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By Martin Herrenknecht

Tunnel boring machine (TBM) development continues to take on not only larger diameters, but also more difficult ground conditions. Ground conditions consisting of unstable faces with water pressures up to 15 bar have required innovative design approaches. A systems approach has been required to produce tunneling machines that can safely excavate the tunnel in an efficient, cost-effective manner that stresses production and labor saving approaches. This article reviews the current design developments and present recent projects where these most recent principles have been applied. The world?s growing population and rapidly proceeding urbanization are boosting an enormous demand for new and high-capacity infrastructures to secure the mobility of goods and people. Densely populated areas face the challenge of providing efficient traffic infrastructure such as a modern public transport system. At the same time, the maintenance and modernization of supply and disposal structures for water, sewage, energy and communication are essential. Last but not least, are supra-regional transportation routes such as long distance water diversion schemes. All of these projects are as demanding and are characterized by a tight time schedule. In this context, the demand for efficient tunnels for traffic and utility lines is increasing, as new infrastructures often leads underground because of limited space above ground. Also, tunnels are the obvious choice to cross natural barriers like mountain ranges. To handle the complex and variable geological conditions and other constraints, such as low overburden, high water pressure or long tunnel drives while facing increasing demand of a quick completion of a project, mechanized tunneling sets standards regarding safety, profitability and environmental protection in traffic tunneling projects as well as in the trenchless construction of utility tunnels. Different machine types and working principles have been developed to master various geological and hydrogeological requirements. Continuous activity in research and development leads to constant improvement of the mechanized tunneling process.

Jan 1, 2008

By H. R. Beard

The Federal Bureau of Mines investigated the absorption of radium and thorium from waste uranium leach liquor by clays and other materials. This work was conducted in support of the Bureau's goal of minimizing the environ¬mental conflicts, impacts, and occupational hazards Associated with mining and mineral processing operations. Tailings and soil samples from Wyoming and Utah were contacted with tailings liquors to determine the degree of absorp¬tion. Absorption ranged from 0 to 99 percent for radium and from 0 to 31 per¬cent for thorium. Some samples, which readily absorbed radium, were contacted with various salt solutions that could be present in tailings solutions to determine their effectiveness as desorbents. The desorption of radium ranged from 0.06 to 100 percent. An alpha-spectrometric method was used to determine the radium and thorium, concentrations in the solutions and the solids.

Jan 1, 1979

By N. F. Mescheriakov

New mechanical and pneumatic-mechanical flotation machines with axial impellers have been developed. Industrial tests show that these machines ensure lower power expenditure (on flotation) by 1.5-2.0 times as compared with reference machines (with the same or improved technological indices). Application of the newly developed axial impeller, with these advantages, is possible in any volume chambers of type OK, Dorr-Oliver, Wemko etc.

Jan 1, 1998

By Kirk A. Mcintosh

Augered, cast-in-place (ACIP) piles have been utilized in the United States for a wide range of projects since the 1950's. Due to the cast-in-place nature of the installation method (and lack of a driving criteria); however, ACIP piles have not been readily accepted by some practicing geotechnical and structural engineers. Since ACIP piles were initially developed, the installation equipment and techniques have been improved and refined and the number of experienced contractors has significantly increased. Over the past 10 to 15 years, the pile type has experienced significant growth in the United States (particularly in Florida) because engineers have become more knowledgeable and comfortable with its use. The Miami area, in particular, has experienced considerable growth in the utilization of ACIP piles primarily due to their usage on the $1 billion Miami Metrorail System project in the early 1980s. The economic advantages over other deep foundation types, coupled with some unique installation advantages, have shown that ACIP piles can be a viable foundation alternative on many projects. Even though ACIP piles have gained respect in the private sector, the pile type has generally not been readily accepted by government transportation agencies. The reluctance to readily accept this foundation type stems primarily from the quality assurance aspect of cast-in-place pile construction. Additionally, there has not been much research activity on this foundation type, technical papers, formal associations (other than the DFI), or a concerted effort to standardize the industry. This paper serves to discuss the state of practice for ACIP pile installation in the state of Florida.

