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By Johannes Jäger

"A composite shell lining typically consists of an outer permanent sprayed concrete shell, a water proofing layer and an inner sprayed or cast concrete shell. Composite shell linings become more and more popular and have been built recently on large scale infrastructure projects. Surprisingly there is very little published literature on the actual structural design of composite linings. As a consequence there is a lack of common understanding on how to design a composite lining structure. Composite action of the outer shell (primary lining) initially carrying short term ground loads and the “unloaded” inner shell (secondary lining) require nonlinear concrete modelling to be able to assess the bearing capacity of the composite lining structure adequately. The composite action of the waterproofing membrane and the inner and outer shells can be considered either by simplified closed form solutions or by numerical models. Strength and stiffness parameters of membrane and concrete govern interaction of inner and outer shell. This paper should contribute to understanding composite lining behaviour with focus on the bearing capacity at limit state by taking into account the actual loading history. Possible ways and concepts on how to deal with these topics are presented, however a broader discussion on limit states of the composite lining materials – also in the long term will be required to come to an agreement on composite lining design methodology. INTRODUCTION Composite Lining Technology Traditionally the construction of shotcrete lined tunnels incorporates primary and secondary linings, separated by a sheet or a sprayable waterproofing membrane. The primary lining shotcrete is considered to be structurally temporary and the secondary lining to be permanent, leading to designs which ignore the bearing capacity of the primary lining in permanent condition. There was general perception that the shotcrete lining installed immediately at the tunnel face, experiencing strains up to 1% and even cracking in the early age, combined with mesh reinforcement additional support measures like lattice girder, spiles and bolts cannot be considered as a permanent structure. But also former shotcrete mixes showed significant weakness with respect to durability suggesting a more temporary nature of primary lining shotcrete. On the other hand it was clear that primary lining shotcrete does not disappear, it may lose probably a certain percentage of its bearing capacity, but discounting any contribution from the primary lining at all was considered inherently conservative. There were different strategies to account for the risk of reduced durability and bearing capacity of the primary lining, either by selecting moderate ground loads for the secondary lining design, by assuming that some residual load will be carried by the primary lining. This approach is very much based on experience. Another more rational possibility is to assume that the primary lining degrades into a rocklike material, which is weaker than the primary lining shotcrete but still imparts some strength to the ground around the secondary lining, but does not need to comply with any concrete design codes any more."

Jan 1, 2016

By G. R. Harrod

Effective mine operation demands that the right people have the right information at the right time. Caterpillar's Mining and Earthmoving Technology System (METS) meets this demand by providing "real-time" information transfer between the mine offices and machines equipped with the Caterpillar Computer Aided Earthmoving System (CAES). Transfers of mine plans from the mine planning software to CAES-equipped machines give operators access to current mine plans within minutes of their creation. Additionally, office personnel have access to a current digital terrain model (DTM) of the mine site as it is updated in "real-time" by CAES-equipped machines. METS provides mine personnel in operations, planning, and management the information they need when they need it.

Jan 1, 1998

By Keith A. Heasley

Historically, the surface subsidence over underground coal mines has been predicted using empirical profile or influence functions which have little or no connection to the actual mechanics of the subsidence. Without a mechanistic basis, establishing the exact site-specific parameters to use in these empirical methods has been problematic. A practical subsidence predictive method based on mechanics has the appealing capability of allowing the determination of site-specific parameters from fundamental properties of the overburden with minimal field calibration work. This paper presents several case studies where a mechanics-based, boundary-element program is used to back-calculate the surface subsidence associated with various panels at several Northern Appalachian coal mines. The program used in this case study is called LAMODEL, and it incorporates a frictionless, laminated overburden into a general purpose displacement-discontinuity code primarily designed for calculating the stresses and displacements in coal mines or other thin scam or vein type deposits. In this paper, the program is used to calculate both the underground convergence and the resulting surface subsidence at five longwall panels and a room-and-pillar section. The fitted subsidence from the model is compared with the field measurements and analyzed. The results from the case studies in this paper demonstrate that the laminated model with calibrated properties can easily provide moderately accurate subsidence predictions and is fairly flexible for fitting measured subsidence. However, additional subsidence predictive case studies arc recommended in order to ultimately evaluate the potential of the laminated overburden model for practical subsidence prediction

