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By H. Blaha, H. Wagner

"Room and pillar workings in salt mines are preferred sites for underground waste disposal. A critical issue in selecting waste disposal sites is long-term behaviour of such workings. The long-term behaviour of salt pillars is controlled by the pillar geometry, i.e. the height, width and length of pillars and the level of pillar stress. The latter has a strong influence on creep characteristics of salt pillars whereas the width to height ratio of salt pillars determines the strength of pillars and the deformation characteristics of salt pillars.Three different regimes of pillar creep behaviour of salt pillars can be distinguished, namely a stress level below which the rate of creep approaches a value of zero, a stress range where the rate of creep is constant and finally a stress level above which the rate of creep accelerates. Long-term stability of room and pillar workings can be assured only when the pillar stress level falls within the first stress regime. Strength and creep tests on model salt pillars have shown that at stress levels below 40% of pillar strength the rate of creep approaches a value of zero, between stress levels of 40% and 65% the rate of creep is constant but increases with stress level. Above pillar stress levels of 65% the rate of creep accelerates.Long-term measurements of pillar deformation and surface subsidence above relatively shallow room and pillar workings in salt mines have confirmed these observations. Long-term strength of salt was found that be between 60% and 65% of short term strength. The evaluation of salt pillar behaviour on the basis of critical pillar stress levels was found to be superior to the traditional factor of safety concept because it allows relating pillar deformation measurements to actual pillar conditions. The approach described in the paper was used successfully to evaluate the stability of room and pillar workings in a salt mine and to design strategies to stabilise critical pillar workings."

Jan 1, 2015

By Duanyou Li, Qing Xiao, Zhiwang Wang, Xiaoqing Gan

"Seepage is a major cause of earth-rockfill dam failure. Numerical simulation of infiltration process, distribution of drift, flow velocity and direction after the impoundment can guide seepage control and evaluate its effects. A double field coupling model is established based on soil consolidation theory and the interaction between the seepage field and the temperature field. The simulation is implemented under the situation of core wall setted, core wall not setted, and core wall setted with concentrated leakage. The results indicated that the saturation line height was significantly reduced due to impervious core wall, and the temperature distribution is uniform above the saturation line. If concentrated leakage occurs, temperature distribution of dam was significantly changed, which is consistent with theoretical inference.INTRODUCTIONEngineering seepage field distribution must be calculated in seepage control design, optimization, and correction of new engineering construction of earth dams, as well as in seepage monitoring and evaluation of existing earth-rockfill dams. The aim of calculation is to identify the important parameters in seepage field, such as the coefficient of permeability, seepage flow, pressure, head, and allowable seepage slope, for effectively implementing seepage control design, correction, safety assessment, and anti-seepage reinforcement. These seepage parameters usually can be obtained by in-situ test and back-analysis based on reliable monitoring data.In order to obtain reliable monitoring data and reflect the earth-rockfill dam seepage state and change process, appropriate monitoring technology and monitoring method is necessary. The traditional seepage monitoring method is through site inspection and sensors (e.g., osmometer, piezometric tube and measuring weir) that buried in the structure and its foundation. However, there are still some disadvantages:"

