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By Eleanor Kentish, Nathan Bond, Edward Batty, Simon Webber, Alan Skarda

"Crossrail is Europe’s largest construction project — a new 100km rail route running through central London. A joint venture of BAM, Ferrovial and Kier (BFK) has constructed the tunnels and escalator shafts at the new Bond Street and Farringdon Stations. The recent trend in the UK industry towards sprayed secondary linings is driven by the potential for significant savings in cost and time. BFK is unique within Crossrail by constructing both sprayed and cast secondary linings. This paper presents a direct comparison between sprayed and traditional cast in situ secondary linings at Bond Street and Farringdon Crossrail Stations. An objective comparison is drawn between procurement and mobilisation periods, production rates, flexibility, tolerances and logistics in the tunnels. The technical challenges surrounding cast and sprayed secondary linings are explored, and recommendations are made of how each method could be improved for future use. INTRODUCTION It is well established that sprayed concrete offers a fast and effective method to seal the face of an excavation. In a relatively short space of time, sprayed concrete can be applied to an open face to support the short term ground loading on the tunnels during construction. Advances in sprayed concrete lining (SCL) technology — such as the use of wet mix processes, improved accelerators, fiber reinforcement, remotely controlled spraying robots, innovative surveying equipment and nozzleman competency schemes — have greatly increased the speed and safety of tunnel excavations using this technique. As a result, design engineers have become increasingly confident to use SCL primary linings as part of the permanent structural lining (Su 2014). Historically, long term ground and water pressure loads have been considered to be carried by the main structural or secondary lining, constructed using cast in situ concrete (Pickett 2014). However, the advances described above have made sprayed secondary linings a viable option, which has already been proven on the A3 Hindhead Tunnel (Arnold 2012). Sprayed concrete secondary linings offer potentially significant savings in cost and time during the construction process. The contractor does not need to procure a bespoke formwork system for each different sized tunnel — the SCL plant required is already on site for the primary lining. Each bay is sprayed with accelerated concrete, becoming self-supporting almost immediately — compared to moving and resetting the shutter, pumping concrete and waiting for it to cure. With sprayed concrete, working sequences and cross sections can easily be changed."

Jan 1, 2016

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 B. Denby, D. J. McMlarnon

During the ongoing research into the possible applications of Virtual Reality in underground operations, the AIMS Research Unit has developed a user-interface driven program which enables a user to input the geometry of underground mines, and add equipment and working processes in order to produce an accurate simulation of their operation. This paper describes the main features of this system (VR-MINE). Virtual Reality is a field which has grown out of three dimensional computer graphics techniques, and allows a user to move freely around a model held within the computer&apos;s memory. Movement around this model is carried out by the use of intuitive peripherals such as joysticks, with the user&apos;s view from their position within the model being produced in real time on a computer monitor or other device (such as a headset). This enables a user to interact with any three dimensional model and see the results of their actions immediately. VR-MINE is broken into two separate programs, both running under Microsoft Windows 3.1 or above. The first, the editor, allows the user to develop the mine layout and add equipment and personnel. The mine geometry is considered to be made up of various types of objects, for example a straight roadway segment which can be inclined, a junction roadway segment, and a turning segment. The geometry can then saved into a file to be loaded in by the second program of VR-MINE, the viewer. This generates a real- istic representation of the mine, with undulating floors and walls. It also has the ability to display multiple windows on the mine at the same time, which are arranged interactively. The simulation occurs within this program, with the user traversing the model in real time to examine possible areas of improvement in operations. This paper gives a number of examples of how the AIMS Re- search Unit has applied this technology to a range of underground mining scenarios to improve the safety of workers in the under- ground environment. The application discussed include computer graphics and Virtual Reality systems to training, risk analysis, visualisation, simulation, accident investigation and major hazard planning.

