Geotechnical Risk Assessment of Mine Development Intersections with Respect to Mining Sequence

Mine developments such as haulage drifts and their intersections with cross-cuts are the only stope access in sub-level stoping mining system. Thus, they must remain stable during their service life. Haulage drift instability could lead to serious consequences such as: production delay, damage to equipment, loss of reserves and high operational cost. The goal of this paper is the stability of mine developments with respect to mining sequence with focus on the performance of haulage drift intersection during the production plan. A case study, the #1 Shear East orebody at Vale’s Garson Mine in Sudbury Ontario will be examined in this paper. A three-dimensional, elastoplastic, finite difference code (FLAC3D) is used for this study. The extent of strength-to-stress ratio corresponds to Mohr–Coulomb strength-to-stress ratio of 1.4 is used as failure evaluation criterion. The unsatisfactory performance is reached when the extent of strength-to-stress ratio exceeds the anchorage limit of the rockbolt. Stochastic analysis; adopting point-estimate method, is then employed with the numerical modelling to tackle the inherent uncertainty associated with rockmass properties. Then, the probability of instability at various mining steps is estimated for the roof and north wall of the studied intersection. The cost of consequence models is introduced to provide an economical solution if the intersection failed, blocked or damaged. Furthermore, the geotechnical risk associated with the instability of mine development intersection is estimated using risk-indexing tool. The results are presented and categorized in terms of probability, cost of consequence and risk-index at various mining stages.     

Mineralogy, fluid inclusion, and oxygen isotope constraints on the genesis of the Lalla Zahra W-(Cu) deposit, Alouana district, northeastern Morocco

The Lalla Zahra W-(Cu) prospect of northeastern Morocco is hosted in a Devonian volcaniclastic and metasedimentary sequence composed of graywacke, siltstone, pelite, and shale interlayered with minor tuff and mudstone. Intrusion of the 284?±?7 Ma Alouana concentrically zoned, two micas, calc-alkaline, and post-collisional Alouana granitoid pluton has contact metamorphosed the host rocks, giving rise to a metamorphic assemblage of quartz, plagioclase, biotite, muscovite, chlorite, and alusite, and cordierite. The mineralization occurs in and along subvertical, 20 to 40 cm thick, and structurally controlled tensional veins composed of quartz accompanied by molybdenite, wolframite, scheelite, base metal sulphides, carbonates, barite, and fluorite. Three main stages of mineralization (I, II, and III), each characterized by a specific mineral assemblage and/or texture, are recognized. Quartz dominates in all the veins and commonly displays multiple stages of vein filling and brecciation, and a variety of textures. The early tungsten-bearing stage consists of quartz-1, tourmaline, muscovite, wolframite, scheelite, and molybdenite. With advancing paragenetic sequence, the mineralogy of the veins shifted from stage I tungsten-bearing mineralization through stage II, dominated by base metal sulphides, to stage III with late barren carbonates and barite?±?fluorite mineral assemblages. Pervasive hydrothermal alteration affected, to varying degrees, the Alouana intrusion, resulting in microclinization, albitization, episyenitization, and greisenization of all the granitic units. Fluid inclusion data yield homogenization temperatures ranging from 124°C to 447°C for calculated salinity estimates in the range of 0.4 to ~60 wt% NaCl equiv. Similarly, the δ¹⁸O values for the three generations of quartz range from 11.7‰ to 13.9‰ V-SMOW. Calculated δ¹⁸O values of the parent fluid in the range between ?3‰ and +9‰ V-SMOW are consistent either with a mixture of water of different origins, including magmatic water, or an origin from seawater or meteoric water that probably exchanged oxygen with rocks at elevated temperatures. The coexistence of CO₂-rich and H₂O-rich fluid inclusions reflect the presence of a boiling fluid associated with the deposition of the early tungsten-bearing stage mineralization at relatively high temperature. The general temperature and salinity decrease with advancing paragenetic sequence suggest that the early high temperature, magmatic, highly saline, and boiling fluid mixed with meteoric non-boiling fluid results in the precipitation of base metal sulphide and carbonate–barite stage mineral assemblages, respectively.     

