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By Y. Nien Wang, Moe Amini, Heiner Sander, Max John

INTRODUCTION As the population increased along the coast route (California Route 1), and the people’s need to have guaranteed access increased, the landslides and related road closures began to have serious adverse economic impacts. Landslides were causing major long-term road closures about every 10 years on average. In 1983, ground movement at Devil’s Slide caused Highway 1 to be closed for an extended period of time which caused significant economic loss to the surrounding coastal communities. A number of options for bypassing the slide area were considered, and the Martini Creek inland bypass was selected for design. Subsequent litigation led to the creation of the Devil’s Slide Tunnel Study in 1996. The results of this study indicated that a tunnel alternative would be competitive with the inland bypass. The final decision was left to the citizens of San Mateo County, who approved the tunnel alternative in the November, 1996 election After completion of environmental studies and the processing of legal challenges, the final environmental document was finished in 2001. The preferred tunnel alternative was designated to proceed for final design and construction. PROJECT DESCRIPTION The Devil’s Slide Tunnels consists of a separated two-lane road, one lane in each direction, which passes through twin tunnels and over twin bridges and then connects with the existing non-separated, two-lane road at each end. The total length of the project is approximately 1900 meters consisting of four main project divisions, which are described below, going from south to north. 1.Operations and Maintenance Center (OMC) area, 2.Southern approach roadways to the South Portals (250 meters), including the South Rock Cut,

Jan 1, 2005

By Russell Barr, Robert E. Cook

As most mining companies are taking advantage of the high market prices for base metals such as steel, copper and zinc, numerous challenges still face them. While demand is strong from countries like China and the United States, demand is still mixed in Europe. This leads to the question of how long these high prices and overall high global demand will last. The tremendous market prices of most precious and base metals have enabled many companies to pay down a significant amount of debt accrued during acquisition and capital expenditure phases. Additionally, mining companies have been able to internally fund and engage in large projects to address future growth, (Less, 2006), thus maximizing the performance of the existing asset base, driving maintenance costs down, and improving and empowering the work-force (Mining Journal, 2006). Market prices and general efficiency gains have addressed these issues to some extent. However, critical issues still face operating managers in the mineral pro-cessing side of the industry. Energy prices, for example, continue to have a negative impact on cash costs for producing an ounce of gold or ton of a given base metal (Cummins, 2003).

Jan 1, 2007

By R. L. Wolfrom, R. Hogg, S. Chander

A gravimetric method for measuring rates of capillary rise in powders was explored. Methods to improve reproducibility and consistency of the results were investigated. In particular, the effects of particle size and packing uniformity were addressed. Studies of the wetting behavior of both spherical glass beads and irregularly shaped synthetic graphite particles by various organic liquids were carried out. Standardized procedures for bed preparation are described. The applicability of the Washburn equation for surface energy evaluation in such systems is discussed.

Jan 1, 2002

By R. P. Stahura

Conveyors are the lifeline of mining and processing operations. They continuously supply materials to and carry finished products and waste away from operations. When conveyors are running at less than maximum efficiency, the operation's productivity is in trouble. Inefficient conveyors suffer carryback, leading to the buildup of materials on idlers and other expensive components. They spill and leak material at loading zones and conveyor transfer points. This causes accumulations that can damage the belt, wear moving components and increase both clean-up labor and maintenance expenses. They wander or mistrack, spilling material and endangering personnel and conveyor components. And through these inefficiencies, they multiply the operation's hidden costs. These added expenses occur in lost production, increased downtime for service and maintenance and replacement costs for prematurely worn equip¬ment. In addition, the attitude that inefficiency is "good enough" is recognized elsewhere in the organization. As a result, other departments relax or operate at less than peak performance. Quality goes down along with employee morale. Costs of inefficient conveyors A key to efficiency is handling a product as few times as is necessary. That means conveyors should be loaded, track true to the unloading point and then be unloaded, all without material escape or waste motion. An inefficient conveyor is often signaled by accumulations of DURT - material that has escaped from the system and is now at large in the plant. This DURT adds costs to an operation that are uncounted and, perhaps, uncountable.