Jan 1, 1996

The value of US industrial mineral output last year was $20 billion, a 12% decline from 1981. A glance at the accompanying table and a review of the comments made by several contributors reveals how poorly many industrial minerals fared during 1982. Bromine and peat posted a 6% increase in production while recovered sulfur showed only a 3% gain over 1981. Pumice, salt, and dimension stone managed to stay more or less even with 1981 production. However, most industrial minerals posted losses for the year from 3% for vermiculite, sodium carbonate, and gypsum to 49% for ilmenite. Naturally, the depressed economy is to blame for decreased production and consumption. Low steel and auto production, lower housing starts, and many other factors impacted the industrial mineral industries. Hopefully the worst is over. Interest rates are down, energy costs are decreasing, the automobile and housing industries show signs of picking up. Perhaps the 1983 annual review will be less gloomy. Many thanks to these industrial minerals technical committee members for their contribution to this year&apos;s annual review: G. S. Austin, E. S. Montgomery, H. P. Ehrlinger III, D. B. Jorgensen, R. L. Parratt, J. F. Burst, W. Mallory, N. C. Trivedi, and N. K. Olson.

Jan 5, 1983

By R. V. Ramani

Control is a vital management function by which operations are brought into compliance with predetermined standards to achieve the goals of an enterprise. Events that are characterized by a low degree of expectation, avoidability, and intent necessarily have a low degree of control. Such events are difficult not only to predict but to control as well. Fortunately, very few industrial situations fall into that category of events. It is an axiom of control technology that in order to control, one must first measure; further to measure, one must know the characteristics of the subject (or environment) upon which the measurement must be made. Finally, if measurements are to be made reliably, the influences that affect the measurement must be known and, if possible, understood. The complete control cycle therefore consists of the following: (1) defining the objective, (2) planning to achieve the objective, (3) putting the plan into practice with appropriate instructions, (4) measuring variables or parameters of interest, (5) transmitting and transforming the measurements to analyze the system&apos;s status and to predict the future outcome, (6) comparing these with the defined objective, and (7) determining and taking corrective actions to bring the actual results closer to the objective. The management principle underlying the control cycle is the principle of management by exception. The application of the principle and the frequency with which corrective actions are taken vary according to the purposes of the review and control. For example, the control of a machine operation (e.g., truck on a haul road) may require adjustments and therefore data, analysis, and decisions, in intervals of seconds whereas the review for ore-grade control may take several hours. Reviews, on the other hand, for cost control may be done in intervals of weeks or months. In any case, three specific purposes of the control cycle are: (1) to correct the operation so that it follows the accepted plan closely, (2) to evaluate the operation and predict future outcomes in light of changes in the environment or of more experience, and (3) to review the objectives and modify these to be reasonable and realistic.

Jan 1, 1979

Passive seismic monitoring is a useful tool for measuring wave propagation in rock mass in deep underground mining. About 20000 mining ? induced seismic events of a hard rock mine, are identified and investigated. The travel times of source-receiver pairs allow us to demonstrate temporal change in velocity. It was found that the average P wave velocity is about 6000 m/s in the mining regions. Velocity investigations on the data during about three months around the main shocks show a significant decrease of the average seismic wave velocity after the main shocks. The sudden drop of average velocity change after the main shocks implies the creation of new fractures in the rock mass due to the main shocks. Afterward, the average velocity increased to a normal level after a time duration of several days. A reasonable explanation for the post seismic velocity increase is that opened cracks begin to close due to crack healing.

Feb 23, 2014

By T. Wohlford

Due to the increases available base of scientific knowledge, increased independent review required by worldwide security exchanges, and the need for accuracy in characterizing mine water resources, it has become necessary to produce a more accurate hydrologic balance. This presentation provides a critical review of the steps and tools to compile a complete hydrologic review of a mine property. The forces of regulation, increased scientific analysis, better tools, and stakeholder expectations have created a perfect storm of accuracy demand. Ausenco has developed protocol to achieve the desired end.

