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By Davar Abi-Zadeh, Cillian Brown, Deepak Kandra

"Grout backfill strategy for a particular subsurface concrete tunnel (~4.9km long, 3.5m in diameter, carrying 20” gas pipeline) was based on achieving 1:100 slope of the fill in order to progressively fill the tunnel, in a series of 350m section. Grout rheology, particularly its non-Newtonian and thixotropic behavior, determines the final fill slope for given backfill strategy. The objective of this study was to simulate the two-phase grout mix backfill process using Computational Fluid Dynamics (CFD) and determine the slope of the fill to validate and optimize the backfill strategy. Three dimensional CFD study showed that for a 500m long tunnel section with a single injection point of grout, given its rheology, it will likely keep flowing without filling the 500m section height wise. Design optimization for filling was carried out using two dimensional studies to make the backfill process “slope independent” by incorporating a 2.5m high bulkhead at ~1,000m. INTRODUCTION As part of a gas field development a 20” onshore gas pipeline is required from the landfall site to the processing terminal some 8km inland. At the landfall site the gas pipeline is routed in a ~5km underground tunnel underneath a bay. For operational reasons and planning consents as well as to mitigate environmental impact based on an environmental impact study, once the gas pipeline and the associated services and spares have been installed, the subsurface gas tunnel will be fully grouted. There will be no permanent access to the tunnel after construction is completed and the site compounds have been reinstated once works are complete. One of the key requirements is that “full grouting of the tunnel” is desired. The grouting material used is a non-Newtonian and thixotropic fluid mixture of bentonite, cement, plasticizer, retarder/stabilizer and water. The tunnel is filled progressively in 350m sections using a combination of existing and new pipework assuming the grout rheology will yield a fill slope of 1:100 in a 350m section. The proposed grouting system used one pump at the grouting compound to pump the grout into the tunnel using the existing tunneling pipework. For the longer runs a second booster pump was used in series to pump the grout to its final discharge location. The filling process is controlled via a system of flow meters, pressure transmitters and a tunnel CCTV system."

Jan 1, 2016

By K. Voltaire

As can be guessed from the subtitle, this paper will not be a geologist's one since neither of the authors is a professional geologist. This will be an attempt to present the various aspects of the legal, economic and geological setting that condition the exploration for mineral resources in Haiti. Before going any further, we are going to present a summary of our rather short mining history. One must first mention that Caribbean countries are latecomers to the mining business. If we go back to the colonial period (1500-1600's) there are net many traces of mining activity. The major exception to this is the recovery of alluvial gold in Hispaniola, Puerto-Rico and Cuba and also some sporadic copper mining in Hispaniola (notably in Haiti near the city of Gonaives and in some of the old mining districts in Santo-Domingo). These easily minable deposits were quickly exhausted and mining quite naturally came to an end as agriculture rose as the major economic activity. In the Haitian case, aside from very erratic mention during the 19th Century of the presence of some minerals (i.e. haematite, chalcopyrite) no serious geological work was undertaken. In the meantime, the peasants in the northern part were still looking for alluvial gold in some streams but this amounted to next to nothing. One has to come to the 1920's to find the first comprehensive geological survey. At the time, the country was under the military control of the United States. The American Government sent a team from the U.S.G.S. headed by the late W. Woodring to initiate a survey of the country. Given the lack of transportation, this was a tough task and Woodring and his associates did it magnificently. As a result of their efforts, they published a very thick piece of work of more than 600 pages. "The Geology of the Republic of Haiti" although it was published in 1924 is a classic and is a must for anyone interested in the geology of Haiti.

Jan 1, 1978

By George R. Powe

If Campbell County, Wyoming were an independent nation, it would rank fifth in the world among countries with known coal reserves. Only the United States, Russia, mainland China and West Germany would have greater volumes available. Not too many years ago that statement would not have seemed important, because oil and natural gas had become our nation's principal fuels. Western coal deposits, particularly those of the Powder River Basin in Montana and Wyoming, and which underlie virtually all of Campbell County, were largely unknown. But recently, in response to the three-pronged stimulus of vanishing gas reserves, rising petroleum prices, and clean environment statutes, these vast deposits have been delineated and have become, in the minds of many, indispensable to our goal of energy independence. Not only does western coal lie in thick seams near the surface where it can be mined in huge quantities at low cost, but also it possesses another coveted attribute in this age of environmentalism: low sulfur content. At Burlington Northern we count ourselves at the forefront of those who believe this coal is essential to any hope for the government's "Project Independence." But to that belief we add another article of faith. We are convinced the economics of unit train delivery of this incredibly immense resource make it the only transportation system that can help us achieve energy self-sufficiency in this country.

