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By Botao Lin, Yan Jin, Hongjuan You, Jingjun Pan, Huiwen Pang, Mian Chen, Sen Chen

"Steam Assisted Gravity Drainage (SAGD) has become the mainstream technology for ultra-heavy oil recovery in Xinjiang oilfield, the success of which depends heavily on shortening of preheating period as well as forming homogeneous and highly permeable zone in land-facies oilsands layer. Towards this aim a special hydraulic fracturing process is required, which is accomplished through controlled water injection to a pair of horizontal wells in order to create homogenously distributed microcracks in the zone between the two wells. The associated mechanical response, however, is unclear for land-facies Karamay oilsands that is loose in texture. In this regard, this research utilizes a triaxial test system on cylindrical specimens extracted from field-collected oilsands cores. Isotropically consolidated drained triaxial compression tests are conducted on both saturated and unsaturated specimens so as to investigate the mechanical response of oilsands at different spots relative to the wellbore. Moreover, acoustic emission and fast pulse-decay permeability are performed to monitor fracture development and permeability evolution. Based on these experimental studies, the mechanism of dilation in oilsands is comprehensively analyzed. The findings reveal distinctive behavior between the saturated and unsaturated specimens as respect to dilation, porosity/volumetric evolution and change of permeability. It is also found that shear bands can be created upon shearing on triaxial specimens, rendering porosity or volumetric strain the factor that is more proper for evaluation of stimulation efficiency in the field.INTRODUCTIONXinjiang oilfield is widely known for its abundant deposit of heavy and ultra-heavy oil that has been estimated to be several hundred million tons. The ultra-heavy oil deposit located in Fengcheng region of Karamay at the northwestern part of the Junggar Basin, Xinjiang, China, has over 360 million tons of resource (Yuan et al. 2013). The resource is deposited in depths from 180 to 450 m and has viscosity over 100, 000 mPa•s at a temperature of 50ºC, bringing technical challenges to recovery activities."

Jan 1, 2015

By K. J. Aglias, M. Jeffery, J. V. Simmons, J. A. Johnston, S. G. Fityus

"Shales and mudrocks undergo weathering in the near-surface geological environment, and degradation when directly exposed at the surface. Despite having superficially similar appearances, many shales have very different degradation behaviours. For example, some shales break down readily upon exposure whilst others remain more or less intact. Further, for those shales which break down, the style of degradation can vary greatly. A phenomenon is described where fresh shale blocks that are exposed at the surface undergo rapid breakdown to a fragmented texture which then persists for relatively long times, without further breakdown to finer soil particles. This is illustrated for some coal mine waste rocks. Furthermore, this metastable fragmented texture seems to be particular to each particular type of shale. The paper presents a conceptual model for this physical breakdown of shales which accounts for the differences in fragmental texture that are observed. The importance of several factors including strength, permeability and expansive clay content are identified for their contribution to the degradation behaviour of different shales.INTRODUCTIONShales and MudrocksThe term shale is applied widely to a class of mudrocks having a range of distinctive but gradational appearances and mechanical behaviours. Mudrocks are sedimentary rocks primarily composed of silt and clay sized particles (Tucker 1982). Mudrocks form in low to very low energy environments such as flood plains, lakes and deltaic environments, where the finest detrital particles are able to settle out of suspension (Reeves et al., 2006; Stow, 2005; Tucker, 2001).Unlike coarser siliciclastic sedimentary rocks, mudrocks do not present with a wide variety of sedimentary structures and textures. The most common texture is a preferred orientation of clays and micas parallel to the bedding plane. This textural component is related to the property of fissility or the ability for such textured mudrocks to split along smooth planes that are parallel to the bedding. Another common structure is lamination, formed by variations of grain sizes and types during deposition, Massive texture describes the situation where no sedimentary structures or textures are apparent (Boggs Jr., 2009; Tucker, 2001). The term shale varies between sources and contexts, with Reeves et al. (2006) stating that a shale is a fissile mudrock, where “fissility is a property that has developed at a certain stage of weathering”."

