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By Carlos Torres, Albert Cabrejo

For the last 20 years mine slopes have been monitored with slope stability radars. Since 2015 a group of dedicated geotechnical engineers dedicated to remotely monitor radars around the world have detected 2000+ slope failures of different characteristics. A statistical analysis of the information gathered of these failures have been made and the summarized results are presented with some degree of analysis appropriate for the vastness of the database. The analysis considers different types of commodities, countries, mining processes, rock types, and weather conditions.

Sep 29, 2023

By Seunghoon Lee

The increase in the number of higher and larger buildings is expected to require the buildings' outer wall maintenance process, which includes cleaning, painting and monitoring, still depends on manpower. In this study, we proposed the robotic building maintenance system and aimed to reduce the jerk effect through the motion control of the system, improve the performance of the maintenance task, and ensure longer life and safety by improving the stability of the building structure and robot system. Through the results of the motion control and field-test with the proposed system, in specific, horizontal sliding module (HSM) showed that the jerk oriented by impact force was significantly reduced, feasibility of the proposed method was verified, and the robotic challenges were explored.

Aug 1, 2013

By Xu Linsheng

Datong coal Mine suffers from delays and sudden caving of its massive competent conglomerate roof. Detailed geological studies of the nature of pebbles and matrix of the conglomerate and its sparse bedding, joint and fracture structure, gave rise to investigation of water injection to destroy its strength and to control caving. Comparative investigations, including porisity, permeability, compressive strengths and water injection of conglomerate and sandstone led to empirical expressions relating various properties and to guidance for effective injection and caving practice. This new safe roof control practice should be even more improved with further research, including modelling.

Jan 1, 1992

By Yongjin S

Datong coal Mine suffers from delays and sudden caving of its massive competent conglomerate roof. Detailed geological studies of the nature of pebbles and matrix of the conglomerate and its sparse bedding, joint and fracture structure, gave rise to investigation of water injection to destroy its strength and to control caving. Comparative investigations, including porisity, permeability, compressive strengths and water injection of conglomerate and sandstone led to empirical expressions relating various properties and to guidance for effective injection and caving practice. This new safe roof control practice should be even more improved with further research, including Modelling.

Jan 1, 1992

By Chengcan Wang, Jin-Tae Han, Young-Eun Jang

"The waveform micropile is a newly developed foundation type for increasing the bearing capacity with the created shear keys on the pile’s shaft. Analyzing the increment of resistance at the shear key zone is a crucial factor in the design of the waveform micropile. Hence, centrifuge tests were carried out employing six different models, including a waveform micropile in the axial loading condition. The analysis results of the load-settlement curves showed that the waveform micropile achieved a higher bearing capacity compared to the micropile without shear keys. In addition, the test results revealed that the load-settlement relationship was affected not only by the pile shape but also by the locations of the shear keysINTRODUCTIONA micropile is a small-diameter pile, typically constructed with a less than 300 mm diameter. Generally, the micropile’s construction involves drilling, grouting, and insertion of a reinforcement material, such as a thread bar. The micopile can be utilized in a variety of fields for reinforcing the foundations of existing structures. It also has advantages for accessing challenging areas like limited-access construction sites, including those with a low headroom space and adjacent structures, due to the small size of the construction equipment. Thus, since it was introduced in 1950 in Italy, the micropile has become one of the preferred solutions when other deep-foundation methods are not applicable to the site.Federal Highway Administration (FHWA) gives the micropile design implementation guideline of neglecting the end bearing due to its small diameter but considering the frictional resistance if the bond zone of the pile is in the soil or on a weak rock. The bearing capacity is considered primarily only if the micropile is founded on a high-quality sound rock (FHWA, 2005). Micropile design in South Korea is currently being performed based on the FHWA manual and taking into consideration the frictional resistance for the design as the pile generally sockets into a weak rock or soft rock. Moreover, the frictional resistance within the soil layer has usually been ignored, considering only the shaft resistance of the rocksocketed length in the conservative design. The design concept excluding the frictional resistance in the soil layer, however, may lead to an extension of the pile socket length, which will increase the construction cost. Hence, many researches have attempted to provide better design and construction methods to increase the bearing capacity in a cost-effective way (Juran et al. 2001; Sadek and Isam 2004; Tsukada et al. 2006; Finno 2002; Gomez et al. 2003; Seo et al. 2013)."