Jan 1, 2015

By R. Kong, X. W. Zhang

"High pressure (up to 50 MPa) isotropic compression tests were performed on marble, gneiss and sandstone specimens, of which represents the typical rocks, to investigate isotropic compression deformation characterization at room temperature. Experimental data with respect to volume change in loading and unloading are presented. An apparent volume change inflection point (sensitive stress) was observed at a lower pressure range for porous sandstone, indicating that the elastic-plastic behaviour arising in the isotropic compression stage, but for tight crystalline rock, the sensitive stress is much higher, not probed prior to 50 MPa. The irrecoverable volumetric strain in the unloading can be seen for sandstone as well. The anisotropic deformation was discussed in terms of the axial and radial strain measurement. It was found that essential features of mechanical anisotropy are the irreversible in deformation range. The deformation feature in the isotropic compression tests is a very complex issue due to the factors concerning the stress history, unloading in sampling and in-situ stress. INTRODUCTIONThe isotropic or hydrostatic compression condition that stress is compressive and has the same magnitude for all direction, which is expressed as s1=s2=s3 in principal stress space. A yield locus of soils subjected to the isotropic and anisotropic compression was widely known, for instance Cam Clay model, which forms a closure cap model. However, the similar isotropic compression yield curves for rocks, especially for hard rock, was not established due to the geo-stress in the rock mass is much less than the socalled isotropic yield stress. And hence, the previous experimental studies on the hard rock have been made tend to on the stress-strain-strength relationship (Handin & Hager, 1957; Edmond & Paterson, 1972; Menéndez et al., 1996). Perhaps the yield curves related to an increasing in the hydrostatic pressure is not forced to construct for hard rocks, undoubtedly, the deformation data in this processing is valuable to assess the bulk module (Fabre & Gustkiewicz, 1997), anisotropy (Niandou et al., 1997), field stress (Hakala et al., 2007). Furthermore, many rocks store much elastic volume strain energy link to the hydrostatic pressure exerted, following a deviator stress applying, to drive the unstable brittle fracture for hard rock. Latter was studied to interpret the incentive of rock burst. However, volume change characteristic in the isotropic compression behaviour have been scarcely studied experimentally to our knowledge, less application related to the fracture in hard rock as well. The mechanical behaviour in the isotropic compression of hard rock is notably affected by the original structure anisotropy, stress history and stress condition before sampling, all of which need reasonably assess. It is also a useful understanding to study isotropic compression that elastic and plastic volume change in the isotropic loading and unloading, and the micro crack evolution throughout it."

Jan 1, 2015

By H. Nagel, A. P. Schissler

"INTRODUCTION Anadarko Petroleum Corporation (Anadarko) owns a region of oil shale properties acquired as part of the original Union Pacific Land Grant of the 1800’s in southern Wyoming. These holdings are greater than 2 million acres and occur throughout the Green River Formation in southwestern Wyoming. One area was prioritized for further study by Anadarko Minerals called the Kinney Rim in the Washakie Basin due to low environmental impact, proximity to infrastructure, high ore grade, and low mining cost. The area is a low-overburden oil shale resource that can be developed using surface mining methods, processed by conventional surface retort, and placing waste rock disposal back on the bench for a design capacity of 10,000 barrel per day. The purpose of this papers is to present the results of environmental analysis and timeline, the mine plan, and surface ore processing to offer a resource-ready energy source.Mineral rights for the Kinney Rim area are owned by Anadarko, the United States Bureau of Land Management (BLM) and the State of Wyoming. Mining of oil shale for this study targets Anadarko owned mineral resources.GEOLOGY The study area is in the Green River and Washakie Basins in western Wyoming. The host geologic member is the Laney Oil Shale. Figure 2 illustrates the Laney shale within a generalized lithologic cross section.OIL SHALE LEASING The proposed Kinney Rim oil shale mining project is located in an area dominated by a 1 square mile checkerboard landownership pattern with every other section typically administered by Bureau of Land Management (BLM) and Anadarko. Surface and mineral ownership is a split estate legal entity. The immediate Kinney Rim mine plan is all on Anadarko sections."

Jan 1, 2015

By Cheryl Devine, Radhakrishnan Mahadevan, Vladimiros G. Papangelakis, Srinath Garg

The microbial-mediated recovery of valuable metals locked in mining wastes presents an economical alternative to conventional hydrometallurgical processes. The present study investigated the bioleaching response of a low-grade nickeliferous pyrrhotite tailings (0.6 wt% Ni) and an upgraded pyrrhotite tailings (1 wt% Ni) produced by Vale Base Metals in the Sudbury Basin of Ontario, with the ultimate aim of maximizing Ni recovery. The initial part of the study focused on the bacterial adaptive evolution protocol, by repeatedly sub-culturing an indigenous culture from an acid mine drainage site on 2% (w/v) pyrrhotite tailings. The results showed that the extent of Ni dissolution is positively correlated with microbial activity. Microbial profiling revealed A. ferroxidans to be the dominant member of the microbial consortium. The enriched culture was used for optimizing the growth medium by varying the concentration of essential growth nutrients. Finally, an aerated biotic and abiotic leach of a 10% (w/v) upgraded pyrrhotite tailings with and without pH control, showed a higher recovery of Ni in the pH controlled experiments. These results demonstrate that a high concentration of the oxidant Fe3+ in solution promotes the dissolution of Ni. Furthermore, the sulphide conversion into So was found to be higher in the pH controlled experiments (32%), relative to the experiment without pH control (10%).