Jan 1, 1997

By Tracy Brettmann

The use of rock-socketed Augered Cast-In-Place (ACIP) piles is new to the Austin and central Texas region. This case history describes the design methodology, load test results, quality control procedures and the rate of production pile installation for the first large commercial project where ACIP piles were used in Austin. The piles were 24 inches in diameter and extended through about 45 ft of alluvial materials to be socketed 6 ft into limestone. A full-scale instrumented load test was performed on a test pile that was loaded to 452 tons and held for 24 hours. Telltales were installed in the middle and the tip of the test pile. As part of the overall quality control procedures, singlehole sonic integrity logging was performed on the production piles to verify structural integrity during pile installation. During pile production, an average of 14 piles per day were installed, which is approximately seven times faster than the original design that consisted of drilled shaft foundations.

Jan 1, 1998

Let’s start off with your assessment of the mining industry. Today, the status of the mining industry is stronger than it has been over the previous few years. While mining continues to be a major part of the world’s economic foundation, the industry is gaining strength due to rebounding metals and minerals prices. And now, with these rising prices and the changes the industry instituted during the years when mining-related commodities were selling at low prices, our stronger, more productive and internationally competitive industry should flourish. Mining remains an essential business and the industry is far ahead of the game when it comes to the trend of globalization as a key to sustained growth. Also, the industry continues to realize increased productivity through technological innovations. And an increasing number of countries are moving towards capitalism, which opens doors for exploration and mining within their borders. After looking at all of these factors, I believe that the mining industry will only continue to gain momentum in the future.

Jan 1, 2004

By Descour Jozef, Suguru Shirasagi, Takuji Yamamoto, Koji Murakami

For TBM tunneling no visual inspection of excavated ground is possible. This may hinder the high-speed excavation, particularly in complex ground conditions. The TBM Excavation Control System was developed for better prediction of geological conditions ahead of the tunnel face during excavation. The seismic reflector tracing produces volumetric images of anomalies in the ground in “near-real time.” These images are verified using logging data from pilot boring and TBM driving data, to improve reliability and precision of ground mapping. Also good correlation was obtained between the rock strength index computed from TBM data, and one derived from volumetric seismic images.

Jan 1, 2007

By R. A. Franks, G. F. Friel, J. C. Edwards, L. Yuan

Two mine-fire experiments were conducted in the National Institute for Occupational Safety and Health's (NIOSH) Safety Research Coal Mine (SRCM) at the Pittsburgh Research Laboratory (PRL) which demonstrated that smoke from diesel-fuel fires of 500 kW and 660 kW heat-release rates in a return airway can develop, without causing a complete air flow reversal, into a roof layer that can migrate upwind forming a counter flow to the primary airflow in a crosscut. Subsequently, smoke can penetrate into an intake airway and create a hazardous atmosphere in the intake airway upwind from the fire. Visibility conditions less than 13 m were created by the smoke in the intake airway downwind from the crosscut. Modeling of the event with a three-dimensional, time-dependent, computational fluid dynamics (CFD) program correctly represented the smoke movement.

By A. M. Neale

Kriel Colliery has experienced some sub-standard blast results on the overburden. Blast results are considered poor when the fragmentation is too big, back break into the new highwall, capping is experienced and/or excess overburden material is thrown into the void. Poor blasting leads to lower productivity, equipment breakdowns, and poor drilling and blasting results on the adjacent blast, contamination of coal or loss of coal. A simulation was developed in Microsoft Excel to model blasting results while changing various parameters. From the simulation results, it could be seen that a change of blast design could be beneficial. As an example, smaller drilling patterns were simulated (10 m x10 m to 8 m x8 m, and 8 m x8 m to 7 m x7 m in Pit 5 and Pit 6 respectively) in combination with changes in explosives (P700 emulsion vs. ANFO) and drill bit diameter (311 mm vs. 251 mm). The results show that each of the options has a specific scenario that will be most beneficial to the mine. These results are quite specific and subject to variable inputs. The purpose of the example is to demonstrate how the simulation can be used as a tool to asses blast design variations.

