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By K. Kovári, G. Anagnostou

Slurry and EPB-shield tunnelling have been successfully applied worldwide in recent years. Under extremely unfavourable geological conditions, however, face instabilities may occur. The present paper aims at a better understanding of the mechanics of face failure. For the case of slurry shield, attention will be paid to the time-dependent effects associated with the infiltration of slurry into the ground ahead of the face. Related topics, such as the stand-up time and the effect of the excavation advance rate, will be discussed. In the case of an EPB-shield, a distinction will be drawn between fluid-pressure and effective pressure in the chamber. The effective pressure can be visualized as a “grain to grain” contact pressure between the muck and the ground at the face. The water pressure in the chamber reduces the hydraulic head gradient in the ground and, consequently, the seepage forces acting in front of the face. The face is thus stabilized both by the direct support of the pressurized muck and by the reduction of the seepage forces in the ground. The paper includes normalized diagrams which allow the assessment of tunnel face stability.

Jan 1, 1997

By D. N. Hedges

This paper discusses the actual recovery and installation of a longwall in a bituminous coal mine in western Pennsylvania. The coal bed mined is in the Lower Freeport seam, which averaged 1.07 m (42 in.) in height locally. Drainage from the mine is about 13.25 ML/day (3.5 million gal per day) of water. This water deteriorates the mine's predominately fire clay bottom making it extremely difficult to move equipment. Support removal is accomplilshed by pulling the 5.44 t (6 st) shields out under their own hydraulic power and transporting them by track 8.05 km (5 miles) to the next longwall panel. This paper also discusses the changes that will be made to aid in the succeeding longwall recoveries and installations.

Jan 1, 1985

By John D. Kalasky

Continuous mining has revolutionized the coal industry but intensified the problems of earlier mechanization. From the installation of the first miner, it was recognized that face ventilation would be one of these problems. To establish an efficient work cycle for the equipment being used, conventional mechanized mining provides four or more development faces. Continuous mining, relying on a single machine, requires only one face, although more than one can be driven alternately by the same machine. In gaseous areas mined by the older methods, the intermittent rate of exposure allows time for the face to bleed off or be cleared, and the width obtained with conventional units makes it possible to hang a brattice line almost to the face. Continuous mining increases the ventilation hazards; there is no margin of time, and very limited space.

Jan 9, 1959

By S. J. Schatzel, J. D. Addis, V. Gangrade, L. L. Chasko, C. A. Hollerich

A ventilation study was conducted at a western U.S. coal mine to evaluate the movement of longwall face air and exchanges between the face and worked-out areas to document the presence or absence of face airflow pathways between these locations. This field study was part of a project investigating the effect of longwall face length and caving characteristics on longwall face air behavior and its potential movement on and off of the face. Tracer gas experiments using sulfur hexafluoride (SF6) were done to describe air movement on the face and in the mined-portion of the active panel. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob.

By S. J. Schatzel, J. D. Addis, V. Gangrade, L. L. Chasko, C. A. Hollerich

A ventilation study using tracer gas was conducted at a western US coal mine. The objective of the study was to evaluate the movement of longwall face air exchanges between the face and worked-out area and to document the presence or absence of face airflow pathways between these locations. The mine operator uses a bleederless longwall ventilation system with a back return and a blowing mine ventilation system. The study was conducted on an active panel and included both underground and surface monitoring sites. The study used sulfur hexafluoride (SF6) released as a slug on the longwall face and in the front of the gob inby the face. The velocity of the tracer gas movement in the gob was 0.019 m/s (3.7 fpm). The rate of movement for the overall tracer gas slug averaged about 0.0091 m/s (1.8 fpm). A separate tracer gas test initiated with the release of SF6 into the legs of the first shield showed the existence of more than one pathway of face air in the general direction from the headgate towards the tailgate corner. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob. A more detailed characterization of longwall system air and gas movement allows a mine to better assess its ventilation design for controlling gas on the face and in the gob.

By Robert A. Haney, Stephen J. Gigliotti, James L. Banfield

A series of investigations were made by the Mine Safety and Health Administration to evaluate the performance of various face ventilation systems as part of a program to reduce frictional ignitions of methane and to develop face ventilation systems that could be used with the line brattice more than 10 feet from the face. Tests were conducted in a full-scale laboratory model of a face area. Systems tested included unassisted blowing and exhaust line brattice, diffuser fan and spray fan systems. Systems were evaluated at air quantities ranging from 1.4 to 7.0 m3/s (3,000 to 15,000 cfm), and brattice-to-face distances from 1.5 to 9 meters (5 to 30 feet.). Tests were designed so that systems could be evaluated for the location of the high-point methane concentration in the face area, methane dilution capacity, and face ventilation index. The methane dilution capacity is the total amount of methane a system can dilute to 1.0 volume-percent. The face ventilation index is the efficiency at which the available face air volume is being used.