Jan 1, 1975

By Dongjie Zhang, Shuxin Liu, Jianduo Wang

Broken rock mass and unreasonable stope structure parameters can cause excessive ore loss and dilution in sublevel caving; this is the main problem faced by caving mining in recent years. This paper proposes a stope structure parameter optimization method suitable for steeply inclined medium-thick broken ore bodies and evaluates the reliability and effectiveness through case studies. To solve the problem of large ore loss and dilution in the high-end wall sublevel caving method of Xilinhot fluorite mine, it is necessary to select proper stope structure parameters. Based on the theory of random media, an end-wall ore drawing experiment was carried out, and the bulk flow parameters needed to optimization of stope structure parameters were determined. In the experiment, it was found the draw-out body of high-end wall ore drawing showed a fine top and a thick bottom; the granular media had good fluidity. The reasonable caving step is determined to be 1.2 m instead of the 1.6 m originally used. Through the optimization experiment of the mining route position along the vein, the study found that the best route position is different with the ore body inclination. When the inclination angle of the ore body was 90°, the reasonable route was located in the center of the ore body. When the inclination angle of the ore body was between 85° and 90°, the route moved from the center of the ore body to the footwall at a rate of 22.5%. When the inclination angle of the ore body was between 80° and 85°, the route moved to the footwall at a rate of 54.8%. When the inclination angle of the ore body is not greater than 80°, the route should be arranged on the boundary of the footwall. Field application results showed the dilution rate reduced by 7.66% and the recovery rate increased by 7.31%. Field test results verify the effectiveness and applicability of the optimized stope structure, which corroborates the effectiveness and applicability of the optimized stope structure.

Mar 10, 2022

By Tadashi Nishida

Subsidence due to mining caused various kinds of damage to the surface structures, and actually great deal of mining damage becomes the severe social problem at some time in many coal fields, but the most of mining damage was restored at present. Recently, the effect of old coal working on the deformation of newly constructed structures has become into question, because it was obliged to plan many engineering structures in old mining areas for the shortage of adequate construction sites and the difficulty of getting location. That is, building, dams, bridges for railroads and highway, power plants, tunnels, storage tanks and so, have to be built on the ground which has old coal working.

Jan 1, 1982

By Sadatoshi Ohmori, Karen Shinoda, Nobuharu Isago

Method of tunnel excavation is generally classified such as full-face excavation, bench-cut excavation, diaphragm with center pillar excavation, center drift advancing excavation and so on. These excavation methods should be selected properly in terms of ground condition, the area of tunnel section, the arrangement of construction. Center drift advancing excavation method in mountain tunnel construction, is often applied under quite weak ground condition, prior to the main tunnel widening excavation. Recently, the advancing drift is for the excavation of extreme larger section in main tunnel to confirm the stability of face. In addition, we make advancing deformation occur in drift when the construction was done in poor ground like squeezing and swelling ground, and the force occurred in main tunnel was expected to reduce by the effect of ‘dodging’ for support structure. Mechanical relation between drift and main tunnel has been mainly grasped on past experiences in Japan. However, the characteristic of tunnel enlargement was partially discussed by using the three dimensional analysis and the result was grasped by past experiences on the basis of each tunnel construction. It is considered that the natural ground stress is normally released as the advance displacement, but it was released after the main tunnel widening, causing a displacement and deformation increase. Up to now, the construction practice has shown the reduced displacement during the main tunnel widening excavation by the drift, and the numerical analysis agreed with above observation. However, there is no report found that the displacement and deformation at the time of widening excavation of the main tunnel become larger in case of a drift application. In Kyusyu area, western part of Japan, the northern part of Yoshinomoto tunnel was applied an advancing bench-cutting method for a center drift for the purpose of obtaining the geological information for support selection of the main tunnel in widening excavation. The shape of center drift was a perfect circle with a diameter of 4.0 m or 6.0 m and the same temporary support regardless of the geological situation. As a result, the displacement and deformation of the main tunnel after widening excavation were larger than the section where the center drift was not applied. Furthermore, the displacement and deformation of the main tunnel after its widening excavation was considered larger in the section where the cross-section of the center drift with 4.0 m diameter was applied than one with 6.0 m. Therefore, the center drift with a high rigidity support structure had the effect of suppressing the advancing deformation prior to the main tunnel widening excavation.