Jan 1, 2015

By Shiqiang (Rob) Hui, Jiaren (Jimmy) Jiang, Rees Llewellyn, Yongsong Xie

Wear has been estimated to cost the Canadian mining/mineral processing industry over $15 billion per year mainly for repair/replacement of worn parts in 2013. The associated production loss is difficult to quantify but add considerably to the problem. The Canadian oil sands sector which has to deal with extremely abrasive and erosive solids, has traditionally incurred extremely severe and often unique attack. Demonstrable progress in mitigating the wear problems has been achieved through materials development, more informed materials selections, and better component and operation condition designs. An integral contributor to these advances is a long-term collaborative research partnership between NRC and the mining/supply industry. In this paper, this continuing collaboration will be described. A main focus is to identify degradation mechanisms occurring in the most severe and important service applications and to correlate these findings with laboratory test data. Relevant abrasion and erosion (often combined with corrosion) properties have been established and correlated with composition and microstructures for all classes of resistant materials ranging from relatively soft elastomers to ultra-hard ceramics. A comprehensive wear properties database has been compiled. This capability has been instrumental in facilitating the development of improved materials, optimizing materials fitness/selection for service, wear failure analysis, and quality assurance.

Jan 1, 2015

By C. H. Lau, I. T. Ng

Uniaxial Compressive Strength (UCS) of rocks is an important mechanical parameter for many civil engineering and rock engineering applications such as tunnel excavation, slope stability and foundation design. Macau is one of the world's fastest growing and most densely populated cities, many large and important infrastructures have been being continuously built using pile foundations which are designed to be supported by granitic bedrock. In Macau, the UCS of the granitic bedrock is required almost for every project involving pile foundations and is always measured directly from UCS test in the laboratory. However, direct measurement of UCS requires high quality rock core sample which is not only time-consuming and expensive but also requires high level of operating skill. In view of this fact, estimation of UCS using some empirical correlations will be more practical and efficient because they are relatively fast and economical compared to the direct measurement from UCS test. In the past, some empirical correlations had been established and widely used for estimating UCS of rocks in common engineering practice. However, it has been well recognized that the rock properties are generally varied with sites or geological regions in other words an empirical correlation developed from one region or one country may not be applicable for other regions or countries. Due to the reason that the empirical correlations for predicting UCS for granite are scarce in practice, in this study an extensive experimental program has been performed and a large database containing data such as UCS, Point Load Index (Is50), Schmidt Rebound Hardness (RL), porosity (?), water absorption (S), specific gravity (Gs) and dry density (?d) has been developed. An attempt has been made for developing a new empirical correlation for estimating the UCS of Macau granite. Accordingly, a comprehensive statistical analysis for correlating UCS with Is50, RL, ?, S, Gs and ?d has been performed and a local empirical relationship based on the developed database is proposed for obtaining reliable estimation of UCS for the granite of Macau. Finally, the performance of the proposed correlation is accessed by using another independent testing database developed in this study. It indicates that Is50, RL, ? and S have strong correlation with UCS whereas Gs, ?d have poor correlation with UCS. This study not only proposed a proper predictive empirical correlation for UCS determination for Macau granite but also provides detailed statistical information which is beneficial to engineers for obtaining better characterization of Macau granite.

Jan 1, 2015

By Bhawani Singh, Mahendra Singh, N. K. C Samadhiya

"Inherently anisotropic rocks occur in abundance at many rock engineering project sites in Himalayan region. These rocks pose difficulty in analysis and design due to their direction dependent strength behaviour. Moreover the strength varies in a non-linear manner with confining pressure. Mohr- Coulomb strength criterion is widely used by geotechnical engineers for defining strength of rocks subjected to given confining pressure. However, the conventional Mohr-Coulomb (MC) criterion suffers from the limitation that the strength is treated to be linearly dependent on confining pressure. In the present article, the MC criterion has been modified by incorporating non-linear term while retaining the original parameters c and ?. The non-linearity with confining stress level has been imbibed through critical state concept (Barton, 1976). The criterion has been applied to a triaxial test data base comprising of more than 1140 triaxial tests conducted world-wide on anisotropic rocks. Statistical evaluation of the goodness of fit of the proposed criterion to the data-base has been carried out. Further the predictive capabilities have been evaluated by determining the error in estimation of triaxial strength if only few triaxial test data are available for determining the criterion parameters. The data base has also been back-analysed to assess the critical confining pressure for anisotropic rocks. Statistically the critical confining pressure, for the present criterion, may be taken nearly equal to 1.25?cmax, where ?cmax is the maximum value of the UCS out of all orientations of planes of anisotropy. It is concluded that reasonably good estimates of the anisotropic strength are possible through the proposed criterion.INTRODUCTIONMany rocks encountered in Himalayan region like shale, slate, schist and phyllite are inherently anisotropic and exhibit direction dependency in their strength behaviour. In addition, the strength of the rock also depends on the confining pressure and, the strength response is non-linear especially when the confining pressure may vary over large range. Conventionally, Mohr-Coulomb criterion is the most widely used criterion for rocks. However, the limitation of this criterion in its present form is that the strength is treated to be linearly dependent on the confining pressure. The present study attempts to address the following two main objectives: i) Include nonlinear response in the Mohr-Coulomb criterion while retaining parameters c and In their original form; and ii) consider anisotropic response of the rock for a given confining pressure. A nonlinear strength criterion, which uses shear strength parameters c and as per Mohr-Coulomb criterion, has been suggested based on critical state concept for rocks."

