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By C. A. Pickles, K. Mackowiak, D. Gajonera

"Shake-flask oxidation tests were performed on Red Dog mine waste to study the initial dissolution behaviours of lead, zinc, and iron. The conditions for accelerated acid generation in terms of Eh and pH were determined. Each mineral behaved distinctly, with galena dissolving first, followed by sphalerite, then pyrite, although there was some overlap in behaviour. Iron was not detected in solution until approximately day 40 and was present at low concentrations. The experimental conditions and the theoretical model results indicated the formation of iron oxyhydroxides at low weathering times and jarosite at longer times.RÉSUMÉ Des tests d’oxydation par agitation en flacon ont été effectués sur les déchets miniers de l’exploitation Red Dog afin d’étudier les comportements initiaux de dissolution du plomb, du zinc et du fer. Les conditions entraînant la production accélérée d’acide en termes d’eH (potentiel d’oxydoréduction) et de pH (potentiel d’hydrogène) ont été déterminées. Chaque minerai se comportait différemment ; la galène a été la première à se dissoudre, suivie de la sphalérite, puis de la pyrite, mais un certain chevauchement des comportements a été observé. La présence de fer en solution n’a été détectée qu’après environ 40 jours et ce, à de faibles concentrations. Les conditions expérimentales et les résultats du modèle théorique signalaient la formation d’oxyde-hydroxyde de fer sur de courtes périodes d’altération atmosphérique, et de jarosite sur des périodes plus longues."

Jan 1, 2017

By T. Mulpeter, G. Deschênes

Sadiola Gold Mine is an open pit operation located in Mali and owned by Anglogold Ashanti Ltd, Iamgold Corporation and the State of Mali. A conventional cyanidation process (cyanidation/CIP) treats 15,000 tpd (of a mixture of oxide and sulphide ores) at an average grade of 3 g/t Au. In 2002, the increasing tonnage of sulphides caused an increase in production costs and a decrease in gold extraction (from 95% to 70-76%). Because of the short retention time of the leach circuit (18 hours) and the refractory nature of the sulphides, gold leaching kinetics are critical. A laboratory investigation was initiated to evaluate actual plant practice and identify a means of improving the gold leaching rate. The study was conducted on a "soft" sulphide gold sample containing 4.96 g/t Au, 0.4 g/t Ag, 2.5% pyrite, 1.2% arsenopyrite, and 0.2% pyrrhotite with a P80 of 74microns. Pre-leaching significantly influenced the gold leaching rate. A short pre-leach (2 hours) performed at pH 8, a DO of 8 ppm, and with 300 g/t lead nitrate added at the start or the end, produced the preferred conditions. Pre-leaching for more than 2 hours was detrimental to gold extraction. The cyanide concentration had to be maintained at 450 ppm NaCN to reach a maximum gold extraction within the retention time of the circuit. A maximum extraction of 81.3% Au was obtained in 20 hours (leach residue at 0.97 g/t Au). A high level of dissolved oxygen in the pre-leach was not of any benefit. Extension of gold leaching beyond 20 hours indicated that all leachable gold had been extracted by that time. Plant modifications were made to allow leaching of oxides and sulphides in separate circuits. Treatment of oxide ores is now performed at a higher rate. Sulphides are processed at a lower throughput, with 300 g/t lead nitrate, to allow a retention time of 22 hours. Combined throughput remains the same, and total gold recovery has increased from 76% to 80% for an additional gold production of 16,000 ounces per year.

Jan 1, 2005

By D. M. Maijer, S. L. Cockcroft, A. B. Phillion, P. Fan, C. Reilly, H. Khadivinassab

A combined experimental / numerical approach is proposed to investigate the bulk transfer of solute due to liquid metal feeding during shape casting of aluminum alloy A356 (Al-7Si-0.3Mg). A dumbbell-shaped experimental casting geometry has been developed, which promotes solute redistribution due to liquid metal feeding. The redistribution of solute in trial castings is evaluated based on the area fraction of eutectic phases. In the numerical model, silicon species segregation during solidification are calculated assuming the Scheil approximation, and are coupled with macro-scale solute transport due to Darcy flow in the mushy zone and feeding flow. The model has been implemented within the commercial CFD software, FLUENT, which simultaneously solves the thermal, fluid flow fields and species segregation on the macro-scale. The experimental and numerical results are compared and contrasted to examine the effects of liquid metal feeding in this casting.