Jan 1, 2015

By Z. Sample, S. Kaushik

"INTRODUCTION Industries around the globe have been making significant advancements in recent years due to innovations in automation technology. With the implementation of modern automation technology, professionals in process automation or plant operations can expect significant and exciting change, and the mining and mineral processing industries are no exception. From 2000 to 2010, the International Council on Mining & Metals (ICMM) reported that an increased output and increased value of most metals has resulted in a rise in global metal and mineral process industries from $214 billion to $644 billion. [1] Since most productivity increases in mining and mineral process industries have been achieved through the ability to process lower grade ores with improved efficiency and larger equipment, these industries have begun to adopt advanced automation and control technologies. Despite a growth slow-down, the mining and mineral processing industries are poised for continued and sustainable growth and development due to an increasing demand for energy minerals and emerging technologies requiring minerals and metals previously not demand. However, as these industries becomes more automated, new challenges are arising on the horizon. DEMOGRAPHIC TIME BOMB John Payne from BP is credited with first using the term Demographic Time Bomb to describe the upcoming crisis in the process industry in finding experienced operations personnel. From a survey of 912 mining professionals, Stratum International found that a mere 0.4% of senior level candidates were between the ages of 25 and 34 and a similar proportion aged over 75 years. This indicates that there is both a deficiency of young skilled workers and a skilled workforce that is retiring earlier than the previous generation. Combined with data published by the US Department of Labor stating that the median age of the mining workforce is approaching 50 years old, this implies that these skilled mining and mineral process professionals are an aging population with irreplaceable knowledge and experience that are expected to retire in the next 5-10 years. While it is projected that the labor pool will be sufficient to fill open positions, the real question is if this young workforce will have necessary skill sets and experiences."

Jan 1, 2015

By J. Kemeny, R. Fuentealba, C. Rodriguez, F. Fernandez, M. Rocha, T. BoBo

"Mathematical modeling in conjunction with mineral characterization is widely used as a method for design and optimization of comminution circuits, to simulate the processes of crushing, grinding and classification. An important input parameter to the simulation models is the Run-of-Mine Particle Size Distribution (ROM PSD). The run-of-mine size distributions due to blasting have a great influence on the performance of a semi-autogenous grinding (SAG) mill. In this paper, a mine case study was conducted where there are four primary geologic units and the material properties between the four units vary considerably. Also, the mixture of the four unit that will be mined at any given time also vary considerably. This presents a challenge in terms of optimizing the blasting for mill production throughout the mine life. As part of the case study, field rock mass characterization, laboratory rock mechanics tests, and laboratory breakage tests were conducted. The field characterization and rock mechanics tests provide material properties used to simulate the effect of different blast designs on run of mine particle size distributions (ROM PSD). The JKSimBlast software was used for these simulations. The rock breakage tests provide material properties used to simulate crushing and grinding performance. The JKSimMet software was used for these simulations. The goal of the mine is a mill throughput of 95,000 tonnes (104,720 tons) per day (TPD). Based on this goal, run-of-mine fragmentation analysis was conducted for four blasting designs resulting in powder factors of 0.44, 0.54, 0.64, and 0.94 kg/t. The powder factor of 0.44 represents a standard blasting design, while the 0.54 and 0.64 kg/t designs are high-energy blasts specifically to assist with mill production. The 0.94 kg/t design was investigated for the one geologic unit with very high strength. The results of the run-of-mine fragmentation analysis was then input into a crushing and grinding simulation model to predict the mill throughput for the time periods of 1-5 years and 6-10 years. The results indicate that certain blast designs are able to achieve the 95,000 tonnes TPD (104,720 tons TPD) goal, while other blast designs were not. A standard blast design with a 0.44 kg/t powder factor, for example, was not able to achieve the throughput goal, while a design with a 0.64 kg/t powder factor was able to achieve the goal in both the 1-5 and 5-10 year time periods. INTRODUCTION In recent years, mathematical modeling in conjunction with mineral characterization has been widely used as a method for the design and optimization of comminution circuits. The Run-of-Mine Particle Size Distribution (ROM PSD) is a function of rock properties and design parameters of the blast and has a significant impact on the crushing and grinding treatment circuit. Traditionally, design of the grinding treatment is estimated using only the F80 value instead of the full distribution of sizes in the feed, but the finer sizes have great influence on the treatment of a grinder, particularly in the SAG mill."