Jan 1, 1982

By W. D. Maier, H. V. Eales

Paper presented at the IAGOD international symposium on mineralization related to mafic and ultramafic rocks held in Orleans, France, 1-3 September 1993. A lithological and geochemical study revealed significant lateral variation of the interval over 170 km of strike, from about 30 m at the Union Section to 220 m near Brits. The cumulates also become more evolved and leucocratic with distance from the Union Section both towards the NE (Amandelbult) and SE (Impala, Rustenburg and Brits). It is inferred that the persistent heat flux from a putative major feeder zone near the Union Section impaired deposition of felsic cumulates in the vicinity, delaying crystallisation of successive phases in parts of the chamber near the feeder. New influxes were therefore deposited on a footwall of varying thickness and lithology in response to different degrees of crystallisation and accumulation along strike. The development of cyclic units of chromitite, harzburgite, pyroxenite, norite and anorthosite was interrupted at different stages in different parts of the chamber

Apr 1, 1994

By Vaughan J. P

The Pegmont deposit is a stratiform Pb-Zn sulphide body occurring in a thin, iron-rich metasedimentary unit situated near the top of the Kuridala Formation, a part of the Mary Kathleen Group of the Middle Proterozoic"Eastern Geosyncline" succession of the Mount Isa-Cloncurry district. The deposit appears to have developed in a shallow basin or depression on a sea or lake floor.Detailed chemical and mineralogical study of seven diamond drill cores through the ore horizon shows that in addition to galena and sphalerite the orebody contains a large range of iron-rich silicates and aluminosilicates.Further, five drill cores selected to represent a section from basin centre to basin edge exhibit clear and systematic chemical and mineralogical changes in the ore horizon in both a vertical and, most importantly, ill a lateral sense.Reconstruction of the sedimentary environment of the ore horizon as a whole shows this to be a silicate facies of a phosphatic, manganiferous iron formation or, more accurately, of "ironstone" in the sense of James (1966, U.S. Geol. Surv. Prof. Paper 440, chapter W).On the basis of both mineralogy and chemistry this silicate facies may be subdivided into three microfacies according to the dominant iron silicates characteristic of each: a fayalite microfacies, a hornblende-clinopyroxenemicrofacies, and a garnet microfacies. Significant Pb-Zn sulphide concentrations are confined almost entirely to the fayalite microfacies.

Jan 1, 1979

By P Rourke

In this climate of increasing demand for commodities, it is becoming necessary to expand and optimise existing bulk material handling facilities in order to increase capacity to satisfy demand. Production capacity in these facilities is often adversely impacted during the expansion process. A successful and proven strategy to reduce this impact is to bring the additional capacity online in stages coinciding with routine maintenance or other short shutdowns. Compatibility of the automation systems with staged upgrades in capacity is the key to achieving a successful outcome. Since 1994, Hatch has been researching a generic, highly configurable product transport control system that can be reconfigured to cater for plant expansions or modifications without incurring significant risk to production capacity. In 2002, BHP Billiton Iron Ore (BHPB IO) recognised the need for such a generic Route Selection and Sequencing (RSS) system and engaged Hatch to build a generic RSS system as part of the $US351 million BHPB IO Products and Capacity Expansion (PACE) project. In 2004, Hatch successfully deployed such a generic configurable control system at BHPB IO Port Hedland Ore Handling Facility. This generic system is known as the Hatch Product Transport (HPT) System.

Jan 1, 2005

The North Saskatchewan River flows southwest to northeast through a 22-km-long valley in the City of Edmonton, supplying the drinking water to dozens of downstream communities. During heavy rains, combined sewers occasionally overflow into the river, which has a significant negative impact on the water quality and the sensitive environment. The West Edmonton Sanitary Sewer (WESS) W12, a syphon connecting the Rat Creek Trunk to the Gold Bar Wastewater Treatment Plant across the river, was designed and constructed to take the overflow to the wastewater treatment plant. Due to the complexity of the project, various 3D technologies were applied to facilitate decision-making processes. 3D models were developed for design review and design conflict detection, while 4D models were established to help create a robust construction schedule. Construction sequencing animation was used to convey design intents and demonstrate construction stages to contractors and workers. The combined applications of 3D technologies helped the project team to identify critical issues, and assured effective communication among engineers, management, contractors, and other parties. Therefore, it provided more opportunities for the success of the project.

