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By Ing. E. h. Martin Herrenknecht, Werner Burger

In recent years, there has been a dramatic increase in the number of machine driven soft ground tunnelling projects. This increase is largely due to the technological development of slurry and EPB Shield systems. A new generation of soft ground tunnelling machines, markedly different from those of five years ago, now overcomes ground conditions that until now were too costly and impractical to undertake. The paper reviews the latest soft ground tunnelling machine developments in material transport, guidance and control, seismic surveying, soil conditioning, settlement control, cutting tool applications and variable mode operating systems. Specific projects where this technology has been applied will be highlighted.

Jan 1, 1999

By Herbert F. Nyberg

The Black River Falls Mine is owned and operated by Jackson County Iron Company, a wholly owned subsidiary of Inland Steel Company. It is located in vest central Wisconsin, seven miles east of the city of Black River Falls. This is the first taconite plant in the state of Wisconsin. Iron mining started in this area in 1856 but soon failed due to the low grade ore and crude methods of mining and transportation. Inland Steel Company acquired the property in 1939. Some drilling and test work was done in 1940, but the economics of developing the property at that time were not favolable. Improved methods of concentrating and pelletizing in the 1960's made it possible to build the present plant. Due to the limited ore reserve of 45,000,000 tons with expected recovery of 33% it was necessary to limit the capacity of the operation to 750,000 TPY with a life of 20 years. There was some concern about an operation of such limited capacity. A million ton operation was considered the minimum size plant for a profitable operation.

Jan 1, 1976

By J. C. Haptonstall

The Bismark Mine is located in northern Chihuahua, 150 km southwest of Ciudad Juarez. The ore deposit was discovered in 1979, and was placed in production in 1992. The production rate is about 2400 tpd from an ore reserve of 8.5M tonnes. Grades average about 8 % Zn, 0.5 % Pb, 0.2 % Cu and 50 g Ag per tonne. Substantial inflows of water into the under-ground mine complicate the operation. Complex metallurgy poses another challenge for the operators. Bismark was operated through a joint venture, Minera Bismark, S.A. de C.V., with U.S. and Mexican partners, but since early 1993, it is wholly Mexican-owned and operated.

Jan 1, 1994

By J. R. Sims

Gold assays from production blastholes in the Mercur Hill Pit were used to delineate known ore zones and to determine how well previous exploration drilling defined these zones. The most important factors causing inadequate ore zone definition were: 1) inappropriate location of drill holes relative to the ore zones, 2) presence of stopes from previous mining, 3) sampling and assaying errors, and 4) smoothing of the ore zone boundaries during ore reserve estimation. Infill drilling strategies were evaluated to determine the efficiency with which a given drill pattern defined the known ore zones. A drilling strategy was developed which improved ore zone delineation when compared to techniques which maintained uniform drill spacing.

Jan 1, 1992

By Steven J. Schatzel, James Addis, K. Vaibhav Raj, Berk Tulu

The National Institute for Occupational Safety and Health (NIOSH) is conducting research to enhance methane control and mine ventilation practices at coal mines, as a method to mitigate hazardous work conditions. NIOSH researchers conducted case studies to investigate the effectiveness of existing systems and improve performance to decrease the potential for unplanned or excessive methane emissions. At one mine, drainage was influenced by hydrofracking inefficiencies where two of the six wells showed good frack development. Methane content was variable, from 300 ft3/t to 600 ft3/t. This paper also summarizes overburden movement during undermining and the estimated quantities of gas transported to the mine using FLAC3D and CFD modeling. The findings from this research effort highlight considerations based on specific mine conditions that may also be applicable to most longwall mines utilizing methane control systems.

