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By Justin Brown, Michael Kobler, Dave Ragland, Bob Shufflebotham

PROJECT OVERVIEW As the sun-bronzed San Diego students strolled casually to class, mining crews from Atkinson Construction were working only 9 meters below the surface. The330 meter long, 11.3 meter diameter squat ellipse NATM tunnel is part of the9.3 kilometer Mission Valley East Extension Light Rail Transit (MVE-LRT) being constructed for the San Diego Metropolitan Transit Development Board (MTDB). The SDSU segment of the MVE-LRT was awarded to the Clark Construction Group, the parent company of Atkinson Construction for $82.7 million. URS CORP was the prime designer and Hatch Mott MacDonald performed the NATM tunnel design. The construction managers were Washington Infrastructure Services with Underground Construction Managers, EPC Consultants, and ILF Consultants. A NATM tunnel design was chosen as the most cost-effective way to minimize disruption of the university activities. The tunnel passes close to several buildings and directly below access roads, tennis courts and a baseball field. The NATM method of conventional mining uses shotcrete for ground support often reinforced with steel orplastic fibers, welded wire mesh and lattice girders. The tunnel runs from a cut and cover box up a 4.2% grade in a 217 meter radius left-hand curve with several spirals and ends at the underground station 330 meters away. The depth of cover varies from 16 meters near the west portal to nine meters at the station. The design called for a two-pass system with a primary lining of 300 mm shotcrete with lattice girders at 1 m centers and two layers of welded wire mesh. The lattice girders are used primarily for profile control and are not considered a structural element. The top heading was designed to be excavated in one of three excavation sequences depending on ground conditions and depth of cover. In sequence one excavation, the top heading is excavated in two halves with a one-meter separation. In sequence two excavation, a side gallery is advanced 8 or more meters ahead of the

Jan 1, 2003

By Anthony Harding

In a world of technology and electronic communication, it is easy to forget what engineers do best with a problem: sitting around a table, exchanging views and ideas with sketches and respecting everyone?s view. This was the approach adopted in the project to arrive at a solution for the cross passage opening sup-port for the Seattle University Link Extension. Schedule and space constraints usually impede concurrent cross passage excavation and tunnel boring machine (TBM) operation. And where the space is constrained, opening support solutions that maximize available cross sections are of great benefit. While there are a number of solutions that minimize space, some of these solutions can require expensive steelwork and extensive drilling and fixing. However, following a detailed round-the-table discussion of the options and constraints, it was identified that a shotcrete shell would not only limit obstruction of the space during installation, but also permit easy installation, particularly around services, and avoid costly steelwork and drilling and fixing.

By Paul H. Johnson

A field investigation was undertaken to study some of the. chemical and hydrological aspects of leaching an impermeable copper sulfide waste dump. Samples, obtained by means of a Becker pneumatic drill from Kennecott's Chino "J" dump, near Silver City, New Mexico, were analyzed for their moisture and soluble-salt content, Fe +2 , Fe +3, Cu +2 , and H in their interstitial solutions and non-water - soluble Fe, Cu, and S in their rinsed residues. Conclusions were drawn from these data concerning the overall chemistry of impermeable-dump leaching and the hydrological characteristics of the dump.

Jan 1, 1970

By Louis M. Perlman

Quantitative methods are, by now, a standard tool of the mining industry, and are commonly used by Research Departments in their evaluation of production methods and schedules, and their associated costs. Indeed, much sophisticated computer work has been devoted to such evaluation of controllable costs and capital requirements. These data are an important input into the project evaluation formula, which is probably the most important single calculation per formed by a mining company, since the result decides whether a particular project is viable. It is instructive to summarize the broad principles of project evaluation, since they are crucial to the remaining sections of this paper. PROJECT EVALUATION The most widely used method of appraising projects is known as Discounted Cash Flow (DCF) method. Two main variants are used; they are known as the 'not present value' (NPV) approach and the 'internal rate of return' (IRR) approach respectively. The difference between the two is that the former takes the firm's interest rate as given and uses this knowledge to calculate the present value of the project; whereas the latter calculates the highest interest rate the project could tolerate and still just breaks even. The technique is more simply discussed in terms of the first method (NPV).

