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By Thomas Konstantis, Spyridon Konstantis, Panagiotis Spyridis

"Tunneling and Underground works are unequivocally subject to a diversity of inherent uncertainties associated with the geotechnical, hydro-geological and environmental regime that surrounds them. On many occasions, these uncertainties can provoke loss events of considerable consequences. The present contribution elaborates on losses that the insurance market has suffered in the recent years, following a construction failure event. These losses are being considered and analysed on a quantitative basis through evaluation of cost related data, with explicit discretization of the applied construction methodology and of the subsequent developed failure type since both of which are considered of major importance. Given the identified persistence and regularity of some loss-contributing factors, recommendations are provided on the basis of a proactive risk engineering management approach that are envisaged to reinforce the understanding of project risks and alleviate the incurred insurance cost. 1 INTRODUCTION The underground construction sector has always been a very challenging area for all involved parties, including the insurance market. Main reason for that remains the uniqueness of the uncertainties sources and the subsequent inherent risks that the tunneling and underground projects are exposed to. In many instances, these risks materialize, leading to loss events with substantially high impact on reinstatement cost and incurred delays, which depending among others on the insurance coverage will have to be bared by the Insurance market. In the recent decades and as the tunneling industry boomed and expanded with many major and significant projects undertaken around the world, the insurance market was faced with additional challenges. Increased competition during tender coupled with the scale and complexity of the projects and politically driven decision making exerted pressure on the project timelines, completion dates and budget. The pressure for on-time or even early project completion- to avoid liquidated damages or achieve bonus payments, respectively- along with cost reduction efforts and the incentive for innovative failure events. That, in turn, put additional pressure on the Insurance market which had experienced a significant amount of losses with substantial cost. One of the triggered mitigation actions was the introduction of the Code of Practice for Risk Management of Tunnel Works (ITIG, 2006 & 2012; MunichRe 2006, Wannick, 2007, Spencer, 2008, Adeyemo, 2011)."

Jan 1, 2016

By Thomas P. Meloy

There is much interest in the automation of entire comminution circuits, At the present technological level it is possible to automate a circuit but to date it has not been done, To successfully automate a circuit, a number of problems must be solved. Not all of them are engineering problems. The purpose of this paper is to discuss some of these problems, as certain the implications of these problems and indicate solutions to them. In this paper the term "automation" is used loosely but in the popular sense. Namely, that a plant is automated if a computer is used to control the basic flow of the materials as well as setting the critical parameters in the process. Specifically, the discussion will concern itself with the control of comminution circuits from the dumping of the ore into the primary crusher until the final interface between the comminution circuit and say, the flotation mill in the case of a sulfide ore.

Jan 1, 1965

By B. Sameti

Blast engineers have been taking advantage of image-based rock fragmentation analysis methods for the past 3 decades to estimate rock size distributions. These methods utilize a wide range of image segmentation techniques, from manual to fully-automated, to delineate the edges of rocks in images. Rock delineation results are then converted to physical rock sizes (and percentage passing curves) by scaling the image pixels to correspond to physical measurements. The size scaling process is critical for acquiring physical measurements, but specific to the limitations of different applications. This article starts by presenting a shovel bucket-based fragmentation analysis system, where scaling is done using the known width of the shovel bucket within the image. Next, it describes methods that use pictures captured by digital cameras with scaling reference objects in the view. Finally, the article presents a method that uses three-dimensional imaging to capture images without the need for scaling reference objects. A portable device which utilizes a three-dimensional imaging method is proposed, and compared with the other methods. The proposed solution combines the generated three-dimensional points with the delineated rock boundaries in the image to reconstruct the surface, and generate accurate rock size estimates and percentage passing rock size distributions. System operation is described and its accuracy and performance are discussed for various scenarios. It is shown that since the device does not require a physical object for scaling reference, it is free from the limitations of other methods, and can be applied for automatic rock size measurement from various sources such as mining shovels, loaders, crushers, stockpiles, haul truck beds, and conveyor belts.

Feb 23, 2014

By Justin Kolster, Donald Benjamin, Kyle White

Expansion of the Plum Island Wastewater Treatment Plant requires interconnection of three operating pump stations using only two existing 10-ft diameter shafts for access. These two existing shafts require additional support to allow access 130 feet below grade. Interconnection requires rehabilitation of an existing tunnel, excavation of two new tunnels, and abandonment of additional existing tunnels. Construction has discovered unexpected conditions at all three connection points. The CMAR contracting method has effectively accommodated project team discussion, value engineering decisions, and allocation of risk during preconstruction and construction phase services.

