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By Nobuharu Isago, Atsushi Kusaka, Kosuke Kawata, Dohta Awaji

"The immediate ring closure method, in which the entire periphery of the excavation area is closed immediately with an initial support within a short distance from the excavation face, has been increasingly used in Japan, especially, as one of the most effective countermeasures against difficult ground conditions in conventional tunneling. For reasonable design of this method, the performance requirements for the initial support should be clearly stated. The analysis of construction data of 30 road tunnels and the three-dimensional numerical modeling based on real data suggest that the immediate ring closure stabilizes the tunnel structure and the ground around it because of the inner pressure effect of the initial support, especially, for low ground competence factor and small internal friction angle. Finally, the bending compressive strength and the cross-sectional geometry of the initial support have to be considered in the tunnel design while considering the earth pressure and ground properties. INTRODUCTION Conventional tunneling methods often deal with difficult ground conditions such as soft ground or squeezing ground conditions. The immediate ring closure method, in which the entire periphery of the excavation area is immediately supported within a short distance from the excavation face (Figure 1), has been increasingly used in Japan as one of the most effective countermeasures against difficult ground conditions in conventional tunneling (e.g. Takahashi et al., 2011; Nakaoka et al., 2013). The immediate ring closure method was empirically identified as effective for reducing ground surface subsidence and tunnel deformation. However, the working effects of the method have not been clarified sufficiently. To improve the design of this method, the working effects of this method and the performance requirements for the initial support need to be clarified. The relation between the effect of immediate ring closure and earth cover has been clarified (Mashimo et al., 2008; Awaji et al., 2013),"

Jan 1, 2016

By Daniel J. Brunner

The U. S. Department of Energy (D.O.E.) requires that the prospective nuclear waste repository in Basalt at Hanford, Washington, comply with State of California mine and tunnel safety orders. These regulations require that all main fans be installed in such a manner as to permit prompt reversal of airflow. This paper evaluates the requirement of air reversal and the appropriateness of imposing such regulations on the proposed nuclear waste repository in Basalt.

Jan 1, 1988

By Panshi Xie, Xicai Gao, Yi Luo, Youfu Zeng, Yongping Wu, Shenghu Luo

For the first time, surface subsidence prediction theory was used to investigate roof movement around longwall face mining in a steeply dipping coal seam. A physical simulation experiment was conducted to quantitatively study the roof migration patterns, the gob materials, and the characteristics of bed separation and compression caused by mining two adjacent panels to gain a better understanding of ground control issues in multipanel mining in steeply dipping seam. This approach provides an in-depth analysis of the movement of the roof. Compared to movement observation of survey point using total station, the Photogrammetry Analysis for Physical Modeling of Mine Subsidence Program (PAPMMSP) method is easier to perform, faster and yields the much higher accuracy required for scale physical modeling. It is also a more effective observation method for underground-mining physical simulation experiments.

By R. S. Das, A. K. Sinha

Modern mine ventilation systems have grown rapidly in recent years both in terms of complexity and value for human health and safety. Although computer models are now available to help the design and operation of mine ventilation systems, considerable differences often exist between the computer-based predictions and practical results. Research conducted to compare computer results with practical measurements made in ventilation circuits simulated in a physical model seems to confirm such differences. It is concluded that although a mine ventilation computer model is a very powerful tool, it can be utilized to its full potential only if reliable input data are provided.

Jan 1, 1987

By Jamal Rostami, Tom Iseley, Saleh Behbahani

Tunnels and underground infrastructures assets, like all assets, deteriorate with time. At some point, they reach the end of their useful life. Therefore, frequent inspections, higher levels of maintenance, and rehabilitation are needed to address loss of life and safety concerns. The repair cost of tunnels will increase if maintenance of tunnels is not satisfactory and timely. Historically, tunnel inspections have primarily relied on visual and manual procedures. Due to their time-consuming nature and susceptibility to human error, there is a demand for alternative automated techniques that can enhance efficiency and reliability in tunnel inspection. By utilizing a tunnel scanning system, such as laser scanner and thermography, or photogrammetry system, tunnel inspection cost, time, and personnel can be reduced. The goal of this study is to utilize deep convolutional neural networks (CNNs) for automated identification of defects in tunnel lining inspection. This paper presents a framework to classify two types of defects in tunnel lining (water leakages and cracks) using CNNs. The CNNs were trained and tested using 4,608 images. The Precision, Recall, and F1 Score were each 99.6%, confirming the viability of this approach in the automated defect identification in tunnel lining.