Feb 23, 2014

By Shingo Morimoto, Toru Sasaki, Masato Shinji

"1. INTRODUCTIONTunnel face stability is one of the most important consideration in New Austrian Tunneling Method. In general, if all of the material properties of ground can be obtained through the field investigations, the tunnel face behavior can be predicted using numerical simulation prior to tunnel construction. However, estimating the safety of a tunnel face is difficult, especially in cases where the ground is very weak such as in an urban area.In this study, numerical analyses of tunnel excavation in very weak ground conditions, such as a low cohesion and low internal friction angle, were carried out. The relationship between the average shear strain distribution on the tunnel face and the overburden was analyzed. This relationship estimates the shear strain of the tunnel face relative to the critical shear strain obtained by the ground properties. The critical shear strain was defined as an allowable value for the maximum shear strain. We proposed the allowable overburden as tunnel face stability index (TFI) that satisfies the critical shear strain criterion of ground. Finally, a design chart of the allowable overburden for various cohesion values and friction angles of ground was created. This chart is useful in the preliminary tunnel design stage to judge the necessity of additional counter measures against normal tunnel support design.2. WEAK GROUND MODELING AND ANALYSIS PROCEDURE2.1 Setting material propertiesWith reference to a past study1), the material properties were adopted on the basis of material properties in the standard worst rock classification case called “DII”2) for standard support pattern of weak ground in Japan. The typical material properties for “DII” are listed in Table 1. In addition, Fig.1 shows the distribution of the representative weak ground according to cohesion and internal friction angle. When the internal friction angle is relatively high and the cohesion is weak, the ground is categorized as sandy ground. Furthermore, when the internal friction angle is low and the cohesion is strong, the ground is categorized as clayey ground."

Jan 1, 2016

By S. M. Khandrika

Most of the coal presently used by the utility industry is cleaned at preparation plants employing wet processes. While water is the mainstay of coal washing, it is one of the least desirable components in the final product causing a reduction of the heating value as well as handling difficulties. Currently available dewatering techniques are inefficient for dewatering very fine coal (minus 325 mesh). The US coal industry has expressed serious concern about utilizing advanced cleaning processes such as column flotation because an efficient and economical dewatering process is not available.

Jan 1, 1992

By C. R. Tinsley

In maybe the world&apos;s first in a mine project financing, a US $55 million Rehabilitation Indemnity was given on behalf of the banks in a US $250 million loan to develop the Ranger uranium mine, Northern Territory, Australia. The basis of the financing was an estimate of removal of the tailings and replacement into the pit. The Indemnity was amortized by a sinking fund from the mine&apos;s revenues. Such a concept could be valuable for mineral developments in sensitive areas or jurisdictions such as British Columbia or Alaska.

Jan 1, 1992

By K. Zhang

Real option value (ROV) method is considered to be more practical and advanced compared to net present value (NPV) method in evaluating a mining project, in particularly when there is substantial uncertainty in the commodity market as well as possible operational flexibility embedded in the project. Usually, it may take months or even years for the commodity product to be available in the market after the mining activation decision is made. The impacts of postponing the delivery of commodity product on the mine?s ROV and NPV are assessed based on the proposed real option method. Postponing the delivery of the products leads to declined NPV and ROV compared to the non-postponing scenario and extended postpone results in higher lost values in NPV and ROV. For a mine with lower mining cost, by postponing the delivery, the exercising threshold of commodity price is lower because the mine owner anticipates that commodity price may rise during the time of postponing. A mine with higher mining cost requires a higher exercising price threshold to ?lock up? the profit when there is ambiguity of market situation due to the postponing of the delivery.

Feb 23, 2014

By K. Fair

Using an agitated column 203 mm (8") diameter by 1829 mm (72") tall with independent agitation units for the gas dispersion zone and the collection zones, respectively, permitted the independent evaluation of the attachment and the detachment mechanisms for the chalcopyrite/ silica system. Three particle size fractions were used in this study, i.e. coarse (+75 µ m), intermediate (-75 µ m + 10 µ m) and fines (-10 µ m). The optimum selection of the two agitation zones for the three particle size fractions were determined as a function of grade, recovery, residence time and air superficial gas velocity.

