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By J. Donovan Jacobs

Many improvements in the art of underground excavation have appeared during the past two decades. These improvements have been both in methods and in machinery and have resulted in more economical construction of today's tunnels. In the realm of machines, the developments of continuous boring heads for either soft ground or rock, random arm excavators and the sliding tunnel floor (Magic Carpet) have each made contributions toward more rapid tunneling. CONTINUITY OF ADVANCE Tunnel boring machines are often referred to as "continuous excavators". Continuous advance (without cyclical interruptions) has not been achieved, however, in any of the machines now in use. In most rotary-head tunnelers the thrust needed to make the cutters bite into the face is obtained from hydraulic cylinders reacting against anchoring devices held stationary by pads which grip against the sides of the tunnel. With this system the forward motion of the cutting head is continuous only until the propelling cylinders have reached their limit of extension. At this point the grippers must be released, moved forward and reset before a new cycle of advance can be begun. Some machines are built to obtain their propelling thrust from hydraulic cylinders pushing backward against newly-installed rings of tunnel support. This is the customary method for propulsion of shields. With it, each cyclical advance or "shove" must await the erection of a new ring of supports. Faster tunnel driving

Jan 1, 1974

By R. Boom, L. Holappa

In the present paper, microstructure changes of solid-state reduction of industrial chromite pellets and lumpy ore were investigated with SEM/EPMA. To simulate the reactions in the packed bed zone of the Submerged Arc Furnace (SAF), carbon monoxide was used as the reducing agent, with the presence of graphite in proximity to chromite. The experiments were carried out at 1500 °C. Scanning electron microscopy was used to observe and analyse the structure and composition changes of the chromite samples. It was found that reduction of lumpy ore generally took place slower than that of pellet. In all samples, chromite reduction proceeded faster in the outer part of the sample than in the centre part. The reaction mechanism is discussed on the basis of experimental results and earlier investigations. The possibilities to optimize the FeCr production process are also discussed.

Jan 1, 2007

By Mohamed Ourriban, Stéphanie Somot, Éric Proulx, Jean-Sébastien Marois, Marjolaine Drouin, Paul Blatter, Ahmed Bouajila, Claude Gagnon

"The mining industry has to face increasing restrictions concerning the use of fresh water in Québec and throughout the world. Increasing recirculated water usage could lead to a better control of the quality and the quantity of water supplied to the mineral processing units. Furthermore, it could reduce the volume of waste water to be managed and treated before its release to the environment. However, process water may have a negative impact on mineral processing operations, thereby limiting the incentive for sustainable development initiatives. As a first step into selecting and testing remediation strategies, one of which being blending local waters, a mapping of process water quality (inorganic and organic fractions) allowed to locate zones in an industrial case study where fresh water is introduced into the circuit and to detect dissolution and precipitation zones. A complementary hydro-geochemical modeling study on water blends was also performed showing encouraging results towards the objectives of the project.INTRODUCTION The industry has to face increasing restrictions on the use of fresh water in Québec (Quebec Government, 2009) and throughout the world (Brown, 2003; UNESCO, 2006). The cost for the use of fresh water and for water management is highly variable and case-dependent (from 0.2 to up to 7 million dollars/year according to available private estimations, excluding the capital expenditure). It may be, or may become, significant for any plant; thus, risk assessment is of concern here. Using recirculated water could lead to a better control of the quality and the quantity of water supplied to the mineral processing units. Furthermore, it could reduce the volume of waste water to be managed and treated before its release to the environment. However, process water may have some positive and negative impacts on mineral processing operations (Janssen, 2003; Johnson, 2003; Rao and Finch, 1989). Negative impacts could limit the incentive for sustainable development initiatives. Water management strategies at mineral processing sites are supported both by a strategic plan and a water management plan. The strategic plan includes legal aspects, investment costs, potential benefits and various risk levels (Corder and Moran, 2006; Côte et al, 2006; Evans et al., 2006; MacIntosh and Merritt, 2003; McLellan et al., 2008; Merritt and MacIntosh, 2006; Robinson and Keddie, 2006; van Beers et al., 2007a; van Beers et al., 2007b; van Berkel, 2007). In practice, the strategic plan evaluates technical possibilities and costs of various scenarios, such as for example: bringing fresh water to the plant or recirculating waters, or using blends of both. Two important factors to consider in order to enhance the future production efficiency and to minimise risks are: the durability and the stability of the resource, both from quality and quantity points of view."