Jan 1, 2016

There are some problems in the beneficiation of fine-grained oxidized iron mineral such as high cost, severe sliming, poor results and low recovery due to the fine disseminated size of the mineral. Taking several representative types of finely-disseminated oxidized iron minerals as examples, the author analyzed the main difficulties in the beneficiation of such kind of ores and discussed the existing problems in grinding-classification, technological process, flotation reagents and separation equipments and the resolvents of these problems.

Jan 1, 2014

By G. Papantonopoulos

Natural stones are extensively used for construction purposes since the dawn of human civilization, due to their unique aesthetical and technical characteristics. Their production and consumption has been continuously increasing over the past twenty years worldwide at an annual rate of 8.8%. European countries lead the race of per capita consumption, with Switzerland being in the first place with a consumption of 144.7 m2 per hundred inhabitants followed by Greece, Spain, Portugal, Belgium and Italy. On the other hand, during the period 2001-2002 the generated stone wastes were 110 million tones according to EU data, from which only about 5 million tones were recycled or re-used mainly in the construction industry. These stone wastes the non-natural wastes such as oils or chemicals coming from the equipment and machinery employed for stone extraction and processing, are disposed in the environment, posing serious environmental threat. To achieve sustainable development of the stone sector appropriate methods that will prevent or reduce waste generation and disposal have to be identified and applied. In this work an extensive study of the stone waste management techniques applied in Europe is carried out, in order to identify the Best Available Techniques (BAT) that can be used according to the type of generated wastes and the waste management hierarchy: Waste minimisation, Re-use, Recycling and Disposal. The identification of BAT was performed based on 14 Sustainable Development Indicators (SDI), which were grouped into three categories: environmental, economic and social. The developed final list of BAT includes waste minimisation techniques, eco-management schemes, in-situ treatment and appropriate storage and selection.

Jan 1, 2007

By Changwoo Lee

Under drastically deteriorated situations, diesel equipment was introduced to some of local coal mines, aiming at higher productivity and better safety. To accommodate various diesel equipment in conventionally developed mines, mining system itself had to be modified; much larger trackless haulage ways were excavated. Possible health hazards of diesel not taken into account at the beginning become a serious concern and effective control measures are being searched for. The purpose of this paper is to study the diffusion characteristics of diesel exhaust in local coal mines. One of the parameters affecting dispersion of diesel contaminants is the coefficient of turbulent diffusion. Since CO2 is known to be closely correlated with other contaminants such as CO, NO, NQ, SO2 and RCD, it was chosen as a tracer gas in a series of dispersion experiments. A large diesel passage as well as a conventional track haulage way were the sites for the experiments. Rectangular dispersion pulses were generated for 30 ~60 seconds and CO2 concentrations were recorded at several locations 50~190 m downwind. The diffusion coefficients calculated graphically vary between 0.10~0.48 m2/s at both haulage ways. The results are analyzed to find any correlation with the air velocity and the distance from the disperser. Skobunov's empirical formula is applied to the experimental data for comparison and the relationship between Reynolds number and Ex/Dp/sci0.4 Sc1…