Jan 1, 1999

By Jianbo Lan, Desheng Huang, Xiaoying Qiu, Zhaohua Ke, Liusheng Ge, Xinjin Xiao, An Guo, Qiaofa Lan

Magnesium salt rare earth enrichment (MREE) is a crucial intermediate raw material in the deep processing of rare earth elements and material preparation, serving as a front-end raw material for the synthesis of rare earth oxides. With the current disposal process for MREE, neutralization slag with high rare earth residue is generated during further extraction of rare earth from the MREE and accumulates in huge piles. Therefore, the combined disposal process of MREE and neutralization slag was put forward. MREE was solubilized using 4 mol/L sulfuric acid to achieve an endpoint pH of 0.75, dissolving the rare earth and obtaining an acid solution. The MREE and neutralization slag were added in a mass ratio of 1:2 to the acid solution sequentially. The pH of the endpoint was controlled to 4.8~5.0 for neutralization and decontamination. This resulted in the production of rare earth sulfate liquid of similar quality to the original MREE disposal process, meeting subsequent extraction requirements. The neutralization slag underwent a water washing process, with two washes (first with 0.2 mol/L acidity water at a solid-liquid ratio of 1:2 and second with deionized water at a ratio of 1:4), resulting in water-washing slag with a rare earth content of 0.24% and a rare earth yield of 97.08%. Notably, zero wastewater discharge was realized. This innovative process effectively addressed the challenges of high rare earth residue in neutralization slag and stockpile accumulation, offering valuable theoretical and practical insights for MREE disposal.

May 31, 2024

By Emanuele Catelli, Paolo Vicentini, Manuel Petitat, Paolo Lanfranchi

"More than 800 million tons of material will be excavated during large underground projects such as tunnels, undergrounds and power plants by 2030 in Europe only. The raw material excavated is often classified as waste, which involves environmental impact and transport issues: landfill areas, CO2 emissions and noise. But how can such massive amounts of material be transported, processed and deposited? Using the example of the AlpTransit Ceneri Base Tunnel (15.4 km), we show that suitable excavated materials can be used sustainably as a primary resource for tunnel concrete. This requires careful planning of the installations and storage areas by the client, timely building of the processing plants and other handling facilities outside the tunnel and a continuous evaluation of the raw material quality. 1. INTRODUCTION Spoil management is a central element of large construction projects. The systematic reuse of suitable excavated material not only saves natural resources, reduces transport distances and landfill volume, but can also decrease overall construction costs. Ideally, all of the concrete needed for tunnel lining can be produced with this on-site material. Such a natural resource management concept was applied for the construction of the new Gotthard Base Tunnel (L = 57 km). Spoil management concepts are, how-ever, difficult to implement and call for innovative techniques, sophisticated logistics and organization. In the context of large projects, environmentally friendly transport, processing and storage of millions of tons of excavated loose material represent another logistics challenge (Simmen & Lieb, 2010). This paper shows key factors that led to the successful completion of spoil management at the Ceneri Base Tunnel, which constitutes a part of the AlpTransit Gotthard Project (Figure 1)."

Jan 1, 2016

By Robert A. Pimentel

Dust is still a major problem in increasing production from longwall faces. Over the last decade, significant improvements have been made in the development of techniques for reducing dust exposure on conventional and continuous sections. But virtually no improvements have been made in dust control on longwall sections. It is true, that there are many more continuous mining sections than longwall sections in the United States and that the number of workers overexposed on continuous miner sections is much larger than the number on longwall sections. However, the problem on continuous miner sections appears much easier to solve and, in fact, we believe that the techniques are available to get virtually all continuous miner sections in compliance. The problems on longwall sections are much more elusive. Also, the number of longwall sections in the United States is expected to increase during the 1980's. Thus, dust control on longwall sections remains a formidable and important problem. Companies operating longwall sections with a dust problem are faced with the tasks of having to quantify the various dust sources, of selecting proper techniques to reduce the problem, of implementing the techniques and of evaluating their effectiveness.

