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By D. E. Hinkle

Past surface-mining operations in Appalachia primarily followed mountain con-tours. It is estimated that about 18,000 mi. of highwalls are exposed throughout Appalachia. An evaluation procedure for determining the secondary mining potential (SMP) of these highwalls has been proposed. Sixteen parameters affecting the SMP were isolated. These are grouped in four major categories: geologic conditions, existing infrastructure, site conditions, and environmental conditions. The parameters were then ranked by their impact on SMP and assigned weighting factors. A simple mathematical procedure yields an SMP number (0 < SMP < 100), which may then be used to compare alternative sites and technologies. Determination of limits and ranges while grouping data was aided by field visits to over 40 exposed highwalls in Eastern Kentucky. An interactive program has been developed to rapidly evaluate the SMP for pre-mined sites. The mathematical procedure estimates the relative potential (i.e., techno-logical feasibility) for remining for three predominant secondary mining methods: augering, Hi-wall mining, and underground mining. Other secondary mining methods are briefly reviewed and compared.

Jan 1, 1989

Two key strategies for a new generation of mining are developing domestic raw material production and doing so in an environmentally responsible way, according to presenters at the 83rd annual meeting of the SME Minnesota Section in Duluth (the 71st annual University of Minnesota Mining Symposium). From technical sessions detailing how to build com-munity support, to a short course on international perspectives in iron ore mining and processing, the two-day meeting emphasized the potential of Minnesota state deposits and the importance of maintaining productive community relations both locally and globally. The meeting of more than 300 mining industry professionals began on April 20 with a traditional convocation celebrating the values of northern Minnesota. The accompanying tradeshow, with a record 131 booths, showed the speed and vigor of the economic rebound. Keynote speaker Scott Anderson, vice president and senior economist at Wells Fargo, stated the prevailing mood of the conference: ?Wow, what a difference a year makes.? With metal prices and sales up and heading higher, he said, it was clear that the production-centered economic recovery is reaching the mining and the minerals industry. However, Anderson sounded a few notes of caution. Serious threats to economic stability remain, including the burgeoning national de?cit, high unemployment and the still out-of-control foreclosure crisis. Overall, he predicted a below-average recovery and stressed the importance of developing a long-term business strategy.

Jul 1, 2010

By B. Samanta, S. Bandopadhyay

Ore grade modeling of a placer gold deposit is considered a challenging problem even today. Typically, gold-bearing deposits show extremely erratic and unpredictable grade variation. This is principally because of isolated occurrences of gold metal within a few high-grade pockets. Because of sporadic fluctuation of high-gold-grade distribution, the overall spatial continuity of the deposit becomes poor. This type of variation is often described by a lognormal or highly skewed frequency distribution, and the spatial continuity of the deposit is characteristically represented by a variogram model that exhibits a high nugget component. Further complicating the matter is the sparse availability of drillholes to capture such erratic variation. Due to the prohibitive cost of drilling, gold grade and reserve estimations are typically carried out using insufficient exploratory data. Use of a traditional estimation technique on limited data often produces an unreliable ore grade model. Kriging and its nonlinear variation, lognormal kriging, are frequently used in gold deposit modeling (Rendu, 1979; Journel, 1980); however, kriging is flawed by the smoothing effect. Moreover, though kriging is known to be globally unbiased, it is not free from conditional bias. As a result, if a deposit is modeled using the traditional kriging technique, a high-grade zone can be predicted to be a low-grade zone and vice versa. Predicting high grade as low grade results in a missed opportunity to exploit profitable ore. On the other hand, prediction of low-grade ore as high-grade ore might result in financial loss for a mining operation. Thus, the use of kriging for ore grade mapping of a gold deposit may not be recommended. Estimation techniques (including kriging) can produce an estimate with minimum error in a minimum-error variance sense. However, no matter which estimation technique is used for grade modeling of a highly erratic deposit like gold, the error margin is bound to be high. Therefore, any grade prediction made for an unknown location is associated with high uncertainty. Since various mine-planning operations, including derivation of grade tonnage curve, pit design and economic analysis of the deposit, are based on estimated grade rather than true grade, a mining project evaluation that depends upon estimation will be subject to considerable risk. Thus, the successful design of a mining project not only depends upon accurate grade estimates, but also upon accurate assessment of uncertainty, for predictive grade is equally important. Although the kriging standard deviation is used as an indicator of uncertainty for prediction, it is flawed by characteristics related to a data-independence property. This study, therefore, investigates the stochastic simulation technique of conditional simulation for ore grade modeling of a placer gold deposit at Nome, Alaska. It is expected that the research will provide a better solution to ore-grade deposit modeling than the kriging technique because (1) conditional simulation preserves spatial continuity as well as reproduces the data histogram, thus avoiding the smoothing problem; and (2) generation of multiple realizations helps to accurately quantify the uncertainty about grade values in the deposit.