Jan 1, 2015

By Shoji Higashi, Nobuhiro Honda, Takeo Asanuma, Tatsuo Nagatsu, Masaki Kitazume, Sachihiko Tokunaga, Shigeru Kubo, Hidenori Takahashi, Tsuneyasu Onishi, Yoshiyuki Morikawa

"Various kinds of civil engineering structures and facilities were seriously damaged in the earthquake in Tohoku and Kanto regions of Japan on 11 March 2011 due to the greatness of its magnitude. In contrast, many structures resisted the large seismic force having been reinforced by the CDM (Cement Deep Mixing) method, which is often used for increasing the bearing capacity of ground and improving seismic performance. This paper summarizes the field survey undertaken to investigate damage to structures and facilities reinforced by the CDM method. Several prefectures and metropolitan areas were selected for the survey, based on the occurrence of strong seismic motions. A total of 847 structures and facilities were studied, in the survey using a questionnaire, which mainly inquired about the appearance of structures and facilities. Of the respondents to the questionnaire, 789 replied that there were no seriously damaged structures. The paper presents the damaged and non-damaged sites of CDM-technique sites and non-CDM-techniques sites. It can be concluded from the field survey that the CDM Method demonstrates high efficacy and durability against a strong seismic motions.INTRODUCTIONDuring the afternoon of 11 March, 2011, a huge magnitude-9.0 Mw (Category 9.0 on the Richter scale) earthquake occurred about 25 kilometers below the Pacific Ocean’s surface off the coast of Tohoku. This massive earthquake, now called the 2011 Off the Pacific Coast of Tohoku Earthquake was the largest earthquake ever observed in Japan. The seismic intensity of this earthquake was measured 7, the maximum on the Japanese intensity scale, as observed 7 in northern Miyagi Prefecture. The earthquake caused severe damage over a wide area from Tohoku to Kanto, and triggered large tsunamis that struck the Pacific coast of Hokkaido, Tohoku, and Kanto. The number of missing and fatalities caused by this earthquake exceeded 18,000 persons, making this an unparalleled earthquake disaster with a cost-in-life toll not experienced by Japan in recent years. Because of the scale of its seismic motions, the earthquake damaged facilities and structures of many kinds. In the years prior to this earthquake, the CDM method was used extensively to increase the bearing capacity of the ground as an anti-seismic countermeasure and to prevent liquefaction. Immediately after the earthquake, the CDM Association visually surveyed the state of damage to about 800 facilities in the Tohoku and Kanto regions where a seismic intensity of 5 or higher was observed. This report summarizes the survey of damage to facilities and structures constructed applying the CDM method in order to confirm the durability and performance of the method against seismic motions."

Jan 1, 2015

By J. Armitage, J. Erskine

Feed level and thickness measurements are essential in the optimization of an electric arc furnace. A precise measurement of the feed thickness and level gives operators the ability to increase the smelter efficiency and reduce the maintenance cost. Hatch has developed a radar system which is an affordable, low maintenance, and accurate level measurement system. The radar units can be installed across the furnace to measure the feed level and the feed thickness can be calculated with one slag level sounding. The present paper describes the development of radar systems as a process optimizing tool by furnace controls. The authors will discuss the challenges involved in installing eight radar units on the roof of a six-in-line electric furnace.