Jan 1, 2012

Few, if any, reliable thermodynamic data are available for the activity of tin oxide in slags. In this work, the activity of the oxide in silica saturated iron silicate slags has been measured at 1573 K using the equilibrium Sn (alloy) + Y2O2-SnO (slag).Slag and a Ag-Sn alloy were sealed in a zirconium oxide crucible to prevent the escape of volatile tin oxide, and the oxygen pressure at equilibrium measured in situ using the zirconium oxide as a solid electrolyte. Activity of tin was calculated from known data for the Ag-Sn system and activity of tin oxide calculated from free energy data. The results have been extrapolated to predict the industrially important distribution of tin and iron between Fe-Sn alloy and iron silicate based slags.

Jan 1, 1983

Several economic factors have caused the surface mining industry to require large-capacity shovels and trucks for efficient, high-production, low-cost operations. Some of those factors include technological advancements in equipment, commodity market depressions, increased labor and maintenance costs, contractural obligations and harsh operating conditions. The difficult operating conditions in surface mines, however, pose challenges to the use of high-capacity equipment. They include space limitations, weak over-burden, and weathered soils and rocks. So mining companies face major challenges in selecting appropriate shovels to meet the technical, operating, safety, environmental and economic requirements of their mines.

Jan 1, 2003

The cost of power is an important matter to mining companies generally and this thought that the members of the Australasian Institute of Engineers, as well as the engineering and mining professions generally would be interested in any proposal for the reduction of that cost has led to the presentation of this paper.The writer trusts that the description will be found clear and increase the interest in this interesting subject. In the up of the electrical arrangements touched on in this paper, the author has had the able assistance of his friend Mr. Mars, to whom he offers his hearty thanks. The selection of the best class of power plant for a mine is a very difficult and large problem and it is quite out of place to dogmatise that anyone of the many systems that offer is better than another, eg that the all electrical is better than the partly direct steam-driven and partly electrical, or that a gas plant is better than a steam plant. Such a selection is one that calls for very careful and close consideration, in each particular case, of a large number of before it is possible to arrive at a proper decision.

Jan 1, 1912

By Abraham Lindo

"Blasting plays a key role in hard rock underground mining. It is by nature a violent and destructiveextraction method designed to economically fragment the rock into a suitable size for it to be loaded and hauled as part of the specific mining process while controlling the amount of damage to the surrounding rock mass."

Jan 1, 2016

By M J. Begbie, P C. Keall, M P. Simpson

The Golden Cross low sulfidation epithermal deposit occurs in pervasively altered andesite of the Waipupu Formation and in the Waiharakeke Dacite. The unaltered, post-mineral Whakamoehau Andesite overlies these units. The Empire zone of the Golden Cross deposit contains a stockwork which is currently mined by open pit methods, and a series of veins that are mined underground. Alteration envelops both the underground and open pit mineralisation. The core of the alteration zone contains silicification, as quartz veins, and adularia. Shallow portions of the system contain illite-smectite and a thermally unstable chlorite, tentatively identified as corrensite, which pass downward into illite and chlorite, respectively. Replacement calcite occurs widely throughout the altered zone; pyrite is nearly ubiquitous. This alteration assemblage indicates formation from near-neutral alkali chloride waters. A late, post-mineralisation alteration assemblage of calcite, smectite, illitesmectite, kaolinite and siderite presumably formed from weakly acidic, steam-heated CO2-rich waters.   We have identified eight stages of vein formation: (1) sulfide veins, (2) black veins, (3) massive veins, (4) banded veins, (5) thin white veins, (6) crumbly veins, (7) massive/platy calcite veins, and (8) flattened rhomb calcite veins. Gold mineralisation occurred relatively early in the lifetime of the system, dominantly during 2 through 4. The late calcite veins (7 and 8) and early sulfide veins (1) are barren.  