Jan 1, 1972

By Rudolph H. Jacobson

The leaching of heaps or sub-marginal waste ore dumps as it is practiced throughout the Southwest as well as other parts of the world, is the major method of secondary recovery of copper. In 1970, twenty percent of all domestic copper was produced by dump leaching operations (l). In recent years, this method has been successfully extended on a limited scale, for the recovery of uranium from low-grade ores (2). It is inevitable that this technique will be increasingly employed in metal production to satisfy the insatiable demand of our mineral based society. Although dump and heap leaching has been used effectively for some time (3) , its application has been more of an art than a science. Therefore, it is essential that we learn about the important factors and parameters affecting this versatile process so that we may make increasing use of this technique in the future. The dump or heap leaching process encompasses the preparation of ore for-subsequent inplace leaching, the flow of solutions and ionic species through porous rock masses, the leaching of minerals with inexpensive and, if possible, regenerable lixiviants under prevailing conditions of the inplace environment, and the recovery of metals from the pregnant liquors. It is evident that this comprehensive scope of dump or heap leaching falls under the realm of interdisciplinary science and engineering requiring the application of the principles of physics, mineral engineering, hydrology, computer modeling, operations research, economics, and allied disciplines. An exhaustive study of the phenomenology of a leach dump or heap requires detailed knowledge of the simultaneous interaction of'

Jan 1, 1972

By N. S. Tanious

This paper summarizes the results of an investigation into possibly the largest coal pillar failure in the USA. The newly opened drift mine is located in Southeastern Kentucky and worked an 11 feet thick coal seam, all other mines in the District worked seams 4-5 feet thick. The initial mine development consisted of 14 main entries (Fig. 1) which were driven in two sets of 7, under increasing depth of overburden. As the left seven entries came under deeper overburden the pillar ribs began sloughing which caused many of the concrete-block ventilation stoppings to crack. The mine management stopped the advance in the left seven and continued with the right seven entries. During the spring of the following year development resumed in the left seven, rib sloughage occurred again and this time severely cracked many stoppings and many were totally disintegrated from the excessive deformation. Within few weeks the sloughage was so heavy that many of these entries behind the active face were filled with piles of sloughed coal slabs. When the face reached a depth approximately 1150 feet, the sloughage became a slow, massive squeeze. The entry convergence (closure) reduced their height from 11 to 7-8 feet and the squeeze spread back to shallower depth covering an area roughly 300 pillars.

Jan 1, 1989

By J. Libaude

The Changement mine in French Guyana has, since 1983, processed gold ore by classical gravity methods. A large part of the gold is in the form of very small, free or enclosed grains. Recovery by gravity methods is thus limited (25-30%) and the present plant produces about 40,000 t annually of auriferous waste assaying about 6 git. The company therefore decided to retreat the waste by heap cyanidation. After laboratory tests which showed the feasibility of the method, a pilot test was set up on site. An experimental 3000 t heap, composed of waste of 0-8 mm grain size, was laid out by bucket loader on an impermeable pad covered by PVC and geotextile cloth. The upper layer of the heap was reworked by mechanical shovel to break up the area that had been compacted by the passage of the loader so as to restore adequate permeability.

Jan 1, 1998

By J. A. Murray

Maintaining satisfactory air quality in electro-winning tankhouses has been problematic and costly, particularly as plant operating current densities have increased. Conventional approaches, including the use of beads, hollow spheres, surfactants and coalescer devices, have not proved completely effective, requiring that powerful ventilation systems be installed. As workplace and environmental regulations become more stringent, containment of the acid mist at its source is more attractive. An electrode cap system based on this approach has been developed and tested in two commercial copper electrowinning tankhouses. The design, development, installation and cost of the new electrode cap system are described.