Jan 1, 2015

By X. G. Zhao, M. Cai, L. K. Ma, P. F. Li

"Crack initiation stress is one of the characteristic stress thresholds in the rock deformation process under compression. By analyzing AE responses of brittle rocks in uniaxial compression, a new method which is called cumulative AE hit (CAEH) method is proposed for determining the crack initiation stress. An advantage of the CAEH method is that the method removes the user's subjective judgment. To verify the CAEH method, uniaxial compression tests with AE measurement using 77 crystalline rock specimens were conducted. The test specimens cover eight rock classes with different mineral grain distributions. Crack initiation stresses of these specimens were determined by the proposed CAEH method and the LSR method, and the resulting mean crack initiation stresses determined using the two methods were comparable. In addition, taking one rock class with 20 specimens for example, the mean crack initiation stresses determined using the CAEH method and those from several established strain-based and AE-based methods were similar. Hence, the CAEH method can be used as an alternative method for crack initiation stress determination.INTRODUCTIONExperimental observations indicate that the failure process of brittle rocks is associated with crack initiation, crack propagation, crack damage and final strain localization (Brace et al., 1966; Bieniawski, 1967; Lockner, 1993; Wawersik & Fairhurst, 1970). Compression tests on cylindrical specimen are often used to characterize the crack development process. The crack initiation stress (sci), crack damage stress (scd), and peak stress (sc) represent important stress thresholds during the failure process of brittle rocks. Among the three characteristic stress magnitudes, sci is difficult to be determined objectively, directly from examining the stress–strain curves. Some researchers argued that sci obtained from laboratory compression tests is an important parameter for estimating the spalling failure observed in brittle rocks around underground excavations (Andersson et al., 2009; Diederichs, 2007; Martin, 1997). sci can also be used to estimate rock tensile strength and Hoek-Brown failure criterion parameter mi (Cai, 2010). Over the last 40 years, various strain-based methods have been proposed to determine the crack initiation stress in compression tests (Brace et al., 1966; Diederichs, 2007; Eberhardt et al., 1998; Lajtai, 1974; Martin & Chandler, 1994; Stacey, 1981). Nicksiar and Martin (2012) proposed a Lateral Strain Response (LSR) method for establishing sci for low-porosity rocks. Meanwhile, they also used different strain-based methods to evaluate sci of Äspö diorite, and the results showed that all strain-based methods gave acceptable crack initiation stress values. Subsequently, they utilized the LSR method to further investigate the crack initiation stresses in igneous, metamorphic, and sedimentary rocks in compression tests (Nicksiar & Martin, 2013). Compared with previously proposed strain-based methods, an advantage of the LSR method is that it removes the user judgment when interpreting sci. However, the use of the LSR method relies on accurate determination of scd and on having a polynomial fitting equation to find the maximum LSR value."

Jan 1, 2015

By F. Pinto, C. A. Prato, R. J. Rocca, P. F. J. Huerta Soaje

"The seismic hazard for civil engineering structures is generally defined in terms of deterministic or probabilistic acceleration response spectra at an equivalent rock outcropping. The design of tunnels, however, requires the definition of demands in terms of accelerations at ground surface (near the portals) and in terms of both accelerations and velocities at different depths within the alignment. The design near the portals is controlled by inertial effects and is often times impacted by the possibility of slope instability and rockfall, whereas the design at deep sections is controlled by kinematic effects. These effects are accounted for in practice by introducing deformation patterns in the structure that are related to an assumed wavefield, often times ignoring the effect of the structural stiffness in the response. This paper presents a study regarding the definition of seismic demands for different sections of 14-km long tunnel in the Andes (Argentina-Chile), with a maximum overburden of 1750 m in a seismically active region. The tunnel will pass through volcanic massifs mainly composed by andesites and rhyolites.The study includes the definition of spectrum-compatible seismograms, deconvolution, and definition of accelerations and peak particle velocities for different overburden conditions. A kinematic interaction study for a 500-m tall ventilation chimney shaft is also described, where a simple formulation for the interaction analysis is considered in order to more accurately evaluate shear and bending demands. INTRODUCTIONThe seismic design of linear underground structures, such as shafts and tunnels, generally considers the inertial forces near the shallow sectors (e.g., portals) and the kinematically imposed deformations for the deep sections (e.g., Hashash et al. 2001). The inertial forces are often times evaluated on the basis of design spectra recommended by seismic hazard studies. The kinematic demands for the deeper sections, however, needs to be defined in terms of additional information which is not always indicated by the seismic hazard studies, e.g.; peak particle velocities and accelerations, and their variation with depth. These parameters can be determined by means of a site response analysis, whereby outcrop motions can be deconvoluted in order to evaluate motions inside the ground mass (e.g., Schnabel et al., 1972). Hashash et al. (2001) defines factors that may be used in order to account for attenuation of motions inside the ground mass. However, these factors are provided for depths up to 30 m only, whereas depths of tunnels structures can range up to thousands of meters."