Jan 1, 1997

By Jeffrey Johnson, Carl Sunderman, Ted Williams, Stephen Signer, Douglas Bayer

To measure the loading behavior of friction bolts, researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) installed strain gauges on the interior of friction bolts and developed a battery-powered miniature data acquisition system (MIDAS) that fits inside the hollow portion of the friction bolt. The advantages of this system are that it is protected from face blasts and eliminates the need for external wiring. Laboratory pull-out tests showed that friction bolts installed in a concrete block with resin were loaded to about 1.8 tons/ft of bolt length; bolts installed without resin were loaded to 1.3 tons/ft. Three strain-gauged friction bolts were installed at Hecla Mining Company’s Gold Hunter Mine, Mullan, ID, in the wall or rib of a mechanized cut-and-fill stope. The object of these tests was to establish an installation procedure for the bolt-and-MIDAS combination and to evaluate performance. The stope was advanced in three 15-ft increments and strains induced in the rock bolts by stress changes in the rock were recorded every 30 minutes. The MIDAS proved to be rugged enough to withstand the shock and vibration from nearby (5 ft) face blasting. Data from MIDAS showed that the friction bolt installed with resin was the most sensitive to each face advance. It showed a steady increase in loading to a maximum value of 1000 microstrain. The friction bolt installed without resin showed stick-slip behavior with loads to a maximum of 400 microstrain before the stope was completed.

By D. E. Calisaya, É. Poulin, A. Desbiens, R. del Villar, A. Riquelme

"A 15 cm diameter by 732 cm height, fully automated pilot column was installed in the Agnico-Eagle’s Laronde concentrator (Québec), for evaluating the performance of newly developed sensors and advanced process control algorithms. For eventual comparison purposes, the pilot column is continuously fed with the same slurry feeding the copper-circuit third cleaner column. It is equipped with electrical conductivity-based sensors for estimating the three variables used in the multi-variable control algorithm under evaluation: froth depth, fraction of wash water underneath the interface and gas hold-up. Froth depth is regulated using a PI controller while a predictive controller is formulated as the minimization of the tracking errors of gas hold-up and bias rate, keeping several operating constraints between their practical upper and lower limits. In particular, an unreachable high set point of gas hold-up can be selected in order to maximize the bubble surface area available for particle collection, while maintaining bias rate above a minimum value required for froth cleaning. The proposed strategy may indirectly help optimizing flotation column operation by using these secondary variables, without the implementation of a real-time optimization layer.INTRODUCTION Flotation columns have already been used for more than 30 years, mainly in cleaning stages, as a result of their froth washing capabilities. Despite their widespread usage, the measurement of some pertaining variables and their use for automatic control is rather scarce. Among the most important variables directly related to the process metallurgy (concentrate grade and recovery), froth depth (hf) is the only one normally monitored and controlled. Even though commercial sensors are available, gas hold-up (eg), a variable directly related to concentrate recovery, is seldom measured and never controlled. Another important variable, bias rate (Jb) responsible for concentrate cleaning, is simply not measured at all, as there is no commercial sensor available. Therefore, besides froth depth, continuous monitoring of process variables is limited to flow rates (gas, feed, tailings, wash water), i.e. to manipulated variables. Some new available sensors have been industrially tested, e.g. the Sonar-TracTM for eg (O'Keefe, Viega & Fernald, 2007) and the McGill hold-up sensor (Tavera & Escudero, 2002). Others, for bias rate and frother concentration, have been successfully validated at laboratory scale by Laval’s LOOP researchers (Maldonado, Desbiens, del Villar & Chirinos, 2008b; Maldonado, Desbiens, del Villar & Aguilera, 2010a). Some devices have been extensively used for monitoring bubble size and space distri-bution, e.g. McGill bubble viewer (Gomez & Finch, 2007) and others."

Jan 1, 2012

By Manqiu Xu, Joe Holmes, Peter Wells, Peter Langlois, Germain Labonté, Jim Barrett