Jan 1, 2009

By Jeff Easton, J Johnson, D. Foot

The Mina Santa Rosa mine in Panama was the victim of a mine closure 24 years ago that left the community in dire straits. The mine showed the potential resources of greater than 1M ounces of gold and 4.5M ounces of silver. Veragold Mining Company decided to reopen the mine and address all the issues that were involved in the startup of an historic mine. This paper provides methods to restore the community trust, provide a transparent process, and develop an environmentally sound flowsheet. Immense scrutiny surrounded the Tailings Storage Facility, and the company developed a plan focused on paste thickening and surface stacking to eliminate the need for a conventional tailings’ facility. Paste thickener principles and benefits are also provided.

Feb 1, 2024

By Michael Prince

"Managing slurry is a constant challenge for mining operations. Since slurries are not uniform, the challenge is complicated by varying rheology, velocity, temperature and pressure, all of which affect how the slurry moves through the pipeline and how destructive it is to the system it is flowing through. Picking the right equipment from the outset — the right size pipe, the right size pump and the proper valves for the application — allows mines to operate more efficiently. Better valve designs deliver multiple benefits — they can lower the cost of operations, reduce the amount of maintenance and associated downtime required and are better for the environment. Historically, modulating systems have used ball, plug and pinch valves to manage the flow of slurry, but each of these alternatives has limitations. Ball valves require ceramic lining in order to delay wear, and once a ball valve does wear, the entire valve must be replaced. Similarly, plugs in plug valves should be coated to perform in control systems, and whole valves must be swapped out upon wear. Pinch valves are expensive and only require replacement of the sleeve. However, sleeve replacement involves an extremely arduous process in which the valve is completely taken apart.Traditionally, designers have avoided using knife gate valves (KGV) in modulating systems because KGVs have not been able to hold up under the harsh operating conditions. The throttling that is required in some of these processes rapidly fatigues conventional KGVs, rendering them useless and in need of replacement. Fortunately, innovative design changes have the potential to change established views.Breaking new groundRecognizing the need for improved components, Victaulic took on the challenge of designing a valve that could withstand abrasive slurry systems for a much longer period of time. The first step in this process was to talk to miners, maintenance personnel, process engineers and operators in the field about the limitations of current offerings and then determine design specifications for an ideal replacement.Many of the responses to these inquiries were very similar and reflected challenges with current operations; the primary objective was to find a valve that would be lighter and cheaper than the valves currently in use. In theory, a lighter valve would be easier to replace, and since replacements need to be performed frequently, a cheaper valve seemed like the right idea."

Feb 1, 2019

By R. D. Ellison, D. K. Shukla, D. E. Stephenson

Seals for man-made penetrations into or nearby nuclear waste repositories require several unique capabilities not common to seals for conventional underground activities. Design criteria include long functional use, extremely low permeabilities of the seal zone (including adjacent disturbed rock), and the potential for retarding radionuclide travel. This paper summarizes comprehensive seal programs being conducted by D&apos;Appolonia for the Office of Nuclear Waste Isolation (ONWI) at Battelle, Columbus. The program schedule requires the first detailed conceptual design for a bedded salt site to be completed in 1982. Conceptual designs for other host media will follow as site exploration data becomes available. The design program is supported by a variety of office, laboratory, and field activities being conducted by ONWI subcontractors. An example is provided to illustrate the variety of efforts directed toward determining the extent of disturbance adjacent to penetrations as a result of in-situ and excavation methods. Also, the current "working design" for the shaft and tunnel seal system at the candidate Los Medanos thick salt site in southeastern New Mexico is presented.