Jun 23, 2024

By R. V. Ramani, J. Qin

During the mining process, the in-situ material is broken into different size ranges, from very large pieces to very fine particles. Some of the fine particles become airborne. In underground coal mining, airborne respirable dust is associated with health and safety of the miners. The amount and size distributions of airborne dust are important parameters to effective dust control measures. The design of underground mine experiments, including sampling procedures and sample analyses methods to determine these parameters are presented in this paper. A total of fifteen continuous miner cuts were sampled. The amount of dust generated during the cutting process and the relationship between total and respirable airborne dust concentrations and amounts are examined. The amount of respirable dust airborne is on the average only 0.016% of the respirable dust generated. On the average, 61% of the total airborne dust measured is in the respirable size range. The amount of respirable airborne is on the average 36% of the respirable size fraction in the total airborne dust. For equal proportion of rock and coal material cut, rock contributes about twice as much fines (=0.22 mm) as coal. Additional fundamental research is necessary to further the understanding of the airborne propensity of respirable dusts in mine atmospheres.

Jan 1, 1989

By A. Kepeski

Cement industry relies heavily on the control of large volume of raw materials in the proximity of plant operations for clinker and cement manufacturing. These mineral resources are perhaps considered as ?low-profile? (mostly comprise limestone's, clays, marls and sands), but their availability, accessibility and suitability ? the later with respect to chemistry, mineralogical and physical characters ? are factors of paramount importance and may largely affect production cost and plant productivity. The combination of scarcity of good quality raw materials deposits and the growing environmental concerns have challenged the cement producers towards sustainability and the responsible exploitation of natural resources. In open pit mining and quarrying, the evaluation of mineral resources vs. handling of the non-usable overburden and other off-spec materials directly affects the medium to long-term production planning, quality control practices and environmental management. It is a general trend for many cement producers and a usual case for a number of Titan Cement plants worldwide, that redesign of quarry pits is necessary not only for stability purposes but also as a result of environmental constraints and emerging issues. The material reserves then have to be re-evaluated in the light of the new final pit design, safety distances from houses, other infrastructure and Law restrictions and according to criteria of safety of operations, reduction of environmental impacts, pit optimisation and proper future reclamation. The paper discusses the case of three active quarries of Usje Cement Plant, in Skopje (Macedonia), namely Usje (marl), Goverlevo (lime-stone) and Ljubosh (sand), where a large campaign of redesign and evaluation of recoverable reserves and the needs in rehabilitation took place in 2004. Technical and environmental issues and criteria are presented in the form of master plans and the highlights of the first attempts to propose and apply a reclamation scheme are discussed, by also examining alternative solutions for each quarry area. Finally, the 2005 progress in applying changes to the design of benches and pit layout, as well as experiences gained, are discussed.

Jan 1, 2005

By J. Y. Kim, S. L. Chryssoulis

Lead ions that originate from galena during the processing of complex sulfide ores migrate onto the surfaces of sphalerite and iron sulfide minerals. This results in poor selectivity during differential flotation. Generally, in sulfide ore processing, the lead-activated minerals float in the Cu/Pb rougher circuit. The surface lead complicates the zinc flotation circuit by lowering the concentrate grade. The effect of lead in the differential flotation of sphalerite from Cu-Pb-Zu and Pb-Zu ores is discussed. Plant and laboratory-test data are interpreted by determining the surface compositions of individual grains of sphalerite and iron sulfide particles. For the first time, surface compositions were determined by using laser-ionization mass spectrometry (LIMS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Cationic and cationic species on the surface were analyzed to elucidate the phenomena. It was proven that these new techniques are very useful in understanding the basic mechanisms of a sulfide mineral-flotation system.