"The flowsheet for the Voisey’s Bay mill had to meet the challenge of processing an ore containing high pentlandite and chalcopyrite values in a largely pyrrhotite/troilite matrix. In the 1994-97 period, circuit development focused on making a high-grade copper concentrate and a relatively low-grade nickel concentrate. However, in 1998 a circuit with copper concentrate, high-grade nickel concentrate and a Ni/Cu middlings concentrate was specified. Following a three year project delay, work resumed on the flowsheet in 2001, and the target for the overall grade of the nickel concentrate was raised from 14% to 20% nickel. To achieve this target triethylamine tetramine (TETA) and sulfite pyrrhotite depressants were used in an all lime circuit. It later became evident that, with appropriate selection of collector and adjustment of the circuit by the addition of a scavenger on the scavenger cleaner, it would be possible to approach the grade of concentrate required without the use of pyrrhotite depressants. The recycle of water and the contained thiosalts was also proven to be instrumental in raising the grade.Construction and commissioning of the mill were fast-tracked with start-up of the mill in September 2005 some six months ahead of the original schedule. Ramp-up of both throughput and metallurgy was faster than any other recent nickel installations with tonnage being limited mainly by concentrate dewatering due to the higher than initially planned ore grades.INTRODUCTIONNickel was discovered in the vicinity of Voisey’s Bay by Chislett and Verbiski working for Diamond Field Resources in 1993 and the Ovoid deposit was delineated in the winter of 1994/95. By the end of 1995 the Ovoid had been well explored and at that time was thought to have a reserve of at least 30 million tonnes with an average grade of 2.83% Ni and 2.0% Cu. Drilling to the east of the Ovoid had indicated the presence of significant mineralization. In June of 1995, Inco Limited bought a 25% share in the Voisey’s Bay Nickel Company (VBNC) which was a subsidiary holding company set up by Diamond Fields. Inco also bought 8% of Diamond Fields and negotiated the right to sell all the nickel produced from VBNC for twenty years as part of this agreement. In April 1996, Inco bought the 75% of VBNC shares that it did not own."

Jan 1, 2007

By M. C. Malamphy

The report of work accomplished on the United States Bureau of Mines' bauxite project in Pulaski and Saline Counties, Ark., is presented in this volume and in a series of Reports of Investigations immediately following this volume. This first volume covers the project as a whole, whereas the subsequent volumes contain maps of local areas and deposits developed, together with logs of the drill holes and descriptions of the separate deposits. The Arkansas bauxite project was initiated in December 1941 and continued for 4 years. The first 5 months were spent in studying the problems presented and in geophysical exploration, Core drilling began in May 1942 and ended in May 1945. The project was one of the larger and more important of those undertaken by the Bureau of Mines for the purpose of developing domestic sources of supply of critical and strategic minerals necessary for National defense and for the successful waging of modern mechanized warfare. Some of the results of the Bureau's bauxite exploratory work have been made available to the public through the medium of press releases, transactions of technical societies, and government publications. More information has been supplied to government agencies upon request and to land owners and mine operators of the deposits concerned in the form of maps showing locations of all holes drilled on the property and logs with chemical analyses of' all cores recovered. In October 1946, the factual data were made avail-able to .the public in manuscript form in an-"open file" at the office of the State geologist, R. B. Foxhall, Little Rock, Ark., and at the office of the. Bureau of Mines in Washington. For the purpose of providing a background for the presentation of the factual data obtained, the history of bauxite is reviewed briefly. Information relative to past production and reserves of bauxite in Arkansas also is given. A resume of the development of the industry in Arkansas, the exploration and mining methods employed, the various uses to which the bauxite is put, and a brief outline of the geology of bauxite in Arkansas complete the -background.

Jan 1, 1948

The Rosebery and Hercules mines, situated in the Rosebery-Williamsford district in western Tasmania, have a history of production dating back to 1896-7, although full scale production did not commence until 1936, following the development of a satisfactory process of selective flotation (Hall, Cottle, Rosenhain and McGhie, 1953). The mineral composition of the Rosebery zinc-lead ores was first described in detail by Stillwell (1934). The Hercules ore is generally similar, but as yet no descriptions of it have beenpublished.Since Dr. Stillwell's paper appeared, the management of the Rosebery and Hercules mines has from time to time submitted a number of interesting mineral specimens to C.S.I.R.O. Mineragraphie Investigations. Examination of these specimens brought to light eight minerals, some relatively uncommon, not previously recognized in these ores.They are cassiterite, molybdenite, stannite, electrum, meneghinite, boulangerite, pyrargyrite and pyrrhotite. Some of the specimens are also rich in tetrahedrite and gold. In addition each of the other ore minerals described by Stillwell, viz. pyrite, sphalerite, galena, bournonite, chaleopyrite and arsenopyrite, was detected in one or more of the specimens examined during the present study. The principal gangue minerals were found to be quartz, manganiferous carbonate, sericite and barite, agreeing closely with the observations of Stillwell.The present study was based on the examination of the following eight specimens.