Jan 1, 1981

By Louis Schaarschmidt, Helmut Mischo, Ibrahim Alsalamin

In order to store high-level radioactive waste underground, the German repository concept considers clay, crystalline and salt formations as suitable host rock materials (National Citizens’ Oversight Committee, 2024). The current research projects of the Chair Underground Mining Methods at TUBAF (Technical University Bergakademie Freiberg) in nuclear waste repositories mainly focus on storage within salt formations. In this scenario, the high-level radioactive waste is supposed to be packed into specifically designed containers and then transported underground and emplaced in horizontal storage drifts. The residual temperature of the radioactive waste leads to the question if there are optimization possibilities for waste handling, the storage and the long-term emplacement of such high temperature level waste. A deeper understanding of the heat transmission from the container into the host rock might lead both towards possibly shorter surface interim storage times as well as size optimization possibilities of the repository itself. TUBAF has conducted research that successfully proved that an optimized container positioning yields more favorable thermal patterns and can be achieved with conventional mining equipment.

Feb 1, 2025

By Frederick McNeill, Mahmood Khwaja, Benjamin Lundsted, David Polcari, Michael S. Schultz, Timothy Clougherty

The City of Manchester, New Hampshire, is embarking on one of its largest public works projects in history to construct a 12,000 foot long, large-diameter, conveyance tunnel through downtown Manchester. This area has challenging geology with undulating bedrock (granite, schist, and gneiss) profile overlain by fluvial deposits. Understanding the subsurface conditions is key to mitigating project risks, establishing plan and profile for the tunnel, and selecting the most cost-sensitive and technically appropriate tunneling method. This paper presents the project team’s approach for conducting the ground investigation, developing preliminary subsurface profile, and the considerations for selecting the tunneling method.

Jun 13, 2023

By Elias Apostolidis

Since 500 B.C. Mt. Penteli has been famous as white marble production site, which provided the birthstones for the construction of Athens Acropolis and Parthenon. The Aloula quarry belongs to ?Dionyssomarble S.A.?, a commercial and industrial marble company, which retreated after 1940. Disturbance in the site was minimal since then. In July of 1994 the reclamation started by a group of quarry workers from Paros, already familiar with traditional marble quarrying techniques, unchanged from antiquity to 1940. The project was complete in 1997. Our main objectives have been to show respect to the area and the art of people, to let nature guide our choices, to use only local stone as a construction means, to imitate the old construction rules and to turn the land use into amenity and civilization. Aloula quarry will become a site restored for amenity and civilisation, including ancient quarrying techniques. The restored quarry is already open to the public, though to a small number of visitors, and soon will become an amenity park and an open space museum of the ancient quarrying art.

Jan 1, 2002

By T. Murt, C. Oñate

In recent years, environmental considerations have played a prominent role in underground construction projects. The management and disposal of the muck produced by an EPB TBM is an important aspect of this topic. Soil conditioners with higher biodegradability and lower eco-toxicity have been specifically developed to comply with strict regulations in several countries around the world, with the goal of reducing the environmental impact of tunneling on soil, water, and living organisms. This paper highlights innovative sustainable soil conditioners and how they differ from traditional products. Additionally, environmental considerations for TBM projects around the world and in North America will be examined.

Dec 1, 2022

By F. J. Sotillo

The objective of this investigation was to determine the feasibility of using a high-pressure roll mill (HPRM) to improve the separation efficiency of dolomite from apatite in downstream operations when treating high-dolomitic pebbles. High-dolomite samples from four phosphate mines were used for the test program. The research work plan included sample characterization studies; INSTRON tests to develop preliminary crushing data; high-pressure roll mill evaluations to determine crushing parameters, such as feed rates, rolls speed and gap, and applied torque, pressure and energy; and screen, microscopy, and flotation studies to assess dolomitelapatite separation efficiency. The results of the HPRM tests show that commercial products for all four mines can be obtained. Recoveries of 74-82% of the P2O5 and rejections of 46-83% of the MgO were reported with an specific energy consumption of 0.2-0.5 of that of a laboratory rod mill.

Jan 1, 1998

By K. E. Yassin, A. Yehia, M. Amar

Phosphate ores are the source of many commodities, such as phosphorus element, P2O5 and fertilizers. Discarding a large percentage of fine phosphate particles produced as slimes during phosphate ore processing represents a severe environmental problem, besides making the beneficiation process uneconomical. The phosphate industry is interested in a process that is efficient, with high grade and high recovery; ensures economical feasibility, with low operating cost; and is environmentally sound, with low toxicity. Numerous investigations have been conducted to try to find better processing techniques and reagents. However, reagent requirements and recovery limitations may be so high that the end does not justify the means. Reagents of biological origin are of special interest because they offer specific interactions with minerals, reduced operating costs, environmental acceptability and flexibility in adaptation. Recently, there has been a growing interest in using microorganisms as flocculants for mineral fines and as flotation collectors. 