Jan 1, 2010

By A. S. Macfarlane

This paper describes how knowledge of the orebody morphology and ore morphology can be used to optimize the planning, mining, and metallurgical output from an open pit copper mining operation, such as to significantly increase the stability of the whole value chain process, and increase the reliability and value of the process outputs. In the case under consideration, the orebody contains both copper and cobalt. This in itself provides a challenge, in that the two metals do not occur in consistent ratios across the orebody as a whole. Furthermore, mineralogical differences within the orebody have a significant impact on plant performance in terms of throughput rates, acid consumption, and recoveries. In order to stabilize and optimize the plant performance, it is necessary to firstly have a complete understanding of the geometallurgical factors that affect performance, and then to have a sound knowledge of how these are distributed within the orebody. These models then inform the mine planning strategy that optimizes cash flow and NPV, and also allow the development of a stockpiling strategy that not only stabilizes the plant, but also allows variations in the plant feed according to ore type and grade in volatile price scenarios. Integral to the realization of these opportunities is the establishment of an appropriate measuring, control, and reconciliation system, customized to the optimization objectives. The paper describes how all of these factors and strategies can be integrated to produce optimal value from the orebody through to final dispatched product. It also shows the significant value that can be released through such an approach.

Jan 1, 2014

By D. Harrington

Dust diseases are much before the public at present, but little reliable information on the subject is readily available to the layman; even those rated as experts usually have a more or less theoretical conception of these diseases, their causes, remedies, and prevention. Until recently little attention has been given to prevention, and the usual attitude of the engineer, upon whom the main reliance for prevention ultimately must devolve, has been to let "sleeping dogs lie" or, more definitely, to "let well enough alone." However, the "laissez faire" attitude no longer is tenable; in the past few years numerous conditions have caused those engaged in industry, including mining, to study the subject with a view to ascertaining the facts upon which to formulate remedial measures, primarily preventive. This bulletin is an attempt to assemble information in convenient form on effects of breathing dusts, largely in the mining and allied industries. The literature on this subject is so extensive that no attempt has been made to include all published material or all types of dust diseases but only to assemble some of the more outstanding data on several aspects of the subject, especially with reference to silicosis.

Jan 1, 1937

By H Firdausi, I Pasek, T Chenier

The Grasberg Block Cave (GBC) Mine is one of the future underground mines of PT Freeport Indonesia (PTFI). Located in the remote highlands of Papua, Indonesia, the GBC mine is scheduled to start production in 2017 reaching its peak production capacity of 160 000 t/d in 2023.In order to reach planned production capacity, the GBC mine will utilise an ore handling system consisting of rail haulage, crushing and conveying. The rail haulage system will utilise over 20 km of track while crushing is accomplished by way of three gyratory crushers each with a capacity of 3300 t/h. Nine conveyors operating in two parallel systems, each system over 3 km in length, will move the ore from the crushers to the stockpiles. These systems require a network of larger tunnels and mass excavations to accommodate the planned production facilities.This paper will describe the ore handling system, tunnel and mass excavation methodology as well as some of the challenges encountered with ground conditions and excavation quality during the execution of the project. A combination of lateral and vertical development methodologies and equipment, including drill jumbos, mechanised raise climbers and specialised ground support equipment, have proven successful in the development of a quality ore handling system.CITATION:Pasek, I, Firdausi, H and Chenier, T, 2016. Development of the ore handling system at the Grasberg block cave mine, Indonesia, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 599–608 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By Stephen L. Chryssoulis, Stamen Dimov

"Preg-robbing has been known for many years, where increased losses are suffered because dissolved gold is removed from solution by adsorption onto carbonaceous matter. In direct cyanidation circuits it is reasonable to conclude that the preg-robbed gold is either in a gold cyanide [Au(CN) - 2, AuCN] or metallic [Au°] form. However, in circuits with a pre-oxidation step possibilities increase and multiply even further because of water recycle streams containing apparent and not-so-apparent gold ligands. It is in these circuits where speciation of sorbed gold, i.e. the identification of the gold compound, is useful. The importance arises from the fact that proper identification of the sorbed gold species can be used to determine how, when, where and why gold was removed from solution, thereby identifying the exact cause of the problem and providing clues as to how it may be rectified.INTRODUCTIONTo the best of our knowledge, this is the first attempt ever to speciate gold preg-robbed by carbonaceous matter using a surface sensitive microbeam technique. This approach enables the direct determination of gold species sorbed on carbonaceous particulates, opening an entirely new field in the understanding of the chemistry of gold sorption on carbon. The reasoning behind this effort was to add to the current knowledge of the detrimental effect chloride ions have on gold recovery by the pressure oxidation and in particular why in the ensuing CIL step, gold is not being desorbed from the surface of the carbonaceous particles (Table 1)."