Jan 1, 1995

By W. Griffith

"While oxalic acid precipitation practices are commonly applied on purified rare earth elements (REEs) pregnant leaching solutions (PLS), few efforts have been reported using oxalic acid (OXA) to recover REEs directly from untreated PLS. High oxalic acid demand is the most significant issue in all these direct oxalic precipitation (DOP) practices. Preliminary research on DOP of REE from a dilute PLS originating from an acid bake followed by water leaching was conducted. At 75°C, the oxalic acid demand was between 12 and 18 times the stoichiometric requirement for complete REE precipitation. Conducting DOP at 25°C had superior REE recovery but the product purity and filterability declined. Between 75°C and 100°C, REE recovery increased with increasing temperature. When sodium hydroxide was used to adjust the pH during DOP, in the range of 0.5 to 1.5, higher pH benefited REE recovery. Using ammonium hydroxide in place of sodium hydroxide, the REE recovery was reduced by close to 5%. Sodium chloride addition to the PLS was also investigated and the results showed that at both 75°C and 25°C, the REE recovery was enhanced substantially. At 25°C, when the oxalic acid addition was controlled at 4.7 times the stoichiometric requirement, the overall REE recovery reached 95% with the addition of 240 g/L NaCl. Other reagents such as KCl, NH4Cl also showed significant enhanced REE recovery at the same oxalic acid addition. The addition of sodium sulphate appeared to largely enhance the precipitation of LREE but inhibited the formation of HREE oxalate. All results indicate the formation of rare earth double salts may play an important role in REE DOP sulphate media.INTRODUCTIONThe conventional routes for recovering rare earth elements (REEs) from a sulphuric acid pregnant leaching solution (PLS) involves an initial purification step for removal of iron, aluminium for example by precipitation through neutralization, followed by precipitation of REEs as hydroxide, oxalate or carbonate salts, or by bulk solvent extraction for REE recovery (Xia, 2013). Another route was used by Bayan Obo in their historical flowsheet, where the PLS was first subjected to double sulphate precipitation, then the remaining REEs, mostly heavy rare earth elements (HREE), were recovered by oxalate precipitation (Li, 2011)."

Jan 1, 2016

By Kihong Park

A hygroscopicity tandem differential mobility analyzer (HTDMA) technique is used to determine size-effect of nanoparticles (NaCl, (NH4)2 SO4, KCl, NH4NO3, MgCl2,CaCl2) on their hygro­scopic properties (deliquescence relative humidity (DRH) and hygroscopic growth factor (GF)). The HTDMA system uses a combination of two nano DMAs and two regular DMAs to measure particle size change in a wide dynamic particle size range. Particles are subsequently analyzed with a transmission electron microscopy to investigate the potential effect of particle structure or morphology on the hygroscopic properties. We found that structural properties of NaCl and (NH4)2SO4 particles also play an important role in determination of the DRH and GF and are more pronounced at smaller diameters. Data show that the DRH of NaCl nanoparticles increased from *75% up to *83% RH at 8 nm and that their GF decreased with decreasing size. The extent to which the GF of NaCl nanoparticles decreased with decreasing size was greater than theoretically predicted with the Kelvin correction. The GF of furnace-generated NaCl nano­particles that have pores and aggregate shape was found to be smaller than that of atomizer-generated particles that are close to perfectly cubic. For the case of atomizer-generated (NH4)2SO4 nanoparticles, we observed no signi?cant size-effect on their DRH, and the measured GF agreed well with predicted values using the Kelvin correction. For furnace-generated (NH4)2SO4 nanoparticles, a gradual growth at moder­ate RH without noticeable deliquescence behavior occurred. Their TEM images showed that contrary to atomizer-generated (NH4)2SO4 nanoparticles the fur­nace-generated (NH4)2SO4 nanoparticles are not perfectly spherical and are often aggregates having pores and holes, which may favor holding residual water even in the dried condition. For atomizer-generated KCl, MgCl2, and CaCl2 nanoparticles, we observed no signi?cant size-effects on their DRH and GF for the mobility size as small as 20 nm.