Jan 1, 2015

By J. P. Harrison, R. Roostaei

"In this paper we investigate the consequences of using conventional triaxial peak strength criteria in the polyaxial stress conditions that occur around the end of a long circular underground opening. A series of 3d boundary element analyses were performed using Examine3D to determine the stresses induced around the tunnel in different in-situ stress conditions. To discuss the applicability of a triaxial strength criterion in failure prediction, strength factors were computed for both the Ottosen polyaxial strength criterion and the triaxial Hoek-Brown criterion. Assuming that the Ottosen criterion is an accurate indicator of strength factor, the discrepancy from this value due to the Hoek-Brown criterion is the error in prediction.In order to simultaneously show the error in prediction and actual strength factor, a quantitative bivariate colour scheme is used to visualize the results. This allows rapid identification of regions with large error, and where either unsafe or overly conservative conditions occur. We show how the inappropriate use of triaxial criteria rather than polyaxial criteria leads to an under- or over-estimation of strength factor, and can result in uneconomic or unsafe design. Extending the analysis to different in situ stress regimes shows how the in situ stress conditions affect the assessment."

Jan 1, 2015

By C. H. Lee, T. T. Wang

"Exampling of the tunneling task in the Tsengwen Reservoir Transbasin Diversion (TRTD) in southern Taiwan, this study investigates the application of the Drilling Survey System (DRISS) in both Drilling and Blasting (D&B)- and Tunnel Boring Machine (TBM)-excavated sections. In the D&B section, a nonlinear relationship exists between drilling energy and uniaxial compressive strength of rock mass, in which a reasonable coefficient of determination can be analyzed statistically. Additionally, the DRISS accurately predicted an unfavorable section with a valuable position. The magnitude of uniaxial compressive strength back calculated using DRISS data also matches those acquired from geological investigations with different approaches. Study results indicate that the DRISS is an effective tool for fore-probing of both D&B- and TBM-excavated tunnels. INTRODUCTIONModern advancements in geological and geophysical investigations, and drilling techniques, have provided valuable information for detecting and interpreting geological conditions of rock tunnels with a resolution of several to ten of meters (Brückl et al., 2001, 2008, Lorang et al., 2005). Nevertheless, construction risks remain considerable during tunnel excavation, especially when a tunnel was excavated by a Tunnel Boring Machine (TBM). Predictions of the local fault, shear zone, and other minor geological features, which may cause moderate collapse or excessive deformation of rocks surrounding the tunnel, before tunnel excavation is highly desirable for high-quality tunnel construction and economically efficient project management.Rather than conventional geophysical prospection methodologies, which always favor large-scale investigation with moderate precision, this study focuses on the drilling method probing ahead of a tunnel. The goal of such an investigation is not only to prevent catastrophic collapse, but also to provide quantitative or semi-quantitative information for estimation of the mechanical parameters of rock mass.For the tunneling task in the Tsengwen Reservoir Transbasin Diversion (TRTD) in southern Taiwan, a drilling survey system is adopted for fore probing. Data collected from both drilling and blasting (D&B) and TBM-excavated sections are analyzed statistically and discussed. The applications of the Drilling Survey System (DRISS) are addressed accordingly."

Jan 1, 2015

By R. J. Hundermark, K. van der Merwe, L. R. Nelson

Taphole integrity is critical to all furnaces, but it is especially important in high intensity electric furnaces processing matte and metal of high superheat. Key furnace dimensions are the electrode proximity to the taphole, hearth sump below the taphole and the shape and location of the taphole in the furnace wall (e.g., circular versus rectangular furnace). In addition, electric furnace power density needs to be matched appropriately to any configuration to achieve operational reliability and furnace integrity. The role of furnace dimensioning is generically reviewed across many pyrometallurgical processes to explore potential impact on furnace taphole performance. Some empirical furnace dimensions and power density ratios of industrial furnaces are then compared to explore to what extent they may indeed influence taphole integrity.