Feb 1, 2025

By L. C. Lang

INTRODUCTION The introduction of 165-mm (61/z-in.) holes to underground mining operations has made possible the application of Canadian Industries Ltd's (CIL) vertical crater retreat (VCR) mining method, illustrated in the accompanying sketches. This unique and revolutionary new application of spherical charge technology (see the Appendix), when applied to primary stopes and pillar recovery, eliminates raise boring, slot cutting, and dilu¬tion of ore by backfill; greatly improves fragmentation; reduces labor and time requirements; eliminates uphole drilling and blasting; and minimizes or completely elimi¬nates damages by blasts to the walls and retreating backs of the stope or pillar. If vertical large diameter holes are drilled on a designed pattern from a cut over a stope or pillar to bottom in the back of the undercut, and spherical charges of explosives are placed within these holes at the calculated optimum distance from the back of the undercut and detonated, a vertical thickness of ore will be blasted downwards into the previously mined area. Repeating this loading and blasting procedure, min¬ing of the stope or pillar retreats in the form of horizontal slices in a vertical upwards direction until the top sill is blasted and the mining of a stope or pillar is completed. The VCR method is also applicable to drop raises and has the potential to replace all other raising methods under most circumstances. PILLAR RECOVERY Levack Mine Inco Metals Co., Ontario Div., provided the first opportunity for the method in pillar recovery. The Levack mine's high grade ore pillar No. 4800 on the 975-m (3200-ft) level was used for the production¬scale experiment (Figs. 1 to 3). The pillar was about 49 m (160 ft) long, 6 m (20 ft) wide, and 20 to 26 m (65 to 85 ft) high. The mined area on both sides of the pillar was backfilled with a 1:30 cement:sand mixture. The pillar was removed in two phases. In phase 1, the standard uphole method was used to blast down the 18-m (60-ft) long section of waste from the bottom of the ore into the undercut. From the pillar's top sill, 165-mm (61/a-in.) holes were drilled downward into the pillar, and by measuring the depth of the holes, the results of the uphole blast were determined and roof line 1 was established. The bottom of each hole was plugged, then filled with sand to place the center of gravity of each spherical charge (loaded from the top sill) at a predetermined optimum distance from the horizontal free surface. The charges were then detonated. After detonation, both draw drifts were full of extremely well-broken material. The depth of each hole was measured again, and the plot of these depths re¬sulted in roof line 2. The same blasting procedure was repeated and the resultant new back elevation was marked by roof line 3. The poor results of the initial uphole blast at one location (notice the peak in area 1) appeared to influ¬ence the subsequent new backs. A third blast success¬fully evened the back, and resulted in roof line 4. An unblasted slab averaging 6.3 m (20.9 ft) thick remained below the pillar's top elevation as the final sill. In all three spherical charge blasts fragmentation of the blasted material was extremely fine. The backfill was fully exposed on both sides of the now-blasted pillar. The backfill remained undamaged and the ore was not diluted by sand. The remnants of all the 165-mm (61/2 -in.) holes remained clean and undamaged, and the holes had well-defined bottoms that could be easily measured and plugged. Each blast took down a 3.9 to 4.2-m (13 to 14-ft) thick horizontal slab of ore. Productivity was three times greater than that of the previously practiced cut-and-fill method. Since this was the first such experiment, blasting the remaining 6-m (20-ft) thick final slab was the sub¬ject of some deliberation. If the described method was repeated, we could have ended up with a 1.8-m (6-ft) thick sill unsafe to work on. It was therefore decided to blast the whole sill using two spherical charges prop¬erly placed in each hole, but with the application of

