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By Kazuya Koyama

We are studying the hydrometallurgical recycling process of indium from an Indium-Tin-Oxide(ITO) target. For this process, it is necessary to remove Sn(IV) ions from the aqueous hydrochloric acid solutions containing In(III). In this study, the removal of Sn(IV) ions by a potentiostatic electrolysis method was examined. The polarization measurements and potentiostatic electrolyses were carried out under a nitrogen atmosphere. In the Sn(IV) solution, current begins to rise at the cathode potential of -0.26 V vs. SHE, and increases with a reduction in the cathode potential. In the In(III) solution, current begins to rise at a cathode potential of -0.43 V vs. SHE. Metallic tin was electrodeposited without indium electrodeposition at the cathode potentials of -0.30 and -0.40V vs. SHE. More than 98% of the Sn(IV) was removed at the cathode potential of -0.40 V after the electrolysis for 3hrs. Both tin and indium were electrodeposited at the cathode potential of -0.50V vs. SHE.

Jan 1, 2006

The library of the above-named Societies is open from 9 A. M. to 10 P. M. except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared, to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape. HARRISON W. CRAVER, Director.

Jan 5, 1919

Systemic process mineralogy study on Baerbulawu refractory hematite ore in Kazakhstan has been carried out. The ore contains Fe 41.34%, and 87.26 % of which exists in hematite. Most hema-tite occurs as fine or ultrafine grains and its average size is only 0.015mm. The gangue is mainly composed of quartz, mica, chlorite, kaolinite and other clay minerals. The liberation of hematite is only 66% when the ore is grinded to 75% ?0.074mm, while part of gangue is already liberated from hematite under this grinding condition, so these gangue can be cast away by magnetic separation in advance. Hematite will not liberate completely from gangue untill grinding fineness reaches 86% ?0.038mm, at the same time, free particles of ultrafine hematite tend to coagulate randomly with quartz and clay minerals, so appropriate dispersant is necessary to pre-vent hematite and clay minerals from coagulation. Based on the process mineralogy research, final technology flowsheet is high-intensity magnetic separation by coarse grinding?rough magnetic concentrate regrinding?inverse flotation, and an ideal index is achieved. The yield of final iron concentrate is 43.46%, and its grade and recovery are 66.76% and 70.55% respectively. The research result is also useful to other similar iron ores.

Jan 1, 2014

By Tomás Guerrero M

Entre 1972- 1974, MINERO PERU realizó trabajos complementarios de perforación diamantina en Quellaveco. Producto de este estudio realizado, se encuentrÓ que el depósito de Quellaveco es un típico yacimiento de pórfido de cobre. En este sentido, el presente texto describe la exploración del pórfido de cobre de Quellaveco, ubicado en el departamento de Lima. Asi también se describe la geología, los trabajos de exploración anteriores, un programa de exploración minero Perú, base topográfica, registro y muestreo, precisión del muestro, ensayes y precisión, cálculo de las reservas, delimitación y dimensionamiento, las características del mineral y el comportamiento metalúrgico que este proceso implica.

Nov 20, 1978

During the first five years of operation, the Lihir gold mine has steadily increased plant throughput rate to over 4 Mtpa, well above the original design capacity of 2.8 Mtpa. Understanding how future variations in ore type impact on plant performance has been an integral part of LihirÆs development program. This paper discusses the key drivers for significant improvements to the plant, including a second oxygen plant, a pilot flotation plant, an autoclave heat recovery circuit, a pebble crushing circuit and additional autoclave feed pumping capacity. The result is a process plant with the flexibility to accommodate variations in ore type without significant loss of throughput.

Jan 1, 2003

The operation of cyclones and cylinders is briefly described and com- pared, and a number of recent applications in mineral, gold and coal plants discussed. The capacity of an existing pump and cyclone in a circuit can be sig- nificantly increased by retrofitting a cylinder in series to predensify the cyclone feed. The cyclone overflow product size can also be adjusted and controlled using a variable aperture valve between the cylinder and the cyclone. This predensifier-cyclone system has been used at plant scale to con- trol the pulp density of the feed to cyanidation in gold plants, to size flotation feeds before split conditioning and to deslime and classify in gravity plants. Application in a typical regrind circuit is considered. Cylinders and cyclones also have numerous applications in water management systems, e.g., degritting mine and plant waters to protect pumps, sprays and other equipment. Screen undersize and flotation con- centrate dewatering circuits are described to illustrate how suitable stream recycles can reduce water consumption, optimize fresh water use and improve efficiency.