Jan 1, 2015

By I. Stefanou, J. Sulem

"In the last thirty years, the study of earthquake mechanisms has emphasized the major role of rock friction. Earthquakes appear to be the result of a frictional instability and occur by sudden slippage along a pre-existing fault or a plate interface. Multiphysics couplings play a major role in earthquake nucleation and seismic slip. The effect of shear heating and thermal pressurization may be of prime importance in the control of the stability of shear deformation inside the slipping zone. Other mechanisms in relation with thermal decomposition of minerals affect the pore pressure and the temperature evolution of the system, and can play a significant role in the extreme strain localization observed in field. The actual width of the localized zone is a key parameter for understanding fault weakening mechanisms. On the basis of field observations, laboratory experiments and recent advanced modeling, these phenomena are analyzed and discussed in order to bring some new insights in the understanding of earthquakes nucleation.INTRODUCTIONIn the last thirty years, the study of earthquake mechanisms has emphasized the major role of rock friction. Earthquakes appear to be the result of a frictional instability and occur by sudden slippage along a pre-existing fault or a plate interface (Scholz, 1998; Sykes, 1978). The conceptual model of spring slider system is commonly used to represent the interaction between an elastic crustal block and a fault zone. Stick-slip instability is possible if the softening rate of the shear resistance of the fault zone is high enough as compared to the stiffness of the crustal block. Therefore, weakening mechanisms that can explain how the frictional resistance of a fault decreases with slip and/or slip rate is of prime importance to understand how an earthquake nucleates. In recent years, several drilling programs in active faults (e.g. the Nojima fault in Japan, Boullier, 2011; the Aigion Fault in Greece, Cornet et al. 2004, the Chelungpu fault in Taiwan, Ma et al. 2006, and the San Andreas fault in the U.S.A. Ellsworth et al. 2000) as well as high velocity friction experiments (e.g. Tanikawa et al 2012a; Tanikawa et al. 2012b) have highlighted the physico-chemical processes involved in the nucleation of seismic slip (see for the example the review paper of Niemeijer et al. 2012)."

Jan 1, 2015

By X. T. Feng, Y. H. Hatzor, Y. Tal, G. Yagoda-Biran

"When studying jointed rock mass deformation around underground openings it is of great importance to model correctly the excavation sequence during the numerical simulation. This is because for effective arching mechanism to develop in the roof minute block displacements must take place and some of the available discontinuities shear strength must be mobilized. If from the beginning of the simulation the underground opening already exists in the numerical model, block displacements into the excavation space will initiate and develop from time zero, before the initial stresses in the model have attained their actual initial level in the field. These initial block displacements are therefore artificial and exist only in the numerical model, not in the physical reality, and may lead to erroneous assessment of the stability of the designed structure, typically on the conservative side. We have introduced sequence excavation capabilities both in the numerical manifold (NMM) and the discontinuous deformation analysis (DDA) methods and show here the advantages of this modification using three different case studies, each illuminating a different aspect of this enhancement.We begin with the 25 meter deep 2000 year old underground Zedekiah limestone quarry below the old city of Jerusalem, Israel, which is still standing today unsupported with a free span of 40 m. We show that when the opening exists from the beginning of the numerical simulation the required friction angle for roof stability is 25 degrees, whereas when the opening is removed after all stresses and displacements in the model have been stabilized the required friction angle for stability is only 15 degrees.We then model the excavation sequence of a tunnel model representing a 2500 meter deep research tunnel in the Jinping hydroelectric project, China, in order to determine the in situ stress field at this depth by a grid search inversion of displacement data obtained using the sliding micrometer technology in the course of tunnel excavation. Thus we are able to constrain the in situ stress field at these depths where standard in situ stress measurement procedures are extremely difficult to execute properly.Finally, we use sequence excavation modeling capability to find the total height of the expected loosening zone around tunnels excavated through columnar jointed basalts which pose a great engineering challenge because of the characteristic dense network of slender prismatic blocks that transect the opening at a steep inclination. We use MPBX data obtained during excavation of a deep tunnel through such a rock mass to validate our numerical results and show that application of standard empirical guidelines for dimensioning rock bolt reinforcement in such rock masses may in fact result in very un-conservative design because existing empirical approaches typically ignore the anisotropic nature of the structure of such rock masses which, as we show, plays a very significant role in determination of the extent, shape, and geometry of the loosening zone around the opening."