Jan 1, 1992

By Paul C. Schmall, Arthur B. Corwin, Derek Maishman

Ground freezing occupies a unique and important niche in underground construction, fulfilling a geotechnical need that is difficult, or sometimes impossible, to fulfill through other groundwater control and excavation support methods. Where complete groundwater cut-off and in-built ground support are required, and deep excavation is planned or the work occurs in difficult or disturbed ground, ground freezing offers the assurance critical to safe and timely construction. Compared with other groundwater cut-off or excavation support methods, a frozen wall is easily connected to underlying bedrock and will also adhere to adjoining subsurface installations or obstructions, if necessary, to provide a composite cutoff structure. Ground freezing is effective in all soil and ground conditions and has been used for emergency situations in disturbed, displaced or loose ground, where detailed soil characterization could not practically be performed.

Jan 1, 2005

By Jozef F. Zurawski

Increasingly new interceptors or new Combined Sewer Overflow (CSO) projects require connections to existing tunnels. More often than not, the existing facilities are old, in poor or questionable conditions, without proper construction records or as-built drawings. Many cannot be easily inspected unless major construction effort provides flow by-pass for safe access. This paper provides general guidelines on how to approach the problem of assessing the condition of old tunnels, how to plan and design the connection with limited physical assessment, how to develop the scope of work for the bid documents and how to provide geotechnical guidelines and designs for the bid documents.

Jan 1, 2008

By J. D. Doll

MSHA has promulgated a rule to limit the exposure of underground metal/nonmetal miners to diesel particulate matter (DPM). In May 2008, the final personal exposure limit will be lowered to 160 µg/m3 total carbon. To comply with this rule, mine operators are implementing a variety of control technologies. In this study two types of control technologies (ventilation and cabs) which are being implemented in limestone mines were investigated. Two stone mines in this study use large diameter propeller fans for main mine ventilation and direct the air to the faces using auxiliary fans, stoppings, and long pillars while bypassing the old mine workings. NIOSH measured for sub-micrometer elemental carbon (EC) using SKC DPM cassettes (analyzed using NIOSH 5040) and a near real time instrument. With the present ventilation and the number and type of vehicles used, the concentration of EC from DPM at the working areas was at or below 400 µg/m3 for both mines and about 166 µg/m3 and 251 µg/m3 at the returns. The real time data showed that the ventilation was reaching the working areas and effectively diluting the DPM. Environmental cabs were also used to reduce DPM exposures in three underground limestone mines. Using NIOSH method 5040 and near real time EC instrumentation, NIOSH sampled inside and outside of a loader cab at one of these limestone mines to determine the effectiveness of the cab. The cab was found to be over 90% effective in removing DPM as long as the cab system was properly maintained, and doors and windows were closed.

Jan 1, 2009

By Timothy P. Smirnoff, Tracy K. Lundin

INTRODUCTION The City of Phoenix, Arizona is located in the Phoenix Basin watershed which is prone to flash flooding several times each year. The runoff from these storms moves from the mountains in the north to the Salt River in the south. An extension of Interstate Highway 10 (1-10) will pass through the city east to west to form an Inner Loop through the downtown business district. PROJECT DESCRIPTION The I-10 Inner Loop extension will be a depressed roadway which would intercept the surface drainage of the Phoenix Basin and separate the watershed into two regions. To prevent flooding of the depressed roadway, runoff storm water collected from the northern half of the drainage area will be conveyed beneath the roadway to its natural outlet at the Salt River. A conveyance system composed of pressure tunnels beneath the city, shown in Figure 1, was proposed to achieve this goal . Table A presents the prominent features of each of the tunnels. This paper will describe geologic and engineering parameters specific to Phoenix which were used in the design of a series of tunnels to convey storm water from the I-10 Inner Loop to the Salt River. The design of tunnel initial and final support is described along with support and construction methods used by the Contractor.