Jan 1, 1996

By J. R. Arnold

The problem of recovering gold from a cyanide solution has been plaguing metallurgists since the cyanidation process was discovered in Glasgow, Scotland.1 The "perfect" method has never been found and this paper will not purport to fill that gap. But we, at Gold Fields, feel that we have developed a workable, cheap and efficient method of producing a refinery - ready product that has several distinct advantages over conventional electroplating techniques. The Gold Fields replating system is presently being used at their Ortiz and Mesquite operations. In short, the system electroplates the gold out on stainless steel wool, instead of mild steel wool as is usually done, then replates the gold by reversing the current onto stainless steel plates. By doing this the steel wool can be reused many times, the gold can be scraped off the plates cleanly and quickly, the operating costs are reduced and the slag production is greatly reduced.

Jan 1, 1986

By C. RAMADINI, F. NURJAMAN, A. SHOFI, B. SUHARNO

Nickel demand is increasing along with the rising need for stainless steel and other alloy steel/iron. The small addition of nickel in such materials can improve impact strength, ductility and corrosion resistance. Nickel is generally obtained from nickel sulfide ores (nickel associated with sulfur) and nickel laterite ores (nickel associated with iron and magnesium silicate). Almost 60 percent of nickel is now produced from sulfide ores, despite its existence in sulfide ores being less than in laterite ores. However, the depletion of sulfide ore reserves makes the mastery of nickel laterite ore processing of important and immediate concern. Selective reduction followed by magnetic separation has been in development in lateritic nickel ore processing to overcome the issues of high energy consumption and pollution associated with conventional pyrometallurgy methods such as blast furnace and rotary kiln electric arc furnace (RKEF).

By Yi Luo, Jian Yang, Hua Jiang

Surface subsidence induced by underground coal mining activities, especially longwall mining operations, can cause various problems to interstate highways ranging from structural integrity to drivability to safety. Accurate subsidence prediction, correct influence assessments and effective mitigation measures are the keys to ensuring the safety of highway traffic. The surface subsidence prediction program, called comprehensive and integrated subsidence prediction model (CISPM), was developed based on the principle of influence function method and has been validated with a large number of subsidence measurements. In this paper, the techniques to use the predicted final surface movements and deformations for assessing their influence on the integrity and functionality of highway structures — such as road surface pavements, concrete slabs and transverse joints — vehicle dynamics, comfort level and drivability are presented. A number of mitigation measures to protect the highway structures and to ensure traffic safety are proposed, along with an application case.

By S. Tandanand

The Bureau of Mines, U.S. Department of the Interior, assessed the geological effects on the ratio of maximum subsidence and extraction thickness, hown as the subsidence factor, to develop a simple method for predicting the maximum subsidence. The study is restricted to the Northern Appalachian Coal basin where data were collected from 13 coal mines. A model previously developed to relate the subsidence factor with the lithology and with the width and depth of working panels was used in the assessment. The result shows the possibility of determining maximum subsidence without resorting to a rigorous method.