Jan 1, 2015

By José L. Carvalho

"Time-dependent swelling deformation of several shaley rock formations in Ontario is a wellknown phenomenon. In shales and mudstones with a higher salt concentration in the pore fluid than the ambient fluid, the outward gradient generates an osmotic pressure which acts as the driving force for swelling. The swelling phenomenon appears to be related to ion exchange between the rock porewater and the surrounding water.The swelling potential is expressed as the percent swelling strain that occurs per log cycle of time, in either the vertical (perpendicular to bedding) or horizontal (parallel to bedding) directions. In addition, the swelling potential is also noted to be stress dependent. In practice, therefore, the conditions required for swelling are (i) the accessibility to water, and (ii) an outward salt concentration gradient from pore fluid of the rock to the ambient fluid. The relief of in-situ rock stress during excavation serves an initiating mechanism (Lo and Micic, 2010).INTRODUCTIONTime-dependent swelling deformation of several shaley rock formations in Ontario is a well-known phenomenon. In shales and mudstones with a higher salt concentration in the pore fluid than the ambient fluid, the outward gradient generates an osmotic pressure which acts as the driving force for swelling. Swelling is also controlled by the inter-particle bonding; if the bond strength exceeds the osmotic pressure, swelling will not occur, and vice-versa. The bond strength can be reflected by the calcite content which forms cementation bond between rock particles."

Jan 1, 2015

By A. Brian Hawkins

"When pyrite oxidizes in dark grey/black, calcareous, mudrocks or in argillaceous limestones, ferrous sulfate is formed and sulfuric acid is released. The sulfuric acid combines with the calcite present in the rock and calcium sulfate (gypsum) develops. When this occurs on the outer edges of aggregate particles, the gypsum forms in the matrix hence there may be little expansion of the general material. However, when the chemical reactions occur within the rock fragments, particularly on microscopic, clayrich, laminae, the developing crystals exert a significant pressure on the host material. If the rock is medium strong to strong, the force of crystallization splits the rock along the weaker planes, facilitating the ingress of the oxidizing agents and the continuation of the chemical reactions. In addition to causing dilation/heave, some of the engineering properties of the material are changed, including the strength, Los Angeles value, water absorption etc. As a consequence material, which at the time of quarrying would be acceptable for use beneath floors or hardstandings, would no longer be considered suitable.INTRODUCTIONMudrocks accreting in aerobic environments are frequently disturbed by organisms and as a consequence there is often little sign of bedding. In contrast, sediments which have formed in anoxic environments commonly have distinct bedding planes which, because of the grain size of the accreting material, are often smooth and planar. These rocks are frequently referred to as shales, which O’Brien and Slatt (1990) define as “characterised by a finely laminated structure, which imparts a fissility approximately parallel to the bedding.” This should not be confused with rhythmic bedding where the variation in grain size results in lithological laminations or colour changes.Early geologists, in the stratigraphic naming of rocks, often used the term shale for material which is now more likely to be described as mudstone or mudrock (Hawkins and Pinches, 1992). In many contexts, the width of the bedding is an important factor, not only in determining the rock name but also in indicating the potential engineering characteristics. Until recently a shale was considered to have bedding separations of less than 20mm, i.e. the bedding was described as laminated. However, in an engineering context, EN 14689: 2003, Annex A, defines shale by specifying a bedding thickness of < 6mm; such a material would be described as thinly laminated in BS 5930:1999. Ideally the term shale should be abandoned and be replaced by fissile mudstone or fissile mudrock."

