Search Documents

By Sam Lo Grasso, Carlos Herranz Calvo, Stuart Warren, Ted Giesing, Charles Marchesano

Mott MacDonald and Project Management Advisors are providing Technical and Project Management services for San Diego County for the Courthouse Commons Project. The Courthouse Commons Project involves the redevelopment of three downtown blocks owned by San Diego County and construction of an Inmate Transfer Tunnel between the County Central Jail and the San Diego Central Court. The tunnel will be 327 feet long, crosses the San Diego Fault and is being constructed using the Sequential Excavation Method (SEM). This paper discusses the history and procure‑ ment strategy for the project, the technical aspects of the transfer tunnel and the con‑ struction progress of the tunnel to date.

Jun 13, 2021

By Yiming Sun, John Stolz, Jakob Walter, Drew Mason

The Courthouse Commons SEM Tunnel was excavated within 6 feet of cover beneath two buildings in downtown San Diego utilizing high-precision geotechnical instrumentation. The excavated dimensions are approximately 25 feet in diameter and 328 feet in length connecting two in-service detentionlevel security buildings. Presupport includes large-diameter grouted canopy pipes and smaller pipe spiles. Initial support consists of fiber-reinforced shotcrete with lattice girders. This paper presents observed ground and structure behavior and lessons learned. During construction an unanticipated brick structure was encountered, and methods were developed to improve adhesion of shotcrete to sandy soil and to reduce rebound

Dec 1, 2022

By L. Watkins, M. O’Kane, A. Weir, D. Portefield

BHP Iron Ore initiated a program in January, 1995 at their Mt. Whaleback operation in Newman, Western Australia to develop a decommissioning plan for the waste rock material. The primary research program includes the development of technology for the long term performance of the waste rock dumps with respect to vegetation, slope stability, surface runoff, erosion, and water infiltration. This paper evaluates field performance of cover systems constructed on a horizontal and a sloped waste rock surface. The cover system is constructed using suitable run-of-mine waste material to minimize closure costs. The moisture is subsequently released to the atmosphere as evapotranspiration. Rainfall entering the waste material is buffered due to the presence of the cover material thereby significantly reducing net percolation to the underlying waste rock. The objective is to control acid rock drainage by preventing moisture movement into and through the waste rock material. Two years of field data are presented to illustrate low percolation rates to the underlying waste rock and key performance characteristics of the moisture store and release cover system design. Field data collected to date demonstrates that a moisture store and release cover system constructed with suitable run-of-mine waste material has good potential as a final acid rock drainage control cover system at the Mt. Whaleback site. The performance of the cover system on a sloped surface was significantly altered as compared to placing the cover system on a horizontal surface.

Jan 1, 2000

By O. Porterfield, M. O’Kane, M. Endersby

BHP Iron Ore initiated research programs in January 1995 to develop long-term plans for decommissioning waste rock material at its Mt. Whaleback operation. More than 2 Gt (2.2 billion st) of waste rock were deposited during the past 30 years. Ultimately, a total of 4 Gt (4.4 billion st) will be deposited in waste rock dumps constructed near the open pit. The Mt. Whaleback operation is located in a semiarid climate adjacent to Newman, Western Australia. The primary research program includes the development of technology for the long-term performance of the waste rock dumps with respect to vegetation, slope stability, surface runoff, erosion and water infiltration. This paper focuses on the design and implementation of a cover system to prevent water infiltration to the underlying waste rock. Data obtained from a laboratory program and from soil-atmosphere modeling was used to design horizontal field test plots. The construction of the horizontal surface field test plots is discussed together with the field instruments installed to monitor performance. The cover system is designed to maximize infiltration during wet periods for subsequent evapotranspiration while minimizing surface runoff. The result is a near-zero net infiltration to the underlying waste material. An important feature of the design is the use of run-of-mine waste material as the cover material. Monitoring is in progress and will continue for at least two annual wet/dry cycles. The optimum cover system should minimize the net infiltration of water to the underlying waste rock while maintaining physical and ecological integrity for long-term performance.

Jan 1, 2000

By Ronald S. Tanaka

In the planning stages for a dozen years, the 9.11 mile long Mount Macdonald Tunnel is the focal point of the $600 million dollar Rogers Pass Project. The paper will discuss the construction of the tunnel that is being carried out from both ends. The eastern portion contractor has used a tunnel boring machine to excavate the upper part of the tunnel and at the west end contractor selected the conventional drill and blast method. A ventilation shaft located near the mid point is the main part of a ventilation system unique in the Western Hemisphere.