Jun 13, 2021

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 R. A. Hevia

Florida Power and Light is the fifth largest investor-owned electric utility in the country. It has a service territory that covers 35 counties, or 28,000 square miles, 2.5 million customers, and serves 5.6 million people. The total installed capacity is 13,470 MW, generated by four nuclear units, 36 oil and/or gas fired units, and 48 gas turbine units. Traditionally, FPL has been an oil-based utility. In 1979, this dependency on oil became obvious when 42 million barrels of oil were burned during the year. At that time, it was also projected that, based on the current estimates of customer growth and available generation capacity through 1990, FPL's residual fuel oil consumption would increase from the 1979 level of 42 million barrels (6.7 million m3) per year to approximately 55 million barrels (8.7 million m3) per year by the mid-1990's. Concern over this was further aggravated by the fact that it was difficult to estimate both the price and quantity of fuel oil that would be available over the next decade since changes in the world market, decisions by oil producers and refiners, and international political developments would all affect the availability of oil. Also, at that time, the price of residual fuel oil had increased drastically, and there was no reason to think that these prices would soon stabilize. Thus, oil back-out became a primary objective of FPL and since then, FPL has been actively investigating ways to decrease fuel oil consumption.

Jan 1, 1985

By V. Herman, B. Knorr, D. Whalen

"Edge effect is a condition widely observed in High Pressure Grinding Roll (HPGR) operations that gives rise to reduced comminution at the edges of the roll surfaces. This effect is caused by a reduction in the local crushing pressure at the edges of the rolls resulting from the sliding friction between the static cheek plates and HPGR feed material. Practically, this has an impact on equipment sizing, as the edge effect leads to coarser particles reporting to downstream equipment in open-circuit operations and increased circulating load and diminished HPGR circuit capacity in closed-circuit operations.To address this, Metso's HRC™ HPGR incorporates an Arch-frame to maintain a parallel relationship between the rolls and allow for the use of a flanged roll design. We conducted a series of pilot-plant tests with a 750 mm by 400 mm HRC HPGR to compare the performance of the flanged roll design against that of a traditional cheek plate arrangement under similar operating conditions. The edge effect was found to be significantly reduced with the flanged roll design. Based on the pilot-plant results, the implications for circuit design, energy efficiency and overall plant performance in a full-scale application were investigated and discussed.IntroductionGlobal trends such as lower ore grades and rising operating costs are driving the market toward more energy-efficient mineral processing solutions, most notably in comminution circuit design. High pressure grinding rolls (HPGRs) have been recognized as an energy-efficient solution relative to more conventional circuit designs. The basic operating principle of HPGRs, in which a fairly uniform pressure is applied to a bed of material in the compression zone, lends itself to this improved energy efficiency (Morley, 2006). Studies have estimated that savings of 10-15 percent are possible when comparing an HPGR circuit with a traditional SABC circuit (Rosario and Hall, 2008). While HPGRs offer a more energy-efficient solution than tumbling mills, there is still room for improvement in many aspects of the design. Edge effect, in particular, is one such aspect that limits the effectiveness of the machines. Edge effect is the impaired performance at the edge of the rolls due to a reduction in crushing pressure (Morley, 2010; van der Meer, 2010). As described in our prior work (Knorr, Herman and Whalen, 2013), edge effect is caused by the interaction between the ore entering the crusher and the relatively static cheek plates positioned at the edges of the rolls. As the material is drawn into the crushing zone, the sliding friction between the ore and the cheek plates inhibits the ability of material to be effectively drawn into the compression zone at the edges of the rolls. This reduces the crushing force in those edge regions relative to the center of the roll where material is being drawn into the compression zone at a higher rate. In addition, the cheek plates of a traditional HPGR design are held in place by spring-loaded brackets that are adjustable to manage the clearance. This spring-loaded cheek plate design prevents full compression of the material in the edge regions of the roll as there is relief at the outer edges."