Jan 1, 2008

By Jianhong Xu, Hailong Hou, Yu Jing, Yundong Wang

Microcapsules containing extractants have been applied to the extraction of metal ions, organic acid, pesticide, and herbicide. The difficulties of conventional liquid-liquid extraction in phase mixing and phase separation (e.g. high energy consumption, emulsification phenomenon, and large equipment requiring housing) could be overcome in a liquid-solid system by using microcapsules. Even some extractants with high viscosity and poison can be encapsulated conveniently into microcapsules. In the work described in this paper, polysulfone microcapsules containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507) were successfully prepared. Then, the extraction rate of lanthanum, samarium, and erbium in dilute solution into the microcapsules containing P507 was studied. An extraction kinetic model is proposed based on the interfacial reaction model accompanied by intraparticle diffusion expressed by Fick’s law. The extraction efficiency was obtained by using the kinetic model with the separately determined complex formation rate constant and the intraparticle diffusion coefficient. From the results, it was confirmed that the kinetic model could predict the experiment in a microcapsule system over a wide concentration range of lanthanide solution. In the future, the model could provide good guidance for the design and application in extraction of lanthanides.

Jan 1, 2014

By N. Dahata

B206 aluminum?copper alloy has a potential for wider use in the automotive industry due to its light weight and relatively superior mechanical properties as compared to aluminum-silicon alloys. The possibility of casting this alloy via Lost Foam Casting (LFC) has not been investigated in detail. Therefore, the effects of foam types (T170B standard untreated EPS and T175-brominated EPS), coating types (Styro Shield 5553 and Styro Shield 5554), copper level (4.5 wt % and 5.0 wt %) and titanium levels (0.5 wt % and 0.25 wt %) were related to fillability, microstructure and microporosity. The metal velocity in T175 EPS pattern was higher than that in T170B EPS pattern. For T175 EPS pattern, the total solidification time was 3% higher and the loss of temperature for decomposition of EPS was lower than those in the case of T170B EPS pattern. The grain size, porosity level and maximum pore size were quantified using Light Optical Microscopy (LOM) and image analysis. The casting with T175 EPS pattern showed larger grain size relative to that with T170B EPS pattern. The porosity level and the maximum pore size decreased significantly when the titanium level was increased from 0.05 wt % to 0.25 wt %.

Jan 1, 2007

By Ezzeddin Bakhtavar

There are several geotechnical challenges and risks inherent in the interaction between the open-pit and block cave mining environments. This is especially true when they have to work simultaneously for a short time, as well as when only the caving operation is continued. Some of these challenges and risks include the induced zones of stress due to the large and deep open-pit, instability of the slope, instability of the crown pillar and water inflows, subsidence, and sometimes instability of the main accesses to the block cave portion of the mine. These challenges usually occur due to cave propagation. In this paper, these geotechnical challenges and associated risks have been studied and discussed. It was concluded that the majority of the mentioned geotechnical risks could be decreased, and often eliminated, by considering the appropriate dimensions of a stable crown pillar, especially in simultaneously working open-pit and block caving operations.

Jan 1, 2011

Grinding and energy input in stirred media mills are studied as functions of grinding time, stirring speed, media size and density, solid concentration, impeller and tank dimensions and design, and other relevant variables. Ground product size and surface area are determined with respect to the above variables. Changes in energy input and media/pulp rheological properties during grinding are described. The best conditions for grinding limestone in the laboratory stirred media mills have been identified. Equations for correlations involving power and modified Reynolds numbers have been established.

Jan 1, 1995

By Bowang Xiao

Recently more and more attentions are paid to high pressure hydrogen quenching (HPHQ) for its advantages such as environmental friendliness, low distortion, etc, compared to oil and water quenching. In HPHQ process, heat transfer coefficient (HTC) usually varies from part surface to surface because of the intense variation of gas velocity around the part. This article studies the effect of HTC distribution on part distortion after HPHQ and shows that finite element simulations considering HTC distribution predict different distortion from these without considering HTC distribution. It is also pointed out in this article that HTC distribution can be optimized by adjusting part orientation and HPHQ condition so that part distortion is minimized.