Jan 1, 1990

By C. Iglesias

Innovation in the tilemaking ceramic industry is stressing properties like powder flowability, ability to toughen green tiles, so turning technological requirements of ball clays ever stricter in terms of plasticity, dispersion in water, rheological behavior, workability in the green state, refractoriness and firing colour. Technological performance of ball clays was improved by taking as benchmark the highest quality raw materials on the market. The mineralogy, plasticity, methylene blue index and ceramic response of the Patagonian ball clays are analogous to those of European clays, but improvement is needed to approach the highest quality materials. On this basis, the Frente A, Super, Puma, and Lote 8 deposits were selected and their characteristics enhanced by additions of highly plastic and white-firing corrective clays targeted on the benchmark. Porcelain stoneware formulations, containing improved ball clay mixes, were experimented at both laboratory and industrial scale. The improved ball clays behave like the best raw materials currently used, although modest changes occur in the mechanical properties, water absorption and whiteness of the fired products.

Jan 1, 2010

By J. Hallowell, M. Conley, R. Cook

Inflatable friction rock bolts (IFRBs) are often considered temporary ground support due to their susceptibility to weakening from corrosion. The effective service life of an IFRB can be difficult to estimate due to the multitude of factors that affect the rate of corrosion. Some mine sites have experienced several-year-long service lives of IFRBs without issue, while others experience corrosion-related falls of ground only weeks after installation. The most common industry method of assessing bolt performance is by pull testing the fixture. However, due to the IFRB’s ability to mobilize its full tensile capacity with less than 2 feet of anchored length, corrosion along the bolt at depths greater than 2 feet from the collar cannot be identified using this approach. Alternatively, reinflation testing is a simple and non-destructive method of evaluating the condition of an entire bolt length for breaches in the bolt wall. This can be particularly useful when assessing the extent of corrosive conditions within a particular mining area where instabilities have already occurred and the condition of nearby bolts is unknown, or when re-entering historic mine workings which have not been monitored.

Feb 1, 2023

By Hans G. Machel

In low-temperature diagenetic environments (0 c T c 60 - 80°C), elemental sulfur forms by six common processes: via (1) inorganic oxidation of H2S by molecular oxygen, (2) inorganic oxidation of H2S by ferric iron compounds, (3) polysulfide disproportion- ation; and via the microbial metabolic actions of (4) colorless sulfur bacteria, (5) colored sulfur bacteria, and (6) some types of thiobacilli. Economically viable deposits of native sulfur usually are formed by only one process: inorganic oxidation of H2S by molecular oxygen. The amount of elemental sulfur is also limited by three common processes that destroy it in low- temperature diagenetic environments: bacterial reduction, bacterial oxidation, and inorganic oxidation. In high-temperature diagenetic environments (80 - 10o°C c T c 150 - 200°C), particularly in sour gas reservoirs, there are seven common processes forming elemental sulfur: (1) SOdH2S reaction, (2) H2S- hydrocarbon reaction, (3) polysulfide disproportionation, (4) catalytic H2S decomposition, (5) C02-H2S reaction, (6) chlorinification, and (7) exsolution of physically dissolved elemental sulfur. Natural processes that destroy or remove elemental sulfur in such settings are hydrocarbon sulfurization, polysulfide formation, and advection. In most sour gas reservoirs, relatively small quantities of elemental sulfur occur as a free phase (solid or liquid). However, elemental sulfur often precipitates in copious amounts from the reservoir fluids via exsolution and polysulfide disproportionation during production of sour gas reservoirs. By extension, elemental sulfur may precipitate from reservoir fluids in relatively large quantities upon uplift and erosion of deep sour gas reservoirs, or from advection of sulfurous fluids into shallower settings via faults or other high-permeability pathways.

Jan 1, 1992

By I. Sanchez

The development of the recent generation of large mining projects in South America has been challenging in many ways, but especially in the management of water in all its aspects. As a result, a number of projects have experienced difficulties and in some cases significant delays due to a lack of a clear and approved definition of the supply, use and discharge of water from mining and processing sites. The development of the recent generation of large mining projects in South America has been challenging in many ways, but especially in the management of water in all its aspects. As a result, a number of projects have experienced difficulties and in some cases significant delays due to a lack of a clear and approved definition of the supply, use and discharge of water from mining and processing sites.