Jan 1, 1985

By T. Payne

Underground heat issues are mainly focused on the detrimental effects to a workers health. However, working in hot, humid conditions has other negative effects. Studies have shown that safety, productivity, workforce morale and operating cost are also worsened in these conditions. The human body has several mechanisms for rejecting heat and remaining cool. However, once the air temperature exceeds about 34°C, the only effective mechanism is by evaporation of sweat from the skin. This is assisted by acclimatisation which is the human body?s enhanced ability to combat extended exposure to heat. The body has to remain well hydrated when working in heat as even small degrees of dehydration cause significant decreases in the ability to work in heat. There are two ways in which heat load can be reduced: Through use of refrigeration/vent/cooling to reduce thermal stress on workers; Reduce the contribution that heat sources have to underground heat load (e.g. reduce idle time, fleet size, etc). Some of the sources of underground heat have the potential to be more manageable than others. Geothermal heat and heat from autocompression will be found in all mining situations in varying degrees depending on geothermal gradient and surface temperature, however, the use of equipment and blasting may be streamlined to reduce the underground heat load. It is through a combination of the available options that most mines will successfully control their heat related problems. Mt Isa, which has been a focus for heat related study in Australia, has successfully implemented protocols for working in heat. Through combining these with the installation of a surface bulk air cooling plant, Mt Isa has consistently reduced the incidence of heat illness. This is likely to be the most cost effective method of reducing heat load for deep mines in Australia. Shallower mines which may only occasionally encounter hot conditions should consider more portable cooling options. This study will review the heat issues in underground Australian metalliferous mines.

Jan 1, 2009

By F. Block, K. Kohli

Outcrop barrier pillars serve to keep mine personnel and the public safe from sudden uncontrolled flows of water accumulated in active and abandoned underground mine workings. When an outcrop barrier fails, the result is an outbreak of water to the surface and is termed as blowout. Mine blowouts are associated with above-drainage mines and can occur through the coal outcrop and sealed portals. A blowout is often catastrophic, a threat to the people on the surface living or working in the path of a potentially large flood. In addition, blowouts can destroy homes, cause landslides and severe erosion and release pollution and acid mine drainage. This paper provides guidance on the planning, design, evaluation and inspection of barriers to address the problem of mine blowouts associated with above-drainage coal mines.

Jan 1, 2007

By C. Allen

Vale Inco Ltd. is trialing several energy conservation initiatives in an effort to minimize costs and reduce green house gas emissions. The Ventilation on Demand (VOD) concept is a major project being carried out in various phases at Vale Inco mines. Due to the complex nature of a dynamic VOD system, Vale Inco is taking a systematic approach of testing VOD system components with milestone evaluations of each project. Coleman Mine was selected to pilot test the functionality and robustness of automated louvers in the underground environment; with the goal of optimizing mine airflow such that ventilation would be available for developing a new ore body. This project involved installing automated louvers in the exhaust raises; and installing variable frequency drive (VFD) starters on auxiliary supply fans. Because the VOD project created efficient utilization of the ventilation air in the 153 OB, the 170 OB is currently being developed without increasing the total fresh air into the mine. This paper describes the louver system component of VOD as applied at the mine.

Jan 1, 2009

By Luke Erickson

San Francisco Public Utilities Commission is planning to replace 5 miles of pipeline under San Francisco Bay. The tunnel will be constructed using an Earth Pressure Balance (EPB) TBM and will be the first TBM-driven tunnel under the Bay. The alignment passes under environmentally sensitive habitats, through interbedded layers of sands and clays, and through a buried bedrock ridge. This paper discusses the geotechnical characterization and anticipated tunneling conditions and presents the analysis of various construction methods that resulted in the selection of an EPB TBM. Considerations related to tunneling with an EPB TBM are described in detail, including ground conditioners, TBM cutterhead wear, muck control, and squeezing ground.