Jan 1, 2014

By W. Dong

This paper presents the fundamental study of the temperature distribution in a reforming planar solid oxide fuel cell (SOFC) using mathematical modeling and experimental testing approaches at Versa Power Systems (VPS). In order to investigate the on-cell temperature distribution under high rates of Natural Gas direct internal reforming (DIR), both the computer simulation approach and the experimental testing approach have been developed. In this work, comprehensive in-house DIR and SOFC models were developed and employed for the computational fluid dynamics (CFD) based 3D computer simulation. The current SOFC module has been corrected to take into account both the on-cell electrical leaking effect and the stack stage structural resistance. Meanwhile, an instrumented single-cell test jig with multiple thermocouples was built, and a series of experimental tests were performed at various conditions. The numerical results based on the single-cell jigs are in very good agreement with the physical test results.

Jan 1, 2005

By J. Bensabat, B. Figueiredo, A. Niemi, J. Rutqvist, C. F. Tsang

"A hydro-mechanical model was developed to study the interaction between mechanical deformation and fluid flow in the fault zones during CO2 injection and storage at the Heletz site which was chosen as a test site for CO2 injection experiments in the framework of the EU-MUSTANG project. The potential reservoir for CO2 storage at the Heletz site consists of three sand layers separated by lowpermeability shale layers. The potential consequences caused by fault reactivation, focusing on the shortterm integrity of CO2 storage, are evaluated. The difference in the results obtained by considering the three-layer as an equivalent layer storage formation is analyzed.INTRODUCTIONLarge-scale storage of CO2 in deep underground reservoirs may cause considerable pore-pressure perturbation as well as flux migration and concern has been raised over whether shear slip displacements may be induced in nearby faults, as a consequence of their reactivation. A state-of-the-art review can be found in Rutqvist (2012), which describes the various possible effects resulting from CO2 injection into a deep sedimentary basin, including those involved in reservoir stress–strain changes, micro-seismicity, caprock sealing performance, and potential fault reactivation. Moreover, several studies have recently shown how CO2 injection may produce seismic events both on major faults (i.e., large faults with large initial shear offset) (Cappa & Rutqvist, 2011a, b, 2012), and on minor faults that might have gone undetected during the site characterization, e.g., faults less than 1 km long and without detected initial offset (Mazzoldi et al., 2012).The present paper is concerned with the Heletz formation which was chosen as a test site for CO2 injection experiments in the framework of the EU-MUSTANG project. The Heletz site located at the southern Mediterranean coastal plain of Israel and the structure is an anticline fold with a crest of about 4 km by 2 km. The structure is gently dipping to the east, truncated by a pinch-out line to the west and subdivided into a number of blocks by transversal normal faults with small displacements. The water table is located at 300 m below the land surface. An areal sketch of the site with the elevation of the caprock and the location of the borehole that has been chosen for the CO2 injection experiment is presented in Figure 1."

Jan 1, 2015

By Laxman M. Amaratunga, Nuri Hrnidi

"Reactive pyrrhotite tailings were agglomerated using the Cold Bond Tailings Agglomeration (CBTA) process with low cost binders; Portland Cement and fly ash. Various chemical additives, were used to retard acid mine drainage (AMD), including acid neutralizers, surfactants, sealants, and bactericides, which were encapsulated into the agglomerates. The choice of these additives was based on their low cost, low toxicity, and environmental friendliness. The main objective of the study was to examine the long term stability of these reactive tailings agglomerates towards AMD when used as aggregates for disposal in underground paste backfill.A carefully controlled kinetic stability test was carried out using specially designed humidity cells suitable for testing pellets. Using the humidity cell test method a 20-30 year AMD test may be accelerated to 50 weeks. During this period the following parameters were monitored: pH, redox potential, conductivity, sulphate, acidity, and dissolved metals.Results indicated that most of the encapsulated additives were successful in retarding AMD, while the control samples produced significant amounts of acid generation. The water soluble surfactant Enviroseal, and the sodium silicate sealant were very effective as a long term retardant for acid generation reactions in the sulphidic tailings when exposed to oxygen, water and iron-oxidizing bacteria.IntroductionThe sulphidic material discharged from concentrators becomes reactive upon exposure to air and/or water. Pyrrhotite (Fe0 S0_1) and pyrite tailings in particular which are discharged from the beneficiation process in the mining and mineral processing activities consist of finely ground particles. Upon exposure to oxygen and moisture, the tailings become reactive due to the instability of the metal sulphide minerals present which undergo spontaneous oxidation, thereby producing a weak sulphuric acid. Therefore, the long-term behaviour of the tailings can have a significant impact on the environment, due to acid mine drainage (AMD). AMD is created during natural atmospheric weathering when leaching action (natural and bacterial) conditions are present in the process wastes discarded during the mining and milling of sulphur bearing ores, and consequently it plays a major role in surface water chemistry."

