores, 12 blacksmith shops, 6 livery stables, 6 jewelry stores, 3 undertakers and 21 gambling houses where all sorts of games are played as openly as the Sunday School sermon is conducted." Additionally, there were 36 brothels. When George E. King and other architects arrived, Leadville took on an air of elegance and sophistication. In sharp contrast to some of the Victorian-style, gingerbread-laced homes in Leadville, its suburbs were comprised of many tenement shacks and plain cabins mixed with a few commercial buildings, many mines and smelters. Mines sprinkled the area east of Leadville like pepper from a pepper shaker. Wherever there was a cluster of mines, a camp usually sprang up. Most were very close together. South of Leadville the giant Arkansas Valley lead smelter sprawled out between Stringtown and Bucktown in an area known as Smelter Valley. Founded in 1879 as the Billing and Eilers Smelter, the Arkansas Valley plant was operated by the American Smelting and Refining Company. Several other smelters operated in the vicin¬ity. In April 1878, Horace Tabor grubstaked prospectors August Rische and George Hook. For $64 worth of supplies and tools, he was guaranteed a one-third interest in their findings. Rische and Hook discovered the Little Pittsburg (often spelled Pittsburgh) Mine and made Tabor an instant millionaire. Tabor once purchased a "salted" mine, the Chrysolite; but instead of considering it a bad deal, he further developed the property and struck rich silver ore. Later, Tabor purchased the Matchless Mine for $117,000, possibly the only investment he made without partners. During its peak years, the Matchless yielded $1 million worth

Jan 1, 1998

By Arthur R. Still, Paul A. Bailly

5.1-PURPOSE, PROCEDURE, METHODS, MANAGEMENT Exploration can be technologically defined, with regard to the discovery of new mineral deposits, as all the activities and evaluations necessary before an intelligent decision can be made establishing size, initial flowsheet and annual output of new extractive operations. The purpose of mineral exploration is the discovery and acquisition of new mineral deposits amenable to economic extractive operations now or in the future. A prime objective of mineral exploration, however, is to find and acquire a maximum number of such mineral deposits at a minimum cost and within a minimum time. Immediately upon the heels of a successful ''exploration" discovery follow activities called, first, development, then operation. Under U.S. Internal Revenue Code regulations (Secs. 1.615.1 and 1.616.1) in effect at the time of this writing, which state that the "development stage" has been reached when "deposits of ore or other minerals are shown to exist in sufficient quantity and quality to reasonably justify commercial exploitation by the taxpayer," exploration in the technological sense may well continue after a mineral property has entered the "development stage" as defined for tax purposes. In many instances continued exploration, after reaching the tax defined "development stage," has disclosed additional reserves which justify a much larger, more efficient and more profitable operation than that which would constitute the minimum feasible. Even after a mine goes into production, continued ore search generally will increase the reserves, either justifying expansions in plant capacity or prolonging the life of the operation, but this work (actually "exploration") is normally considered, for bookkeeping and tax purposes, a part of mine development. Each exploration entity defines its own objectives in terms of acceptable mini- mum rate of return on investment for any deposit found and retained, and in terms of which commodities, and markets, are to be involved. For these reasons, exploration programs, and aims, will vary over a wide range, although all have the common objective of endeavouring to create new profit centers for the future. 5.1.2-EXPLORATION METHODS Exploration has evolved in the past several decades into a highly sophisticated and expensive endeavor in which large corporate entities, or subsidaries, normally are directed and staffed by highly trained exploration specialists. In some instances consultants, with expertise in a given field, are utilized to the benefit of such corporate groups. The "grasshopper" approach to exploration-searching only for outcropping minerals and/or investigating only mineral prospects offered by the discoverers of such outcrops has given us most of the past and present mines in the US., but this method is rapidly approaching the point of diminishing returns in areas that have been thoroughly prospected for currently marketable commodities. With