Jan 1, 1988

Harrison W. Craver, Director The Library of the above-named Societies is open from 9 A.M. to 10 P.M., except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 5, 1917

By H. N. Wolcott

AMONG the many cases of replacement of one mineral by another, that of quartz or silicates by pyrite, or even other sulphides, is not uncommon, but the reverse of this process does not appear to have been recorded, even if it has been observed. It, therefore, seemed to the writer that the case described below was worthy of record. FIG. I.-GROUND MASS OF CHALCOPYRITE (C) CONTAINING ROUNDED GRAINS OF PYRITE (P) SHOWING DIFFERENT DEGREES OF REPLACEMENT BY QUARTZ (Q), AND ALSO QUARTZ VEINLETS CUTTING THROUGH THE PYRITE. (PHOTOGRAPHED BY REFLECTED LIGHT.) The specimens described in this paper were obtained by R. B. Morton of Idaho Springs, Colo., from the Old Town Mine, in Russell Gulch, and are in the collection of Cornell University, where the writer studied them. In the rough, the specimens appeared to consist largely of chalcopy- rite, with some grains of tetrahedrite. The polished surface of some of

Jan 6, 1917

By AIME AIME

The following abstract of the minutes of the final Adjourned Annual Business Meeting, held Nov. 12, 1912, in the office of the Institute, 29 West 39th Street, New York City, is here presented for the information of the membership at large. On the announcement by the Secretary that there was a quorum present, President James F. Kemp called the meeting to order. The minutes of the Adjourned Annual Business Meeting of Oct. 7, 1912, were read and approved. (Sec p. xi,Bulletin No. 71, November). Prof. Jos. W. Richards, in behalf of the Special Committee of the Board of Directors and the Council (Messrs. Richards, Kirchhoff, and Rand), withdrew the two proposed amendments to the Constitution offered by the said Committee at the Adjourned Annual Business Meeting of Oct. 7, 1912. (See Bulletin. No. 70, October, 1912, p. vi., and Circular Announcement No. 8, Oct. 15, 1912, p. 15.) Professor Richards presented a syllabus of the proposed amendments to the Constitution and By-Laws prepared by the Special Committee. Several members present discussed various sections of the proposed Constitution, and the Committee advised that the suggestions would he duly considered before submitting the final document, which would be duly presented and sent to the membership at large at least 30 days before the next Annual Business Meeting, Feb. 18, 1913. Professor Richards presented a resolution, seconded by Mr. Kirchhoff, making a change in the present Certificate of Incorporation, so that it would conform to the proposed changes in the Constitution and By-Laws; said resolution was unanimously adopted. Professor Richards presented another amendment to the Constitution, which had been purposely omitted from the printed list, but had been requested by many members, namely, the creation of a " Class of Fellows." This question was freely discussed at the Cleveland meeting (see Bulletin No. 71, November, 1912, p. 1348), and in view of the diversity of opinion it was-decided to present it in separate form for separate action of the membership at large at the Annual Business Meeting, Feb. 18, 1913. In answer to question, the President announced that the proposed amendments to the Constitution and By-Laws presented by Messrs. Corning and Stone at the Adjourned Annual Business Meeting, Oct. 7, 1912, and published in Circular Announcement No. 8, Oct. 15, 1912, were still on record. Professor Richards presented a syllabus of the proposed amendments to the By-Laws, and several sections were discused by members present, but no action of record was taken. Mr. Charles F. Rand read a letter from Mr. L. K. Armstrong, Sec-retary of the Spokane Local Section of the Institute, referring to the proposed amendments to the Constitution, and he announced that many of Mr. Armstrong's suggestions were, in one form or another, already incorporated in the proposed amendments submitted by the Special Committee. A special vote of thanks was passed to Dr. Albert R. Ledoux for the valuable assistance rendered by him to the Special Committee in the preparation of the proposed amendments to the Constitution and By-Laws.