Jan 1, 2008

By Eldon L. Abbott, Rebecca K. Bolan

The Florida Department of Transportation, Florida’s Turnpike Enterprise is studying the feasibility of a 1128 meter (3,700 foot) vehicular tunnel to provide direct access for Port of Miami traffic to/from I-395, I-95, SR-836 (Dolphin Expressway) and Miami International Airport. Both Bored and Immersed Tube tunnels were evaluated and re-evaluated for constructing two, two-lane, 11.9 meter (39-foot) diameter tunnels beneath the Main Shipping Channel lying between Watson Island and the Port of Miami on Dodge Island in Biscayne Bay, Miami, Florida, USA. Bedrock Geology of South Florida is predominately very permeable, vuggy limestone with sand seams and occasional voids. Groundwater inflows in deep cut-and-cover excavations, tunnel buoyancy, grouting, maintenance of Port operations and potential/possible environmental impacts to Biscayne Bay were significant issues.

Jan 1, 2005

By A. D. Davis

The Gilt Edge Superfund Site is a former heap-leach gold mine that currently is being remediated in the Black Hills of South Dakota. Mine runoff water is treated before release from the site. The field pH, before treatment, is about 3, and the water contains arsenic and some heavy metals, in addition to sulfate concentrations of about 1400 to 1500 mg/L. In the Keystone area of the Black Hills, naturally occurring arsenic has been detected in ground-water samples from wells. Keystone City Well #4, which is not used currently, showed arsenic concentrations of 36 parts per billion (ppb) and sulfate concentrations of about 19 mg/L. With field samples of water from these sites, a limestone-based method was successful in reducing arsenic and heavy metals concentrations. The results are significant because previous research with the limestone-based method mainly had involved samples prepared with distilled water in the laboratory, in which interference of other ions such as sulfate did not occur. The research indicates the potential for broader field applications of the limestone-based removal method.

Jan 1, 2011

By G. Wahl, H. Danilkewich, T. Mann

Developers of advanced mining projects face the challenge of how to craft a “Request for Proposal for a Feasibility Study” that will result in bids that are comparable and will lead to a successful execution of the study. Mining engineering consulting firms are challenged by “Request for Proposals” that may consist of a limited description of the Scope of Services and other items, which could present difficulties in the subsequent financing and/or development of the project. Changes in international disclosure requirements have also changed the landscape on how resources and reserves are reported by introducing new disclosure requirements and concepts such as qualified persons. This paper lays out a strategy for preparing a Feasibility Study “Request for Proposal” based on the experiences of a mining engineering consulting firm working on a diversity of projects around the world, and in light of the recent changes in international reporting standards for reserves.

Jan 1, 2002

By Jafar Khademi Hamidi

The Zagros long tunnel is one of the main components of Sirvan water transfer project in western Iran. It is approximately 48 km in length and consisted of two lots. The second 26 km lot of this tunnel is under construction by a 6.73 m diameter double shield (DS) TBM. The tunnel passes through several formations with wide range rock mass qualities. During the tunnel alignment, changes in rock quality were highly frequent from poor to very good. The encountered geological conditions required TBM operation to change frequently from hard rock to soft, dry to flowing, sticky to nonsticky ground (and vice versa), more often than expected. In the course of tunneling, the machine has encountered nearly many adverse geologic conditions. The most important problems have been sudden high volume water inflow into the tunnel, sticky ground, and gas seepage, all of which resulted in reduced TBM advance rates. This study will high-light two difficult ground conditions including large water ingress and sticky ground and also the related problems encountered by the TBM along 8 km of excavated tunnel. In sticky grounds, cleaning of the clogged cutter head caused many delays and contributed to additional downtime. Application of some operational modifications, including decreased TBM thrust showed satisfactory results in such cases. While reduced thrust resulted in reduced penetration rate, but the overall TBM advance was greatly improved by the increase utilization rate and elimination of down time related to cleaning of the head. To cope with high water inflow, application of preventive measures such as pre-grouting has proved to be a more efficientsolution. The sealing of ground water inflow also decreased seepage of dangerous H2S gas and other chemicals such as hydrocarbons accompanying the groundwater.