Jan 1, 1973

SOLUTION MINING Solution mining techniques present a means of extracting soluble ores, particularly such materials as salt and potash, from horizons which are not accessible by conventional mining. In the process of dissolving materials, it is evident that solution may be complete or partial. In general, the solution mining operations described in the following section relate to complete solution of the desired compound. Even though the solution of material is complete, there may be instances in which insoluble material is present to a large extent either as granular separated particles or as insoluble layers. The process required for obtaining the desired product involves access wells to reach the deposits, sufficient water supply to yield the production goals, and the development of an underground cavity. The process of solution mining, therefore, depends to a great extent on three factors: availability of a relatively pure strata or formation of salt or potash to be mined, access well or wells, and adequate control of the solutioning process so that enlargement of underground cavities can be fairly well delineated. Since halites represent the most general ores mined by this procedure, the considerations which follow are based primarily on the production of sodium or potassium chloride. The producing formations may be in the form of bedded evc~porites wherein the salt member may be some 30 to 500 ft thick or from salt domes in which great depths of salt occur. Solution mining has been carried out to depths of nearly 10,000 ft. The recovery of saturated brine from wells drilled to effect the solution-mining process leads to further processing. In many instances, the procedures are relatively simple and involve simple recrystallieation or fractional crystallieation, while in others more complex flow systems are required before a final product is obtained. The intent of this section is to provide information relative to the basic procedures for obtaining materials which are soluble in water and to acquaint the engineer with the various aspects of the overall problem which in many instances, may become quite complex and present numerous difficulties. The storage of fluids, particularly hydrocarbons, underground has proven to be a very important part of industry operations. Cavities formed in salt provide excellent storage facilities. The formation of well-defined controlled configurations of such cavities has been possible because of better understanding of the solution process, wide experience gained over nearly 30 yr, and improved technology in drilling and completing wells, surveying caverns, and the operation of numerous types of systems. Solution mining techniques will improve in the future. Many facets of the simple operation of pumping solvents and extracting valuable minerals require further study. Developments undoubtedly will occur to further the processes of mining by solution. In addition to those whose names appear in connection with the individual subjections which follow, a major role in assembling and processing the material in this section was played by Dr. D. A. Shock, Central Research, Continental Oil Co., Ponca City, Okla.

Jan 1, 1973

By Dan Nilsson

INTRODUCTION There are many mine planning factors in sublevel caving, as in the other mining systems, which when varied can substantially alter mining costs and profit¬ability. In this chapter, the following four topics are addressed with regard to economic optimization of sub¬level caving: production planning, haulage level spacing, orepass spacing, and extraction cutoff. The costs used here are the right order of magnitude but since each mine is unique, they should be considered only as examples. The objective is to demonstrate the tech¬niques which can be used. In a real mine, the evalua¬tions must be done using actual costs and conditions. It is difficult to predict exactly the costs involved, and therefore it is valuable to perform a sensitivity analysis to evaluate the effect of making incorrect as¬sumptions. Since the mining industry is very capital intensive, the effect of the interest rate must also be studied. PRODUCTION PLAN FOR AN IRON ORE DEPOSIT Introduction The first and most important thing to do before de¬signing an underground mine is to establish a long-range production plan. Such a plan is necessary for all eco¬nomic evaluations and should provide information about the lifetime of the mine, how much ore and waste must be handled per year, how much development per year is required, etc. An example is given in the following section. Problem In an iron ore mine sublevel caving is used. The iron content is 42%, and the mine supplies a pelletizing plant with an annual capacity of 3 million t/a. The ore body is shown in Fig. 1. The length of the ore body is 1000 m and the width is 100 m. Each slice is 10 m high, and there are 10 m be¬tween crosscuts, each of which has an area of 20 m2. The density of the ore is 3.5 t/m3. The spacing between rings is 2 m, and the extraction is 100%. The iron con¬tent is 66% in the pellets and 6% in the tailings. The problem is to develop a detailed production plan. A typical sublevel caving sequence is shown in Fig. 2. Solution Amount of ore per meter of crosscut: 20 X 3.5 = 70 t. Number of crosscuts per slice= 100. Length of crosscuts per slice: 100 X 100 = 10 000. Ore from crosscuts per slice = 10 000 m X 20 m2 X 3.5 = 700 000 t. Number of sublevel caving rounds per slice: 10 000/2 = 5000. Area for each blast in sublevel caving: 10 X 10 - 20 = 80 m2. Amount of ore per blast: 80 m2 X 6 m X 3.5 = 560 t. Extraction: 100% (see extraction curve Fig. 12). Loaded ore per blast: 75% or 420 t. Loaded waste per blast: 25% or 140 t. Total: 560 t. Total amount of rock from each blast in the sublevel caving: Ore: 560 t of which 2 X 70 = 140 t from develop¬ment work and 420 t from sublevel caving. Waste: 140 t. Total: 700 t. The ore needed per year is 3 X (66-6)/42-6 5 mil¬lion t. Necessary number of blasts per year= 5,000,000/ 560 = 8929. Distance to develop per year = 8929 blasts per year X 2 m per blast 17 858 m. Total amount/year: Ore from development work 17 858 m x 70 t/m = 1.25 million t/a Ore from sublevel caving: 8929 blasts per year X 420 tons per blast = 3.75 million t/a 5.00 million t/a Waste rock dilution: 8929 blasts per year X 140 tons per blast 1.25 million t/a Total amount to hoist 6.25 million t/ a The amount of ore from development work will in¬crease a little if the horizontal drift is placed in the ore body and not in the footwall. In this example the ore loss in 20%, and the waste rock dilution is also 20%. After taking the ore loss into account, the lifetime for 100 m of the ore body will be:

Jan 1, 1982

By Bo-Hyun Kim, Mark K. Larson

"Researchers at the National Institute for Occupational Safety and Health (NIOSH) have advocated the use of instrumentation in underground mine ground control studies to aid in understanding failure mechanisms and to calibrate numerical models. The purpose of these efforts is to reduce accidents and fatalities in underground mines resulting from inadequate design of mining layout or supports. A recent examination of some results of stress change measurement raised some questions about the validity of elastic solutions in ground, such as coal. Particularly under deep cover as is prevalent in the western United States, the coal around a borehole would likely have yielded so that post-yield behavior would govern the response of the instrument.A numerical experiment was conducted by NIOSH researchers using the FLAC software (Itasca Consulting Group, 2016) to investigate the response of the borehole pressure cell (BPC) and the biaxial stressmeter to varying degrees of plastic behavior. The pre-encapsulated BPC cell pressure exhibits increasing departure from the elastic case with decreasing post-peak-strength slope of the stress-strain curve. On the other hand, because the BSM usually provides much more confinement to the surrounding rock than does the BPC, the measurements obtained from the BSM do not depart significantly from the changes in secondary principal stresses and directions as calculated by the elastic solution.INTRODUCTIONSeveral years ago, Larson et al. (2000) described several instruments that NIOSH had used in underground field studies and how to monitor them with dataloggers. This information is still relevant because of the need to understand how excavation affects the stability of mines and thus, the safety of mining personnel. One class of instruments described in that paper includes those instruments that measure change in rock stress. Although several such instruments might be used to measure stress change, the focus of this paper is on two instruments with which NIOSH has had more recent experience—the borehole pressure cell (BPC) (Geokon, 2018a; RST Instruments, 2018) and the biaxial stressmeter (BSM) (Geokon, 2018b). Other instruments, such as the CSIRO hollow inclusion stress cell (HICell) (Earth Sciences, 2019; Worotnicki and Walton, 1976) may be included in future studies.Early studies in the development of the BPC were those of Panek and Stock (USBM, 1964), Sellers (1970), Lu (1984), and Babcock (1986). Babcock’s work is particularly useful, but his setting and testing range was far below what we experienced in the NIOSH study, and it was Babcock’s data reduction scheme from his laboratory experiments that was used to calculate stress change in the NIOSH study (NIOSH, 2019a)."

Jan 1, 2019

By R. R. Fernández

Newmont Mining Corporation has been processing refractory gold ores by roasting since January 1995. The ores are refractory due to the association of the gold with iron sulfides, namely pyrite and marcasite, and the presence of carbonaceous components and is oxidized in an oxygen-enriched gaseous atmosphere. The structural characteristics of the calcine have a strong influence on the eventual recovery of gold by cyanidation. These characteristics are strongly dependent upon the roasting conditions, mainly the roasting temperature. Originally, the sulfides and carbonaceous matter were oxidized at a temperature that typically ranged between 535 and 560 °C. Controlling the roasting temperature within the lower and narrower range of 510 to 515 °C produced a calcine with a larger surface area(e.g. higher porosity), which resulted in a gold recovery increase of3.3 percent in 2001 equivalent to 5.1 million dollars of additional gross revenue. The new strategies of operating at temperatures never tested before are discussed. It constituted a great challenge to the control room operators for the lower operating temperature falls much closer to the ignition temperature of the sulfide ore and smaller and more frequent adjustments in operating parameters were needed to improve and maintain high gold recoveries. Based on the encouraging results that were achieved in 2001, a decision was made to install a “smart” process control system because the roaster temperature control was performed by manual inputs from the control room operators. The development and implementation of the control system to reduce or eliminate the temperature variability between the different control room operators commenced in June of 2002 and was fully operational by the end of October. Lower roaster temperatures were achieved (500 to 505 °C), which resulted in further increase of gold recovery by about two percent. The overall recovery increase equated to 8.0 million dollars of additional revenue for the first 10 months of 2002.