Dec 1, 1912

By J. R. Linney

THE Eastern Magnetite Industry produced approximately 7,850,000 long tons of crude ore in 1945 from which was obtained approximately 3,650,000 long tons of shipping product or a ratio of 2.10 to 1. Lack of skilled or experienced miners was the greatest handicap. Veterans returning to work improved the underground labor shortage in some localities but as a whole the labor shortage was keenly felt throughout the industry. One cannot now predict what may be accomplished in 1946 but barring major steel strikes a worthwhile improvement can be expected. At the Richard mine of the Richard Ore Co., the shipping product for the year amounted to approximately 124,650 long tons of concentrate and lump ore. Crude-ore production was 160,600 long tons. The average analysis for lump ore was 63 per cent iron and for concentrates 66.05 per cent. The Warren Foundry and Pipe Corp. at their Mt. Hope mine produced 73,000 long tons of lump ore averaging 59.5 per cent and 57,000 long tons of concentrate averaging 67 per cent. The total mine hoist was approximately 209,000 long tons. Operations were commenced through the new Leonard shaft on Jan. 18; the Brown shaft through which operations had been conducted since 1912 caved beyond repair on Sept. 26. No one was injured but pumping facilities were somewhat disrupted. In order to reach designed capacity a total of 400 men will be required with 300 underground. Due to shortage of labor all operations in 1945 were concentrated on the 1700 level. As fast as men can be hired and trained development of the 2100 and 2500 levels will commence. Mt. Hope has a consider-

Jan 1, 1946

By N. S. Stoloff, K. R. Jordan

The temperatwe and grain size dependence of the mechanical avoperties of ordered and disordered Fe-49 pct Co-2 Pct V were investigated. The yield and flow stresses obeyed the Hall-Petch relationship u = ai + kd-&apos;I2. Ohdering reduced the intercept stress cjj and raised the Petch slope, k, at all temperatures. Ordering also increased the temperatwe dependence of k. The ductile to brittle transition temperature increased with order and grair~ size. Cleavage fracture was nucleation limited and the fracture stress did not zlary linearly with d-&apos;". A quantitative test of the Cottrell-Petch fracture theory (and recent modifications which consider the influence of slip mode), demonstvated that this theory is not applicable to FeCo-V. COTTRELL&apos; and etch&apos; independently suggested that a criterion for cleavage failure at the yield point, a,, based on dislocation pileups at a grain boundary or other obstacle to dislocat.ion motion, is: aYYkd&apos;I2 1 opy [ll or, equivalently, aikz,d112 +k:)bpy [2] where a, and ky are the Hall-Petch intercept and slope, respectively, 2d is the grain diameter, P is a geometric factor dependent on the macroscopic ratio between shear and tensile stress, p is the shear modulus, and y is the true elastic surface energy. When the product of quantities on the left side of the equation is equal to or exceeds that on the right, cracks should be able to nucleate and propagate at the yield stress, as shown schematically in Fig. 1. Therefore a high intercept stress, high Petch slope, or coarse grain size favors brittleness. petch3 associated the existence of a ductile to brittle transition in ferrous alloys with the temperature dependence of ai. One of the earliest modifications of the Cottrell-Petch theory was presented by ~rmstrong,~ who derived an expression for transition temperature in terms of several measurable flow and fracture parameters. The latter paper was able to rationalize situations in which the transition temperature increases with decl-easing grain size, as in the case of molybdenum,&apos; and also suggested that Ppy should be a function of grain size as well as temperature. More recently Johnston et a1.6 and Smith and worthington7 have suggested that the temperature or composition dependence ol&apos; ky must also be taken into account if there is any cha.nge in deformation mode, as from wavy to planar slip, or wavy slip to twinning, with change in temperature or solute content. Armstrong %as suggested that for hcp metals changes in o;k,dw> o;k,d1/2< / is / ^^^^ / / y_______________________________________ d-"2 Fig. l—Schematic representation of grain size dependence of yield stress, cry, and fracture stress, CTF. Intersection defined by Cottrell-Petch equation. slip mode should be incorporated in the theory through changes in the critical resolved shear stress for the slip system which controls ky. The purpose of the present investigation was to critically test the modified677 Cottrell-Petch theory of fracture in the superlattice alloy Fe-49 pct Co-2 pct V, by studying the grain size dependence of the yield and fracture stresses over a range of temperatures, in conjunction with an investigation of slip mode and fracture behavior. Previous work has shown that long range order results in a sharp decrease in flow stress, a small increase in work hardening rate and a drastic upward shift in the ductile-brittle transition temperature of F~CO-V.~&apos;~ The only comprehensive study of slip character in this alloy has been reported in a preliminary account of the present investigation.10 EXPERIMENTAL PROCEDURE The experimental work was carried out on material produced from a 10 lb vacuum melted ingot, of composition 49.32 wt pct Co, 2.09 wt pct V, balance Fe. 30-mil thick sheet samples with a 1; in. gage section were machined from cold rolled stock. The degree of cold work ranged from 85 pct for the finest grained samples to 5 pct for the coarsest grain size. Details of ingot fabrication are reported elsewhere." Equi-axed grain sizes in the range 12.7 to 75.4 p were obtained by annealing for varying times at 850°C. (Re-crystallization annealing time, rather than temperature , was varied to control grain size to insure that samples of all grain sizes contained equivalent quenched-in vacancy and interstitial concentrations.) Grain sizes were measured by the line intercept method on several specimens of each grain size. Following recrystallization, all samples were disordered by quenching into iced brine.