Dec 1, 2022

By James A. Curry

Table I identifies the maximum cost of the individual provisions with spoil disposal in Appalachia leading at $3.98 per ton, This was followed by deep mine subsidence control and monitoring at $1.66 per ton. At the request of the U.S. Department of Energy, the Bowser-Morner Testing Laboratories of Dayton, Ohio, evaluated Consol's cost estimates for 14 of the 21 regulatory provisions the company studied. It is interesting to note that Bowser-Morner concluded that Consol's estimates of costs were very conservative and that the actual costs will be substantially higher than what the company reported. In 1978 a joint committee of the National Coal Association and the American Mining Congress made estimates of cost impacts under 11 OSM permanent rules (see Table II). Six rules applied to mid-western strip mining were projected to cost $6.52 to $17.17 per ton. Five rules applied to mid-western strip mines showed costs ranging from $.91 to $6.11 per ton. Three rules applied to deep mines (regardless of region) were seen raising costs from $ .57 to $2.67 per ton. The joint committee reported trouble developing overall figures because member firms used widely different assumptions in calculating their costs. That same statement could no doubt be made when comparing most cost data available today.

Jan 1, 1980

By M. A. Boucher

The purpose of my presentation is threefold: a) to make you aware of what is available in Canada in terms of refractory minerals. b) indicate the mineral deposits that have potential for development. c) show the advantages of Canada as a supplier of electrical energy necessary for the production of electrofused minerals. Canada is a producer of natural refractory minerals, electrofused minerals, and synthetic refractory minerals. Several deposits also have good potential for development. The natural refractory minerals produced in Canada are shown in Table 1. The major minerals by decreasing order of importance in terms of tonnage and values are: dolomite, graphite and magnesite.

Jan 1, 1992

By Manuel Gomez

This, report presents correlative data on ash and sulfur forms for Pittsburgh seam coal from Greene County, Pa. Prediction equations were developed for sulfur form distributions and washability characteristics. The equations developed were evaluated with an independent set of exploration core samples. It was demonstrated-that both sulfur distributions and washability characteristic's can be predicted from exploration core data ahead of mining. This information can improve the efficiency of selective mining techniques for the production of a uniform metallurgical coal product.

Jan 1, 1967

By W. H. Langer

Quaternary alluvial deposits in the modern stream channel of the Agua Fria River west of Phoenix, Arizona, is mined and processed to provide aggregate to the greater Phoenix area. The alluvium occurs as three distinct, stratigraphic layers. Samples from each of the three layers were examined for gravel clast lithology, grain size distribution, and engineering tests, which revealed noteworthy differences in properties. The engineering properties of the gravels are dependent on a combination of factors including gravel clast lithology, the distance the gravel clasts have been transported from their source areas, the age of the deposits, and the degree of weathering. Knowledge of these characteristics may affect the methods that aggregate operators employ to extract and process gravel from the Agua Fria River.

Jan 1, 2010

By Donald B. Buddecke

The large walking dragline has been the most commonly used overburden-stripping equipment in Texas lignite mines. These draglines, operating on the highwall side of the pit, can excavate to a depth of 45 m. Considerable overburden rehandling is required beyond 30 m and may reach 100 percent by 45m. As pit depth increases, dragline operation also becomes more complex, with two or three passes being necessary to make a cut 30 to 40 m wide. Multiseam operations also require extra passes. At pit depths greater than 45 m, the dragline must be operated also from a spoil bench. This can be difficult in the unstable alluvial deposits in which lignite occurs.

Jan 1, 1985

By A. K. Stagg

Toxic substances in On solutions can retard biological leaching of copper sulfide dump ores. On solutions were analyzed for metals, organics, and chloride, and showed inhibitory concentrations of aluminum, manganese, and chloride. Inhibition of bacterial activity by the solid fraction of On solution, with and without the organic constituents, was evaluated. Toxicity to bacterial species was evaluated by monitoring bacterial numbers, pH, Eh, and rates of iron oxidation. The On solution solids were toxic at 50 -60% of their field concentration. Most of the toxicity of the On solution was due to the organic fraction. Different SX reagents show varying degrees of inhibition of T. ferrooxidans. Bacterial inhibitory effects of carriers and lixiviants used in the SX plant should be determined so that entrained SX reagents do not retard biological dump leach systems. The reagents used should be the most cost effective and the least toxic.