Jan 1, 2004

By L. A. Cramer

South African platinum mines produce the world?s majority of platinum metal that is used in autocatalysts and jewellery. As the platinum market is forecast to grow at healthy rates into the future, the South African producers, Anglo Platinum, Impala, Lonmin and Northam, are planning to expand in the next decade. Furthermore, a number of smaller producers who are accessing other mineral rights are entering the buoyant market. The South African platinum mines have traditionally exploited the Merensky Reef of the Bushveld Igneous Complex (BIC); however, the mining of this reef is reaching depths that require significant vertical shaft systems and costly refrigeration for access to the orebodies at deeper levels. In the past decade all of the producers have begun to mine the less attractive UG2 reef because of its cheaper mining costs. This UG2 reef contains significant quantities of chromite with typically a chrome-to-iron (Cr/Fe) ratio of 1.35. UG2 ores can contain between 10 and 25% Cr2O3dependingupon the reef width and the selected mining method. It is relatively cheap and easy to extract a portion of the chromite from a platinum concentrator tailings stream at a grade of between 40?42% Cr2O3. However, it is only in recent years that some ferrochrome producers have begun to source some of their chromite from the tailings of platinum producers. South Africa is also the world?s largest single producer of ferrochrome and supplies much of the world?s stainless steel producers and thus the growing market for their product. As the traditional sources of high Cr/Fe ratio ores have been depleted at the shallow economic depths and thus have become more expensive sources of chromite, technical developments have improved the ability to use fine chromite economically to make acceptable grades of ferrochrome. Thus UG2 fines are now becoming possible cheap sources of acceptable feed to the ferrochrome industry. The abundance of feedstock for ferrochrome production and the lessening dependence on mined material will impact upon the structure of the ferrochrome business in South Africa. With continued platinum mining from UG2 reefs, South Africa is set to remain highly competitive in the world?s ferrochrome/stainless steel industry.

Jan 1, 2004

By A. Adu-Acheampong

A geotechnical study was conducted to identify the cause(s) of stope instability at the Ashanti Mine (Obuasi, Ghana). As part of the investigation, laboratory testing of rock was performed and the rock mass was classified according to the Q-System (Barton et al., 1974).Numerical analyses were performed using the computer program FLAC (Itasca, 2001). The observed failure zone around the stopes was simulated using both Mohr-Coulomb and Hoek-Brown (Sheorey,1997) models. Yielding along peripheral graphite bands and tensile failure were clearly identified to be the major contributors to stope instability.

Jan 1, 2003

By B Murphy, A Uliana, P STrgio de Oliveira, G Ara·jo de Souza Franco, T Miettinen

Outotec has performed numerous research and development projects and various surveys in the study of reverse iron ore flotation. Over the past four years their TankCell-70 and TankCell-160 flotation cells at the Germano concentrator of Samarco in Brazil were extensively surveyed. These surveys have revealed some extreme operating conditions in reverse iron ore flotation and are the subject of this paper. Some of the findings include large variations in the content of solids in the various flotation stages. At the bottom of the cleaner cells, the content of solids by weight reached over 60 per cent, whereas at the bottom of the scavenger cell this was less than 50 per cent. Froth carry rates were also significantly different in the various flotation stages. In the case of coarse material, the scavenger cells operated at a froth carry rate of over 40 t/h.m2. With fine material, however, froth carry rates of less than 10 t/h.m2 were measured. High froth carry rates caused significant changes in the residence times at Samarco. In the rougher cells, the fifth cell had more than double the residence time of the first cell. This was even more pronounced with the scavenger cells, where the second cell had more than triple the residence time of the first cell. High froth carry rates also caused losses in iron recovery. As a consequence of such findings, it appears that different rules apply in the sizing of reverse flotation circuits compared to direct flotation circuits. Different operating parameters (mixing intensities and air flow rates) must also be used in the rougher, cleaner and scavenger cells in order to optimise the metallurgical performance. Outotec has also been working on a number of new technologies aimed at improving the metallurgical performance of iron ore reverse flotation circuits by increasing froth carry rate and decreasing fine iron entrainment.CITATION:Miettinen, T, Uliana, A, Ara·jo de Souza Franco, G, STrgio de Oliveira, P and Murphy, B, 2013. TankCell flotation at SamarcoÆs Germano concentrators, in Proceedings Iron Ore 2013 , pp 441-444 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