Jan 1, 1970

By John B. Cocanour

The U.S. Bureau of Mines (USBM) has developed a laboratory-scale on-line analysis and process control system for a decopperization electrolytic circuit. This system is software driven, running on a 486DX-33 personal computer (PC) utilizing a portable energy- dispersive x-ray fluorescence (XRF) spectrometer as the sample analyzer. The XRF copper reading obtained was used as the control variable through an RS-232 serial interface to the PC for software-based control of feed flowrates. When the copper concentration in the electrolytic cell (as measured by the XRF) deviated from the set point, the feed flowrate to the cell was automatically altered using software-based proportional-integral-differential (PID) computer control to yield the desired copper concentration at the electrolytic cell outlet.

Jan 1, 1994

By Hatch, A. Reple, W Valery

The mining industry is facing declining feed grades which require the mining and processing of larger volumes of material per tonne of product. Pre-concentration aims to remove barren material at as coarse a particle size and as early in the process as possible to reduce processing costs, energy consumption, water losses, and greenhouse gas emissions while increasing production and profitability. This may be achieved using bulk ore sorting—the separation of barren gangue from a fully loaded conveyor belt based on the grade as measured or inferred from a sensor. This paper evaluates the technical and economic viability of bulk ore sorting for the PanAust Phu Kham copper deposit in Lao PDR. Bulk ore sorting technology is described briefly along with discussion of appropriate sensor and diversion systems for the Phu Kham operation. To evaluate the economic implications, the actual mined material and costs from 2014 were used as the base-case. Sampling data was not available; therefore, the ore grade variability that would feed a bulk ore sorter was estimated using geo-statistical tools based on mine grade control data. The sorter performance when treating this material was simulated considering the accuracy of the sensor measurement and errors associated with material diversion. The impact on inferred cash flow was estimated for several different scenarios considering the additional costs for sorter operation and reject handling. The evaluation demonstrated that bulk ore sorting at Phu Kham has the potential to increase the amount of metal in product and/or reduce processing plant throughput (and costs) to improve the annual inferred cash flow for the conditions investigated. The sorter is the gatekeeper – only material above the cut-off grade (value-adding) reports to the processing plant; no waste dilutes the feed. Likewise, above cutoff grade material is not lost to waste; preventing lost revenue.

Jan 1, 2016

By Changwoo Lee, Jan M. Mutmansky

"This paper results from the research at The Pennsylvania State University into establishment of standard procedures for characterization of respirable coal dust performed by the Generic Mineral Technology Center for Respirable Dust and supported by the U.S. Bureau of Mines and the Mining and Mineral Resources Research Institute at The Pennsylvania State University. The research performed within this particular project is oriented primarily toward standard methods of sampling and characterizing respirable coal mine dust underground so that the chemical, physical, and morphological characteristics are known and can be related to the incidence of coal workers' pneumoconiosis (CWP) in Pennsylvania.The research was initiated by con¬ducting a search of the literature to determine what coal and geologic variables may be related to CWP. The effects of coal rank, free silica content, the mass of respirable dust, and the level of trace elements were the major variables studied. It seems to be evident that the free silica content, the rank of coal, and the mass of respirable dust are the major concerns in defining the causes of CWP. However, based on the literature survey, the authors have concluded that verification of the causes of CWP is a multivariate problem and must be analyzed in an appropriate statistical manner.The results of a multivariate analysis of ten trace elements recorded on Pennsylvania coals are presented. Five of these trace elements were found to be of use in differentiating one coalfield from the others. Of these five elements, chromium and zirconium showed a strong positive correlation with the rank of coal while strontium showed a negative correlation.The design of the field sampling work and its application in future research is the final topic discussed. The sampling plan is oriented toward continuous miner sections with eight-stage impactors as the collection equipment. All of the field work will be conducted in the coal measures of the Allegheny Formation and above with both dust and channel samples being collected in the same mines.Coal workers' pneumoconiosis has been an important topic of concern to miners, mining engineers, and epidemiologists for decades. The general cause of the dis¬ease, the inhalation of coal mine dust, is well known, but the specific coal and geologic variables that affect the incidence and severity of the disease are still subject to debate and study. The primary objective of this study is to identify those variables of Pennsylvania coals that contribute to the CWP problem. To accomplish this task, a field sampling program is to be conducted to relate the characteristics of the coal dust, the coal seam properties, and the geologic variables to the occurrence of CWP.The first year of this study has been involved with both a literature review and experimental work oriented toward identification of causal variables related to CWP. The results of this work are presented here along with plans for implementation of the findings in future research.The previous studies of CWP causal variables have been conducted by scientists, engineers, and medical personnel. Many different types of studies have been performed with emphasis on interpreting the effects of dust mass concentration, mineralogy of the coal, the rank of the coal, and trace element concentrations upon the incidence of CWP in various coalfields. Most of the research has been conducted during the last two decades, with the British Isles, West Germany, and the United States being the primary countries involved.The review of the literature was conducted to determine which variables are likely to warrant further study in Pennsylvania. Previous research studies have related CWP to free silica and other mineral content, the rank of coal, the mass of dust in the working place, and the trace elements in the coal and lung dust. In the following sections, each of these topics will be discussed and analyzed."