Jan 1, 1982

By B. Mirabile, B. Stables

Standing support is often used in conjunction with underground retreat mining. Knowledge of the load-displacement behavior of a standing support, and loading induced by the mine opening is critical to proper support selection. The NIOSH STOP database contains load-displacement laboratory test data for most commonly used standing supports. Hydraulic load cells currently used to measure in-situ loading of standing supports have exhibited leakage under load, producing irregularities within the dataset. An improved hydraulic load cell eliminates leakage and produces more consistent data. INTRODUCTION A hydraulic load cell, more commonly known by “flat jack” or JackPack, is a device installed to determine the loading characteristics of roof to floor supports. These standing or roof to floor supports include, but are not limited to: pumpable cribs, cans, wooden cribs (4-point, 9-point, etc.), metal props, wood timbers, concrete donut cribs, and other variations of these standing supports. Flat jack devices have been used previously to determine the loading of such roof to floor supports. The most commonly used load cell for standing supports is based on a design intended for pre-stressing standing supports, not load measurement. These load cells are produced in South Africa, and can be formed into several different shapes depending on the applications (Barczak). Flat Jacks are manufactured in various shapes and sizes depending on the application, common shapes are square and round that are 25.4 mm (1.0 inch) thick when collapsed as shown in Figure 1. The sheet metal that makes up the bladder is comprised of 19 gauge or 1.11125 mm (0.04375 inch) thickness, the top and bottom pieces of sheet metal are resistance seam welded around the perimeter. There are two different ports installed on one of the bladder skin corners of the flat jacks; these ports allow a fluid to fill the unit and the other port has a relief valve. The fill port is comprised of a check valve. The pressure relief valve is located in the second port; preset to 1724 kPa (250 psi), pressure relief valve will keep the load cell from bursting. Bursting of these load cells typically causes a small tear in the metal skin allowing the fluid to leak out without a large catastrophic failure. The effective inflation range of these load cells is between 25.4 mm (1.0 inch) to 254.0 mm (10.0 inches) thick. Different types of fluids can inflate these load cells but the most common and easily accessible fluid for testing applications is water. Water pressure from the mine supply line can inflate these load cells to the desired load. Depending on the pre-stressing requirements a pneumatic powered pump, hydraulic pump or hand pump may be required to inflate the load cells.

Jan 1, 2019

By Richard L. Gordon, William A. Vogely

ENERGY POI.ICY-PRINCIPLES AND THEIR PRACTICE Persistently, at least since the end of World War 11, governments have intervened broadly, deeply, and incoherently in major energy markets. If we take a broad definition of energy that encompasses gas distribution and electric power, we can observe regulations of even older vintage. This trend, of course, is not unique to energy. Expansion of government controls has occurred in many areas. The relevant basic question about energy regulation, therefore, is not why is energy special, but whether any general principles exist to explain the wisdom of existing regulations. This review takes place at a time, the middle 1980s, in which a massive onslaught is being undertaken against government regulation. However, the present chapter is influenced primarily by my observations of the failures of energy regulations and not by any inspiration from those ideologically opposed to government intervention. Several subquestions arise in policy appraisal. A primary need is to establish clear objectives and determine the consistency between these goals and the policies imposed. Thus, the first step is to set objectives. The next is to outline ways to attain these goals. However, it should be recognized that many apparently distinct options are economically equivalent. When the goal is to charge producers or consumers for something, it is possible to attain the same result through either government ownership or taxing private transactions. The tax can raise the price to the level the government would have charged if it were the owner. Creation of a Department of Energy is not necessarily any different from having separate energy agencies well coordinated by some small supervisory body. Thus, a distinction should be made between substance and form in policymaking. The critical substance concerns such matters as whether the government imposes financial penalties, incentives, or rules to attain a goal. Then, there can be many equivalent ways to implement the basic policy form. The second prior illustration suggests that one favorite question is how to attain proper integration of policy. At various times, voices on either (or even both) sides of the Atlantic have called for a coordinated energy policy. The U.S. Paley Commission made this a primary goal for future policy. The western European governments that were the founding members of the Coal and Steel, Economic, and Atomic Energy Communities spent much time in the middle fifties and much of the sixties trying futilely to agree on an energy policy. (See Gordon, 1970 for an annotated review). The energy price rises of the 1970s rekindled United States interest in coordination. However, astute observers of the problem such as O. C. Herfindahl of the United States and Maurice Allais (1 962) in France warned the discussions confused form with substance. The crucial issues were what were the goals and what were the best types of policies to attain such goals. Policy suffered, not from poor organization, but from discord about the goals and how to attain them. All this suggests that we need principles to guide policy appraisal. The branch of economic theory known as welfare economics concentrates on providing guidance about the problems of policymaking. The theory examines both what

Jan 1, 1985

By N. W. Stump

New developments in on-stream analysis using immersed radioisotope gauges including results from plant installations are described. The control of grinding and flotation using a small digital computer has been complemented by this development. A control scheme for grinding which is based on maximum throughput at constant product size and preliminary work in flotation control are also outlined.