Jan 1, 2016

By B. G. Long

Coastal States Energy Company (Coastal), a wholly-owned subsidiary of The Coastal Corporation of Houston, Texas, owns coal mining operations in Utah and Kentucky. One of the Utah operations, Southern Utah Fuel Company (SUFCo), located 30 miles west of Salina, Utah, has been operated by Coastal since 1974. This operation is a single-seam, six-section mine operated from one portal area. It produces 2.2 million tons of coal per year and has a payroll of approximately 300 employees, Coal is mined by continuous miners, hauled by diesel-powered haulers and transported by belt conveyor to outside crushing and screening facilities. Sized coal is hauled by contract truckers 80 miles to a unit-train facility located at Levan, Utah.

Jan 1, 1983

By A. I. Johnson

The pegmatites of the Black Hills of South Dakota are the coarse-grained differentiates of the Harney Peak Granite. The Harney Peak Granite was intruded into the Pre-cambrian schist and quartzites and resulted in the Black Hills uplift. In the outer adzes of the granite intrusion occur the pegmatites. In the zoned pegmatites, representing the most highly differentiated portions of the parent magma, occur most of the minerals produced from pegmatites. These are of economic importance and they are the subject of this paper. The various mineral products will be taken up separately.

Jan 1, 1978

By Chris Mills

El papel de la separacion gravimétrica en la industria minera es brevemente considerado en perspectiva. Las pruebas e intentos de laboratorio y mineralógicas para el diseñio de los procesos gravimetricos son examinados poniendo especial énfasis en la selección de la tecnologia del proceso. Es tratado y comentado el material disponible en equipos para pequeña escala y trabajo de pruebas-piloto, particularmente en relación a la escalacion y a la adquisición de datos precisos y fiables. El transporte del comportamiento de los datos desde la planta piloto a la planta a escala es igualmente explicado. Son resefiados todos los tipos de equipos a escala total existentes para la separacion gravimétrica, poniendo de relieve las unidades de alta capacidad. Es considerada la disposicion de la planta y la seleccion de 1os equipos auxiliares.

Jan 1, 1982

By Jianmin Qin, R. V. Ramani

The major parameters affecting dust flow at a longwall face are dust generation rate, air velocity and quantity distribution at the face, and the characteristics of the dust such as particle size distribution, density etc. Previous studies have identified the longwall shearer as the major source of the airborne dust in the faces. In this study, the effects of dust generation rate and shearer speed on the levels of ambient dust concentration are investigated. A series of experiments were performed under controlled conditions in a full scale simulated longwall face at the Lake Lynn Laboratory mine of U.S. Bureau of Mines using characterized bituminous coal dust. A trickle-duster was moved up and down the longwall face to simulate the shearer. In each experiment, a known amount of dust was dispersed by the trickle-duster into the air and the average dust generation rate was calculated. At the same time, gravimetric respirable and total airborne dust samples were collected and air velocity measurements were made along the face. The experimental conditions, data, and results are presented and discussed in this paper. The airborne dust concentration and air velocity data indicate that the concentration increases and air velocity decreases with distance from headgate for the first half of the face. Towards the tailgate, the air velocity increases with increasing distance but the dust concentration levels off with some variations. The data show that a higher dust generation rate results in higher dust concentration levels. More importantly, the data show that the rate of increase of airborne dust concentration is higher than that of dust generation rate. For the same air velocity distribution and dust generation rate, lower speed of the dust source results in higher airborne dust levels at the face.

Jan 1, 1991

By M. Stefanakis, M. Errington, A. Kontopoulos, J. M. Prevosteau, K. Adam

The Olympias arsenical pyrite concentrate assaying 25 g/t Au, 40% S, 40% Fe and 12% As is highly refractory in nature; an oxidation pretreatment step is required to liberate gold and render it amenable to cyanidation. In the present study mineralogical analysis techniques including Image Analysis, SEM, EPMA, SIMS, Mossbauer, ICP/MS, etc., have been employed in order to investigate the mode of gold occurrence within the Olympias pyrites. Bacterial oxidation was used as a case pretreatment route and bacterially leached products were examined under SEM. The mineralogical observations and the relevant metallurgical and cyanidation test data were combined to establish a correlation between the mineralogical characteristics of the raw and oxidised products and conditions prevailing over the oxidative pretreatment step and the gold liberation achieved.