Jan 1, 2015

This paper presents a case study where Cenozoic age detritals and an ancient buried landslide have been modelled in the final walls of an iron ore pit. Orebody 25 is located in Western Australia’s Pilbara region and is an operating pit where a redesign of the final wall cutback was required. The existing slope design utilised a simplistic geological model of mixed conglomeratic, calcretic and clay –dominated detritals overlying deformed bedrock sequences. This simplicity resulted in a conservative design that was not reflective of the slopes performance to that point. Further field investigation was carried out with the results assessed in conjunction with historic drilling, mapping and laboratory testing. A detailed geotechnical model was developed including three conglomerate and two clay dominated units and laterstage calcrete overprinting. The clay units were of significant importance to the stability assessment and resulting slope design due to the thickness and poor strength conditions indicated by the laboratory and field testing. However, the drilling investigation shed only limited understanding as to the origin of the clays and thereby how they should be treated as a component in the stability analysis. A comparison of the ratio of various geochemical elements measured by assay was made between the clays and 1) shale bedrock and 2) clays of known detrital origin from other nearby sites. This indicated the clays had a strong affinity with weathered bedrock. This and other textural features resulted in the interpretation that the clay units were relic debris preserved following ancient landslides in bedrock shale. Using laboratory testing data and calibration of results for a landslide origin, stability analyses were run, resulting in a steeper slope design being implemented. Excavation of the final cutback is now in progress with the model confirmed as appropriate.

Jan 1, 2015

By Vicken Aprahamian

"The Royal Canadian Mint (RCM) operates a gold and silver refining toll operation in Ottawa, Ontario, Canada. The silver refining line is a recent addition and was commissioned in 2005. One source of silver in the refinery is from gold doré which undergoes Miller chlorination before electrorefining to 99.99% cathode gold. Treatment of the Miller salt or silver-copper chloride produced consisted of a 2-stage high temperature reduction process step using soda ash prior to 2005. Copper-rich silver bars were produced and shipped offsite for further refining.The copper-rich bars could not be blended into sufficient high grade silver doré to dilute the copper and allow electrorefining in a silver nitrate medium. A new wet process was developed and commissioned to replace the high temperature reduction and allow removal of bulk copper. Thus upgraded impure silver produced was cast into anode for electrorefining to 99.9% purity silver flake. The 2005 RCM Hydromet Slag process is presented as well as its more current version. In addition, mention is made of a novel processing scenario for the introduction of Miller chlorination silver into the electrorefining circuit."

Jan 1, 2015

By E. Poiate, P. R. Cabral, A. V. N. Santos, P. V. M. Costa, C. S. Amaral, A. M. Costa

This paper discusses the design of underground salt caverns, opened by solution mining, for the production of brine and storage of natural gas under high pressures. The caverns are located in the salt basin in Maceio City, Alagoas State, at the northeast region of Brazil. Special attention is given to the geomechanical structural design of the caverns using computer codes specially developed for the simulation of excavations in salt rock formations, considering validated constitutive creep laws under different initial stress states and temperatures. The behavior of sedimentary rocks intercalations presented in the salt layer is simulated using elastic-plastic models. The excavation of the caverns by solution mining is also simulated starting from a geostatic initial equilibrium state of stresses, with a unique formulation only implemented in these computer codes, without the need of the application of boundary stresses to the model in order to develop the initial state of stresses. These computer codes have being used in the design of several clusters of caverns for brine production used as raw material of Poly Vinyl Chloride (PVC) of the Chemical Industryin Brazil. These computer codes and methodology were also applied to the design of the underground conventional potash mine in the state of Sergipe, overlying tachyhydrite and carnallite with very high creep strain rate. They have also been used in the design of the pre-salt oil wells through thick layers of stratified salt rock in Santos Basin, for the exploration and production of the pre-salt reservoirs in Brazil. The constitutive creep equations implemented in the codes are based on a double mechanism creep law. The creep constants adopted in the simulation are taken from a previous investigation carried out on an experimental panel of the potash mine, considering the stratified geology with different salt rocks of the basin where the mine is located. These constants were also obtained by lab tests under different confined and differential stresses and temperatures.