Jan 1, 1987

By Kai Koosmen, Mehdi Serati, Tengzhou Wang

Spalling and rockburst are unwanted brittle failures at the boundaries of underground excavations that are commonly observed in hard rock and high-stress environments at significant depths, although, spalling has also been observed in comparatively shallow soft rocks. The crack initiation (CI) stress threshold (representing the stress level at which new micro cracks begin to form in an intact rock) is widely used to establish the in-situ spalling strength, and is generally regarded as the lower limit of the long-term rock strength. This study analyses the evolution of CI and other mechanical properties for a high-porosity sandstone with an average UCS of 38 MPa under unconfined cyclic compressive loading. The results indicate that rock properties are variably affected by cyclic loading with; no significant effect on Youngs Modulus; a moderate increase in Poisson’s ratio and fracture angle; a moderate decrease in UCS; and a major reduction in the CI stress threshold. All of these changes were generally amplified by cyclic loading at higher stresses. From the results, it is concluded that rockburst and spalling limit in underground structures may reduce over time if the rock is subject to repetitive cyclic loading, and that the reductions will be greater for higher cyclic stresses. This may be a significant factor in the design and operation of some deep underground structures.

Apr 26, 2022

By Erik S. Bernard

"INTRODUCTION Conventional steel bar reinforcement is used in many tunnel linings to provide high flexural and tensile load resistance. These Reinforced Concrete (RC) tunnel linings may suffer flexural cracking during service or, in the case of precast concrete segments, during production, handling, or installation. Cracks can lead to corrosion of steel reinforcement, so limits are placed on maximum acceptable crack widths to reduce the likelihood of corrosion during the intended design life (AFTES, 2013; MC2010, 2012). However, the relatively light level of reinforcement used in many applications can result in quite wide in-service crack widths, so either additional steel bar reinforcement is required to limit maximum crack widths, or fibers can be included to control crack widths. Numerous investigations have been undertaken into the efficacy of including steel fibers to reduce crack widths in conventionally reinforced members (Stang and Aarre, 1992; Abrishami and Mitchell, 1997; Bischoff, 2003; Dupont and Vandevalle, 2003; and Jansson et al, 2010), but steel fibers suffer the problem that they are at least as sensitive to corrosion at cracks as steel bars and therefore have similarly tight limits placed on acceptable crack widths (AFTES, 2013). An alternative means of maintaining narrow crack limits in RC members has therefore been sought. The current investigation was instigated following an observation that theories promoted as an explanation for the ability of steel fibers to reduce crack widths in reinforced concrete flexural members (Deluce et al, 2014) do not depend on the material composition of the fibers used but instead depend primarily on the tensile stress generated by the fibers across cracks. Since it is known that macro-synthetic fibers are capable of equaling the post-crack tensile capacity of steel fibers, it has been hypothesized that macro-synthetic fibers are also capable of reducing crack widths in reinforced concrete flexural members but with the added advantage that macro-synthetic fibers are completely immune to the effects of corrosion. Use of macro-synthetic fibers to reduce maximum crack widths in reinforced concrete flexural members subject to aggressive environmental exposure is more rational than use of steel fibers because steel fibers are very sensitive to the corrosive effects of environmental exposure at cracks. The current investigation was therefore undertaken to explore the potential use of macro-synthetic fibers to reduce maximum crack widths in reinforced concrete members subject to flexure. Barchip BC54 fibers were selected as they are one of the most widely used and competitive high performance macro-synthetic fibers currently available."

Jan 1, 2016

By Terry W. Mellors, Robert J. F. Goodfellow

The underground industry has been forced to reconsider risk management sincethe introduction and implementation of the “Joint Code of Practice for Risk Management of Underground Works in the UK” published in 2003 and the subsequent international version published by the ‘International Tunneling Insurance Group’ (ITIG) in January 2006.What does this mean for major tunnel projects in the US and elsewhere? The discussion will highlight the implementation of the Codes to date, risk management principles embodied in the Codes and the use of risk registers as a projectmanagement tool and the management of risk.