Jan 1, 2015

By S. B. Kim, J. Hong, K. Park, W. Kim, H. Kim, Y. Han, J. Choi

"For the first time, the influence of stearyl trimethyl ammonium chloride (STAC) as a collector, on the flotation behavior of lepidolite (Uljin, South Korea) was systematically examined in Denver Sub-A cells. Flotation tests were carried out by varying amount of STAC (50–200 g/ton), feed size (-65, -100, -150, and -200 mesh), and solution pH. The impeller speed of 1000 rpm, flotation time of 10 min and AF-65 (a frother) of 250 mL/ton were invariably applied. In order to complement flotation experiments, zeta potential measurements and XRD analysis were conducted. XRD results showed that the ores were mainly composed of lepidolite, muscovite, quartz, calcite and albite. In addition, zeta potential results showed that isoelectric points were about 2.5, 2.3, and 9.7 for quartz, albite, and calcite, respectively, and lepidolite was determined to be less than 2. Overall, the results of 3-stage flotation showed that Li2O grade and recovery tended to increase with increasing STAC dosage and decreasing feed size. In addition, Li2O grade increased with decreasing pH. The results were explained by the extent of the interaction between STAC and each mineral.INTRODUCTION A great number of potential applications of lithium are being developed currently by the thermonuclear fusion power generation industry(1,2) as well as by the battery and fuel cell industry(3). Even though lithium is mainly consumed in the form of lithium metal and some lithium compounds, about 10% of total lithium production is consumed directly as mineral concentrates by the ceramic industry for the manufacture of special ceramics and mica based glass-ceramics(4). Granitic pegmatites normally contain feldspars, quartz, and mica in addition to lithium-bearing minerals such as spodumene (LiAl(SiO3)2), petalite (LiAlSi4O10), and lepidolite (KLi2Al(Al,Si)3O10(F,OH)2). The amount and grade of metallic minerals tend to gradually decrease and become lower, leading to the increase in the price of base metal or metallic compound(5). Accordingly, recent studies have been extensively devoted to developing the technique to improve the grade of metallic minerals from low grade metallic ores(6,7). Nevertheless, studies regarding the improvement of Li grade from lepidolite ores are very scarce. Lepidolite is a phyllosilicate mineral of the mica group and is often associated with other minerals such as calcite, muscovite, feldspar, and quartz, which need to be separated for lepidolite enrichment(8). Many studies have reported the flotation techniques for separating calcite, muscovite, feldspar, and/or quartz from various targeting minerals(9-11); however, there has been no attempt to investigate physico-chemical properties of lepidolite and its separation from such types of gangue minerals through flotation. Hence, in this study, for the first time, flotation has been carried out for the quaternary ammonium salts (stearyl trimethyl ammonium chloride (STAC, (CH3)3CH3(CH2)16NCl))-lepidolite system based on only the electrokinetic property of minerals that consist of lepidolite ores without adding any depressant to get an initial insight on its flotation behavior. The experimental variables that influence the lepidolite flotation such as amount of collectors, feed size and solution pH have been also examined."

Jan 1, 2015

By J. B. Boisvert, W. Board, C. R. Mooney

"Traditional geostatistical modelling methods are difficult to apply to heavy-tailed deposits because the extreme positive skew of the grade distribution leads to bias. The focus here is on an innovative method of modelling the high-grade population by conditionally simulating discrete volumes (nuggets) of gold with marked Poisson and Cox processes. Capping and other ad-hoc manipulation of the assay data is not required; however, an intensity map for the point processes is required. The method is demonstrated on a dataset from an epithermal deposit and demonstrates an improvement in reducing smearing and controlling the skew of the grade distribution.RÉSUMÉ Les méthodes traditionnelles de modélisation géostatistique sont difficiles à appliquer dans des gisements dont la distribution de la teneur est à queue lourde car l’extrême asymétrie positive de la distribution de la teneur génère des biais. Dans le présent article, l’accent est mis sur une méthode novatrice de modélisation de la population à haute teneur par la simulation conditionnelle des volumes discrets d’or (pépites) au moyen de procédés marqués de Poisson et de Cox. La limite d’utilisation et d’autres manipulations ad hoc des données ne sont pas requises; toutefois, il faut une carte des intensités pour le processus ponctuel. La méthode est démontrée sur un ensemble de données d’essais provenant d’un gisement épithermal et elle montre une amélioration dans le lissage du flou et dans le contrôle de l’asymétrie de la distribution de la teneur."