Jan 1, 1994

By Michael A. Redfearn

The use of nitrogen in molybdenite flotation circuits is a relatively new concept utilized by only a few mines around the world. This paper briefly discusses circuit chemistry and the reason for its success. It follows the entire testing process which resulted in a sodium hydro-sulphide dosage reduction from 18.5 to 4.4 lbs/ ton (9250 to 2200 g/t) through to the final installation of an inert gas generator which will produce reagent savings in excess of one million dollars annually. A description of the various types of nitrogen generators commercially available is included.

Jan 1, 1983

By N. Ripepi

"The Langmuir model has been widely used for the coal-methane sorption process via an isothermal test. However, even though the temperature-dependent Langmuir model were recognized theoretically and experimentally, the quantitative relationship between the Langmuir’s constants (a & b) and temperature have not been clarified and confirmed by lab test data. This paper collects 158 methane-coal sorption data under different temperatures, which apply the Langmuir model to consider the relationship between Langmuir’s constants (a & b) and temperature (see APPENDIX I). Even though the Langmuir model cannot be used to show the physical state of methane adsorption on coal, it is widely used because of its simplicity and the reasonable explanation of its parameters (a & b). The results from these published isothermal tests confirm that 1) there is no consistent relationship between Langmuir’s constant-a and temperature; 2) the Langmuir model is a temperature-dependent model, and the temperature-dependent feature is mainly shown by the relationship between Langmuir’s constant-b and temperature; 3) The relationship between Langmuir’s constant-b and temperature can be described by both the exponential and linear relationship with dried coal. This paper provides a database for temperature-dependent Langmuir’s model, which can be used for reservoir simulation of coalbed methane reservoir, coal seam degasification modeling for underground coal mines considering the heating effect induced by geotherm and heat injection (via hot water, hot steam, ultrasonic, etc.). INTRODUCTION The isothermal test for gas sorption on coal is one of the fundamental tests in Coalbed Methane (CBM) recovery fields, such as underground coal mine methane degasification, CBM gas-in-place estimation, and carbon dioxide sequestration in un-minable coal seams. Generally, two methods, volumetric and gravimetric, are employed to obtain isothermal data (Bush, A. & Gensterblum, Y., 2012). Based on these two approaches, a series of commercial and self-assembled instruments are built and several calculation methods are used to obtain isothermal data (Bush, A. & Gensterblum, Y., 2012, Gasparik, K., 2014; Goodman, A. L., et al, 2004; Zhang, L., et al, 2013). In the post-processing stage, many models are provided to analyze isothermal data in order to understand the storage mechanism of gas in coal. Common models include the Langmuir model (and its extended forms), the pore-filling model, multilayer adsorption model (BET), and the Gibbs’ model. Among these models, the Langmuir model is the most widely used for its simplicity and functionality. The Langmuir model is expressed as follows:"

Jan 1, 2016

By K. L. Kayler

The Bardon Trimount, Inc. stone quarry in Ashland, Massachusetts was the recent subject of a quarry closure review report. The quarry produces aggregate using standard drilling and blasting techniques. Stone is processed at an on-site plant. Noise monitoring data collected during the closure review indicate that the quarry generally operates within the quiet range. There is a decrease in noise while the quarry is not operating. Levels of dust associated with the quarry are low. Unpaved roadways are the greatest contributors of fugitive dust associated with the mining operation. The quarry cannot be seen from any homes within the town of Ashland, except during the winter months. The visual impact of the quarry on surrounding properties is minimal. Further quarry development is likely to reduce visibility of the quarry from some areas.

