Stability analysis of ore pass systems at Brunswick mine

Des cheminées à minerai sont utilisées dans des mines pour transférer par gravité le minerai des niveaux supérieurs de la mine aux niveaux inférieurs. L'intégrité des cheminées à minerai peut être compromise par des changements des contraintes et par les structures géologiques en place dans le massif rocheux. Par ailleurs, le passage du minerai participe à l'usure des murs des cheminées, causée par les charges d'impact et par l'abrasion aux parois. La revue de la littérature pertinente sur la dégradation des cheminées à minerai, suggère que tous ces mécanismes peuvent potentiellement agir simultanément bien qu'un d'entre eux soit habituellement le plus dominant. La majorité des études abordant ce sujet ont considéré l'influence d'un seul mécanisme de rupture sur l'intégrité des cheminées à minerai ou n'ont pas pris en considération, de manière réaliste, l'interaction des différents mécanismes de rupture. L'objectif de cette thèse était d'analyser la stabilité des cheminées à minerai à la Mine Brunswick. Une campagne de collecte de données a été réalisée à la mine. Une analyse qualitative et quantitative des données rassemblées a permis l'identification des pratiques actuelles et passées à la mine. Cette analyse s'est concentrée sur l'influence de la géométrie et de la configuration des cheminées à minerai, du massif rocheux, du régime des contraintes et des pratiques sur les problèmes opérationnels observés, reliés à l'utilisation des cheminées à minerai. Des cheminées à minerai avec des signes de dégradation majeure, ont fait l'objet d'une investigation plus détaillée. En particulier, l'évolution de la dégradation a été documentée et les mécanismes critiques de dégradation ont été identifiés. Une approche de modélisation numérique étapiste a été utilisée pour étudier la stabilité des cheminées à minerai. L'approche utilisée considère l'interaction de l'influence des contraintes, de la fracturation inhérente au massif rocheux et de l'usure due au passage du matériel comme étant des mécanismes de dégradation des cheminées à minerai. La première étape de cette approche était l'utilisation des modèles d'analyse des contraintes 3D utilisant le logiciel Map3D pour calculer les contraintes globales. La seconde étape était la construction d'un modèle synthétique du massif rocheux qui simule plus adéquatement le comportement d'un massif rocheux fracturé. Le logiciel Fracture-SG a été utilisé pour représenter la géométrie du réseau de discontinuités existant, tel qu'observé sur des sites choisis à la Mine Brunswick. Le système de fracturation modélisé est ensuite couplé avec un modèle tridimensionnel d'éléments distincts, le Particle Flow Code (PFC). PFC simule la roche intacte comme un ensemble de plusieurs particules sphériques, aux dimensions uniformément distribuées, liées entre elles aux points de contact. Un modèle synthétique du massif rocheux peut être soumis à différents niveaux de contraintes tridimensionnelles. Selon le niveau des contraintes imposé, le massif rocheux synthétique peut céder par la rupture des portions intactes de roche ou par le glissement des discontinuités. Ceci est une innovation importante dans la simulation d'un massif rocheux fracturé. Cette façon de modélisée un massif rocheux synthétique a été utilisée pour faire la rétro-analyse d'une cheminée déjà dégradée à la Mine Brunswick. Un modèle de fracturation du massif rocheux a été généré en utilisant des données quantitatives obtenues pour un sulfure massif à la mine. Un modèle synthétique du sulfure massif a été construit en intégrant la géométrie du réseau de discontinuités modélisé dans un modèle PFC. Le modèle PFC a été ensuite calibré suivant les propriétés mécaniques des échantillons de roche intacte de sulfure massif testés en laboratoire. Ensuite, les contraintes aux frontières du modèle synthétique ont été appliquées et les volumes des cheminées à minerai ont été extraits du modèle. Ceci a permis la quantification de la grandeur des zones d'effondrement crées par l'interaction des contraintes et des structures en place autour de la cheminée à minerai. On a observé différents mécanismes d'effondrement tels que la rupture de portions de roche intacte entre les discontinuités préexistantes suivi par la chute de blocs rocheux générés par la propagation et l'intersection des discontinuités. L'influence de l'impact associé à l'écoulement des particules a alors été intégrée en projetant un fragment de roche (simulé par une particule sphérique rigide) sur les murs de la cheminée à minerai modélisés. Cette thèse présente un cadre d'analyse portant sur l'étude de l'interaction et de l'influence des différents mécanismes de rupture sur la dégradation des cheminées à minerai. Utilisant des données de terrain amassées à la Mine Brunswick, il a été démontré que cette approche a des ramifications importantes sur la conception des cheminées à minerai. Elle peut potentiellement être employée pour la conception des cheminées à minerai dans une gamme de régimes structuraux et de contraintes. Cette approche peut faciliter le choix des configurations des cheminées qui peuvent atténuer la dimension des zones d'effondrement autour d'elles. Une contribution importante de cette thèse est l'intégration de l'influence de l'impact de matériel. Ceci peut aussi faciliter le choix d'une configuration de cheminées à minerai qui atténuerait l'apparition de dommages aux parois en raison de l'écoulement du matériel dans la cheminée. Ces techniques de conception améliorées peuvent potentiellement augmenter la longévité du système de cheminées à minerai et réduire les besoins en réhabilitation. Ceci aura des ramifications importantes sur l'investissement et les coûts opératoires

Estimating geometrical and mechanical REV based on synthetic rock mass models at Brunswick Mine