Jan 1, 1982

By B. Birol, M. N. Saridede

"Slag density is a significant factor in determining the process efficiency of the electroslag remelting (ESR) process, where calcium fluoride (CaF2)-based slag is formed synthetically to refine metal ingots. Although there are some former studies investigating the density of CaF2-containing slags, the prediction models focusing on them are applicable only to some specific systems. The present study aims to build a model to predict density for a wide range of CaF2-containing ESR slags. To investigate density for various slag compositions, CaF2-Al2O3-based and CaF2-Al2O3-CaO-based slag compositions were prepared. Additionally, some minor constituents like FeO, MgO and MnO were added to a 5:3:2 CaF2-Al2O3-CaO slag in order to investigate the effects of these constituents on the slag. The volumes of the prepared slags were measured in a tube furnace at 1450-1550 °C using the sessile drop technique, and their densities were calculated. The results showed that for the slags, density is related to optical basicity, and therefore a prediction model based on an Arrhenius equation was built. The model was tested with data from literature, and its limitations and validity are discussed.IntroductionThe electroslag remelting (ESR) process is a refining method in which a metal ingot is remelted under a synthetic slag. These synthetic ESR slags are mainly composed of calcium fluoride (CaF2), calcium oxide (CaO) and aluminum oxide (Al2O3). Other constituents like iron oxide (FeO), magnesium oxide (MgO), manganese oxide (MnO) and chromium oxide (Cr2O3) are added to this system in relatively low amounts, according to the type of steel ingot to be refined. The prediction of slag properties, such as electrical conductivity, viscosity and density, is crucial for the selection of the synthetic slag in order to obtain the required process parameters, like temperature, the passing time of the molten metal droplet through the slag, and metal-slag separation (Akbari, Reitz and Friedrich, 2009; Hara and Ogino, 1981; Mattar, El-Faramawy and Fathy, 2002; Mehrabi, Rahimipour and Shokuhfar, 2005; Presoly, Korp and Schneider, 2008).As slag density affects metal-slag separation in the ESR process, predicting the density of an ESR slag is important for appropriate refining and improved product quality. Although there are many studies investigating the density of slags (Akbari, Reitz and Friedrich, 2009; Aune, Hayashi and Sridhar, 2005; Hara and Ogino, 1981; Matsushita, 2011; Mills and Keene, 1987, 1981; Seetharaman et al., 2013; Shu, 2007; Shu and Chou, 2013; Sikora and Zielinski, 1974; Xu et al., 2012; Zhang and Chou, 2010), the prediction models built are generally valid for oxide-containing slags (Aune, Hayashi and Sridhar, 2005; Bottinga and Weill, 1970; Mills and Keene, 1987; Seetharaman et al., 2013; Shu, 2007; Xu et al., 2012; Zhang and Chou, 2010). These models were built on either the molar volumes of the constituents (Bottinga and Weill, 1970; Mills and Keene, 1987) or the thermodynamically calculated enthalpy or free energy of mixing, which can be applied to a system containing constituents sharing an ion, such as an O- ion for oxide systems (Aune, Hayashi and Sridhar, 2005; Hillert, 1980; Persson et al., 2007). Some recent studies modeled the density of some oxide slags on their optical basicity (Shu, 2007; Shu and Chou, 2013; Xu et al., 2012; Zhang and Chou, 2010)."

Jan 1, 2016

By Yushuai Xian, Youjun Tao, Fangyuan Ma

This study compared particle size distribution and density distribution of crushed products for waste printed circuit boards (WPCBs) before and after heat treatment. The crushing process for heat-treated WPCBs is a selective crushing process; more metal is concentrated in the coarse particle range of 1.0–0.5 mm and high density range of 2.8–2.96 g/cm3. WPCBs were separated using the Falcon separator to recycle useful metals. The Box-Behnken module of Design-Expert was used to obtain optimal separation parameters, namely, rotational frequency of 25 Hz, recoil water pressure of 0.025 Mpa and feed speed of 34 ml/s. On this basis, the separation indexes for WPCBs with and without heat treatment were compared. Experimental results show that the recovery effect is better for heat-treatedWPCBs than for thosewithout heat treatment. Comparedwith the non-heattreatedWPCBs, the product grade of heat-treated WPCBs is 1.95% higher, and its recovery is improved by about 14%. Finally, characteristics ofWPCBs before and after heat treatment were analyzed on the basis of stress experiments and scanning electron microscopy (SEM), respectively. Results of mechanical characterization indicate that the stress experiment for non-heat-treated WPCBs has a maximumpressure load of 212 N and displacement of 20mm, but heat-treatedWPCBs only need 140 N stress and 14 mm displacement. SEM shows that copper foil and fiberglass cloth are deformed in different directions and sizes after heat treatment to form gaps, which promote liberation of copper foil and fiberglass cloth.

Sep 10, 2020

By Mike Ghassemi

It is clear that precise overground and under-ground mapping is an important factor for all designers. Due to rapid changes in underground construction, tunnel designers are increasingly in need of updating project information. This article explains the latest techniques for detecting under-ground utilities as well as underground mapping. Global Positioning System (GPS) is a very ac-curate and popular navigation and mapping system that has been used extensively above ground, but is not used for underground mapping as signals are not strong enough to pass through ground or water. Most underground techniques were developed for military applications during the first and second world wars. Later, the techniques became public. For example, ground penetrating radar was developed for the military in 1970 to be used for locating tunnels under the demilitarized zone between North and South Korea. Later, the same technique was used for detecting unexploded ordinance such as plastic land mines.