By Xuezhong Wang, Hao Guo, Tao Tu, Qingsheng Liu

The scheelite concentrate was leached with a mixture of sulfuric and oxalic acids. Chemical compositions, mineral phases, and morphology were characterized by XRF, XRD, and SEM–EDS. Based on the results of the single-factor experiments, the response surface methodology (RSM) was chosen to optimize the leaching parameters: temperature, time, and concentrations of sulfuric and oxalic acids. The RSM results indicate that the optimum values for those parameters are as follows: temperature 72 ℃, sulfuric acid concentration 1.48 mol/L, oxalic acid concentration 0.96 mol/L, and reaction time 2 h. Under the optimal leaching conditions, the model predicts a maximum leaching yield of 99.5%, compared to the value of 99.1% obtained experimentally, that is, a discrepancy of only 0.04%. This good correlation shows that the quadratic polynomial equation obtained by the RSM optimization is reliable. The importance on leaching parameters of scheelite is, in decreasing order, temperature, time, sulfuric acid concentration, and oxalic acid concentration.

Oct 11, 2021

By Bill Dershowitz

Consider a deep gold orebody with grade of 4 g/t (0.11 oz/st). At the time of this writing, with gold prices at historic highs, it could be a good, but not great, prospect. But if it is a vein deposit, and those veins are 200 g/t (5.8 oz/st), it would be significantly more attractive if there was a way to produce directly from those veins, leaving the rest of the rock in place. [Figure 1 The red around each of the four injector wells shows areas of high pressure, where the lixiviant fluid is pumped into the rock mass, with orange and yellow indicating dissipated pressure. The black lines indicate some of the fracture pathways through which the lixiviant, with absorbed metal, flows toward the central recovery well where low pressure is indicated in blue. Lixiviant is pumped out through the recovery well. Image courtesy of Golder Associates.] There is a way to do this, in situ leach (ISL) or solution mining. It has been a viable commercial technology for more than five decades.

Jan 1, 2011

By Jue Kou, Hongda Xu, Tichang Sun, Shichao Wu, Wenli Han

To investigate the effect of simultaneous change in particle size of raw materials (including ore, reductant, and dephosphorization agent) on the direct reduction process of high-phosphorus oolitic hematite, the experimental research of method with direct reduction and magnetic separation was conducted to investigate the effect of simultaneous change in particle size of raw materials on the final reduction products in the form of mineral composition, reduction speed, metallic iron particle morphology, phosphorus distribution, and powdery reduction iron. The results revealed that under the same conditions of reduction temperature, the raw material particle size affects the mineral composition of the final reduction product, the coarser the raw material particle size, the slower the reduction speed, the lower the metallization rate, and the larger the final metallic iron particle size formed. Under the same conditions of raw material particle size, the reduction temperature affects the mineral composition of the final reduction product, the higher the reduction temperature, the faster the reduction speed, the higher the metallization rate, and the larger the size of metallic iron particles within a certain reduction time. Neither the raw material particle size nor reduction temperature affects the form of phosphorus present in the reduction product. Both the raw material particle size and reduction temperature affect the grade of powdery reduction iron to a less extent, but affect the recovery rate and phosphorus content significantly. At the same reduction temperature, the recovery of powdery reduction iron and phosphorus content gradually decreases with the increase in raw material particle size. For the same raw material particle size, the recovery of powdery reduction iron gradually increases, and the phosphorus content gradually decreases with the increase in the reduction temperature. The results identified the effect of simultaneous changes in particle size of raw materials on the direct reduction process of high-phosphorus oolitic hematite and provide a basis for the selection of raw material particle size for the industrial application.