Jan 1, 1990

By J. M. Goris

The U.S. Bureau of Mines, in cooperation with the Homestake Mining Co., and the University of Utah, is conducting a field demonstration to evaluate the behavior of rock masses supported with cable bolts. One of two rock masses being studied is supported with both conventional and birdcage cables. This rock mass is located between the 6500 and 6650 levels of the 45-4BN stope. 21 ledge. The second rock mass is the hanging wall of the D-limb stope between the 3500 and 3650 levels near the Ross Shaft and is supported with conventional cables. The primary objectives of the project are to monitor the behavior of the two rock masses during mining using extensometers and cable support strain gauges, after which the rock will be modeled using the finite-element code UTAH III. Field data will be used to verify the modeling. In addition. a comparison between the effectiveness of conventional and birdcage cables will be made.

Jan 1, 1991

By Hooman Askari-Nasab, AHLAM MAREMI, EUGENE BEN-AWUAH

In oil sands mining, tailings are voluminous unwanted by-products generated from extracting the desired mineral from the mined ore. Dyke construction and backfilling activities require well-managed techniques to facilitate progressive reclamation at the earliest opportunity. This directly affects the sustainability and profitability of the mining operation. This research introduces a goal programming framework that simultaneously optimizes the (1) production schedule with limited duration stockpiling and directional mining; (2) dyke construction schedule; (3) size, shape, and location of tailings-cells; and (4) mining and processing production targets. The results show that in creating in-pit tailings-cells designs, decreasing the mining-cells volume and increasing the number of mining-cells improve the net present value of the operation due to increased operational flexibility. The model generated a uniform schedule for ore and practical tailings-cells designs for backfilling activities. Integrating tailingscells optimization into oil sands mine planning and waste management ensures the efficient use of in-pit mined-out areas required for sustainable operations.

Apr 14, 2021

By Thomas A. Wheeler

The reagents commercially used in coal flotation and their roles are reviewed and discussed According to their function the reagents are divided into often overlapping groups: 1. Collectors 2. Frothers 3. Conditioning Reagents Frothers have by far the largest effect on the amount of coal recovered They act not only in their traditionally accepted function of “bubble makers”, but in coal flotation they serve in a seldom acknowledged role of collectors. A lab flotation study on four samples of different coal ranks shows how these react to various frother families and proves that no froher is the optimum reagent for all types of coal. The advent of new technology in flotation equipment in the past decade has resulted in various novel designs of column cells, Jameson and Centrifloat™ cells, air-sped hydrocylones, etc. All should require special frothers or blends of frothers to meet their specific needs.

Jan 1, 1994

By J. S. Roti

Calcium-based scale precipitation is a common problem in mill reclaim waters. An accumulation of these adherent deposits can result in a rapid reduction in water flow, loss of pump efficiency and eventual interruption in ore production. Heap leach applications can also experience the added problems of plugged sprinkler heads, blinded leach pads and fouled carbon columns when scale control is not maintained. The primary cause of scaling in precious metal recovery is the relative insolubility of calcium carbonate. The presence of the calcium ion and bicarbonate alkalinity is common in almost every water source. If the temperature or pH of the water is allowed to increase, the bicarbonate breaks down to carbonate and combines with calcium by the following reaction: Ca +2 +2HCO3 ? CaCO3 + H2 + CO2

Jan 1, 1986

By Andrew J. Neale, Brian C. Flintoff

A review of the current literature, combined with the authors' knowledge of the western Canadian coal industry, indicates that the development and implementation of process control in coal preparation, particularly in flotation applications, is significantly lagging behind that seen in mineral processing. The reasons for this include the lack of inexpensive and reliable sensors, incomplete understanding of the flotation process, limited experience of process control in the coal preparation industry and depressed coal prices, all of which have combined to hinder plant automation. This paper illustrates the benefits of process control in coal flotation, provides a general discussion of the control problem and concludes with two examples drawn from Australian experiences.

Jan 1, 1989

By Edward C. Dowling

Cleveland Cliffs and affiliated companies have established a commitment to the development and use of integrated process control. Substantial capital investments in process control, coupled with the dedication of human resources to effectively use the information, have generated meaningful business results. Improvements in productivity, operating costs and product quality have been realized. This paper presents an overall process control and information strategy, specific case studies, lessons learned and the current view of the next steps in the continued journey toward integrated process control and information management.

Jan 1, 2000