Jan 1, 2011

The National Institute for Occupational Safety and Health (NIOSH) conducted field tests to evaluate the effectiveness of a wet head continuous mining machine for reducing dust exposure for continuous miner operators. Wet head technology delivers water via sprays to the continuous miner?s cutter head as opposed to traditional standard sprays located on the boom and body of the mining machine. The sprays, positioned directly behind each bit on the cutterhead, deliver water at the point of attack, serving to cool the bits during mining to reduce the potential for frictional ignitions. The sprays also flood the coal with water to potentially suppress dust generation. Dust surveys were conducted at several mines to evaluate the wet head?s effectiveness to control respirable dust exposure at the continuous miner operator location and in the immediate return. Results show that the wet head miner generally improved air quality at both sampling locations to varying degrees in some, but not all, mines when compared to a continuous miner with a standard spray system.

Jan 1, 2010

By Robert D. Saltsman

The inadequacy of our knowledge of the coal combustion process has long been recognized. This was expressed very well by Spicer and Finney (1). "The control of combustion processes in industry and the design of the equipment necessary for efficient burning to take place have always been very much branches of an industrial art rather than of an exact science. This has been especially true of the utilization of coal, a substance so hetrogeneous and complex in character that all too little is known about its chemical and physical composition.' During the past several years one branch of coal utilization, that of high temperature carbonization; has made significant advances from being an art into being an exact science. This has been accomplished by the development of petrographic techniques for identifying, measuring, and determining the thermal properties of the organic materials which affect the carbonization of coal and the correlation of this information with a pre-existing standard of coke quality, the stability index.

Jan 1, 1964

By ANDREW HOBERT, Maoming Fan

Low-cost and environment-friendly green froth flotation modifiers of plant origin, such as guar gum, carboxymethyl cellulose (CMC), and starch, have been used in flotation of some sulfide and non-sulfide minerals. Certain green modifiers may be used as dispersants, flocculants, depressants, or activators. The functions of green modifiers in froth flotation highly depend on their molecular composition, flotation slurry chemistry, hydrodynamic conditions, etc. This paper will discuss the fundamentals, current applications, and potential new applications of guar gum, CMC, and corn starch in valuable minerals (phosphate, potash, and iron ores) and the unwanted gangue minerals (silica and clay minerals) flotation. In this study, improved flotation performance was achieved using some green modifiers in flotation columns with the more plug-flow environments than in conventional flotation cells approaching perfectly mixed conditions. This is because the hydrodynamic cavitation-generated ultrafine bubbles could help bridge ultrafine particles to form aggregates, promote the formation of flocs, and increase the stability of flocs.

Jan 6, 2022

By Madan M. Singh

A new mining project can raise questions about what effect it will have on the community after it closes. Historically, little was done by communities to plan for and accommodate the changes in the economic infrastructure when a mine project is finished either after the ore runs out or if market conditions deteriorate and make it unprofitable. Projects that were underfunded were generally unable to withstand periodic market downturns. However, data in a recent study conducted by the Seidman Research Institute leads to the conclusion that, even when a mining project is terminated, there can be (and, in the specific case studied, is) a residual beneficial economic effect in the community, which lasts for a long period of time.

Jan 1, 2010

By A. Bhattacherjee

Industries in general and the mining industry in particular have become more safe than ever before. However, there is a need to increase the search for the causes of mining work-related injuries and to contribute to their reduction through job design, work procedures, and worker training. Mine accident and hazard control has to be practiced in a manner which is consistent with the overall objectives of the mine management, among which are the optimum allocation and effective utilization of the resources. The purposes of this paper are to (i) review the role risk analysis in safety management with references from mining and other industries; (ii) discuss the risk measures appropriate for injury analysis; (iii) present a set of analytical tools to injury experience data in under-ground coal mines; (i v) apply these tools on case study example; (v) discuss the results of the case study; and (vi) amplify the application limitations and the future research needs.