Jan 1, 2015

By Randy R. Williams, Brian W. Wilson, George M. Filz, Marina S. W. Li, Donald A. Bruce

"In-situ wet grab sampling and post-installation coring of soil-cement structures are typically carried out for Quality Control (QC) and Quality Assurance (QA) of deep mixing (DM) schemes. Wet grab sampling and testing is used to provide data to indicate that performance requirements are being met during production, in advance of coring, which typically occurs at 28 days or later, following installation. While unconfined compressive strength (UCS) tests from wet grab samples provide good production indicators, industry practice often requires that acceptance criteria of soil-cement structures be based on UCS results from representative core samples.This paper outlines the approach adopted for field sampling and QA/QC testing carried out in highly variable subsurface conditions at a site located in northern British Columbia (BC), focusing on postinstallation soil-cement coring and strength testing for an extensive deep mixing scheme. A discussion on suitable methods of coring soil-cement structures and appropriate selection of samples for testing that are representative of the in-situ soil-cement structures is provided. This paper also discusses the selection strategy adopted for verification of strength and modulus parameters used for design, providing spatial and time coverage, as well as the acceptance criteria implemented, and provides comparisons with published industry recommendations.BACKGROUNDAn extensive deep mixing ground improvement scheme was completed for the development of a Liquefied Natural Gas (LNG) Facility to be located in Bish Cove, BC, Canada. The deep mixing scheme was implemented to treat very weak native deposits in-situ to support two mechanically stabilized earth (MSE) walls up to 20 m (66 ft) high, and their associated bulk earthworks. Within the DM area, the subsurface conditions were highly variable, ranging from deep (up to 21 m (69 ft) thick) deposits of very soft to soft clayey silt to silty clay, overlying layers of dense to very dense gravelly sand to sand and gravel, to compact deposits of silty sand (up to 15 m (49 ft) thick), overlying dense sand and gravel. Bedrock was encountered beneath the granular deposits and generally comprised granodiorite with occasional andesite dykes."

Jan 1, 2015

By Mansoor Barati, Xue Yin, Yanhui Sun, Alex McLean, Yindong Yang

The formation and evolution of inclusions in Ti-Stabilized, 17Cr Austenitic Stainless Steel produced by the ingot casting process were investigated through systematic sampling of liquid steel and rolled products. Analysis methods included total oxygen and nitrogen contents, optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The results indicate that the composition of inclusions was strongly dependent on the types of added alloying agents. During the AOD refining process, after the addition of ferrosilicon alloy and electrolytic manganese, followed by aluminum, the composition of inclusions changed from manganese silicate-rich inclusions to Al2O3-rich inclusions. After tapping and titanium wire feeding, pure TiN particles and complex inclusions with Al2O3-MgO-TiOx cores coated with TiN were found to be the dominant inclusions when [%Ti] was 0.307 in the molten steel. These findings were confirmed by thermodynamic calculations which indicated that TiN inclusions could be formed in the liquid phase due to the high contents of [Ti] and [N] in the molten steel. From the start of casting to the rolled bar, there was no obvious change in the composition of inclusions compared to the titanium addition stage. Stringer-shaped TiN inclusions elongated along the rolling direction with lengths varying from 17 to 84µm were observed in the rolled bar, which could detrimentally impact the mechanical properties of the stainless steels.

Jan 1, 2015

By G. Minhas, M. Pule, Y. Laffitte, M. c. McGurn, T. Tzanetakis, Peacey. J., R. Susilo

Titanium (Ti) metal production from titanium tetrachloride (TiCl4) using magnesium (Mg) as a reducing agent is the well-known Kroll process. A chloride route is used to avoid oxidation of the titanium sponge. The sponge is consolidated into ingots and can then be made into powder by melting and atomizing or by hydriding/dehydriding. Attempts at direct powder production have met with difficulties, including low Ti yield and the formation of very fine particles (particles between 25-100 µm are desired). This paper discusses two methods to produce Ti powder in a molten salt medium using magnesium powder as a starting material instead of a pool of molten magnesium. The first method is a direct reduction of gaseous TiCl4 injected in the melt with the magnesium powder in suspension in the molten salt. The second method is a two stage TiCl4 reduction reaction where recycled Ti was used to form titanium dichloride (TiCl2) in the first stage followed by addition of magnesium powder into molten salt in the second stage. A correlation between Ti yield and processing variables such as TiCl4 to Mg ratio, Mg particle size, TiCl2 concentration in the melt, and reaction temperature was studied. The Ti powder formed was also analyzed for particle size distribution. Despite challenges and difficulties encountered, this paper shows some promising results which could provide guidance to others working on direct Ti powder production.