Jan 1, 2015

By Ning Zhang, Yan Chen, Qikang Yi, Linjian Ma, Guoan Wang

Laboratory tests were performed to explore the effects of frequency on the deformation property of rock salt subjected to cyclic loading under confining stress condition. A two-stage (transient and steady) evolution law of axial cumulative strain was obtained through cyclic stress-strain curves complied from the loci of minimum load of each cycle. The unloading modulus decreases with loading cycles/time as a negative exponential function. The damage of rock salt under cyclic loading is reflected by the degradation of elastic modulus. A unified damage evolution equation considering the effects of frequency and time was established based on the experimental results. A new creep damage model for rock salt was proposed by introducing the non-stationary modular components in Burgers creep equation according to the Lemaitre equivalent strain theory. Comparative study indicates that the new model can accurately describe the creep deformation and damage evolution of rock salt under different loading frequencies. This paper provides a more reasonable model and relevant mechanical parameters for the stability analysis of compressed-air storage cavern in the injection and withdrawal durations.

Jan 1, 2015

By Yin Wang, Lin Li, Zhongwei Bi, Like Wei, Wen Li, Shaogang Li, Bin Zhang, Hongjie Li

Presently,Many long-wall fully-mechanized faces in shallow depth coal seams are below room and pillar goaf in Shendong mining area. When the working face is advanced out of concentrated coal pillar in upper room and pillar goaf, strong strata behaviors often cause support crushing accident. Aiming at a support crushing accident which happened in Shigetai coal mine of Shenhua group in Shendong mining area, this paper analyses the stress transfer process while mining out of concentrated coal pillar by numerical simulation software FLAC3D. According to the feature, simplifying the roof of upper room and pillar goaf as supporting-beam structure explains mechanism of large area collapse in room and pillar goaf roof. Based on the feature of supporting-beam structure, deep-hole blasting concentrated coal pillar technology is proposed to control the strong strata behaviors in Shigetai coal mine. The blasting control effect is confirmed through characteristics of strata behaviors, growth circumstance of ground crack and multi-point extensometer monitoring results. By using control technology, Shigetai coal mine has been successfully avoided support crushing accident.

Jan 1, 2015

In the last five years, new iron ore pellet plants have been built with significantly reduced air pollution levels compared to the older generation of plants. European and American pollution controls are more stringent that in China and Brazil. The recent American plants have successfully employed circulating fluidized beds for sulfur control, baghouses for particulate control, activated carbon injection for mercury and a new design of specialized low-NOx burners.

Jan 1, 2015

By Sergio Segovia Parra, Victor Hernan Sheen Uriol

This contribution of the concept of mass blasting both closing and production allows breaking paradigms, to limit the number of tons to thunder. The areas of geotechnical different mining large mining companies worldwide and especially from the National Copper Corporation (CODELCO, Chile) has been declining volumes closing blasting and production, with the misconception to protect the end walls of the pit, before any geotechnical risks caused by various types of faults; especially the circular faults. A blasting of small tonnage can do more damage to a wall when it is not properly sequenced, leading to the coupling of the wave train and therefore the exponential damage in/s (peak particle velocity, PPV) on the wall of the Tagus. Blasting closing mass production and contribute technically and operationally in the dynamics of the following operations: loading, hauling, crushing, processing and preparation of the final product; eliminating delays to return to thunder small volumes where one must stop all mine equipment, incurring high costs and especially losing valuable time in the continuity of the following unit activities.