Jan 1, 1998

By H. Matsuoka, M. Kawata, K. Mitsuhashi, C. Tokoro, T. Kato

Copper sulfide minerals such as chalcocite, bornite, and chalcopyrite exhibit high floatability, thus they can be recovered as a froth product by adding only a collector in flotation process. However, when their surface is oxidized, the floatability decreases and the simple addition of collectors is no longer effective. In this case, flotation activators are required to improve the floatability. Sodium hydrosulfide (NaHS) acts as an activator for chalcocite and bornite by re-sulfurizing their oxidized surface portions. Nevertheless, the flotation conditions still require optimization in order to achieve a satisfactory recovery of copper minerals. This work addresses the study of the effect of pH and NaHS dosage on the flotation of a complex Chilean copper ore containing chalcocite, bornite, and chalcopyrite. Flotation experiments were conducted using a Denver-type flotation cell and by investigating the effect of two NaHS dosages (50, 100 g/t) and three pH values (8, 9, 10). Following this process, the surface interaction between the minerals and NaHS were analyzed using zeta potential measurements. INTRODUCTION In recent years in the mining area of metal resources, the complexity of ores and the fineness of grind required to liberate minerals have become serious problems. When ores are complex, several valuable minerals may interact with each other and reactions may become more complicated compared with an ore containing only one valuable mineral. Therefore, more processing steps may be required than for a simple ore. When the valuable minerals exist as fine grains, it is difficult to liberate them and more grinding time is required. Furthermore, the probability of collision of fine particles with bubbles in the flotation process declines and it takes much time to recover them. Flotation is one of the most applied methods to separate valuable minerals from unwanted ones using the difference of hydrophobicity (or hydrophilicity). In the flotation method, the air is fed to a cell filled with the pulp of the mineral of interest and agitation is implemented to introduce air and generate bubbles. The hydrophobic particles attach themselves to the bubbles and float along with the bubbles while the hydrophilic particles remain in the pulp. Copper sulfide minerals such as chalcocite (Cu2S), bornite (Cu5FeS4), chalcopyrite (CuFeS2) are widely known abundant copper resources. Generally, flotation is used to recover and concentrate these minerals. Copper sulfide minerals usually have high floatability. However when their surfaces are oxidized, their floatability becomes lower. When the sulfide surfaces are oxidized, activators are added before flotation to modify the surface property of the Copper sulfide minerals so that they can be floated. Sodium hydrosulfide, NaHS, is known as one of the activators. Zhao (2018) reported that NaHS is often used as a sulfurizer for oxidized sulfide minerals (Becker (2014), Clark (2000), Newell (2006), and Newell (2007)). In earlier work, the authors performed flotation tests on a sample of Chilean copper ore which contained chalcocite, bornite, and chalcopyrite using a Denver-type flotation apparatus. The sample was ground to P80 70 µm with a rod mill and ball mill. In these tests, the following conditions were used: natural pH (about pH 8.5), flotation time of 45 min, 60 g/t AP3477 (sodium diisobutyl dithiophosphate) as collector, and MIBC (methyl isobutyl carbinol) at appropriate dosage as frother. NaHS was applied at the dosage of 0, 67, and 120 g/t, respectively at the conditioning. The concentrates were collected at 6, 18, 30, and 45 min. The weights of the concentrates and tailing were measured and they were assayed for copper by ICP-AES (Optima 5300 DV, PerkinElmer Inc.). The flotation recoveries of the copper minerals were calculated from the results of MLA (mineral liberation analyser) (MLA 650, FEI) measurements.