Feb 23, 2014

By Apostolos Vrakas, Georgios Anagnostou

"INTRODUCTION The small strain assumption routinely made in tunnel analyses remains sufficient from an engineering point of view as long as convergences do not exceed 10%. More specifically, small strain theory assumes that deformations are so small (in relation to the size of the underground opening) that any geometric change in the continuum can be disregarded (Fig. 1a). In fact, however, the geometry is updated during loading (or unloading) according to large strain theory and thus equilibrium and stiffness are evaluated on the deformed configuration of the continuum (Fig. 1b).In problems involving large deformations, where the undeformed and the deformed tunnel geometry differ significantly, small strain theory leads to erroneous and sometimes even nonsensical results (i.e. it can predict wall displacements even greater than the excavated radius under conditions of very low stiffness and strength, high in situ stress and low support pressure). This can easily be verified from the widely applied relationships for the ground response curve. For example, in the ideal case of linearly elastic behaviour, the convergence of an unsupported opening equals (1+?) s0 / E (where E, ? and s0 denote the Young’s modulus, Poisson’s ratio and initial isotropic stress, respectively) and is greater than 100% for E < (1+?) s0. Although convergences are less than 10% in the great majority of tunnelling projects, very large deformations may take place when tunnelling through weak rocks under a high overburden (Fig. 2). This paper will first present a very simple and practicable way to account for large strains, based entirely on the results of routine small strain analyses, and will subsequently show the importance of addressing large strains in tunnel analysis and design with reference to three typical case studies of tunnelling in squeezing ground."

Jan 1, 2016

By R. Bhaskar

The objective of the project was to optimize the ventilation parameters of a continuous miner underboom scrubber to further control. the amount of airborne dust discharged during mining, to further reduce the exposure of face personnel for an exhaust brattice ventilation system, and avoid recirculation of contaminants at the face. This research was performed in an underground coal mine in Utah. The tasks included preliminary face ventilation evaluation and optimization of the scrubber system to eliminate recirculation of the scrubber discharge air. Airflow tests were conducted on the currently used dust control system and the modified scrubber system. Tracer gas tests were performed to evaluate face ventilation effectiveness. Confirmatory tests of the scrubber system under actual operating conditions, modifications to the scrubber system, and a comparative evaluation of the scrubber system vs. the existing system were performed. This paper presents the results of the airflow pattern tests and the respirable dust levels in the modified scrubber system and the existing system. The optimized face ventilation parameters and the developed operating guidelines may provide the benefits of dust reduction, better face ventilation, and improved visibility.

Jan 1, 1994

By K. J. Shoop

This study investigates the use of a horizontally-baffled column (7.6 cm inside diameter by 344.2 cm high) to reduce the ash content of a high ash bituminous coal. Tests were carried out to determine how the baffled column responded to changes in feed rate, reagent dosage, and feed quality, and to compare its performance with a conventional column installation in an operating plant. In this paper, the results of this investigation will be reviewed and discussed.

Jan 1, 1997

By D. Spitty

Mining companies often have many disparate systems and repositories of data in their organization for planning and scheduling outbound mining supply chains. To optimize ore quality, throughput, transport logistics scheduling and delivery to contract, planning teams need to model and manage the value chain accurately and achieve a consolidated, enterprise view of operational performance. Planning teams coordinate a complex series of activities to ensure production forecast accuracy. They also negotiate and execute complex contracts often with disconnected and limited visibility of production forecasts, quality, and variability with little ability to accurately market potential product specifications over longer time horizons. This market is becoming increasingly dynamic, with increasing variability and the time for planning teams to react is decreasing. This is driving the need towards using science to generate the necessary scenarios required to support the decisions made by planners on a frequent basis. Resource-to-Market is a highly flexible, user-configurable supply chain management system for the mining and metal processing industries. This provides an integrated view of the supply chain that supports the dynamic nature of planning in a mining company, embraces variability of elements across the supply chain with the ability to optimize across all the functional areas of the operation to enable optimal decision making for often competing objectives such as throughput, quality, cost, revenue and profit.

Feb 23, 2014