Aug 1, 2013

By M. Khaled, K. Abdel Rahman, M. Khattab

Helwan limestone quarry is located at a distance of 35 km (21.7 miles) to the south of Cairo downtown. Drilling and blasting operations are used to extract the limestone for the Helwan Cement Company (HCC). In 1980’s a new urban community was constructed adjacent to the quarry. This situation led to shifting of the old quarry 5.0 km (3.1 miles) to its current location, to avoid causing blasting problems to the new community. Unfortunately, the new quarry is opened in a highly faulted area, with weak zones of brittle materials. The drilling and blasting crew is facing many difficulties due to the geological complexity along these zones. Moreover, the extension of this community towards the new quarry makes the control of ground vibrations is very important.

Jan 1, 2008

By K. D. Eng, W. T. Tierney

"During the past century, the development of vehicular transportation has benefitted tremendously from the performance improvement in engines in a situation where low-cost, plentiful fuel supplies were the order of the day. Engine advances were enhanced by and also dictated fuel modification to better adapt the energy source to the power plant.In discussing the several aspects of the change in approach from ""an engine and its fuel to a fuel and its engine"", the authors touch on the following areas:1. Description of an engine concept that provides the needed flexibility in fuel appetite at good efficiency to cope with future requirement s.2. The constraints placed on liquid fuel resource energy utilization efficiency by special engine-required fuel properties and the fuel efficiency of the various engine types available.3. Future vehicle engine fuel sources. This review will put into perspective the problem associated with the net energy available from future fuel sources under extensive research and development at present.4. A brief review of test data to show that fuel-tolerant and fuel-efficient engines are viable and that, in a fuel-resource-limited future, they can be a ""light at the end of the tunnel.""The Texaco Controlled Combustion System (TCCS)The TCCS is a unique means for stratified charge operation of an internal combustion engine in such a manner as to eliminate the requirement for octane or cetane number specification for the fuel. Octane rating is an empirical engine test method that evaluates a gasoline's resistance to spontaneous ignition or ""knock."" Cetane is based on a different engine test, which determines a diesel fuel's ease of spontaneous ignition . High cetane number enhances cold starting and permits high-speed diesel engine operation. As one would expect, the fuels in current use cover a band when the two values, octane and cetane, are plotted against each other."

Jan 1, 1982

By Paley N, Cameron A, Townson P

Although blasthole deviation is a problem which can seriously affect blasting operations, there is little practical emphasis on controlling this deviation and no practical emphasis on understanding its practical behaviour. The most common way of dealing with it involves tight control over drill set up and surveying hole paths. The surveying might involve simple collar location and inclination measurement to estimate the hole's actual path. At best, some operations routinely survey hole paths after all holes in a stope have been drilled. In addition, although there is an expectation that holes will deviate, there is no planning for this behaviour in order to reduce its impact on the blast. Design decisions are invariably made with the assumption that holes are straight. If and when surveys reveal problems it is possible only to adjust charging and initiation to 'work around them'. In extreme cases the drill might be recalled to fill in gaps. The lack of planning and the lack of understanding are doubtlessly linked.A model is presented that will predict the expected path of a drill hole. By knowing how a selected few holes deviated it is possible to make a good estimate of the deviation of other holes in the same rock mass. After minimal calibration the model can be used to increase the amount of information for a given amount of surveying or the amount of surveying can be reduced while maintaining the same level of knowledge of blasthole deviation. Equally important is the ability to plan for the deviation in future drilling through altering the initial collar angles or drilling from different locations. It is the authors' hope that planning for hole deviation becomes as much a part of the design process as planning for detonator delay scatter and explosive performance variation.

Jan 1, 1992

By Marcelo Gagó M.

El presente trabajo señala la factiblidad del método de explotación "Trackless" en la mina Huarón, Pasco a través del sistema de conjunto semi-mecanizado, donde la formación de la unidad de explotación requiere la incorporación de vetas estrechas en arranque selectivo a las vetas anchas. En este sentido, se evalúa la aplicación de vetas con potencias entre 0.40 a 2.80 metros cercanas las unas a las otras, cuya interceptación se sirva de eje, al tiempo que se aproveche de una sola unidad de limpieza.

Oct 14, 1980

By Chririnos. J.