Jan 1, 2019

By M. Dupuis

It has been previously demonstrated [l] that there is no obvious thermal balance related issue limiting the size of a Hall-Héroult cell. Yet, it is well known that a forced-air sidewall cooling system is part of the AP50 cell design [2], In the present study, the authors analyze the impact of thermal loading on the mechanical deformation of high amperage cell potshells. The effect of adding cooling fins or a forced-air sidewall cooling system is then assessed.

Jan 1, 2005

By H. Henao, F. Canales

The present work evaluated the use of copper ore flotation tails as flux in the process of smelting copper concentrates. For this purpose, experimental and simulated liquidus lines were obtained at different ratios of tail/flux. Experimental variables included temperature, partial pressure of oxygen and sulfur dioxide and the conditions of tridymite or spinel saturation. The results indicate the feasibility of replacing the flux by increasing the temperature of the smelting process by 20°C. Results of simulation using FactSage and HSC confirm that the required increase in temperature can be achieved by increasing the flow of concentrate, enrichment of oxygen or increasing the matte grade. INTRODUCTION In the pyro-metallurgical process of copper production, the smelting stage produces two liquid phases, a sulphide phase rich in copper and another composed mainly of oxides called slag. The slag phase is the product of oxidation of the iron contained in the flotation concentrate. The smelting process which is carried out at temperatures of 1250°C, require the addition of silica as a flux and the injection of air enriched in oxygen (Schlesinger 2011). Currently, one of the most important aspects of the mining industry is the minimization of costs, the optimization of the use of available resources and the reduction of environmental impact. Under this context, the use of flotation tails from as a flux in the copper smelting process has the potential of reduced production costs and generate an environmental benefit by reduce the disposal amount of this waste material Regarding the use of copper tails as flux in the copper smelting process, a thermodynamic simulation study using the FactSage software had been reported in the literature (Parra et al., 2011). The results indicated an increase of 35°C in the temperature the liquidus for the equilibrium matte/spinel and a subsequent requirement of energy in the process of approximately 350 [MJ/ton slag]. Given that the calculated viscosity remains in the same order of magnitude, the melting temperature is a more relevant parameter for the evaluation of the use of tailings as flux.

Jan 1, 2019

By M. Askari, M. H. Parsa, S. Kashani-Nejad

Sarcheshmeh refractory consumption rate is about 7.5 - 8 kg/ton of the produced copper, which is almost three times higher than the other smelters practice. High destruction rate of tuyere zone refractory controls vessel productivity and operational lifetime. In this research with the aid of cold model and computational fluid dynamic (CFD), melt recirculation pattern and gas - liquid plume properties in the wide range of gas blowing conditions were studied. Results revealed that in addition to the well-known mechanical refractory destruction mechanism, fast tuyere zone refractory destruction could also be related to the cold bubble cluster formation near tuyere tips and introducing severe thermal shock to the refractory surface. Removing accretion and its strong bonds to the refractories around tuyere tip, causes refractory mechanical destruction and increases tuyere diameter. Increased tuyere diameter, in turn assists gas discharge in the bubbling regime. Air blowing in the bubbling regime result in the formation of big bubble clusters, bubble breakup and back attack occurrence which all found to have major impact on the refractory lifetime. Outcomes of this research, contributed to the plant converting management, blowing hardware and instrumentation improvement.

Jan 1, 2004

By J. Qi

Based on the commercial steel 42CrMo (4140, SCM440), a new generation of CrMo steel was developed by increasing the content of Mo, adding the alloy element of V and Nb, and decreasing the content of P and S. This new CrMo steel has higher strength of 1500MPa and better delayed failure property. TEM and EDS were used to study the distribution and function of the alloying elements in this steel. A new EELS technique was developed to study the bonding strength of the grain boundary in the steel. The mechanism of strengthening of the new steel has been studied.