Jan 1, 1974

By M. J. Virnig, Peihao Qi, J. Brent Hiskey

The mechanism of gold uptake from iodide solutions by carbon has been investigated. Adsorption isotherms for gold and iodine were established. For activated carbon, approximately 300 mg of gold and 1000 mg of iodine were extracted per gram of carbon at maximum loading. Examination of loaded activated carbon particles by scanning electron microscopy reveals isolated patches of gold deposited on the carbon surface. High-resolution transmission electron microscopy shows that fine gold particles (1-4 nm diameter) are uniformly distributed within the carbon. Iodine was also observed throughout the matrix. The uptake of gold by carbon from iodide solution involves a combined reduction and adsorption process, where the gold iodide species is reduced to the metallic state superficially and adsorbed in the porous structure of carbon. A few experiments for the gold-chloride and gold-bromide systems were carried out for comparison.

Jan 1, 1993

By John C. Draper

The principal object of an underground coal mine transportation sys- tem is to move coal from the face where it is produced to the outside of the mine where it is prepared for market. In addition to the movement of coal, a transportation system must also move supply materials to the inside; it must move men in and out of the mine; and it must move rock and other debris out of the mine for disposal. Usually, mine haulage is divided into three categories named for the various areas of the mine served : 1) Pace Haulage. This is used at face from the mining machine to the intermediate transport system. 2) Intermediate or Secondary Haulage. Generally this is used between face haulage and main haulage. Sometimes this is merely an extension of the main haulage. 3) Main Haulage. This extends from the secondary haulage to the outside and is usually either a track or conveyor system, sometimes a combination of both. Transportation modes of coal in the various areas pose different problems, but the whole system must be synchronized. For instance, at the face the coal should be removed quickly from the various places to facilitate the movement of machines, whereas the intermediate system just passes the same coal on to the main transportation system. Selection of the transportation system must be based on the seam height, mining methods used to extract the coal, capacity required, ease of coal handling, and haulage efficiency. When driving rooms, mine cars can be used. They often simplify supply haulage and rock handling because they can also handle these items. Conveyors could be used and would have a greater haulage capacity but they cannot handle supplies easily or segregate the rock. When using a different mining method, such as longwall, mine cars cannot be used because there is not sufficient space to move the cars at the face nor can the cars haul the coal without delays which would cause excessive losses in production. As for ease of handling at a longwall face, conveyors are convenient because of their low height, ruggedness, and ability to operate while being advanced. Similarly, in low seam heights, conveyor systems are easier and more economic to operate than the regular track haulage because roof has to be taken down for handling mine cars of adequate size.

Jan 1, 1981

By Jacques B. Wertz

Although fracture intersections and "domes" seem at a number of places to be the basic structural combination for the occurrence of a mining district, of the porphyry-copper type particularly, this situation is, of course, not always to be expected. For instance, the group of mines comprising Superior, Ray, Miami, Globe, Christmas appeared from the beginning of these structural studies as typical exceptions, and there are others. One had to expect additional parameters to allow for any mineral concentration to occur. One of these apparent parameters is here considered. From the result of stratigraphic studies related to ancient formations in Southeast Arizona, the Martin limestone (Devonian in age) was retained as having a possible relationship with the structure-economic studies in progress, as evidenced for instance by the mineralized O'Carroll bed located at the base of the Martin. This limestone formation has been rather extensively investigated in the past and there are many known sample localities. For this work, the isopach map was drawn by computer to insure more objectivity and, in addition to the available data points, a number of dummy points with a zero value were added around the assumed form-

Jan 1, 1971

By Newell H. Orr

Titanium's performance characteristics in acidic oxidizing and mildly reducing environments make it applicable to numerous currently defined and many projected hydrometallurgical applications. With titanium's current and projected availability and price stability increased use in pressure leach, piping systems and electrorefining is practical.