Jan 1, 2007

By C. J. Monahan

INTRODUCTION With the introduction of large diameter hole drilling to underground mining, a need for the development and utilization of new blasting technology has arisen. This new technology has resulted in more efficient blasting and in easier and cheaper mining. The application of spherical charges to the crater blasting method is an im¬portant part of this technology. Spherical charges, or their geometric equivalent, make for highly efficient use of explosives in the cratering application. Their geo¬metrical configuration, normally a length :diameter ra¬tio of <6:1, limits their charge weight size. For exam¬ple in a 165-mm (61/2-in.) hole a spherical charge weighs approximately 34 kg (75 lb). These dimensional and weight restrictions require careful engineering design and control in the production application. Strathcona mine, a large tonnage mechanized cut¬and-fill and blasthole stoping operation located on the north rim of the Sudbury Basin, has successfully em¬ployed the crater blasting method in production blasting for the past two and a half years (as of 1979). As a result, this method, using spherical charges, has made possible the development and implementation of a verti¬cal retreat blasthole mining method which is being used for rib pillar recovery. The crater method used at Strathcona essentially in¬volves blasting off horizontal slices of ore into an under¬cut while retreating vertically to the pillar overcut elevation. Loading and priming of the holes is achieved from the overcut and the blasted muck is recovered by load¬haul-dump (LHD) units through a drawpoint system. Valuable experience on the behavior and performance of explosives in large diameter holes has been gained in both the operating and engineering fields from the appli¬cation of this blasting method. It has been used in drop raising and is currently being evaluated for use in pri¬mary stoping operations. Also, serious consideration is being given to its use for the recovery of post pillars in mined-out and backfilled cut and fill stopes. The method has significant advantages over conven¬tional methods of pillar recovery from economic, ground control, and safety points of view. These include cost benefits due to a minimum stoping development, less ground support, reduced labor requirements, and faster mining rate. Research on the blasting mechanism indi¬cated the method should result in less damage to fill walls than would be normally expected with conven¬tional longhole or large diameter hole cylindrical blast¬ing (benching). This is primarily due to the limited charge weight per delay because of the size dimensions of a spherical as compared with a cylindrical charge and also because the large diameter holes experience less de¬viation than standard-sized longholes. Experience has shown that wall damage has been minimized with the use of this method. The safety aspects of the working environment are also improved as there is no require¬ment for manpower to go under exposed backs after blasting, which is a significant improvement over the cut-and-fill method. CRATERING THEORY General The term cratering, in blasting, is applied to the for¬mation of a surface cavity in a material as the result of detonating an explosive charge in that material. This blasting concept was initially used as a tool in the eval¬uation of explosives performance; however, it has been utilized more recently on surface and to a lesser extent in underground blasting operations. Explosive charges used in crater method are nor¬mally spherical or the geometric equivalent, as research into the application of this breakage mechanism to rock indicates that spherical charges or their equivalent pro¬duce optimum results. In blasting practice, spherical charges have been defined as having a length to diameter (L: D) ratio of 4:1 or less, and up to, but not exceeding a L: D = 6:1. Thus, for holes 165 mm (61/2 in.) diam, a charge 165 mm (61/2 in.) diam, and 990 mm (39 in.) in length would constitute a spherical charge. Crater Testing Crater testing for underground application is nor¬mally accomplished by drilling smaller than production sized horizontal holes into drift walls, placing relatively small charges of explosives in the holes at various depths of burial, firing the charges, and measuring the results. The results are scaled to develop charge weight size and depth of burial parameters for production hole sizes. In theory, this procedure is valid and is appli¬cable for surface blasting; however, in underground applications where the craters are inverted, there is some question as to whether extrapolation of the test results is appropriate. As well as the fact that craters are in¬verted with resultant gravity stresses, testing is often done in a waste rock drift where the properties differ from those in ore rock. There is also some question as to whether a 51 or 76-mm (2 or 3-in.) diam charge behaves similarly to a 165-mm (61/2-in.) charge in a confined borehole. Crater testing at Strathcona involved drilling 76-mm (3-in.) diam holes at various depths ranging from 1 to 3 m (3 to 10 ft). The test holes were drilled in the wall of a predominately waste drift as well as in a stope wall. Charges were placed at various depths of burial, were confined, fired, and the results measured. Although the results were somewhat erratic, possibly because of the aforementioned reasons, they did provide guidelines for basic design for production application. MINING METHOD APPLICATION FOR PILLAR RECOVERY Following initial crater testing, assessment, and tech¬nical evaluation, it was decided to use this blasting tech¬nique in a production application, and to incorporate

Jan 1, 1982

By Curt Morgan

This paper will discuss the value of cream a common information model for the mining industry. Information models are a proven technique for quantifying diverse information in a non-proprietary and easily understood manner. Combining information models with emergent data exchange technologies such as XML and SOAP, the mining industry could substantially reduce the costs of sharing information, reduce dependence on proprietary information systems, leverage inexpensive PC desktop technology, and provide a solid foundation for simplifying mine information systems. The paper will provide an overview of information modeling, discuss practical and proven applications of the modeling technique in the mining industry, propose how such a model could be developed in a collaborative manner and discuss the benefits of such an effort.