Jan 1, 1995

By D. T. Jr. Tarr

History of Development The hydrocyclone, probably because of its basic simplicity, has been used for various classification applications since before 1890. A patent was granted in the United States in 1891 to Bretney on a device for separating sand from water, collecting the sand in a closed chamber for intermittent discharge, practically identical to some present-day water desanding cyclones. Between 1900 and 1937 there were 30 or more additional patents issued on liquid cyclone configurations or their use. About 1937 liquid cyclones began to be used commercially in the treatment of cellulose fiber in the pulp and paper industry separating contaminating particles from the fiber in water suspension used for making high grade paper products. Nichols Engineering & Research Corp. of New York was marketing a liquid cyclone for cleaning sand and din particles from fiber suspensions in the pulp and paper industry by 1937. The designs during this period were such that the cyclones discharged a small amount of relatively high density material into a chamber connected to the cyclone apex which in turn discharged the collected dirt material intermittently. By the early 1940s hydrocyclones as we know them today began to appear both in the pulp and paper industry and in coal prorzssing.18 Considerable experimental work was done on small, mostly 3-in.- diam, cyclones operating at relatively high pressure drops, in the range of 50 psi, to remove very small contaminating particles from cellulose fiber in the production of high-grade writing papers in the paper industry.18

Jan 1, 1985

By Hamid Maleki

Rock mechanics models are “data-limited,” i.e., one seldom knows enough about a rock mass to use computational models unambiguously. Statistical methods, however, are capable of being applied where there are good data but a limited understanding of certain natural phenomena, such as the creep of rock salt or elevated risk domains associated with violent failure of strata commonly referred to as coal bumps and coal bursts. Important to these evaluations are (1) having statistically valid data collected consistently and (2) incorporation of analytical calculations for quantifying geologic, mining and particularly geotechnical variables. By combining the strength of the statistical and analytical models, an improved “hybrid” model is created and utilized. To demonstrate the use of hybrid statistical-analytical techniques in rock mechanics problems, three case studies are used. The first case study involves a historic examination of a nuclear waste repository in rock salt, where mathematical models are built using excavation con- vergence data to identify significant variables and estimate future deformation and stability. This case study uses the convergence rate at up to 121 locations of different ages and geometries using monitoring data over the facilities' footprint excavated through 1998. The second case study focuses on ongoing analysis of coal burst mechanics and associated factors. Within the last three decades, a hybrid statistical-analytical methodology has been applied for identifying significant factors affecting coal bursts. This final hybrid model utilizes data from 30 case studies from Utah, Colorado, Kentucky, and other Eastern U.S. mines providing predictive capability for the entire United States coal fields. The last case study is the assessment of Castlegate Sandstone escarpment stability using historic data collected over 17,000-ft of sandstone escarpment exposure in the vicinity of longwall operations in Utah. Results from all three case studies are used for demonstrating the utility of the method in solving ground control problems.

Jun 25, 2024

By D. H. Stonehouse

There is no such thing as an industrial minerals industry. There are, however, many industries operating in the general field of industrial minerals. And although we use the phrase "industrial minerals industry" out of sheer convenience, the only common denominator among, say, the potash mining and processing industry, the sulphur-sulphuric acid industry and the granite industry is, in fact, that they each are exploiting an industrial mineral resource. May I quote the person whom I consider to be the reigning Mr. Industrial Minerals, Robert L. Bates, who in the 4th edition, 1975, of Industrial Minerals and Rocks states: "An industry is considered to belong to the industrial minerals field if its operations consist of extraction and processing, but not manufacturing. Thus the mining and beneficiation of feldspar is a mineral industry, but the manufacture of ceramic products is not. In the cement and lime industries, processing merges into manufacture, and the line is less distinct. It disappears altogether in a plant that extracts salt as artificial brines, and makes sodium and chlorine chemicals, all under the same roof."