Jan 1, 1997

By R. H. Clarke

"INTRODUCTION Characterization of waste rock is frequently an oversight in mine planning which can contribute to significant delay in permitting and ultimately development. Thorough waste rock characterization is now a prerequisite to developing operating and closure plans acceptable to regulators and the public. BACKGROUND A long history of mine development has placed virtually all focus on the economic extraction and beneficiation of ore materials, while waste rock characterization and management received substantially less attention and consideration. Inadequate waste rock characterization has contributed to planning and management practices that are having unintended and unforeseen impacts to surface and groundwater, and in some cases lead to significant long term closure liability. In response, the regulatory community has developed guidelines for performing waste rock characterization during the pre- mine permitting process that in some cases seem onerous (BLM, 2013). Additionally, where a project proponent has not met these guidelines or results have been deemed “inadequate”, the Nevada Division of Environmental Protection and Bureau of Land Management (regulatory agencies) will only issue operating permits with rigid management practices to address the uncertainty, including requirements for lining waste rock facilities. WASTE ROCK CHARACTERIZATION FOR NEVADA PROJECTS Newmont Mining Corporation (Newmont) operations in Nevada approaches waste rock characterization like ore characterization, as it requires a similar investment of time, funding and attention to detail in order to pass public and regulatory scrutiny. Newmont follows a tiered approach to characterization that creates three over-lapping data sets representing an “escalation” in analysis at each tier, an approach that has thus far gained regulatory approval. “Tier 1” waste rock characterization for most Newmont projects begins with exploration drilling which follows internal standards and procedures. 20-foot composite samples are prepared from all drilling and analyzed for multiple trace elements using inductively coupled plasma mass spectrometry (ICP-MS) methods and for acid-base characterization using method ASTM-E1915. If the exploration program is successful and further resource or reserve development is recommended, the Tier 1 data are used to prepare a Waste Rock Characterization Plan (Plan) that will be presented to regulatory agencies as a part of baseline project characterization."

Jan 1, 2015

By Marian Radetzki

The economic developments and industrial behavior patterns that led to a lasting excess capacity in the world non-ferrous metals industries from the aid-1970s are explored. Detailed attention is devoted to analyzing and defining crucial concepts like "capacity", "excess capacity", "capacity maintenance" and "investments". Empirical evidence of capacity utilization and capacity growth in the industries under study is provided. The coincidence of excess capacity and low prices on the one hand, and investments in capacity maintenance and capacity expansion, on the other, is seen as a consequence of substantial declines in the metal industries' investment and production costs during the period studied.

Jan 1, 1989

By H. Wu, V. Izaxon

Intensive ventilation is required during the excavation of a mine opening and the subsequent exploitation of the mineral resources. The exchange of heat between the ventilation air and the rock mass has a major influence on the thermal regime of a mine, especially in the initial segment of the airway. In frozen ground, heat flow into the rock mass from the ventilation air can result in the eventual thawing of the permafrost, which can result in roof-rock instability. This paper presents a mathematical analysis of the dispersion process of ventilation-induced heat by thermosyphons placed on the surface of the mine. The principal uses of thermosyphons in the Arctic are to reduce the ground temperature to prevent potentially unstable permafrost from thawing and to increase the bearing strength of the material. The mathematical model of the physical problem, generally known as "the Stephan problem," takes into account the varying thermo-physical properties of air and the frozen and thawed rock mass, the thermal properties of the freeing fluid in the thermosyphons and the phase change of water. Finite-difference techniques were employed to determine the temperature isotherms around the thermosyphons. It was found that two rows of thermosyphons on a 10- x 10-m grid provide an acceptable design spacing for reducing the ground temperature around the mine airway.