Identification of the behavior of sandy soil to static liquefaction and microtomography

In this paper, undrained triaxial compression tests were performed on specimens obtained in Oued Rass sand (Chlef, Algeria). The objective of this study is to investigate the effects of specimen deposition methods, the initial density, and the confining pressure on the undrained behavior of this sand. The test results show that the initial confining pressure and the relative density affected, in a significant manner, the resistance to liquefaction. However, it increases with confining pressure and relative density. The results also show that the specimens prepared by dry deposition method have a greater resistance to liquefaction than those prepared by moist tamping. A nondestructive comparative analysis of the deposits by X-ray microtomography carried out at the granular scale made it possible to characterize more precisely the difference of the obtained structures for the two deposition modes.     

A shock‐produced (Mg,Fe)SiO3 glass in the Suizhou meteorite

Abstract— Ovoid grains consisting of glass of stoichiometric (Mg, Fe)SiO₃ composition that is intimately associated with majorite were identified in the shock veins of the Suizhou meteorite. The glass is surrounded by a thick rim of polycrystalline majorite and is identical in composition to the parental low‐Ca pyroxene and majorite. These ovoid grains are surrounded by a fine‐grained matrix composed of majorite‐pyrope garnet, ringwoodite, magnesiowüstite, metal, and troilite. This study strongly suggests that some precursor pyroxene grains inside the shock veins were transformed to perovskite within the pyroxene due to a relatively low temperature, while at the rim region pyroxene grains transformed to majorite due to a higher temperature. After pressure release, perovskite vitrified at post‐shock temperature. The existence of vitrified perovskite indicates that the peak pressure in the shock veins exceeds 23 GPa. The post‐shock temperature in the meteorite could have been above 477 °C. This study indicates that the occurrence of high‐pressure minerals in the shock veins could not be used as a ubiquitous criterion for evaluating the shock stage of meteorites.     

Effect of Water and Leachate on Hydraulic Behavior of Compacted Bentonite,Calcareous Sand and Tuff Mixtures for Use as Landfill Liners

Compacted soil–bentonite liners, consisting of a sandy soil mixed with bentonite as backfill, are used extensively as engineered barriers for contaminant containment. This paper studies the valorization of local materials containing calcareous sand, tuff obtained from Laghouat region (in the South Algeria), to associate with bentonite in order to improve their hydraulic characteristics for use as landfill liner material. Firstly, a geotechnical characterization of mixtures chooses from a fixed percentage to 10% bentonite and different percentages of calcareous sand and tuff so that they are complementary to 90% by not 10%. Thereafter, the determination of saturated hydraulic conductivity at falling-head permeability (K_v) and oedometer (K_id, indirect Measure) tests of all compacted mixtures at Optimum Normal Proctor have been carried out using both permeates by tap water and a landfill leachate in order to simulate long-term conditions. The results showed that the saturated hydraulic conductivity of tap water is relatively lower than the one saturated by leachate in the falling-head test, unlike the oedometer test. The B₁₀CS₂₀T₇₀ mixture has satisfied the hydraulic conductivity criterion of bottom barriers (i.e. water permeated: k_v20° = 1.97 × 10^?9 and k_id from 7 × 10^?9 to 1.83 × 10^?10 < 10^?9m/s; leachate permeated: k_v20° = 2.91 × 10^?9 and k_id from 7 × 10^?9 at 1.44 × 10^?10 < 10^?9 m/s). Finally, a comparison between direct measurements of the saturated hydraulic conductivity by triaxial (K_d) test and oedometer test (K_id) in the range of effective stress applied 100–800 kPa led to propose equations of correlations between these two methods. In conclusion, adopted formulation B₁₀CS₂₀T₇₀ perfectly meets the regulatory requirements in force and constitutes an economic product based on available local materials for engineers barriers.     

消泡压力对消泡率的影响及基于数值模拟的消泡器结构优化设计

在泡沫钻进过程中,现有的消泡器往往不能很好地达到消泡的目的。笔者建立了消泡器室内试验台,进行了消泡压力对消泡器消泡能力的影响试验,通过测试不同压力与不同泵转速确定了消泡压力与消泡率的关系,同时借助FLUENT软件对消泡器的扩散管和消泡管内部的压力分布,进行了数值模拟与分析。根据分析结果对消泡器进行了优化设计,将消泡管的长度从15cm增加至65cm。对改进后的消泡器进行室内试验,其消泡率达到80%左右。     

Geologic relationships and mineralization of peralkaline/alkaline granite-syenite of the Zargat Na’am ring complex, Southeastern Desert, Egypt

Tungsten-bearing hydrothermal veins range from tensional veinlets to lodes containing multiple injections of hydrothermal quartz veins. Major composite lodes display greisen alteration envelopes characterized by enrichments in volatiles, K2O, Al2O3, Rb, L…     