Jan 1, 1981

By W. F. Riggs

INTRODUCTION Flotation equipment is becoming more definitive in design as well as greater in dimension. The last ten years have witnessed the implementation of large flotation cells ranging in size from 28 to 85 cubic meters. However, small plants still operate with cells as small as 3 cubic meters. These changes have increased the operational sensitivity of the flotation system to the chemical reagents used. No scientific study has been undertaken to develop the relationship between the size of equipment and the response of reagents in the flotation system. Hence, this article is an attempt to present several observations from past experience for the purpose of stimulating future research in an area previously ignored and perhaps subsequently not used to advantage. CONVENTIONAL FLOTATION Recent advances in conventional flotation cell design have been made in two areas: a. Flotation cells are becoming larger, and b. Basic design of flotation cells has changed. They can be classified into two types: deep cell and shallow draft cell. Size and design changes of flotation cells have a greater effect on frother performance than on the performance of other chemical reagents. Hence, the discussion in the following sections is restricted to the impact of frothers in the flotation system. Flotation Cell Size The advent of increasing flotation cell size has resulted in the increase of frother consumption. There appears to be a correlation between reduced horsepower (kilowatt) consumption and increased frother consumption per ton of ore processed in the circuit. This is more prevalent when the frother chemistry remains unchanged. Another reason for increased frother consumption is the increased distance between the rotating central shaft and the lip of the cell for larger flotation machines. Increasing this distance results in increased surface area corresponding to the larger cell size. Reduced power input per ton combined with the need for longer, stronger load support of the froth bubble as a result of increasing cell size has resulted in the development of a new series of stronger and more persistent frothers. By the same token, these newer, stronger frothers are difficult to control when applied to the smaller cells. This is true even at lower dosages because the break point between too much frother and not enough frother for optimum metallurgy is normally very narrow. This problem is often exaggerated when operators have established an optimum setting for pulp level and air for the particular frother in use. Generally, the tendency is to operate the flotation cells simply by adjusting frother dosage. The increase in frother strength to accommodate the large cells often results in the realization, after a retrofit, that the existing pump box or sump which is still handling the same volume of concentrate is no longer adequate in size. Flotation Cell Design The two most common flotation cell designs installed during the past ten years are the deep cell and the shallow draft cell. The deep cell provides for complete mixing of air and pulp at the bottom of the cell. The shallow draft cell does all the mixing/pumping in the bottom haft of the cell whereas the mixing of the air is performed further up the shaft and is brought into contact with the pulp midway up the vortex. There are many preferences for one or the other. It is the author's contention that both designs have very valid concepts and must simply be suited to the particular situation as required by the operator. The following comments are subjective observations which should be explored in greater detail. The deep cell mixes both air and pulp together at the bottom of the cell requiring a full depth ascending of the homogenized air to the surface to form the froth layer. This design, in combination with charged air, provides for good concentrate grade control under adverse conditions of selectivity, especially when faced with a fine grind and a slime-laden gangue. A selective frother can be applied without a competitive loss in recovery. One of the conditions for good selectivity in this environment is operating at medium pulp solids concentration in the range of twenty-six to thirty-four per cent (26-34%). When a higher solids concentration is used in combination with a coarse grind, it becomes difficult to maintain the same recovery with a selective frother due to higher pulp viscosity. This condition sometimes results in an unacceptable coalescence of the air bubbles as they ascend the full height of the deep cell. The increased pulp viscosity at higher solids concentration can also retard the flotation kinetics. The combination of decreased surface area of dispersed air and slower kinetics can result in reduced recovery causing coarse particles to continue to drop

Jan 1, 1989

By R. M. G. Machunter

The presence of ultra-fine particles affects the separation performance of wet gravity separation equipment. Several studies have been undertaken to establish the maximum level of these particulates that can be tolerated by spiral separators and it has been found that unless the ultra-fine material is effectively processed, relatively low proportions in the ROM material combined with high feed rates can result in degradation in plant performance and/or excessive water consumption. The maximum level of particulate material in the process water has been determined by examination of separation performance of spiral separators under varying slime loading. This work has been conducted utilizing various feed sources and a robust ‘rule-of-thumb’ has been derived.

Jan 1, 2005

By R. J. Roman

The results of column leaching tests on 3 different mixed oxide/sulfide ores from a Chilean deposit are presented. The 3 samples contained different ratios of oxide copper minerals to chalcocite and chalcopyrite. The results of the column leach tests are interpreted in light of the shrinking core model for coarse particle leaching. The copper recovery from the oxide minerals and the sulfide minerals each conforms to the shrinking core model with the total recovery equal to the weighted average of the individual minerals. The use of column test results to predict field heap leaching results using the multi-mineral shrinking core model is discussed.

Jan 1, 1993

By H. N. McLeod, B. C. Butler, S. R. Rice

Tius paper describes the key considerations for design of impoundments for gold mine tailings. Design options available for construction are presented. The key considerations for design of a safe, economic and environmentally sensitive design are discussed. The dam design must also balance these conventional considerations with the pragmatic aspects of construction and operations and the risk of system upsets. Case examples of tailings facilities in Canada and Papua New Guinea are discussed.

Jan 1, 1991