In the Ngakuru area, zeolite deposits occur in late Quaternary lake sediments and ignimbrites. The deposits are associated with sinters, hydrothermal eruption breccias, and quartz-adularia altered fault breccias: all indicators of a shallow epithermal environment. Several of the deposits are adjacent to epithermal gold prospects. Zeolites are most abundant in lacustrine tuffs of the Ngakuru Formation, a 100-300 m thick sequence of siltstone, tuff, diatomite, sandstone and conglomerate. The formation overlies the Ohakuri Ignimbrite dated at c. 270 Ka, and is unconformably overlain by alluvial sands and gravels which are younger than 20 Ka. Individual zeolite deposits contain 30-80 per cent zeolite over a thickness of up to 45 m in thinly stratified tuff beds. The tuff beds are locally overlain by diatomite. The tuffs are composed mainly of glass shards and pumice clasts, with minor volcanic plagioclase, quartz and biotite crystals. Glass shards in the tuffs are replaced by the silica-rich zeolites mordenite and clinoptilolite. Amorphous silica (opal A), opal-CT, K-feldspar and smectite are also present. The distribution of the Ngakuru Formation is controlled by northeast trending normal faults, which separate it into the Ngakuru and Guthrie grabens. A silicified (quartz-adularia altered) hydrothermal breccia along one of the fault zones suggests that the faults acted as feeders for heated water that caused the deposition of the zeolite minerals. Some of the zeolite deposits are adjacent to sinters and hydrothermal eruption breccias. The location of the sinter about 20 m above one deposit indicates that the zeolites were formed at a depth of 20 to 70 m below the paleosurface. The hydrothermal eruption breccias contain clasts of altered ignimbrite, which contain geochemically anomalous gold and silver values. By analogy with their occurrence in active geothermal systems in the Taupo Volcanic Zone, mordenite and clinoptilolite in the Ngakuru deposits probably formed at temperatures of 60-150oC from near-neutral pH waters as a result of interaction with glass-rich tuff beds. The Ngakuru zeolite deposits are therefore interpreted as shallow hydrothermal alteration zones within larger epithermal gold-bearing systems.

Jan 1, 2002

By Donald W. Mitchell

Research shows that water neutralizes the explosion hazard of coal dust when present in sufficient quantity and when intimately mixed with the dust. The quantity of water required to neutralize coal dust and coal-rock dust mixtures is about equal to the limiting moisture adsorptive capacity of the dust; the adsorptive capacity increases with increase in the fineness and volatile content of the coal. Pools of water or high atmospheric humidity do not reduce the explosion hazard. Although wetted dust is less dispersible than dry dust, poor dispersibility cannot be relied on as the sole safeguard against explosion. Dust mixtures that contain water in excess of their limiting adsorptive capacity are dispersed and ignited by severe initiation sources. Pure coal dust adsorbs water with difficulty and retains water poorly; adsorption and retention is increased by the addition of rock dust the coal; the rock dust agglutinates wetted coal and assures that incombustible is present should drying occur. Therefore, it is advantageous to rock-dust wet areas in bituminous coal and lignite mines. When coal-rock dust mixtures are wetted and subsequently dried, the explosion hazard is about the same as for dust which was not wetted.

Jan 1, 1962

By Alastair Grogan, Ron Elliott, Dale MacLean

Blasting for armour stone presents many unique challenges. Often, blasters get themselves into trouble when they assume that they can simply modify a production blast design to produce the required fragmentation size. They bid on the project using typical production blasting costs, and then find that they cannot produce the required fragmentation size and quantity with an acceptable waste factor. This paper outlines industry best practice guidelines for the production of riprap or armour stone. The paper examines the importance of initial geological mapping to determine the average in-situ block size, and the advantages to be gained from working with the geology to maximize production of the required block sizes. The paper also outlines the importance of proper explosives selection as well as blast designs that are unique to the production of riprap. The paper reviews challenges and experiences realized from multiple projects in differing rock types.

Researchers from the National Institute for Occupational Safety and Health (NIOSH) are developing a coal pillar rib rating (CPRR) technique to measure the integrity of coal ribs. The CPRR characterizes the rib composition and evaluates its impact on the inherent stability of the coal ribs. The CPRR utilizes four parameters: rib homogeneity, bedding condition, face cleat orientation with respect to entry direction, and rib height. All these parameters are measurable in the field. A rib data collecting procedure and a simple sheet to calculate the CPRR were developed.

Jan 7, 2020