Jan 1, 2015

By K. Lagnese, C. Robinson, S. Muddasani

"Mine water generated from underground coal mining operations contains both dissolved and particulate solids. Dissolved solids primarily consist of sodium, calcium, magnesium, potassium, chlorides and sulfates. When discharged to a receiving stream without treatment, these constituents create a potentially toxic environment for aquatic life. A case study is presented to discuss how a centralized treatment plant treats mine water from six locations to meet discharge limitations for chlorides. Located in West Virginia, this facility consistently achieves less than the NPDES permit limitation of 218 mg/L chlorides in the discharge while generating almost zero liquid waste. The dissolved solids concentration in the influent ranges between 5,000 and 10,000 mg/L, with chloride concentrations of 1,000 to 2,000 mg/L and sulfate concentrations of 2,000 to 6,000 mg/L. The mine water is treated using advanced treatment technology to produce clean water for discharge or reuse. The treatment process comprises aeration, softening, filtration, reverse osmosis, RO reject softening, evaporation, crystallization, final effluent remineralization and sludge dewatering. The solid waste generated in the treatment process is landfilled on site. The leachate is sent back to the facility’s thermal treatment process. Because no liquid waste leaves the property, this plant is termed a “Zero Liquid Waste” (ZLW) facility. INTRODUCTION The advanced water treatment system was built to meet a new 218 mg/l regulatory limitation imposed by the West Virginia Department of Environmental Protection for chlorides discharged to surface waters. The system is designed to treat a maximum flow of approximately 5 million gallons per day (795 m3/h) of mine water. The treatment process utilizes reverse osmosis (RO) membrane treatment to achieve the effluent criteria, and evaporation and crystallization technology to manage the RO concentrate from the water treatment process. As a result, the system produces clean water for discharge while generating zero liquid waste. The effluent water can be used for industrial purposes or discharged to a receiving stream. A Water Impact Index (WIIx) study indicated that discharge of this high-quality water into the Monongahela River watershed may improve the water quality for downstream water users. The waste produced in the treatment process, including softening sludge and salt, is disposed of in an on-site landfill."

Jan 1, 2015

By R. Panchadhara, P. A. Gordon

"A non-local formulation of the classical continuum mechanics theory called peridynamics is used to study driven dynamic fractures in the near wellbore region. The controlled application of pressure on the inner walls of the borehole can create multiple fractures that initiate from the borehole and propagate radially outwards. The number of fractures and their final length is primarily controlled by the loading conditions and the in-situ stress state. It is the objective of this study to use a novel numerical technique called peridynamics to investigate: 1) the influence of loading conditions on the fracture pattern, and 2) the effect of in-situ stress anisotropy on fracture propagation. In peridynamics, the momentum equation from the classical theory of solid mechanics is replaced with the integro-differential momentum equation of peridynamics. As a result, discontinuities in the body, such as fractures, occur spontaneously. The material is represented by a continuum body with material points that interact non-locally with all other points within a specified distance. Fractures evolve using a damage evolution law, wherein, damage at any point is represented as the ratio of the number of broken bonds in the current configuration to the total number of bonds in the undeformed configuration.Simulations are performed on simplified test cases and the results are compared to relevant experimental and numerical studies found in the literature. It is shown that the loading rate significantly influences the number of fractures initiated from the borehole as well as their extent. Low loading rate produces fewer fractures, whereas, high loading rates produce longer and a greater number of fractures from the borehole. The numerical method successfully predicts the fracture pattern obtained from a wide range of loading conditions. Predictions also indicate that the resultant fractures are shorter when in-situ stress is applied. Numerical results show that the fracture extension is largest in the direction perpendicular to the minimum compressive stress for the range of loading rates used in this study."

Jan 1, 2015