Jan 1, 2002

By I. Nimmo

Since the beginning of Aluminum mining and refining the industry has lived with distributed control rooms and suffered from many behavioral problems common with this design. When Human Factor/Ergonomic design is introduced to a Western Australian installation a common centralized control room realized many improvements including economic payback. Communications issues were resolved, better coordination of materials, improved situation awareness during startups, abnormal operations and an opportunity to make improvements during normal operations characterize the changes at the Worsley Refinery. This presentation will review the reasons for the change. Since the beginning of Aluminum mining and refining the industry has lived with distributed control rooms and suffered from many behavioral problems common with this design. When Human Factor/Ergonomic design is introduced to a Western Australian installation a common centralized control room realized many improvements including economic payback. This presentation will review the reasons for the change, what changed and the process of changing the culture from reactive to predictive and what difference that has made.

Jan 1, 2011

By J. P. Earnhardt

Recycling of such municipal solid wastes as glass containers, metal cans, and newspapers has received increasing attention recently. However, municipal solid wastes account for only 1% of the total solid waste stream in the United States. The remainder includes hazardous and non-hazardous industrial wastes. Generators of industrial wastes are facing higher landfill costs. Future liability potential, and public image concerns which are forcing them to seek innovative and often profitable solutions to minimize, reuse, and recycle their waste streams. Opportunities for the mining industry in industrial recycling include recovery of mining wastes and by-products, and utilization of mineral products for treating waste streams.

Jan 1, 1993

By John E. Tilton

The ability of companies and countries to mine copper and other mineral commodities competitively and in the process to generate new wealth depends on their mineral endowment. Chile, for example, produces and exports copper because it is well endowed with high-quality, low-cost deposits. This production creates wealth that benefits mining companies and their stockholders, the government, local communities, as well as copper consumers around the world. The widespread perception that mineral endowment must largely determine competitiveness, or what economists call comparative advantage, must be true at any particularly moment. Countries with abundant reserves must be competitive. This follows from the definition of reserves — the quantity of a mineral commodity found in discovered deposits that are profitable to exploit under current conditions. As a result, it is a tautology and not particularly interesting. The important question is what causes reserves to change over time, producing in the process new wealth and shifts in competitiveness?

Jan 1, 2003

By Glenn Melchert, Paul Eger, Jon Wagner, Dave Antonson, John Folman

Current approaches to reclaiming acid generating tailings include permanent water cover or encapsulation with various synthetic liners and/or clay. Although these methods can be effective, some ongoing maintenance will be required in perpetuity to ensure that water levels are adequately maintained or that the integrity of any capping system is protected. The successful creation of wetlands in tailings basins offers the possibility of creating a stable environment for the tailings with minimal maintenance. Acid-generating tailings from a massive zinc sulfide deposit in Winston Lake, Ontario, were placed in small cylindrical tanks to examine the feasibility and effectiveness of creating wetlands and mitigating acid and metal release. Two uncovered controls were established in addition to the five treatments, which were done in duplicate. Each wetland tank was 117 cm in diameter and contained 6 1 cm of tailings. Treatments included 61 cm cover of wetland soil, 61 cm of glacial till, 61 cm of tailings, and two tanks with 71 cm of water. One of the water covers included the aquatic macrophytes: Elodea canadensis, Potamegeton sp., and Ceratophyllum demersum. Cattails (Typha latifolia) were planted in the plots with substrate cover, and the initial water level was set at ten centimeters. The pH within the tailings in the treated tanks generally ranged between 6.0 and 6.5 and zinc concentration ranged from 0.02 to 0.1 mg/L. The drainage from the controls had an average pH of 3.3, and 7,700 mg/L of zinc.