Contribution to a geodynamic reconstruction of the Anti-Atlas (Morocco) during Pan-African times with the emphasis on inversion tectonics and metallogenic activity at the Precambrian–Cambrian transition

New geochronological analyses (U–Pb SIMS zircon ages) have yielded ages of 552 ± 5 Ma for the Bou Madine rhyolitic dome (Ougnat, eastern Anti-Atlas), 543 ± 9 Ma for the Tachkakacht rhyolitic dyke (Saghro–Imiter, eastern Anti-Atlas), and 531 ± 5 Ma for the Aghbar trachytic sill (Bou Azzer, central Anti-Atlas). Inherited zircon cores from the Aghbar trachytic sill and from the Bou Madine rhyolitic dome have been shown to be of Statherian age (ca. 1600–1800 Ma) and Palæoproterozoic (>2100 Ma) age, respectively, suggesting that a significantly older protolith underlies the Pan-African rocks in the Central and Eastern Anti-Atlas. Granodiorites and rhyolites from the Saghro–Imiter area have similar low ⁸⁷Sr/⁸⁶Sr (0.702–0.706) and ¹⁴³Nd/¹⁴⁴Nd (0.5116–0.5119) initial ratios, suggesting a mixture of mantle and lower crust sources. This can also be inferred from the low ¹⁸⁷Os/¹⁸⁸Os ratios obtained on pyrite crystals from the rhyolites.A recently published lithostratigraphic framework has been combined with these new geochemical and geochronological data, and those from the literature to produce a new reconstruction of the complex orogenic front that developed at the northern edge of the Eburnian West African craton during Pan-African times. Three Neoproterozoic magmatic series can be distinguished in the Anti-Atlas belt, i.e., high-K calc-alkaline granites, high-K calc-alkaline to shoshonitic rhyolites and andesites, and alkaline-shoshonitic trachytes and syenites, which have been dated at 595–570, 570–545 and 530 Ma, respectively.The accretion of the Pan-African Anti-Atlas belt to the West African super continent (WAC) was a four-stage event, involving extension, subduction, moderate collision and extension. The calc-alkaline magmatism of the subduction stage was associated with large-scale base metal and gold mineralisation. Metallogenic activity was greatest during the final extensional stage, at the Precambrian–Cambrian boundary. It is characterised by world-class precious metal deposits, base–metal porphyry and SEDEX-type occurrences.     

Apport de la gravimétrie à l'étude de la structure du bassin des Triffa (Maroc nord-oriental) : implications hydrogéologiques

Various techniques (horizontal and vertical derivatives, upward continuation, Euler deconvolution) have been applied to the gravity data from the Triffa's plain and the north flank of the Beni-Snassen massif to delineate various major geological structures such as faults and basins. These results allow the production of a structural map showing the fault systems for the survey area. This map forms the basis for planning future hydrogeological research in this region. To cite this article: D. Khattach et al., C. R. Geoscience 336 (2004).     

Photocatalytic activity evaluation of TiO<Subscript>2</Subscript> nanoparticles based on COD analyses for water treatment applications: a standardization attempt

Evaluation of the photocatalytic activities of TiO₂ nanomaterials based on the chemical oxygen demand (COD) analyses under identical experimental conditions was not previously reported. In this work, COD has been selected as an adequate industrial water quality measure toward the establishment of a representative standard test method. The initial COD values of six organic pollutants representing dye, surfactants, phenols and alcohol were set at 30 ± 2 mg/L. Ten of different commercial and synthesized TiO₂ samples representing anatase, rutile and mixed phases were used and characterized. The data of photocatalytic processes were compared to that obtained using the commonly widespread Degussa-P25 TiO₂ (TD). The COD of all pollutants was completely removed by TD at UV exposure dose ≤9.36 mWh/cm². Consequently, the maximum irradiation dose was set at this value in all experiments. The percentages of COD removal as well as the values of the accumulated UV doses required for complete removal of pollutants were measured using the different TiO₂ samples. TiO₂ samples show different performance abilities toward the various pollutants compared to TD. Based on the obtained data, TiO₂ photocatalysts were divided into two categories according to the hydroxyl radical formation rates. Comparison with previous studies reveals that the photocatalytic efficiency evaluation depends on the method of measurement. COD is recommended to be used as an adequate technique of analysis that meets the purpose of water treatment applications.