Jan 1, 1960

As ore deposits become finer grained the requirements for regrinding before cleaning or leaching have increased substantially. Despite this increasing need, there is no standard test to predict grinding energy requirement below 70 microns. The standard Bond Mill test applies for coarser ball milling, but is not appropriate for stirred milling with fine media grinding to 70 microns. With no industry -standard test, the energy requirement is often made on the basis of supplier estimates or benchmarking against similar applications. Yet suppliers use vastly different scale-up methods which result in widely different energy estimates. Estimates can differ by 100-300% even for similar mills. This must result in serious errors to install either too much or too little grinding power. This paper explores this by comparing the actual performance of full scale regrind mills against their original design estimate. It confirms that serious scale-up errors have been made, and have then been perpetuated by ?benchmarking?. The test conditions to achieve accurate power estimation are discussed. The essential test conditions are: continuous (not batch) tests, ensure steady state (no coarse fraction retained in test mill), correctly account for classification, measure energy directly (not inferred), and using the same media size as the full scale installation. Failure to correctly address even one of these factors can bias results by 40%; failure to address several multiplies the error.

Jan 1, 2011

By Andrea Lisjak Bradley

Clay shales are currently being assessed as possible host rock formations for the deep geological disposal of radioactive waste. However, one main concern is that the favourable long-term isolation properties of the intact rock mass could be negatively affected by the formation of an excavation damaged zone (EDZ) around the underground openings. The goal of this thesis was to develop and validate a mechanically-based model of the deformation and failure process of a clay shale, namely Opalinus Clay (OPA), with particular focus on the influence of anisotropy on the short-term response of circular tunnels. To achieve this goal, a hybrid continuum-discontinuum numerical approach was developed in combination with new field measurements from the Mont Terri underground research laboratory. The response of OPA during the excavation of a full-scale emplacement (FE) test tunnel was characterized by geodetic monitoring of wall displacements, radial extensometers and longitudinal inclinometers. The deformation measurements indicated strong directionality induced by the combined effect of in-situ stress field and bedding planes striking parallel to the tunnel axis, with the most severe deformation occurring in the direction approximately perpendicular to the material layering. Computer simulations were conducted using a newly-extended combined finite-discrete element method (FEM/DEM), a numerical technique which allows the explicit simulation of brittle fracturing and associated seismicity. The numerical experimentation firstly focused on the laboratory-scale analysis of failure processes (e.g., acoustic activity) in brittle rocks, and on the role of strength and modulus anisotropy in the failure behaviour of OPA in tension and compression. The fracturing behaviour of unsupported circular excavations in laminated rock masses was then analyzed under different in-situ stress conditions. Lastly, the proposed modelling methodology was applied to the aforementioned FE tunnel to obtain unique insights into the EDZ formation process around emplacement tunnels for nuclear waste. The calibrated numerical model suggested delamination along bedding planes and subsequent extensional fracturing as key mechanisms of the damage process potentially leading to buckling and spalling phenomena. Overall, the research findings are already having a direct impact on the preliminary design process of an underground repository for nuclear waste in Switzerland.

Jan 1, 2015

By M. Batzle

The upper Arkansas basin has some of the greatest potential for geothermal development in Colorado. Over several summers, students conducted an investigation using seismic, gravity, and magnetics in order to help identify the large structures and basin fill associated with the Rio Grande Rift. Adjacent to Mount Princeton Hot Springs, near surface geophysics was conducted to help understand the faulting and fractures that act as a conduit for hydrothermal flow. The methods used included high frequency 3D seismic, magnetics, gravity, D.C. resistivity, and self potential. Throughout the Mount Princeton area, passive seismic, vertical seismic profiling, and well logging were also used to better understand the geology and activity of the region. The results indicate for the area northwest of the hot springs, a 40 to 50 m thick unconsolidated layer overlying the fractured granitic basement. The DC profile shows a deep geothermal anomaly of low resistivity which correlates with a positive SP anomaly in the same region. In the Chalk Creek valley, a shear zone extends from the north east to the south west, just south of the Chalk Cliffs. There appears to be an upward migration of the water through this shear zone which then flows along the porous sediments towards the south in this area. The deep seismic data collected in the center of the basin suggests that the depth to the basement is approximately 2000m. Also identified on the deep seismic are two major faults on the west end and two minors at the east end of the cross-section. An alteration zone is identified between the faults and a possible Precambrian northeast trending shear zone. The potential for developing an Enhanced Geothermal System (EGS) near the center of the valley is high. Our geophysical results indicate a deep basin fill near the center of the basin providing high temperatures. The range front (Sawatch) fault is observed to penetrate under the center of the basin and is an attractive target for natural fractures.