Jan 1, 1983

By E. K. H. Goh

A reliability-based engineering design approach for the effective design of reshaped spoil dumps was developed with the aim of obtaining structurally reliable spoil dumps at optimum reshaping costs. The aim was also to satisfy environmental erosion standards and community expectations. This approach encompasses the linking up of three major components: erosion appraisal of spoil dump designs, reliability-based engineering design of spoil dumps and costing of spoil dump reshaping practices. This paper addresses the application of the reliability-based engineering- design approach to the assessment of spoil dump designs for erosion control. Included are various types of erosion prediction models and reliability-based engineering-design analytical techniques. Also included is a case study that demonstrates the application of this approach.

Jan 1, 2000

By Kenneth J. Miller

A novel two-stage froth flotation process to remove pyritic sulfur from fine- size coal is described. The process consists of a first-stage, standard coal flotation step in which high-ash refuse and some of the pyrite are removed as tailings. The first-stage clean coal froth concentrate is then repulped in fresh water, and a coal depressant, a pyrite collector, and a frother are added to float the remaining pyritic material. Laboratory and pilot plant flotation results with coals from the Lower Freeport and Pittsburgh beds are given. The pilot plant test results show that up to 80 percent pyritic sulfur reduction was achieved with the Lower Freeport bed coal and up to 50 percent with the Pittsburgh bed coal. Laboratory and pilot plant results were in excellent agreement, indicating that the process is a viable means of removing much of the sulfur from some coals.

Jan 1, 1974

By Duluth Engineers' Club, Engineers' Club of Northern Minnesota

The Mesabi Range extends continuously from near Grand Rapids, on the Mississippi River, E.N.E. for a distance of about 1120 miles to near Birch Lake, where it is covered by the large gabbro flow which forms the base of the Keweenawan series. The same formation (Mesabi) appears again near Gunflint Lake on the international boundary, and shows as far east as Thunder Bay on the north shore of Lake Superior. Between Mesabi station, on the Duluth and Iron Range Railway, and Birch Lake, although considerable exploration work has been done, there is no evidence of concentration of ore in workable bodies. The Gunflint beds are thin alternating layers of chert and hematite. Alt the workable deposits at present known, on the Mesabi, lie between Mesabi station and Grand Rapids, the greater number being St. Louis County simplified geologic column is given herewith instead of the complete correlation table given by the United States Geological survey.

Jan 1, 1920

By A. S. Haugh

OHSAS 18001 is a series of international standards for occupational health and safety management. It is comprised of two parts, 18001 and 180029. OHSAS 18001 was formulated by international certifying bodies and is based on BS8800 and was first published in 19996,11. OHSAS 18001 was developed to be compatible with ISO 9001 and ISO 14001 in order to facilitate integration of quality, environment, and occupational health and safety management systems5. It is a voluntary standard and the overall aim of OHSAS 18001 is to enable organizations to control their occupational health and safety (OH&S) risks and improve overall health and safety performance5. OHSAS 18001 is widely accepted in the UK, Europe, and Asia, is gaining momentum in North and South America, and it was used as the basis and conforms to the requirements of ANSI/AIHA Z.10-2005: American National Standard for Occupational Health and Safety Management Systems. It defines a set of requirements for an occupational health and safety management system suitable for any kind and size of organization4. Businesses of all sizes are developing and implementing occupational health and safety management systems (OHSMS) that are in compliance with the OHSAS 18001 standard.

Jan 1, 2012

By Dirk van Zyl, Clint Strachan

A study was conducted to assess the feaeibility of increasing the heap height above one lift at the Alligator Ridge Mine. This study concentrated on the physical aspects of the heap and liner performance. Two principle aspects were addressed during this investigation: (a) the adequacy of heap permeability under present and future loading conditions; and (b) the adequacy of the liner to limit seepage losses. Field and laboratory test a were performed and their details and results are presented. It was concluded that the permeability of the heap would remain adequate for higher heap. The geometry of the heap will be the major constraint. It was also concluded that the liner would perform satisfactorily beneath higher heap.