Jan 1, 1983

By Ruipeng Qian, Pengfei Wang, Guorui Feng, XianJie Du, Jun Guo, Yuxia Guo, Tingye Qi, JinWen Bai

"A numerical modeling was conducted to describe the behavior of overlying strata on the longwall top coal caving face for exploitation of a 16.8 m thick coal seam. Three typical structural models, including the Cantilever Structure (CS), Lower Cantilever and Upper Hinged Arch Structure (LC&UHA), and Lower Arch and Upper Voussoir Beam (LA&UVB), were developed. Based on mechanical analysis of the different structures of the key strata, and considering the behaviors of the broken igneous rock strata, a method was proposed and applied to estimate the structures of the overburden strata. The results had been verified by a field micro-seismic monitoring test. The paper provides a foundational method to determine the shield loadings for the top coal caving longwall face.INTRODUCTIONLongwall top coal caving (LTCC) is a highly productive underground mining technology which has been widely applied to the exploitation of the thick coal seams in China and other countries due to its high efficiency (Ju and Xu, 2013; Ju, Xu, and Wang, 2011; Liu et al., 2009). In recent years, a large amount of research on mining pressure forecast, strata control, and mechanical equipment improvement of the LTCC technology has been carried out, which greatly advances the field application of the technology (Liu et al., 2009; Yu, 2016; Dou et al., 2014; Feng et al., 2011; Chen and Li, 2011; Yin, Yan, and An, 2008). In 2006, the LTCC technology was first applied to the exploitation in a 20 m thick coal seam at the Tashan Coal Mine in China (Yan et al., 2011). Ten years of mining at the Tashan Coal Mine has highlighted the importance of the support management in controlling the roof strata on the extra-thick LTCC face. The mining pressure is closely related to the structural features of the overlying strata and its movement laws (Yu, 2016; Dou et al., 2014; Feng et al., 2011). However, the distributions of three zones—caving zone, fracture zone, and deformation zone—on the fully mechanized caving longwalls changed significantly with the increase in thickness of the coal seam (Chen and Li, 2011). The behavior changes of the roof strata led to abnormal pressure in the mining face and resulted in the difficulty of surrounding rock control (Yin, Yan, and An, 2008; Liu et al., 2009; Yan et al., 2011; Gong and Jin, 2008). Therefore, the theoretical research focused on the behavior of overlying strata to reveal the laws of mining pressure has important theoretical significance and practical value.Many classical studies (Qian and Shi, 2003; Feng, 2010; Yu, 2015; Yu, Yan, and Liu, 2012) had been done to describe the behavior of overlying strata in the mining process. It has also been reported that magma intrusion causes an important effect on the surrounding rock, coal, and methane (Wang et al., 2005; Liu et al., 2007). On the one hand, the property and structure of the coal seam was obviously changed by the magma intrusion and resulted in a potential danger of a gas outburst during the mining process (Chen et al., 2012; Wang et al., 2014). On the other hand, the hard igneous strata and the joints occurred with the magma cooled, causing an abnormal behavior of overlying strata and resulting in a series of dynamic disasters during mining (Xuan, Xu, and Lu, 2014; Lu et al., 2016). In fact, many coal fields in China are intruded by igneous sill, including the Datong, Shuozhou, Huainan, and Xuzhou coal fields (Chen et al., 2014; Wu, 2011). The 3–5 coal seam at Tashan Coal Mine in Datong coal field is very thick and is intruded by a large area of layered lamprophyre rock. Face falls and shield failures occurred frequently during the face retreat."

Jan 1, 2019