Jan 1, 1988

By Indranil Roy

Gua supergene enriched iron ore deposit from Jharkhand, India has been geostatistically modeled. Population modeling shows a negatively skewed 3-parameter log-normal fit for Fe and positively skewed 3-parameter log-normal fit for Al2O3 and SO2. Semi-variographic studies for Fe indicate spherical function fit using point kriging cross-validation technique with Co=4.06(%)2, C5.11 (%)2, Co+C=9.1 7(%)2 and &apos;a&apos;=348m. Kriging with 50mx50mx 10m block size at 740mRL led to a global mean kriged estimate of 61.98% and kriging variance of 4.04(%)2 for Fe with central 90% geostatistical confidence limits at 61.39% and 62.24% for that level. This led to an ore inventory at 740mRL as 7.29 million tonnes of ore.

Jan 1, 2002

By Z. H. Xie, D. S. He, W. M. Xie

China has rich phosphate rock resources, but with their continuous depletion, the rich ore resources have become increasingly scarce, which makes the exploration of collophane more important. Medium- and low-grade phosphate rock cannot be utilized until their impurities have been removed through mineral processing. However, due to the similar physical and chemical properties of dolomite and phosphorus minerals, the separation of dolomite from phosphate

By Seshadri Seetharaman, Nurni N. Viswanathan, Haijuan Wang

The present work aims at some process modifications in specified metallurgical processes, wherein CO2 can be used successfully as an oxidant for decarburization in steelmaking and applied in some non-ferrous metals production processes. During the decarburization of Cr-containing high alloyed steels, the present researchers investigated the possible use of CO2 instead of Ar-O2 mixture and could successfully decarburize the steel melt without significant loss of alloyed Cr to the slag phase. A mathematical model was developed based on the bubble formation accompanying the chemical reaction: C(molten steel)+ CO2(gas)= 2 CO(gas). The model predictions were tested by laboratory scale (1 kg) experiments carried out in an induction furnace and very good agreement between the model predictions and experimental results were observed. A national project has been sanctioned in China for the implementation of CO2 in decarburization of ferroalloys as well enable the addition of pig iron in the electric arc furnace process when the scrap supply is limited. New processes have been developed for the utilization of CO2 in the case of non-ferrous processes. A novel method of treatment of Al dross by leaching with water and capturing the evolved NH3(formed by the hydrolysis of AlN) has shown very promising results.

Jan 1, 2015

By A Cranley, A Giblett, S Thacker

The Newmont Tanami Operations are located in the Northern Territory, approximately 550 km north-west of Alice Springs. The Granites process plant commenced operations in 1986 as a 300?000 t/a ball mill / carbon-in-leach (CIL) plant and has undergone numerous expansions between that time and the current day, with project-to-date gold production exceeding 6.5 Moz. Annual plant throughput has exceeded 2.8 Mt/a while processing a blend of open pit material and ore from the Callie Deeps underground mine, with annual gold production exceeding 400 koz. In 2013 the operation processed 1.8 Mt of underground ore for the production of 323 koz of gold.This paper reviews the operation and expansion of The Granites process plant since the mid to late 1980s with particular focus on the gravity gold recovery circuit. The Tanami ores contain significant levels of free gold, and gravity recovery has long been an integral component of the metal recovery process at the Granites plant. The results of ten years of gravity circuit performance analysis and optimisation are presented.CITATION:Giblett, A, Cranley, A and Thacker, S, 2014. Three decades of gold production at the Newmont Tanami operations, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 209–216 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By B. P. von der Heyden, P. Neethling, M. Tadieb, L. Babedi