Jan 1, 2000

By Charles H. Jacoby

Introduction Although, in general, the openings created in domes or diapiric type salt deposits during mining operations are larger than those created in bedded deposits, the openings in bedded salts are of significant lateral extent. Thus, this paper will deal primarily with the dome deposits of the Gulf Coast and more specifically with the Avery Island dome operated by the International Salt Company where recent development activities have materially increased the sizes of previously standard openings. Geology The geology of salt deposits is the governing factor in the rock mechanics associated with the opening which is being created in the salt. Bedded salts are customarily characterized by having experienced solution along the interface between the top of the salt and the overlying bed. Thus, as the salt slowly dissolves there has been left behind a layer of laminated insolubles which is often incompetent. In most cases, this incompetent rock must be supported by a thickness of bedded salt which is left in the roof as support. Where this salt is of secondary deposition (recrystallized halite) with included moisture, additional thicknesses of roof salt are necessary to achieve stability. The salt which forms the domes of the Gulf Coast regions is from the Louann formation of the Jurassic period. These formations are dipping toward the Gulf of Mexico so that the upper tier of domes which have formed across northern Louisiana in an east-west direction into Mississippi and Texas have a salt source some 10 to 15,000 feet

Jan 1, 1976

By M. J. Blattman

Upon completion of an underground mine design, the planning engineer is faced with a surprisingly complex problem, “What development and mining sequence should be implemented so as to maximize the return on investment?” The problem relates to the scheduling of development headings to access stope production areas in such a way that the most money is made as quickly as possible for as long as possible. The total dollar value of the stopes, the average grade, the total tonnage, nor even the profit margin do not accurately give an indication of the “proper” mining sequence on their own. This paper will outline a method being developed by the author that can create a sequence of events that maximizes the net present value (NPV) of a given development and production design using information already being generated during the design process.

Jan 1, 2003

By Z. T. Bieniawski

After many significant advances in mining including development of sophisticated methods for strata characterization and numerical modeling analyses, the engineering design process in mining is as primitive as it was two decades ago. Yet, major advances in design methodologies have occurred in other branches of engineering. Is creative design in mining a myth only? Are we deluding ourselves when we talk about innovative mining design of today? What is the reality of the situation? This paper explores the methodology of creative engineering design as a new recognized discipline. It warrants applications in mining since design experts are sometimes unaware of their own decision-making processes.

Jan 1, 1988

By Mark P. Juzli

During the 1980s, a revolution has been taking place in industrial minerals marketing. Transportation deregulation and a handful of creative marketing and distribution managers have completely changed the rules for marketing many industrial minerals. Minerals are being transported much farther than in prior decades and at much less cost. Bulk and package terminals are becoming increasingly common as a means to take advantage of freight rate savings and to provide enhanced service to faraway customers. Water and rail transportation are being used increasingly to penetrate markets considered unreachable just a few years ago. No longer do the textbook rules of thumb for industrial minerals marketing apply. This author recalls three of those rules he was taught in mineral economics graduate school in the 1970s. As recorded in class notes: • construction aggregates are seldom shipped more than 32 km (20 miles) from the quarry; • cement is sold within 240 km (150 miles) of the mill; and • industrial sand is sold regionally - it is freight constrained to a market radius of no more than 320 to 400 km (200 to 250 miles) from the plant. And yet, the author looks up in 1989 and observes overland movements of aggregates of many hundred miles, overland movements of cement and industrial sand of 1600 km (1000 miles) or more, and water movements of both aggregates and cement into the United States from sources halfway around the world. Truly, industrial minerals are in the midst of a marketing revolution. The companies that have led this revolution have enjoyed considerable financial success in the 1980s. They have enhanced their profitability by increasing market share, capacity utilization, and average selling prices by taking product to remote markets where premium prices are available. They have consistently outperformed their competition, many of whom remain unaware that the marketing revolution going on around them is actually a transportation/distribution revolution. The successful industrial minerals company of the next 10 to 15 years must participate in the transportation revolution as it continues to evolve. Additional human and capital resources must be committed to maximize the effectiveness of a company&apos;s transportation and

Jan 1, 1989

Published by ?MILOS CONFERENCE CENTER ? GEORGE ELIOPOULOS? Editor Professor Z. AGIOUTANTIS Editorial Coordinator HELIOTOPOS ? PROFESSIONAL CONGRESS ORGANIZERS Layout IRINI KALOGIRU Production PALLAS Co Cover PANAYOTIS PAPASTAMATIS HELIOTOPOS - PROFESSIONAL CONGRESS ORGANIZERS

Jan 1, 2003

Published by ?MILOS CONFERENCE CENTER ? GEORGE ELIOPOULOS? Editor Professor Z. AGIOUTANTIS Editorial Coordinator HELIOTOPOS ? PROFESSIONAL CONGRESS ORGANIZERS Layout IRINI KALOGIRU Production HELIOTOPOS ? PROFESSIONAL CONGRESS ORGANIZERS Cover PANAYOTIS PAPASTAMATIS HELIOTOPOS - PROFESSIONAL CONGRESS ORGANIZERS

Jan 1, 2003