Jan 1, 2004

By Hang Zhao, Xinping Li, Pingan Wu, Yi Luo

"The deep-buried rock surrounding the Jinping II Hydro-power Station was taken as the engineering background. Using model specimens of classified rock materials to simulate fractured rock mass under high in-situ stress conditions, the test about acoustic propagation law on single fracture model of specimen under different pressures and different angles were carried out. The variation of p-wave velocity in fractured rock mass and axial stress-strain relationship in the whole test procedure was also studied. Based on damage mechanics principle and the acoustic wave propagation in cracked rock mass, comparative study on damage constitutive relation of fractured rock mass under high in-situ stress in consideration of equivalent strain and equivalent energy was performed. As the results showed, with the change of axial stress level under constant confining pressure, the change in wave velocity can be divided into three stages: slow increase (small variation in amplitude), rapid reduce (large variation in amplitude ) and accelerate reduction. When the confining pressure is constant, the maximum p-wave velocity and the peak strength of specimens increases with the decrease of the crack angle.When the crack angle is constant, the maximum p-wave velocity and the peak strength of specimens increases with the increase of confining pressure.It is identified that the theoretical calculation results of constitutive relation about elasto-plastic damage model containing variable wave velocity in the fractured rock mass is consistent with the model test results.Therefore,the constitutive relation can provide reasonable suggestions for engineering practice. INTRODUCTIONThere are a lot of joints and fractures in surrounding rock mass of deep-lying in the Jinping-II hydropower station, which has a great influence on the physical and mechanical properties of rocks and effects the acoustic wave propagation and attenuation law in rock. Many previous research and project examples has proved that sound propagation parameters are closely related to crack and stress condition. Thus, it has certain theoretical significance and practical application value to carry out researches on sound propagation characteristics and establish damage constitutive model of fractured rock mass which is related to sound propagation parameters."

Jan 1, 2015

By Hang Zhao, Xinping Li, Pingan Wu, Yi Luo

The deep-buried rock surrounding the Jinping II Hydro-power Station was taken as the engineering background. Using model specimens of classified rock materials to simulate fractured rock mass under high in-situ stress conditions, the test about acoustic propagation law on single fracture model of specimen under different pressures and different angles were carried out. The variation of p-wave velocity in fractured rock mass and axial stress-strain relationship in the whole test procedure was also studied. Based on damage mechanics principle and the acoustic wave propagation in cracked rock mass, comparative study on damage constitutive relation of fractured rock mass under high in-situ stress in consideration of equivalent strain and equivalent energy was performed. As the results showed, with the change of axial stress level under constant confining pressure, the change in wave velocity can be divided into three stages: slow increase (small variation in amplitude), rapid reduce (large variation in amplitude ) and accelerate reduction. When the confining pressure is constant, the maximum p-wave velocity and the peak strength of specimens increases with the decrease of the crack angle. When the crack angle is constant, the maximum p-wave velocity and the peak strength of specimens increases with the increase of confining pressure.It is identified that the theoretical calculation results of constitutive relation about elasto-plastic damage model containing variable wave velocity in the fractured rock mass is consistent with the model test results.Therefore,the constitutive relation can provide reasonable suggestions for engineering practice.

Jan 1, 2015

By Sadough vanini Ali

The silicon anisotropic wet chemical etching technique is widely employed for fabricating various microelectromechanical system (MEMS) structures for advantages such as simple etching equipment and its capability to fabricate special microstructures. In this paper, we consider a complete theoretical derivation of the analytical solution based on geometrical and kinetic aspects of step flow on any surface and with a mathematical method we derive new equation for calculating the microscopic etch rates of surface atoms for a new range of concentrations and temperatures. Furthermore, a novel equation is presented for the calculation of the microscopic activation energies for some typical surface atoms and a new comparison of activation energies between some atoms is made that divides atoms into three categories. The results demonstrate agreement with the experimental results.

Oct 1, 2011

By Z. Liang, Z. Q. Liu, X. F. Li, H. L. Zhang

"Dynamic characteristics of frozen soil is important for the safe, effective and rapid construction in cold regions and artificially frozen engineering. In this paper, dynamic characteristics of frozen clay with various low temperature and different strain rate were studied by using Split Hopkinson Pressure Bar (SHPB) test and numerical simulation test. Variation of dynamical parameters and dynamic stress-strain curves of frozen clay were obtained and analyzed. The results of these test show that: Frozen clay exhibits temperature effect and strain rate effect that the failure type tends from plastic failure to brittle failure with the increase of strain rate or decrease of temperature; Under impact loading, frozen clay exhibits three typical dynamic stress-strain curves as strain rate increases, and the maximum strain of frozen clay only linear increases with strain rate.INTRODUCTIONArtificial freezing technology has been widely used in the construction of underground engineering, such as the coal mine shaft, the deep foundation pit, the urban metro and subsea tunnel, etc. Research on dynamic mechanical behavior of artificial frozen soil will provide supports for these artificially frozen engineering (Xu et al. 1998; Ma 2009). However, the dynamic mechanical research on frozen soil is mainly carried out at low frequencies or small amplitudes of the waves, behavior of frozen soil under impact loads or high strain rate loads has not been made clear."