?Classification System Efficiency (CSE)? is a simple, powerful concept which can be used to measure and improve ball mill circuit efficiency. This paper describes six plant case studies which demonstrate the use of CSE to diagnose and/or improve grinding circuit performance, with related improvements in circuit efficiency ranging from 3 to 30 percent. The increased effective mill grinding energy is recaptured from energy that was going into over grinding, which can greatly benefit downstream mineral separation. The achievable CSE for given circuit design/operating variables is described, providing every plant metallurgist with the means to determine the potential for increasing their particular grinding circuit?s efficiency through increased CSE.

Jan 1, 2012

By J. Evans

Including: Tailings thickeners, CCD?s, paste thickeners, HI-rate thickeners, lamella thickeners, high compression thickeners, clarifiers etc. Flocculant dosing control for mining thickeners and clarifiers is influenced by a number of process factors. 1. Flow rate into the thickener or clarifier a) As the flow rate increases into the thickener or clarifier ?retention time? decreases which causes a greater affect hydraulically on the settling solids. So as the flow rate increases it will generally mean an increase in flocculant dosing rate. b) As the flow rate decreases into the thickener or clarifier the retention time increases which reduces the hydraulic affect on settling, improving settling rates. This will generally mean that as the flow rate decreases, we will decrease the flocculant dose rate.

Jan 1, 2011

By A. Bobet

Design of a new underground laboratory is underway through the auspices of the United States National Science Foundation. The Deep Underground Science and Engineering Laboratory (DUSEL) is scoped to provide a diverse group of researchers with a dedicated underground facility capable of supporting a broad spectrum of fundamental and applied research at depth in the Earth?s crust. Key research partners in the endeavor are physicists, biologists, geoscientists and engineers. Engineers are not only designing the underground facilities, but are also actively involved in developing research initiatives. This paper will introduce the DUSEL engineering research program to the mining community, provide an overview of the site, geology, and laboratory facilities, and describe some key program initiatives. The particular technical challenges and opportunities afforded by the construction of DUSEL and the performance of the integrated science-engineering program will be discussed by reference to a subset of research initiatives that are currently under development: Cavern Design, CO2 Sequestration and Transparent Earth. These research initiatives target the development of new techniques that can support improved subsurface investigation, design and construction procedures. An increased use of the subsurface can actively contribute to the development of new, more sustainable solutions for use in mining and civil engineering practice.

Jan 1, 2011

By F. Bruey

The Factorial Model Experimenters are often interested in systems that are multi-factorial. A multi-factorial system is one whose output is believed or known to be dependent on the particular settings of several inputs, or factors. We can think of these factors as defining a space, with each point in this space corresponding to a particular set of factor settings. Experimenting can be thought of as exploring this space - finding out how the response of the system changes as factor settings are changed. There are several challenges in this exploration, among which are deciding what region to explore, designing an experiment that explores it most effectively, and describing the results of the exploration. This paper deals principally with the last of these; it shows how the factorial model can be used to describe how the response of the system changes as factor settings are changed. A strength of the factorial model is that it treats the factors as causes of change in the system's response and focuses on relations among these causes. In particular, the factorial model focuses on whether causes act independently on the system (in a sense to be explained below), or whether they interact. This is important because the experimenter generally seeks to control the system, and because control based on causes that act independently of other causes is relatively simple, whereas control based on causes that interact is more challenging. Also, mapping the space - finding out how the response of the system changes as factor settings are changed - will require less work if, during the exploration, it can be determined which of the causes act independently. For the sake of example, let us assume that the space we are exploring is three-dimensional, and that we have already defined, for each of the three factors, the range of interest. Let us consider all the ways in which the response of the system might depend on the settings of these three factors. In the simplest case, the response in this region does not depend on any of the factors. The response is constant throughout the space, at say, 80 units.

Jan 1, 2007