Jan 1, 2003

By J. E. Carr

A bewildering number of continuous thickeners and clarifiers are used in mineral industries and other heavy industries. General types are: 1. Conventional Thickeners (Fig. 1). 2. Thickeners with Flocculating Feedwells (Fig. 2). 3. Solids Contactors (Fig. 2). 4. Tray Thickeners (Fig. 3). 5. Lamellas (Fig. 4). 6. Conventional Thickeners with Lamellas 7. High Flow, Fluid Bed Thickeners (Fig. 5). These units must be adapted to varied applications. They must provide operating flexibility to meet process needs. Such factors multiply the decisions which must be made prior to the selection of a thickener. The seven types of thickeners listed above, with their variations, share design concepts which limit their application and which can be used to evaluate their performance. Some of these are listed: 1. Feed velocities must be limited and/or controlled. 2. Natural or reagent flocculation is necessary. 3. Horizontal settling area is the basis for capacity. 4. Overflow velocities must be limited and/or controlled. 5. A controlled underflow is necessary. Applying these needs to the basic process concepts is thickener selection. The basic function of a thickener in the minerals industry is the separation of a thickened sludge containing fine solids from water. To this primary separation function are frequently added others to give a list as follows:

Jan 1, 1977

By S. A. Beeson, C. Poole

This paper describes the development of a novel selective flocculation technique for recovering phosphate values from ores containing silicate or carbonate gangue minerals. Data from initial flocculation response and reagent adsorption studies on component mineral suspensions and synthetic mixtures were used to assess the influence of various process parameters (e.g., reagent dosages, particle size, solids concentration, and conditioning regimes) on single-stage selective flocculation tests involving natural silicate and carbonate ores. In these tests a high degree of selectivity was achieved using low dosages of a low-molecular-weight cationic dispersant and a mid-range molecular weight cationic flocculant. Testwork was then extended to the evaluation of several floc recovery systems (sedimentation, hydrocyclones, and floc flotation) in a multi-stage process involving redispersion and reflocculation. Results from these tests clearly demonstrated the feasibility of producing marketable phosphate concentrates from both ore types.

Jan 1, 1999

By Sidney V. Gold

Should Gold Producers Hedge Their Positions Through : Sales on Forward Markets? Purchases of Put Options? Sales on Spot Market? Forward Markets Assumptions 1. Producer has a known amount of Gold to sell in year ahead. 2. Effect on price is the same whether sold Forward or Spot Market. 3. None of us have knowledge of Future Price Trend. 4. Contange Market prevails in which Forward price premium is approximately equal to rate of interest.

Jan 1, 1983

By B. H. Gardner, S. Serata, D. Dickie

Since 1958, the Sifto Salt Division of Domtar, Inc., has operated the Goderich (Ontario) salt mine in Michigan basin bedded halite, with shafts located on Lake Huron's eastern bank. Initial mining utilized a conventional room and pi1lar pattern. However, roof deterioration developed. Incidence of progressive upward failure of saltback and over1yings ha1ey-do1omite layers intensified with entry aging. Studies were therefore initiated on new mining patterns utilizing the Serata Stress Control Method. Pursuant thereto, three test areas, indicated in the mine plan of Fig. 1, were designed and excavated. Full conversion to Stress Control mining was effected in January, 1983. This paper focusses on the instrumentation work in the third test area. Test Area 3 was designed to validate the excavation geometry of the new stress-controlled main entry system. The testing of that design was accomplished, in part, by comprehensive in situ stress, property, and deformation measurements on the performance of the model main entry section of Test Area 3. The paper describes: (1) the theoretical background of the SPDR/Stress Control Method; (2) specific problems and objectives addressed by the 1983 program of in situ measurements, (3) measurement results; and (4) conclusions drawn therefrom.

Jan 1, 1986

By Barry A. Hillman

Respirable (PM-10) crystalline silica is regulated by the State of California as a carcinogen. The risk-management of this material by the State exemplifies the inherent problems in the development of regulations based on current risk-assessment practices. The influence of extremely conservative risk-assessment and risk-management can be expressed in economic impacts including the increased cost of production, reduced competition, increased prices, reduced employment and redistribution of income. This paper attempts to contrast theoretical risk- assessment and risk-management with current application using crystalline silica as an example. Based on health information pertaining to silica, the paper examines federal and State of California regulatory and public policy positions. Using current risk factors and empirical data for the Central Valley of California, the projected incidence of lung cancer in humans is examined. While such an analysis would project an extremely high incidence of lung cancer as well as silicosis, not a single case of either lung impairment has been recorded within the study area or throughout the world in the general population. This suggests that sound guidelines for the analysis of scientific information have given way to the assumption that virtually any information representing a substance as a carcinogen is to be considered valid with little or no qualification.

Jan 1, 1992

By D. Park, V. Gall

The three-dimensional finite element technique combined with a progressive failure approach were used to simulate stress distributions in a complete mine section that occur in response to a longwall mining operation. Due to the availability of a Cray supercomputer, a large-scale, three-dimensional, finite-element model was developed for the analysis. The Hoek-Brown failure criterion, which describes a realistic behavior of rock masses, was used for the simulation of progressive failure. A comparison of calculated and monitored stresses in the mine has shown that the model gives a good representation of stresses in the mine structure.

Jan 1, 1992