Jan 1, 2010

By H Fukui, K Ichikawa, K Aikou, E Suzuki

An electronic delay detonator (EDD) consisting of a digital-base electronic delay module and a conventional instantaneous detonator module, designed for series connections with a special adjustable-output blasting machine, is described and shown to provide a delay time accuracy some four to twelve times higher than that of pyrotechnic millisecond and decisecond delay detonators, together with the other performance characteristics necessary for practical use. Also described is a blasting design system which allows effective reduction of ground and air vibration, through the use of EDDs with optimum delay times as determined by accurate computer simulation based on wave form and other data obtained from an on-site single-shot test blast.

Jan 1, 1989

By Shen Zhengchang

Based on the flotation features of coarse particle mineral, a new type of impeller & stator unit is developed. Particles suspension state generated by this impeller & stator unit under different speeds are tested in laboratory, and critical impeller speed suit for coarse particles flotation is presented. Comparing particle suspension parameters of the new impeller & stator unit with that of KYF impeller and stator unit, it comes up that the distance between the interface of two slurry circulation channels and the cell bottom is larger in the flotation cell with new impeller & stator unit. The test results indicate that the new type of impeller & stator unit is suitable for processing coarse particles due to its good suspension capacity for coarse particles. Keywords: coarse particles, flotation, suspension, critical speed, impeller and stator unit

Sep 1, 2012

By Bok-youn Kim

Presently, mobile diesel equipments contributes a lot in improving the economical feasibility of underground mining and tunneling operations. Even in Korea, quite a large number of diesel equipments is being applied to the underground workings already. This paper introduced the production procedure, characteristics and evaluation technology on diesel particulate matter(DPM) that is known as a carcinogen For easy measurement of DPM using laser dust monitor, the conversion factor(K) to gravimetric concentration was acquired. The field measurement of DPM was conducted to make a comparison between locally manufactured on-road equipments and imported equipments specially designed for underground use. According to the Government regulation revised h 1996, it was learned that the critical pollutants among the diesel exhaust is DPM instead of NOx which have been considered as a critical pollutants.

Jan 1, 1997

By Margaret Armstrong, Normand Champigny

"In order to define the ore/waste boundaries as finely as possible, mine planners often insist on kriging very small blocks (relative to the spacing of the available sample grades). These kriged estimates for very small blocks are over-smoothed. For several simple sampling patterns the relation between the block size and the variogram range, and the kriging results were studied. Meaningful estimates of individual blocks are obtained when the variogram range is large compared to the block size and the sample spacing. For a variogram range less than half the sample spacing, the kriged block estimates were found to be uncorrelated with the actual grades. The over-smoothed estimates should not be used for calculating recoverable reserves IntroductionNowadays most mining companies know that the geostatistical estimation method, kriging, gives the best estimates of individual block grades. As most mining engineers and geologists are now familiar with the basics of geostatistics, the definitions of the variogram and of kriging will not be repeated here. An appendix containing definitions and mathematical formulae is given at the end of the article for the sake of completeness.Even though it is well known that the kriged estimates for very small blocks are over-smoothed, mine planners who want to define the ore/waste limits as finely as possible (especially for selective underground mines), are often tempted to krige very small blocks. So we ask how small is ""too small""? Clearly ""smallness"" cannot be expressed in yards or metres. It depends on the nature of the orebody under study and this is reflected in the variogram model chosen to describe it.To answer this question, the changes in four key parameters are studied:• the kriging variance,• the variance of the estimated grade,• the slope of the linear regression of the true but unknown grade on its estimated value, and• the coefficient of correlation between the actual grade and the estimate;as a function of the block size and the variogram range. (Definitions of these four parameters are given in the appendix). Ideally the kriging variance should be low while the variance of the estimated grade should be equal to the dispersion variance of the blocks. The slope should be l.0, and so should the correlation coefficient.These four parameters have been calculated for several simple 2-D examples. The effect of using kriged block estimates that are too heavily smoothed are shown, and the dangers of trying to use these estimates for predicting recoverable reserves for small blocks (i.e. selective mining units) are pointed out."

Jan 1, 1989

A Study on Main and Interaction Effects of Operating Variables of Column Flotation

Sep 13, 2010