Jan 1, 1987

By R. Bruce Sheibach

The Picher Mining District, located principally in north-eastern Oklahoma, was one of the world's largest lead-zinc mining areas during its 55 year life. The field covers an area of approximately 72 square miles (186 km.-); an estimated 1.6 x [103 yds3 of material (1.22 x 103m3)] worth in excess of one billion dollars, has been mined. Mining activities were typified by surface exploratory drilling identifying ore distribution and extension of underground workings to the lead and zinc deposits outlined. Exploration holes were either left unplugged or plugged at the surface with a section of a telephone pole. Low grade ore and waste rock were discarded in mined out portions of drifts. These waste piles containing pyrite and marquisette were left underground and oxidized during the many years of active mining. Upon cessation of mining activities in the mid-1960's, the drifts and shafts of the abandoned workings began to flood as the cone of depression filled in, leading to the dissolution of the oxidized sulfides and the formation of large volumes of acid mine water in the mined out openings. The resulting poor quality water, with high concentrations of cadmium, iron, lead and zinc, began discharging at the surface in 1979. Contamination of the underlying aquifer supplying local residents was first detected on a localized scale in 1980. The present surface water and ground water contamination have lead to the area being classified as one of the top ten hazardous waste sites in the U.S. by the EPA under the superfund program.

Jan 1, 1982

By Christopher Haycocks

The growth of computer and ground control technology in recent years, combined with an urgent demand for low-cost fossil fuels and mineral resources, has set the stage for full-scale utilization of computers in mine planning. Steeply rising production costs and the need to preserve the environment are placing great demands on engineers to improve their mining efficiencies, which can best be accomplished by applying the full capabilities of the computer. Pressure to develop and perfect programs with an immediate potential for improving mine de- sign, reducing mining costs and extending the viable coal reserves of the country has already come to bear in the form of exploding energy requirements, environ- mental considerations and the visible limitations of other energy sources. The computer program discussed in this paper, RAMPLAN (Rock Mechanics Applied to Nine Planning), was constructed as part of a continuing effort at Virginia Polytechnic Institute & State University under the sponsorship of the Office of Coal Research to develop a suite of programs to benefit the mining engineer in improving mine design and evaluation techniques. This program averages out structural data values obtained from randomly placed or gridded point sources across a mining property and uses these values in structural design equations. The basic purpose of the program is to provide accurate estimates of mineable tonnages, based on a realistic assessment of structural conditions existing in the deposit, for use in subsequent evaluation programs. Program output, however, also provides sound engineering data for the mine planner to use in planning and laying out new properties. Mining dimensions produced by the program provide a good starting point for initial layouts; and as more refined procedures are developed for increasing and improving the quality and quantity of information from boreholes, this information may be used with increasing confidence. The rock mechanics principles utilized in the program are generally well-established with full details provided to the user. To produce meaningful results extensive input data, obtained from exploration borehole core data, outcrop sampling points, or mine samples, are required. To assist the engineer, details of the types of tests that should be conducted have been listed. By including all of the ground control equations in the program the otherwise long and tedious calculations can be performed easily and quickly, and the work can provide the basis for a more detailed ground control study. The program is written in Fortran IV Level G to run on an IBM 3701155 ASP and requires 156K storage.

Jan 1, 1973

By Xiaozhen Song, Ashish Ranjan Kumar, Shimin Liu

To investigate the influence of boreholes, fans, and curtains for large opening underground mines (LOUM), we conducted a field survey for LOUM with the survey data serving as the numerical modeling inputs using computational fluid dynamics (CFD) models. Five different CFD modeling results were obtained with different borehole, box fan, and curtain setting conditions. The results indicate that most air quantity directly escapes through outlet 1 after coming into the inlet, causing a huge loss of airflow; volumetric air exchange index (VAEI) and minimum hours of fully exchanging the air (MHFEA) measure air exchange efficiency, with zone 2 of case 5 having the highest VAEI; The borehole minimally affects zones 2, 3, and 4, but drastically alters airflow direction in zone 1; The box fan enhances airflow to zone 2, improving ventilation efficiency and increasing VAEI; Curtains have little effect on distant working faces but influence airflow near inlets and outlets. This study provides a foundation for future research on the influence of boreholes, fans, and curtains, as well as optimizing their placement and effectiveness in face ventilation.