Jan 1, 2015

By Yongquan Zhu, Zhengguo Zhu, Zhichun Liu, Chao Kong, Xinqiang Gao

"The aim of the study is to have a good understanding of the change in the seepage field during and after the tunnel excavation in weathering alteration rock. Field tests are used to monitor the changes of the water table and the numerical model is used to analysis the influence of the seepage filed with different operation conditions during and after the tunnel excavation. Results indicate that the depth, diameter and pumpage of precipitation well are the main factors that have a great influence on the drainage effect. Results also indicate that different operation conditions had various effects on the decrease in water yield during tunnel construction and the recovery in groundwater level after construction.INTRODUCTIONAs a potential disease during tunnel construction, Gushing water not only affected construction schedule, increased construction cost, as well as affected tunnel stability and safety during operation, but also decreased ground-water level. What’s more, the fall of water table caused by gushing water in tunnel would have influenced surrounding residents’ living water, agricultural water and ecological environment around tunnel. In recent years, enough emphasis has been paid to the influence on environment due to the construction of tunnel as a result of the reinforcement of people’s environmental protection awareness.As a result of water collection and drainage after excavation, groundwater was discharged into the tunnel, which caused a loss of water resources in the adjacent mountain mass. Furthermore, during tunnel operation, it was difficult for groundwater level to resume its original condition, which caused a bad ecological environment, because drainage system during tunnel construction destroyed its original hydrologic dynamic balance.In order to study whether decreased groundwater level resulting from tunnel construction could be restored during operation to its original condition, this paper gave a field monitoring on tunnel displacement during construction and simultaneously, generalized model of regional hydrogeology was created according to field hydrogeology to carry out a calculation of stable seepage flow and draw comparisons between recovery conditions of various water levels."

Jan 1, 2015

By Wei Yun-Jie

Columnar jointed basalt is a fractured rock, with a lot of small spacing structural planes and poor integrity of the rock mass. On the basis of the comprehensive study of the columnar shape of Columnar joints, rugosity of the fracture surface and the chemical composition of basalt, columnar joints of Bai hetan dam area were formed as a result of the cooling and shrinkage effect of magma. Columnar joints basalt are mainly chlorite, kaolinite, epidote, tremolite chemical reactions and the content of columnar joints are mainly chlorite by slice identification and chemical analysis. Columnar joints basalt showed high uniaxial tension test, low coefficient of friction and high cohesion by indoor physical and mechanical test. Columnar joints rock mass showed high strength and large deformation by field shear test and deformation test. Columnar joints basalt can be used directly as a foundation of dam as long as we follow the rules and reduce disturbance strictly.

May 1, 2009

By Han Xing, Cui Jianzhong, Qin Ke, Shao Bo, Zhang Haitao

In this paper, a new approach that uses hot-top DC casting process to producing multi-alloy ingots is present. The different type and size of composite and coated ingots (4045/3004/4045 three-layer composite ingots with section 630mm by 1500mm and 4045/3003 coasted ingot with F140mm/F110mm in diameter) are cast by this approach. The macro-morphologies and microstructures of the composite ingots, the temperature distribution and the element distribution in the interface zone were investigated, also and the interface bonding strength was measured. Results show that the solid supporting layer formed on the cooling plates plays a key role in the casting process of composite ingots. The solid supporting layer can prevent the blending of two melts by resisting the impact of alloy melt, which ensures the stable casting process and casting high quality composite ingots, because the contact height is increased using hot-top DC casting. In addition, fabrication and properties of 4045/3004/4045 three-layer composite ingots with section 630mm by 1500mm are reported in detail.