Jan 1, 1997

By Janet A. Johnson, T. B. Borak, K. J. Schiager

INTRODUCTION In the USA regulatory agencies have adopted standards which limit the allowable concentration of ore dust in underground uranium mines. The American Conference of Governmental Industrial Hygienists has recommended a threshold limit value for silica which has been incorporated by reference in federal regulations (30 CFR 57, 1980). The Nuclear Regulatory Commission (NRC) imposes a limit for unprocessed uranium ore dust for reducing the exposure to radioactive materials from inhalation (10 CFR 20, 1980). We have been unable to trace the origin of the NRC standard. Recently the ICRP has published recommendations concerning limits for intakes of radionuclides by workers (ICRP, 1979). We have used the ICRP methodology to compute the dose equivalent commitment to lung and bone from inhalation of insoluble ore dust particles. These values were used to derive air concentrations which would provide an acceptable risk for induction of cancer from occupational exposure. Results indicate that the new ICRP recommendations are more restrictive than the present NRC standard for radioactivity. The maximum allowable dust load in a uranium mine will depend on both the concentration of silica (% Si02) and the amount of radioactivity (% U308). We have combined these standards assuming complete independence of biological hazard to establish boundary conditions for which either silica or radioactivity is the dominating factor. Based on these results we present suggestions for analysis of ore dust to insure compliance with regulatory agencies. SILICA STANDARDS Silicosis, fibrotic lung disease produced by crystalline silica, was one of the earliest forms of occupational disease to be recognized. The pulmonary lesions caused by silica, silicotic nodules, consist of concentrically arranged bundles of collagen fibers. Fusion of these nodules results in progressive massive fibrosis causing alveolar changes which decrease ventillation and blood flow in the lungs. The current Threshold Limit Value (TLV) for mineral dusts is based on the concentration of free silica. The standard is expressed in three forms: (1) Particle count standard: TLV (mppcf) = 300/(% Si02 + 10) (mppcf = million particles per cubic foot) (2) Respirable dust mass standard: TLV (mg/m3 ) = 10/(% respirable Si02 + 2) (3) Total dust standard: TLV (mg/m3 ) = 30/(% Si02 + 3) The most commonly used form is the respirable mass standard. These curent values for silica are based primarily on epidemilogical studies of Vermont granite workers and other occupationally exposed workers. In the Vermont study no cases of silicosis were seen in individuals employed after dust control measures were initiated and whose subsequent exposure averaged less than 5 mppcf. The free silica concentration in the airborne dust to which these workers were exposed averaged 25%. A concentration of 10 mppcf of granite dust is considered equivalent to 0.1 mg/m3 quartz. The current respirable mass standard allows a maximum silica concentration of 0.1 mg/m3. NIOSH (1974) has recommended a reduction in the current TLV for respirable silica to 0.05 mg/m3 Si02. As with radiation standards, the TLV for mineral dusts is an upper limit for time weighted average exposure. It is recommended that dust concentrations be maintained as far below the TLV as current practices permit. RADIATION STANDARDS The present concentration limit for airborne natural uranium in ore dust prior to chemical separation is 75 µg of uranium per m3 of air ( 10 CFR 20, 1980) . This corresponds to 1.85 Bq/m3 (50 pCi/m3 ) of natural uranium, U-238, U-235 and U-234 and is equivalent to 3.7 Bq/m3 (100 pCi/m3 ) of gross alpha activity with radioactive equilibrium between the long-lived alpha progeny through Ra-226. The origin or basis for this standard is not known, but it presumably includes both chemical toxicity and risk from somatic radiation injury. Recently the International Commission on Radiological Protection (ICRP, 1977) has published recommendations concerning the objectives and criteria for limiting radiation exposures. This was followed b y a revision of the limits for intake of radionuclides by workers (ICRP, 1979; ICRP, 1980). The previous compilation of limits for internal emitters was published by ICRP Committee II in 1959 (ICRP, 1959). The latest version includes new methodlogy outlined in ICRP Publication 26 (ICRP, 1977) as well as extensive metabolic information

Jan 1, 1981

By W. H. Langer

The U.S. Geological Survey (USGS) in cooperation with the New Mexico Bureau of Mines is conducting an assessment of mineral resources in the 36,800 km2 Mimbres Resource Area, southwestern New Mexico. Included in the assessment is a literature-based evaluation of sand and gravel that utilizes third party geologic information. The USGS has developed a method based on existing 1:500,000 scale geologic maps supplemented by remote sensing, statistical models, and point data such as test hole or pit records. The method defines the areal extent, quality, and quantity of aggregate.