Feb 22, 2026

By C. E. Jordan

The Tuscaloosa Metallurgy Research Center of the Bureau of Mines, U.S. Department of the Interior, is investigating the recovery of phosphate from beneficiation slime, as part of the Bureau's efforts to conserve mineral resources through increased use of wastes. Phosphate equivalent to about two-fifths of U.S. production is discarded annually in the wastes. Exploratory flotation tests on the plus 5-um fraction of a slime sample showed promise for a classification-flotation technique. Onsite classification tests at six phosphate washing plants were conducted with a two-stage hydro cyclone system designed to recover the plus 5-um material. The cyclone underflows contained 8.3 to 19.1 percent P2O5, and the recovery of the plus 5-um PZOS values ranged from 81 to 95 percent. The percent P2O5 recovery from the total slimes ranged from 38 to 47 percent. Batch-flotation studies are currently being conducted.

Jan 1, 1978

By A. Balint

The Photometric Optical Separation process is introduced and examples of sorting machines are given. Applications of the process are outlined in general terms with reference to specific types of industrial installations. Brief description is given of the capabilities and limitations of available equipment, including cost estimates.

Jan 1, 1967

By F. M. Doyle, P. E. Richardson, E. Peters

A number of studies have attempted to correlate the semiconducting properties of mineral sulfides with their chemical reactivity. Frequently such studies are conducted on polished or abraded electrodes. Defects produced by abrasion may mask the influence of the semiconducting properties of electrodes, e.g., by pinning the Fermi level at the surface or by reducing the lifetimes of photogenerated charge carriers. It is shown that pyrite and galena electrodes have photocurrents that are extremely sensitive to abrasion of the electrodes. On freshly fractured galena surfaces, the space charge layer is readily polarized. Wet-abrasion is shown to produce a relatively thick ptype layer on galena electrodes and this p-type layer has a pronounced effect on the photoresponse. On freshly fractured pyrite surfaces, the Fermi level at the surface is pinned by a surface state. Wet-polishing reduces the magnitude of the photocurrent by over an order of magnitude.

Jan 1, 1993

By James L. Evers

The development of hydraulic mining in the United States has had an uneven record of progress. The shifting of coal extraction from one government agency to another has not provided an environment for a focused national research program. This paper presents an update on hydraulic mining research in the United States. A comparison is made between the development of the technology in this country and the state of the art in other parts of the world.

Jan 1, 1983

By Marvin P. Barnes

An attempt has been made to compile and code geologic data relating to twenty of the major porphyry copper districts of North America in such a manner as to permit the use of modern electronic digital computers to retrieve, compare, and build statistical mathematical models from the input. In the exploration process as part of his broader efforts to evaluate the potential of some prospective region, district, or ore body, the experienced geologist consciously or subconsciously compares and fits the observed geologic features to similar phenomena associated with known ore bodies with which he is acquainted. Thus an adequate conceptual "model" of the total geologic environment and type of ore body sought is an essential requirement for the successful exploration effort. Numerous such models of porphyry coppers already exist in the minds and notes of many experienced geologists today. These models are, of necessity, couched largely in qualitative terms and though they may be quite definite in the mind of the porphyry copper expert, the total concept of what constitutes a porphyry copper deposit and environment is difficult to convey in very precise terms. There probably is no such thing as a typical porphyry copper deposit. However, it is well understood that most of the deposits that have been studied have many geological characteristics in common. A logical question then might be: What characteristics are most common or how often do they occur in common, and what is their relationship to other common characteristics ?

Jan 1, 1970

By W. R. Bull

This paper examines water-only cyclone performance for the cleaning of fine coal, and the effects of changes in feed flow rate, feed pulp density, and vortex finder diameter. A model is presented for performance simulation which can be used to predict products obtained based on feed washability data.

Jan 1, 1987