Jan 1, 2015

By L. Yuan, J. H. Rowland, R. A. Thomas, D. Bahrami, G. P. Cole

"The past several decades have seen a steady increase in the use of atmospheric monitoring systems (AMS) in underground mines as sensor technology has advanced and costs for this technology have decreased. The AMS is a reliable tool for early mine fire warning by detecting gaseous products of combustion in underground mines. During a mine fire emergency, mine decision makers rely heavily on the prompt and accurate knowledge of the ventilation and fire situation in the mine, such as fire location, fire size, and the spread of smoke to make effective and efficient decisions on firefighting strategies and miner evacuation. Meanwhile, a prediction of the potential for fire development at a later time, such as whether the currently designated mine escapeways will be contaminated by smoke and toxic gases with the progress of the fire, is critical for effective decision-making to save lives that are in danger. The AMS monitoring data, including carbon monoxide (CO) concentration, airflow rate, smoke, etc., can provide information as to whether the smoke has reached the locations where AMS sensors are installed and if a mine-wide smoke spread has occurred. The National Institute for Occupational Safety and Health (NIOSH) has undertaken a task to integrate real-time AMS monitoring data with the mine fire simulation program, MFIRE, to simulate and predict the spread of smoke and toxic gas in a ventilation network based on the real-time AMS data. This paper reports the developed real-time method for characterizing the size and location of an underground mine fire and for predicting the spread of contaminants throughout the mine ventilation network using sensor data from the AMS.INTRODUCTIONNIOSH conducts research to develop workplace solutions to improve detection of and reduce the risk of hazardous conditions in underground mines. The advancement of senor technology and the increasing demand for real-time mine parameters monitoring have led to extended applications of atmospheric monitoring systems (AMS) in underground mines worldwide. In the United States, AMS is primarily used for early mine fire warning by detecting carbon monoxide (CO) in fire hazard areas, such as belt entries. Mine fires can grow rapidly, and time is the critical element. Prompt detection, timely and accurate warnings to those miners potentially affected, and a proficient response by underground miners can have a tremendous impact on the social and economic consequence of a small underground mine fire (Conti et al., 2005). The early detection of a mine fire could gain time for the first responders to put out the fire before it develops into a disaster. An AMS system with CO sensors has especially played an important role in the early detection of mine fires. The continuous monitoring of an underground mine atmosphere with an AMS could generate a large amount of data in a mine fire event. However, the current application of AMS is mainly limited to sending out an alarm when monitored CO concentration exceeds a certain level. An opportunity arises as to whether these data can be further used in fire emergency response. In order to make effective decisions on firefighting strategies, mine workers’ seeking refuges, evacuation and escape, and the timing on when to send rescuers, decision makers need accurate and timely knowledge of the ventilation and fire situation in the mine. Information about the fire intensity, where in the mine the smoke and toxic gases have spread, and whether designated mine escapeways have been compromised by smoke and toxic gases from the fire would greatly increase the effectiveness of these decisions. However, the monitored AMS data only provides atmospheric conditions in the vicinity of sensor locations. What is concluded from the monitored AMS data highly depends on the decision makers’ capability and experience. Predictive insight into fire growth and smoke transport would greatly help decision makers during a fire emergency."

Jan 1, 2019

By Y. W. Pan, Y. R. Liu

The disturbed natural rock mass tends to equilibrium state accompanying with non-equilibrium evolution process which has significant influence on the long-term stability of engineering structure. The deformation development in the non-equilibrium evolution is determined by two intrinsic processes, trend to equilibrium and damage development, which can be illustrated by evolution of excavated tunnel. Thus the creep and damage must be taken into account in study of non-equilibrium evolution process. Within Rice’s irreversible thermodynamics with internal state variable (ISV), the conjugate force function which equals to zero is a convex surface which divide the stress space into two parts, called equilibrium and nonequilibrium stress space respectively. The concept of effective stress of non-equilibrium has been proposed, in which the stress difference (d - d ) are the effective driving forces of non-equilibrium evolution process with hardening and damage effective. The formulations of inelastic strain rate and energy dissipation rate have been recast in the form of effective stresses. The inelastic complementary energy (ICE) is proposed to measure intensity of non-equilibrium evolution of material system. The specific equations of conjugated forces and kinetic equations of internal state variables are presented. The ICE and rate of energy dissipation are all calculated to be used to evaluate long-term stability of geo-engineering. The results show that rate of energy dissipation may be more convenience and flexible than ICE for internal state variable constitutive equation of rock mass.

Jan 1, 2015