Jan 1, 1996

By W. Nazarewicz

The introduction of continuous papermaking in the early 1800's was the beginning of the industry as we know it today. Since that time, the majority of the paper produced has employed an acid process. However, in the mid 1960?s, European producers began a transition to an alkaline papermaking process. Early European mill conversions to alkaline papermaking begun in the 601s, accelerated during the 1970's influenced by the dramatically higher cost for OPEC energy as well as the high cost of fiber and imported filler clay.

Jan 1, 1986

By Anibal Gajardo

Clays for building bricks and roofing tiles in Chile are classified as common clays and ball clays, with deposits of sedimentary and residual origin, both Cenozoic in age. Deposits are known from north to south, through 11 of the 13 Chilean Administrative Regions, 18° to 39° South latitude, and from west to east, through three of Chile's main geomorphic features, namely the Coastal Plains, Coastal Range, and Intermediate Depression. Alluvial and lacustrine sedimentary common clay deposits are located in the northern and southern Intermediate Depression. The average chemical composition of clay deposits in I and I1 Regions, is 58 percent Si02, 16 percent A1203, and 4 percent Fe203 by weight; the primary minerals are sericite, quartz, feldspar, and albite. The average chemical composition of clays in Metropolitan, VI, and VIII Regions, is 52 percent Si02, 16 percent A1203, and 6 percent Fe203 by weight; the primary minerals are montmorillonite, quartz, and plagioclase. Residual common clay deposits occur in the Intermediate Depression and in the Coastal Range internal basins, VII, VLII, and IX Regions, and they represent surficial alteration of pumice beds and crystalline rocks. The average chemical composition of clay deposits derived from crystalline rocks is 58 percent SO2, 17 percent A1203, and 9 percent Fe203 by weight; the primary minerals are sericite, quartz, and clinochlore. Clay deposits formed from pumice beds contain 47 percent Si02, 24 percent A1203, and 10 percent Fe203 by weight; the primary minerals are kaolinite, feldspar, and cristobalite. Sedimentary ball clay deposits are located in the Coastal Plains and Coastal Range, VI, VII, VIII, and IX Regions, between 34" and 39" South latitude. The average chemical composition of the ball clay deposits is 51 percent ,902, 28 percent A1203, 5 percent Fe203 by weight; the primary minerals are kaolinite, quartz, and sericite (illite?). These clay deposits supply the Chilean building sector with over one million metric tons (mt) (1.1 million short tons [st]) of material per year. The average growth rate of clay consumption during the period 1993 through 1997 was 10 percent annually. The clays are used by both mechanized plants and handcraft facilities.

Jan 1, 2001

By A. D. MacPhail

The Highland Valley Copper partnership was formed in July 1986 and was the logical result of a mine with a large ore reserve but no adequate mill, and a mine with a large, modem mill but dwindling ore reserves. The original partners -Cominco and Lornex -were joined in January 1988 by Highmont Mining Co. which contributed a two-line concentrator. During 1988/1989, the Highmont mill was moved 7.5 km to adjoin the Lornex mill, forming what is now called the Highland mill, with a current nominal capacity of 130 000 tonnes per day. The mine is located 220 km northeast of Vancouver, British Columbia and is close to four communities in which personnel make their home: Logan Lake, Merritt, Ashcroft, and Kamloops. The map in Figure 1 2.2 shows the general area. Kamloops is a major service centre and is serviced by two railways, two major roads and a regional airport.