Jan 1, 1991

By William Gleason

For the first time in many years, the Liebherr Group chose to host its annual conference for the international construction trade press in the United States. The reason for the move is simple ? mining. Like other large corporations, especially those in the construction fields, Liebherr felt the effects of the global economic crisis that began in 2008. The slowdown in the housing market was especially hard on Liebherr?s mobile crane and earth moving divisions. The mining division, however, while affected by crashing commodity prices that led to cancelled orders and the loss of financing for some customers, was not battered as badly as the other divisions. And now, with the price of commodities once again on the rise, it seems that it will be Liebherr?s largest machines that lead the family-owned company to better days. ?We can report that our generally optimistic view during the crisis has proved adequate,? said Joachim Janka, president of Liebherr mining equipment, at the conference in Williamsburg, VA, just down the road from the company?s mining truck division global headquarters in Newport News, VA. ?Since the third quarter of 2009, our mining equipment activities have been recording once more a strong and steady demand. This has already yielded a substantial increase in market shares for our product lines of large mining shovels as well as for mining trucks.?

Jan 1, 2011

By Abdelaziz Baçaoui, Imane Aarab, Mohammed Derqaoui, Abdelrani Yaacoubi, Khalid El Amari, Abdelmoughit Abidi, Abderahman Etahiri

Numerous researchers have addressed the complexity of the direct flotation separation of apatite from low-grade phosphate ore. The majority of these studies were limited to the micro-flotation scale. In fact, there is no warranty that a reagent scheme that showed a direct flotation of apatite at a micro-flotation scale on pure minerals would automatically replicate the same expected results on the natural ore in the mechanical flotation cell and so was the case for the phosphate ore studied. The overall trend was concentrating apatite in the non-float product. This study aspired to thoroughly assess the flotation performance of this never-exploited low-grade sedimentary phosphate using design of experiments (DOE). Unveiling new insights on such a strategy twist, various parameters and operating conditions, namely, desliming, type of collector and depressant, reagents dosages, conditioning times, flotation time, and pH, were addressed by multiple-factor screening using asymmetrical fractional factorial design followed by statistical interpretations. The collectors tested were the sodium oleate and a fatty acid mixture (FAM). The depressants tested were sodium alginate (NaAL), corn starch, carboxymethylcellulose (CMC), and sodium silicate. The results of the multivariable analysis revealed that desliming, pH, collector dosage, and flotation time significantly influenced the flotation process. Desliming was beneficial for the yield, P2O5 recovery, and SiO2 removal; however, there was still a compromise between grade and recovery. A strongly alkaline pH value of 12 stood out from the whole range. P2O5, CO2, and SiO2 grades of the products and flotation recoveries were improved, except for P2O5 recovery, which was negatively affected. A collector dosage between 2000 and 3000 g/t increased the P2O5 grade and reduced CO2 grade and recovery, enhancing the apatite/carbonates separation. A flotation time of 15 min was significant for P2O5 grade and CO2 recovery, nevertheless, at the expense of yield and P2O5 recovery. The products having initial concentrates of 28.08% P2O5 with a recovery of 88.96% and 29.41% P2O5 with a recovery of 62.71% were obtained using 25 g/t of NaAL and 2000 g/t of the collector FAM and sodium oleate, respectively, at pH 12.

Jun 5, 2022

By K. P. Wang, Ta M. Li

The Chinese energy and mineral industries are readying themselves for a period of dynamic transition, unprecedented in the country's long and sometimes turbulent history. The transition comes as a result of the government's new program of "Four Modernizations" in its agricultural, defense, industry, and science and technology sectors. The announced program is generally considered by Western observers to be a moderate, pragmatic approach to get China on the road to industrial parity with Western nations by the year 2000. The game plan calls for integration with the West to beef up Chinese know-how and the purchase of foreign technology to supplement areas where China lacks the ability to do so itself. While the role of energy and minerals is not specifically mentioned in the program, it was made clear to ME that China realizes the basis of any sustained modernization program is tied closely to the health of its minerals sector. Various published reports have indicated the existence of an already vibrant energy and minerals sector with world rank production in coal, iron ore, tin, antimony, cement, pyrite, asbestos and tungsten to name just a few. For the most part, except for the export metals, the primary focus of China's production has been on fulfilling domestic needs. Now the new initiatives are aimed not only at self-sufficiency, but also on propelling the country's natural resource clout into international prominence. With a mineral resource base that is considered by many westerners a potential bonanza, China's new long march toward modernization will be an exciting adventure, well worth watching. Big Projects Spark Excitement China's renewed commitment to a more liberal program is as much a desire to "walk on its own two legs" as it is a backlash from the frustrating years that followed the Cultural Revolution of the 1960s and early 1970s. Much of the early excitement was initiated by China's Premier and Party Chairman Hua Guo-feng in speaking to the fifth National People's Congress (NPC) in 1978. Here, Chairman Hua presented the Communist Party's 10-year blueprint for economic development. Specifically, the Party's plans called for completion of 120 large-scale industrial projects by 1985. Mentioned were 10 new iron and steel works, 30 power plants, six new railways, 10 oil and gas fields, nine nonferrous metal