Ante el desabastecimiento del método de explotación de tajeo abierto ascendente con sostenimiento de puntales, empleado en la mina Algamarca, Cajamarca, se sugirió la aplicación de dos nuevos métodos de explotación: almacenamiento provisional y corte de relleno. El primer método es aplicable en aquellos casos donde las rocas de caja sean consistentes y que la veta uniforme que no sea arcillosa, mientras que el segundo, es factible en aquellos blocks donde las rocas de caja sean poco consistentes. En este sentido, el objetivo del texto es señalar la factibilidad de ambos métodos sobre diversos aspectos de carácter técnico-económico, considerando que el ancho de la explotación sea de 0.94 m, para que la utilidad sea más provechosa.

Nov 20, 1972

By Luisa Perez, Carlos Perea

El método de explotación por subniveles es uno de los más utilizados en operaciones mineras de mediana y gran escala, como es el caso de la minería de zinc en Perú. Para seguir la secuencia de explotación, este método requiere el relleno de los caserones vacíos, como por ejemplo el relleno en pasta, el cual se produce mediante la mezcla del relave producto de la planta concentradora de mineral con un 3.5 % de cemento, con el fin de que dicho relleno actúe como pilares de gran dimensión que aporten el sostenimiento necesario a la mina (0,8 MPa). Sin embargo, esto genera una dilución con el mineral a explotar al momento de avanzar en los tajos aledaños. Por ese motivo, y por la necesidad de lograr la automatización de la operación minera, se decide evaluar el relleno detrítico cementado, evaluación que se realiza mediante el análisis de resistencia, estudios de factibilidad, rendimiento en costos, aumento de productividad y seguridad en la operación. El resultado son valores máximos de resistencia de los pilares de 1,6 MPa, que evitan la dilución y mejoran el porcentaje de recuperación de mineral.

Sep 20, 2019

By Luisa Pérez, Carlos Perea

En el caso de la minería de zinc es común emplear el método de explotación por subniveles, el cual exige rellenar los caserones vacíos, por ejemplo, con una mezcla del relave producto de la planta concentradora de mineral con un 3.5% de cemento, lo que actúa como pilar de sostenimiento de la mina (0.8 MPa). Debido a que al momento de avanzar en los tajos aledaños se producía una dilución con el mineral a explotar y, también, a que era necesario automatizar las operaciones; se decidió evaluar el relleno detrítico cementado, mediante análisis de resistencia, estudios de factibilidad, rendimiento en costos, aumento de productividad y seguridad en la operación. Como resultado, se obtuvieron valores máximos de resistencia de los pilares de 1.6 MPa, lo que evitó la dilución y mejoró el porcentaje de recuperación de mineral.

Jun 30, 2020

By Alberto Pacheco

El presente trabajo es un análisis del sistema de organización del sistema de seguridad a través del modelo Reason de causalidad o de "queso suizo", donde se identifica qué aspectos y decisiones se convierten en un factor condicionante para un accidente y también cómo la organización puede aprender de un accidente perfeccionando sus defensas en un ciclo de mejora continua. De forma que este modelo explica que un accidente es la consecuencia final de una superposición de fallas que va desde la última línea de defensa, pasando por el acto inseguro, la condición insegura, la falla de la supervisión, la falla de la asesoría (seguridad) hasta la falla de la organización. Para solucionar dicho problema, se realiza una gestión del error que incluye una serie de medidas preventivas como descubrir, evaluar y eliminar los factores que producen el error dentro de la fuerza laboral y así desarrollar la realidad intrínseca de la organización contra los errores humanos.

Sep 13, 2001

By Patricio Jones

Veladero es un depósito epitermal de metales preciosos de alta sulfuración hospedado en brechas y rocas de litologías brechadas y está situado en San Juan, Argentina. Regionalmente, se localiza en el cinturón volcánico terciario del Valle del Cura (Argentina), que es adyacente al cinturón de El Indio (Chile). En ese sentido, el presente texto describe los factores que descubrieron el depósito, menciona las principales referencias respecto de su geología local y regional y enfatiza los aspectos institucionales y técnicos del descubrimiento, realizado por Minera Argentina Gold S.A. (MAGSA).

Apr 24, 2001

By Ariel Orellana Wiarco

Para diseñar un sistema de ventilación de una mina subterránea se debe determinar la cantidad total de aire necesario y la caída total de presión. Con estos datos se planean las obras y se selecciona el equipo de ventilación adecuado Así, el objetivo de este diseño de sistema de ventilación es proporcionar condiciones ambientales subterráneas seguras, sanas y saludables. En este sentido, el presente texto refiere la forma en que la fricción, densidad, humedad, temperatura, determinación de requerimientos de aire, dimensiones, contaminantes de escapes de motores diesel, ventilación natural, envases y difusores entre otros factores afectan el diseño de sistemas de ventilación para minas subterráneas.

Mar 1, 1983