Jan 1, 1993

By H. T. Mikkelsen

Mineral production implies emissions of particulate matter (dust), noise and vibration that may cause conflicts with neighbors living nearby. In Norway a few conflicts has been brought to court, the latest in 2006. This paper discusses dust emissions and dust depositions (dustfall). The pollution authorities have accepted monitoring of dustfall instead of suspended dust as the first step in conflict cases concerning small and medium sized enterprises. In the case of exceeded limit values, the second step is to require monitoring of suspended dust and next the implementation of control actions to reduce dust emissions. Dustfall monitoring programmes carried out at six mineral production plants in Norway, show that the mineralogical rates of dustfall are rather low a few hundred meters away from the plants or the tailings disposal. They are mostly considerable lower than the limit value of 5 g/m²/30days accepted by the authorities. Seasonal variations between mineralogical and organic dust fractions can be observed in Norway, with higher content of mineral dust during winter time. Other sources to mineralogical dust can be recognized. During winter time wear of road pavement and sand on icy roads can give high emissions of mineralogical dust to the ambient air. Parallel monitoring of suspended dust and rates of dustfall indicate that dustfall can be used to estimate the level of suspended dust. A model for estimating suspended dust based on records of dustfall is presented.

Jan 1, 2007

By Wen H. Su

Extensive investigation has been conducted to determine the causes of a series of roof falls occurring in a room-and-pillar working located in southern West Virginia. Underground observation, along with laboratory testings and finite element analyses were conducted to search for possible mechanisms for the roof falls. Results of the investigation have led to a better understanding of the mechanisms involved in the roof falls. Necessary modifications of mine layout and roof support plan are proposed for improving safety and profitability at the mine.

Jan 1, 1984

By G. S. Dobby

Particle collection is considered to occur by particle collision with the bubble followed by the particle sliding over the bubble during which attachment may occur. Collision is quantified by a collision efficiency, EC. The existing model for EC is extended by including particle inertia. Attachment is quantified by an attachment efficiency, EA calculated as the fraction of particles which reside on the bubble for a time greater than the induction time. These calculations use recent data on the liquid velocity distribution over the upper half of rigid spheres. Collection efficiency, EK is given by EK = EC ? EA. Detachment is not considered. The mode is examined and shown to agree with much experimental data. For example the maximum observed in recovery vs particle size (d) can be explained as E increases with increasing d , while EA decreases. The decrease in selectivity at fine sizes is in accord with the model result that for dp < 5µm, EA ? 100% (i.e. EK ? EC) almost regardless of induction time. A decrease in bubble size does increase EK but does not improve selectivity. A high particle density (> 5g/cm3) is shown to cause a sharp peak in recovery vs size and a decreased maximum size of floatability. Finally, the possible effects of bubble and particle concentration are explored.

Jan 1, 1985

By Bekta? Uz

In this research, geological characteristics of sand quarries around the village, Kemerburgaz Akpinar, are studied and the mineralogical, petrographical, chemical and technological characteristics (such as sieve analysis, relative density, water absorbtion etc.) of the sand samples, obtained from the area are explained. In the general area sand&apos; quarries, being in lacustrine formations belonging to Neogen, the stratigraphic location of the sand occurences take place at high levels of these formations, geologically. All of this pattern, being under 1 mm with a ,particle dimension, it ranges from 0,5 mm in the quantity of 99 % to 0,25 mm in the quantity of 15 relative density is 2,65 g/cm3 ; water absorbtion is 0,9%. Mineralogically, the sand samples contain Quartz (84%), Feldspar (3%), Calcite + Aragonite (10%), Pyroxen+Amphibole (1-2%), Garnet+Tourmaline (0.5%), Olivine (0.1-0.5%). Besides, sand samples contain SiO2 with the quantity of above 90%. Containing Quartz at high levels for mineralogical, petrographical and chemical characteristics, Akpinar sand will be evaluated as silica sand when the carbonate mineral is removed with the method of ore preparation such as leaching.

Jan 1, 2005