Jan 1, 2015

By K. J. Palmer, D. A. Silva

"Evaluating resources and reserves requires the reliable modelling of geological domains and their grades. “Multiple point statistics” simulation is a relatively new geostatistical method to generate complex, high-resolution geological models by extracting high-order spatial relations from training images. A method based on combining multiple training images is developed to obtain the correct amount of large-scale continuity and short-scale variability. A calibration process matches the geological spatial variability between the final realizations and the drillhole dataset. A case study with data from the Red Dog mine, Alaska, United States, shows an appropriate reproduction of short-scale variability along boundaries between geological units.RÉSUMÉ L’évaluation des ressources et des réserves exige une modélisation fiable des domaines géologiques et de leur teneur. La simulation par « statistique multipoint » est une méthode géostatistique relativement nouvelle pour générer des modèles géologiques complexes à haute résolution par l’extraction de relations spatiales d’ordre supérieur à partir d’images d’entraînement. Une méthode basée sur la combinaison de multiples images d’entraînement est développée afin d’obtenir la bonne quantité de continuité à grande échelle et de variabilité à petite échelle. Un processus d’étalonnage fait correspondre la variabilité géologique spatiale entre les réalisations finales et l’ensemble des données de forage. Une étude de cas avec des données de la mine Red Dog, Alaska, États-Unis, montre une reproduction adéquate de la variabilité à petite échelle le long des limites entre les unités géologiques."

Jan 1, 2015

By O. K. Mahabadi, A. Lisjak, B. S. A. Tatone, N. Vlachopoulos

"Numerical simulations are widely adopted in the design of several types of rock structures, including tunnels, caverns, rock cuts, and open pit and underground mines. In recent years, analyses based on the hybrid finite-discrete element method (FDEM) have been shown to provide a realistic representation of rock mass deformation and fracturing processes. To date, the FDEM approach has successfully yielded qualitative and quantitative results for several practical rock engineering applications, yet it has lacked the ability to consider the implementation of rock-reinforcement measures. Since rock reinforcement is often used in civil and mining applications to improve the strength and deformational behaviour of a rock mass, the ability to incorporate such features into FDEM analyses is essential to extend its applicability to a broader range of problems. The work presented in this paper represents an important first step towards developing a simulation tool that can be used for practical rock engineering applications, including the design of underground excavations and rock slopes.INTRODUCTIONRock support and reinforcement measures are often employed in civil and mining rock engineering projects in order to maintain or improve the strength and deformational behaviour of rock masses. The preferred type of reinforcement or support elements along with the preferred layout and timing of installation depend on the in-situ ground conditions, the nature of the rock mass and excavation method. Over the last two decades, numerical modelling has been increasingly used to design and attempt to optimize rock reinforcement and support systems. As such, most rock engineering-specific modelling software now offers various approaches for modelling different rock reinforcement and support elements."

Jan 1, 2015

By Michael W. Driller, Wen Yan (Grace) Chen, Steven J. Friesen

"Remediation for Perris Dam has been proposed in response to deficiencies identified in a seismic stability study prepared by the California Department of Water Resources (DWR) in 2005. Lenses of potentially liquefiable soil have been identified within the dam foundation which may lose strength during a seismic event. The remediation was designed primarily to limit deformation of the dam. Nineteen construction methods were compared and evaluated for the remediation. The final decision was to use cement deep soil mixing (CDSM) to strengthen the foundation and to construct a downstream berm to stabilize the dam. The entire CDSM treatment will cover over 4,000 linear feet of the downstream toe of the dam. Over 300,000 cubic yards of CDSM will be used to strengthen the foundation. The construction of the project started in Fall 2014 and is anticipated to take approximately 3 years. This paper describes the design aspects of using CDSM to treat the foundation, including laboratory testing, investigation of overstressing/cracking, extent of treatment, effect of CDSM on pore pressures under the dam, and the results of a full-scale CDSM test section.INTRODUCTIONPerris Dam is a zoned earthfill dam with a length of 2.2 miles, a maximum height of 128 feet, and a capacity of 131,450 acre-ft of water. The dam is located in Riverside County, California at the terminus of the East Branch of the State Water Project. The embankment was constructed between 1971 and 1973 over an alluvial deposit between the Bernasconi Hills to the South and Russell Mountains to the North. A rock outcrop divides the dam into left and right reaches when viewed from the reservoir looking downstream. The embankment soil was obtained from a borrow source at the North end of the reservoir. The dam has a sloping sandy clay core (Zone 1) with a 10-foot deep cutoff trench and a silty sand shell (Zone 2) with a downstream chimney and blanket drain (Zone 3 and Zone 4) as shown in Figure 1."

Jan 1, 2015