Jan 3, 1980

By Mahmud Esad Uluer, Seyed Hassan Amini, Aaron Noble, Matt Shigo

Airborne coal mine dust is an unintended and unavoidable result of coal extraction operations that raises notable health and safety concerns. Modern mining techniques utilize several dust mitigation strategies, and the flooded-bed dust scrubber (FBS) is one such technology used extensively on continuous miners. The conventional static panel filter, instrumental in most scrubber designs, is fundamentally limited in collection efficiencies due to a high clogging rate and a tradeoff between mesh density and airflow rate. To overcome these deficiencies, a novel vibrating mesh panel is proposed. In this study, a laboratory-scale dust scrubber unit was used to investigate the efficacy of concept as compared to that of a static mesh. A statistical design of experiments study was first used to determine the effective vibrational parameters and scrubber operational parameters on dust collection and clogging mitigation. Optimized results from this study were then evaluated against those of a static mesh to determine performance improvement while investigating the mechanisms controlling dust collection and particle department through the scrubber system. Results show that the vibrating mesh conditions and higher water flow rates led to an improvement in the collection efficiency of the scrubber system. Compares to a static-mesh, the vibrating mesh FBS showed a significant reduction in pressure drop across the mesh screen indicating lower air loss through the test duration. Overall, the findings confirm that vibrating filter mesh reduces filter clogging while maintaining high collection efficiencies. This research supports further technological advancement in mine dust mitigation technologies.

Dec 27, 2023

By Lynn B. Hales

Unfortunately, the term "control" has a negative connotation in the minds of many of our operating plant personnel. Whereas the opposite is true of those associated with research and technical centers in our industry. The magnitude of this difference in opinion and actual experience has often proved to be a major factor influencing the success or failure of process control applications. Through the years, many plant people have endured a number of unsuccessful attempts by "outside" people to "optimize" their plants; and these experiences have proved to have had quite a callousing effect on them. On the other hand, in many plants, successful process control efforts have made firm allies of the operating personnel, and have increased the number of metallurgical people who are well qualified and experienced in process control. The instrumentation industry, computer industry, and the mining industry's ability to quantify what is really happening in our processes have grown and developed rapidly since the first control efforts were made in the 1930's (1). Because of this-,: new control opportunities are becoming increasingly more feasible and older well established ones are becoming even more practical and necessary with regard to the economic s of our industry.

Jan 1, 1979

By S. Healey, P. Jean, G. Deschenes, M. Fulton

Three years ago, the New Britannia Mine started a project to improve productivity of its cyanidation plant. Results indicated that gold dissolution was strongly influenced by sulphide minerals and that the slower gold dissolution rate had a detrimental effect on overall gold recovery. The leaching strategy had to be modified to address this issue. Changes to the leaching circuit proved to be very successful. The first action was to introduce lead nitrate in the leaching circuit. The strategy of addition of lead nitrate was upgraded in three steps. An on-line free cyanide analyser was installed and the strategy of cyanide addition automated. The enhancement of the leaching kinetics have resulted: an 4% increase of gold recovery, from 87.8% in 1996 to 91.9% in 1999, which represents a reduction of 0.17 git Au in the leach residue; an average of 1330 additional extracted gold ounces per year from 1997 to 1999; a 21 % reduction in the cyanide consumption; the shut down of the cyanide destruction plant; and finally a contribution to the 27% reduction in the overall production cost per tonne of ore.($ 3 per ton). The significant increase of the throughput was instrumental in the reduction of the processing cost. In 1999, the improvement of gold recovery represented an additional gross revenue of $c""l.9 Million. The project is discussed in details in this paper.

Jan 1, 2000