Dec 20, 2022

By Ying Lu, Jeffrey C. Johnson, Chen-Luh Lin, Jan D. Miller, Sindhoora Puvvada

The amount of energy used to break rock is of interest in mine-to-mill operations to minimize energy consumption during blasting at the mine site and comminution at the processing plant. In this research, a direct energy measurement was made using high-velocity impact to cause breakage of long granite cores, and to study the energy dissipation along the entire bar length. The results show the formation of three zones of damage — fragmentation, fracture and elastic — that have been characterized in 3D using X-ray tomography. The fragmentation zone of the granite bars was studied in detail to describe the particle size distribution and the particle shape characteristics. The experimental energy dissipation in the fragmentation zone was found to be in close agreement with the expected energy calculated from the Bond work index (BWI) equation [1] when the anisotropic granite particles in the fragmentation zone are defined by length rather than by sieve size. The results increase our understanding of rock breakage and energy consumption and may find future applications in mine-to-mill operations.

By P K. Kaiser, D A. Malovichko

Highly stressed excavations in hard brittle rock may fail by self-initiated, triggered or dynamically loaded strainbursts (Moss and Kaiser 2021). The low-frequency part of seismic radiation associated with strainbursts is described by a crush-type seismic source mechanism with a significant negative (implosive) isotropic component and a ‘pancake-shape’ CLVD deviatoric component. The seismic source is co-located with the excavation damage site. For such strainbursts, the ejection velocity is primarily related to the depth of strainbursting, the rock mass bulking characteristics, the duration of the bulking process, and the effectiveness of the support system. For dynamically loaded strainbursts, the displacement and energy demand may be augmented by the impact of the stress wave from a distant seismic event. This article describes the failure process and factors contributing to rock deformation and energy demands for support design. Case examples are used to demonstrate the dependence of rock displacements, rock ejection and energy demand on the factors described above. A seismic source model is proposed to assess the depth of strainbursting and the duration of the related bulking process by using seismic monitoring data. The implications for support design are briefly discussed.

Apr 26, 2022

During the past year a number of significant advances in geostatistics have been published. These were presented at the 13th APCOM Symposium in Clausthal, Germany and at a NATO Advanced Study Institute on Geostatistics in Rome, Italy. Of greatest importance is the work that has been done in establishing methods which correctly predict the cutoff grade-tonnage curves, and the average grade of ore-tonnage curves for deposits in which ore and waste are intermingled. Grade-tonnage curves based on estimates made from widely spaced exploration data have been found to underestimate the grade of ore and overestimate the tonnage present. This problem has been remedied by the calculation of conditional probability distributions for the unknown grade of a block. Another advance has been made in the field of geostatistical estimation for deposits in which a trend is present. Previously a technique known as universal kriging has been used, which involves much subjective judgement as to the trend fitted. A new technique, generalized increments, allows computer estimation of such deposits with much less subjective judgement. Computational efficiency of geostatistical methods has continued to improve to a point where a geostatistical estimate can be obtained for little more than the cost of any other computerized method.

Jan 1, 1976

By David J. Hatem

Public-private partnerships (PPP) are gaining in popularity at the federal, state and local levels as the public sector seeks private capital to finance infrastructure and other projects that traditionally have been funded with public funds. In general, a PPP involves a development agreement between a public owner and a private sector concessionaire. Under the development agreement, the concessionaire is responsible for financing, designing, constructing and typically operating and maintaining the completed project for a concession period (often multi-decades in duration). The concessionaire typically enters into an agreement ? the design-build agreement ? with a design-builder to design and construct the project. The concessionaire may secure financing from banks, investors or from a combination of these and other sources (collectively the financier). While the PPP experience in the United States has been modest to date, an increasing number of projects involving tunneling or other significant subsurface work are already being delivered in the PPP mode. Public owners have significant options to address risk allocation for subsurface conditions on PPP projects. The same sound and fundamental principles of fairness in risk allocation that apply in other major subsurface projects should be applied and adopted in the PPP context

Mar 1, 2014

By G. ALBORNOZ, S. Utili, A. AGOSTI, C. VALDERRAMA, R. PELL

The steepness of an openpit mine’s slopes has a substantial influence on the mine’s financial return. This paper proposes a novel design methodology where overall steeper pitwalls are employed without compromising the safety of the mine. In current design practice, pitwall profiles are often planar in cross section within each rock layer: that is, the profile inclination across each layer tends to be constant. Here, instead, a new geotechnical software, OptimalSlope, is used to determine optimal pitwall profiles of depth-varying inclination. OptimalSlope seeks the solution of a mathematical optimization problem where the overall steepness of the pitwall, from crest to toe, is maximized for an assigned lithology, geotechnical properties and factor of safety (FoS).