Jan 1, 2011

"Exploitation of an ore deposit can be optimized by adapting the beneficiation processes to the properties of individual ore blocks. This can involve switching in and out certain treatment steps, or setting their controlling parameters. Optimizing this set of decisions requires the full conditional distribution of all relevant physical parameters and chemical attributes of the feed, including concentration of value elements and abundance of penalty elements. As a first step towards adaptive processing, the mapping of adaptive decisions is explored based on the composition, in value and penalty elements, of the selective mining units.Conditional distributions at block support are derived from cokriging and geostatistical simulation of log-ratios. A one-to-one log-ratio transformation is applied to the data, followed by modelling via classical multivariate geostatistical tools, and subsequent back-transforming of predictions and simulations. Back-transformed point-support simulations can then be averaged to obtain block averages that are fed into the process chain model.The approach is illustrated with a ‘toy’ example where a fourcomponent system (a value element, two penalty elements, and some liberable material) is beneficiated through a chain of technical processes. The results show that a gain function based on full distributions outperforms the more traditional approach of using unbiased estimates."

Jan 1, 2015

By Matthias Baeßler, Markus Herten, Ernst Niederleithinger, Steven Georgi

"Abstract: BAW and BAM have performed a large scale comparison and calibration test on static and dynamic load capacity evaluation of bored piles in glacial sandy soil. The test was performed using eight piles at the BAM test site for technical safety at Horstwalde 50 km south of Berlin. The test area has been prepared and investigated in great detail using boreholes, cone penetration tests, pore pressure sensors and geophysical methods to assure controlled conditions for all piles and tests. The piles (10 m length, 0.9 m diameter) are mainly friction piles (low toe resistance) and have been checked by integrity testing. Five piles have been tested by five contractors using the dynamic method in a blind experiment, the other ones piles by static load and/or later on by the dynamic method. Some piles have been equipped with additional fibre optic instrumentation which proved to be robust and helpful in interpreting the results of static, dynamic and integrity tests. We have experienced a deviation of the dynamic load test results gathered in the blind experiment from the static values of up to 20% in most cases, sometimes even up to 30%. This can be related to the known soil inhomogeneities, interpretation and modelling in CAPWAP and method inherent uncertainties. In cases where the static values were known by the testers for calibration, the deviations were significantly smaller. It has to be taken into account, that the two static load tests showed different results as well. Due to the low toe resistance, use of a big drop weight (11 tons) and large drop heights most piles suffered from cracking, which was clearly seen in follow up integrity tests and confirmed by excavation. The piles are available for further research.IntroductionBored piles are used in many construction projects of the German waterways authorities, e. g. bridges, piers or locks. Their load carrying capacity varies with pile type and geometry as well as soil type, parameters and structure and is thus not easy to calculate in advance. Dynamic pile testing as a cost effective addition or replacement for expensive load tests is accepted in many places (Beim and Likins 2008) but still doubted in others. Inspired by the international prediction event for piles in residual soil carried out in the frame of ISC’2 (Viana de Fonseca and Santos 2008), governmental research institutes have designed an experiment in a geological setting typical for glacial and post-glacial areas in northern Germany. Some results have already been presented by Niederleithinger et al. (2012), Herten et al. (2013) and Baeßler et al. (2013). It was intended to perform a blind test for load capacity estimation using dynamic pile testing on six drilled shafts involving five test crews. Two other piles would have to be tested thereafter using static and dynamic methods."

Jan 1, 2014

By Sam S. Taylor

[The discovery of many oil fields in Illinois since 1936, and their rapid development have brought the problem of brine disposal to the foreground in that State. The ultimate magnitude of the problem is not yet known, but already it is treat enough to warrant technical investigation. The Bureau of Mines, therefore, has made a general survey of the methods of handling oil-field b brines in Illinois rend has studied in detail three subsurface disposal systems.]

Jan 1, 1940

Exerting the Advantages of National Key Discipline, Outstanding the Training of Engineering Capability, Cultivating Talent to be with Innovation Ability

Sep 13, 2010