The effects of trace element substitutions in sphalerite mineral structure on optimised floatation response have, as yet, not been fully constrained or fully understood. To further this important field of study, this contribution focusses specifically on mineral and surface chemistry, and electro-chemistry of Cd- and Co- substituted synthetic sphalerites using Raman spectroscopy and Zeta potential experimentation. Raman spectroscopy illustrates that the presence of these impurities results in the introduction of a new mode, the relative intensity of which can be correlated (Cd r2=0.95 and Co r2= 0.99) to the dopant concentration. Comparison to X-ray Diffraction results measuring the unit cell parameter further shows that this relative intensity (Cd r2=0.81 and Co r2= 0.99) may provide insights into the degree of lattice strain within the mineral structure. The zeta potential distribution of an un-activated Cd-sphalerite show no detrimental effect as function of Cd content. Although the iso-electric point shifted from 2.45 at 1 wt.% Cd to 2.69 at 3.68 wt.% Cd, the zeta potential remained negative at alkaline media. Conversely, cobalt at low concentration of 0.36 wt.% had a detrimental effect on the surface charge, resulting to a close to neutral zeta potential at different pH. The adsorption of Cu ions on the surface of Co-bearing sphalerite conditioned in an alkaline media slightly increases the zeta potential of Co-sphalerite. While the Cd-bearing sphalerite decrease in negative zeta potential at >1 wt.% Cd indicating a complete exchange between Cu and Zn. The results presented herein illustrate that, based on the chemical nature of the substituting metal; sphalerite will exhibit multiple response to flotation reagents. Maximum recovery of zinc can thus only be achieved through multidisciplinary study and fundamental understanding of the effects of cation substitution on mineral structure and surface chemistry, the latter necessarily affecting the floatation response.

Jan 1, 2018

By Thang V. Nguyen, Lisheng Shao, Gary E. Taylor

"The Community Memorial Hospital of Ventura, California, proposed to build a new state-of-the-art Cancer Treatment Center with radiation shielding walls and roof. The loose silty soils at the site had the potential to liquefy during an earthquake, which would result in significant settlement under the heavy footing loads. Treatment options included various deep foundation alternatives, as well as several ground improvement methods. The choice of wet soil mixing minimized the disturbance to the adjacent hospital during construction and potential settlement. Wet soil mixing allowed the structure to be supported on a raft foundation, meeting the stringent building total and differential settlement criteria. The authors also performed unit cell 3-D finite element analyses to evaluate the behavior of the wet soil mixing system in seismic loading conditions. This paper highlights the ground improvement design, construction, QA/QC, and the research related to evaluating the effectiveness of soil mixing for liquefaction mitigation.INTRODUCTIONThe Ventura Community Memorial Hospital proposed the construction of a new Cancer Treatment Center to replace the existing structure, which was built in 1901. The hospital complex is located in a wellestablished residential neighborhood. The soil conditions at the site of the proposed structure required ground modification to support the very heavy radiation treatment section of the building and limit settlement. Originally, 90-foot-long precast piles were considered for foundation support. Based on supplemental Cone Penetration Tests (CPTs) performed, the deepest CPT did not encounter competent pile bearing strata at a depth exceeding 30.5 m (100 ft). This could result in failure of the piles under long-term conditions, especially if hydro-consolidation occurs. The more realistic pile penetration depth would have been 36.6 to 45.7 m (120 to 150 ft). In addition, the excessive noise in association with pile driving would have been unacceptable to the community, patients, and staff of the hospital, so an alternative ground improvement solution was required.The specialty geotechnical contractor recommended wet soil mixing, an economical solution of creating a soil-cement product known as soilcrete that would significantly reduce the construction related noise and provide a more complete deep foundation for the structure.SOIL CONDITIONS AND SETTLEMENT CONCERNSThe subsurface soils were interbedded (Fig. 1) consisting of loose to medium dense silty sands, and soft to medium stiff silty clays to a depth of 30.5 m (100 ft). Groundwater was encountered at depths of 9.1 m (30 ft) and historical high groundwater was at 8.5 m (28 ft) below the ground surface."

Jan 1, 2015