This paper uses a case study from Brunswick Mine in Canada to determine a representative elementary volume (REV) of a jointed rock mass in the vicinity of important underground infrastructure. The equivalent geometrical and mechanical property REV sizes were determined based on fracture systems modeling and numerical experiments on a synthetic rock mass. Structural data collected in massive sulphides were used to generate a large fracture system model (FSM), 40 m×40 m×40 m. This FSM was validated and subsequently sampled to procure 40 cubic specimens with a height to width ratio of 2 based on sample width from 0.05 to 10 m. The specimens were introduced into a 3D particle flow code (PFC3D) model to create synthetic rock mass (SRM) samples. The geometrical REV of the rock mass was determined based on the number of fractures in each sampled volume (P30) and the volumetric fracture intensity (P32) of the samples. The mechanical REV was estimated based on the uniaxial compressive strength (UCS) and elastic modulus (E) of the synthetic rock mass samples. The REV size of the rock mass was determined based on a series of statistical tests. The T-test was used to assess whether the means of the samples were statistically different from each other and the F-test to compare the calculated variance. Finally, the coefficient of variation, for the synthetic rock mass geometrical and mechanical properties, was plotted against sample size. For this particular site the estimated geometrical REV size of the rock mass was 3.5 m×3.5 m×7 m, while the mechanical property REV size was 7 m×7 m×14 m. Consequently, for engineering purposes the largest volume (7 m×7 m×14 m) can be considered as the REV size for this rock mass

Capturing the complete stress–strain behaviour of jointed rock using a numerical approach

This paper presents the results of a series of numerical experiments using the synthetic rock mass (SRM) approach to quantify the behaviour of jointed rock masses. Field data from a massive sulphide rock mass, at the Brunswick mine, were used to develop a discrete fracture network (DFN). The constructed DFN model was subsequently subjected to random sampling whereby 40 cubic samples, of height to width ratio of two, and of varying widths (0.05 to 10 m) were isolated. The discrete fracture samples were linked to 3D bonded particle models to generate representative SRM models for each sample size. This approach simulated the jointed rock mass as an assembly of fractures embedded into the rock matrix. The SRM samples were submitted to uniaxial loading, and the complete stress–strain behaviour of each specimen was recorded. This approach provided a way to determine the complex constitutive behaviour of large-scale rock mass samples. This is often difficult or not possible to achieve in the laboratory. The numerical experiments suggested that higher post-peak modulus values were obtained for smaller samples and lower values for larger sample sizes. Furthermore, the observed deviation of the recorded post-peak modulus values decreased with sample size. The ratio of residual strength of rock mass samples per uniaxial compressive strength intact increases moderately with sample size. Consequently, for the investigated massive sulphide rock mass, the pre-peak and post-peak representative elemental volume size was found to be the same (7 × 7 × 14 m)

Stability analysis of vertical excavations in hard rock by integrating a fracture system into a PFC model

This paper presents an implementation of a comprehensive engineering approach to the analysis of the stability of vertical excavations in rock. This approach relies in the generation of discrete fracture systems to better capture the structural complexity of the rock mass. The resulting fracture system is consequently linked into a distinct element stress analysis. The particle flow code was selected as it potentially allows greater flexibility in representing a fracture system. In the first example a 3D fracture system was linked into a 2D PFC model. Although this has allowed for an improved quantification of stress structure interaction it necessitated important simplifications which may not be necessarily appropriate. These have been overcome by providing a complete integration of a 3D fracture system to a 3D PFC model. This will potentially lead into a design tool that adequately account for the stress structure interaction on the stability of vertical or near vertical excavations in hard rock

Determining the lethal concentration (LC50 96h) of butachlor herbicide for Acipenser persicus and Acipenser stellatus fingerlings

The toxic effects of the herbicide Butachlor were studied using a concentration of 0.4-1.3ppm and 0/1-1ppm on fingerlings of the Persian sturgeon, Acipenser persicus, and Stellatus sturgeon, Acipenser stellatus, respectively in 1999. We carried out six treatments with three replicates and used one control based on the static O.E.C. D. method. Over the experiments, pH ranged between 6.7 -8.2, total hardness was measured to be 230 mg/l, water temperature was 20 plus or minus 1 degrees centigrade and dissolved oxygen was above 6 mg/l. We found that the LC50 96h of the Butachlor on fingerlings of the Persian sturgeon, Acipenser persicus, and Stellatus sturgeon, Acipenser stellatus, weighing 1-3 grams was 0.44 and 0.07 mg/l respectively. Also assessed the LC10, LC50, LC90 of the herbicide on the fingerlings of the sturgeons using the Probit Analysis procedure. We determined the maximum allowable concentration of the Butachlor herbicide for the fingerlings of the Persian sturgeons, Acipenser persicus, and Stellatus sturgeons, Acipenser stellatus, to be 0.044 and 0.007 mg/l. Based on the standards, the herbicide is considered highly toxic for the studied fingerlings

The effect of massage on pain intensity in patients with knee surgery by Arthroscopy technique

Background: Pain as a main social problem has involved millions of people. Surface massag is one of the effective ways for reducing pain after surgery. The aim of this study was to evaluate the effect of surface massage technique on pain intensity in knee surgery patients with Arthroscopy technique. Material and Methods: This is a clinical trial study on 60 Knee surgery patientsSamples were selected using conveniencecontinuity method and then they were randomly divided into intervention and control groups. In intervention group, besides routine treatments, patients were taking surface massage technique by the researcher for 20 minutes each day and pain severity was evaluated before and after the surface stroking technique. Control group received only routine medical care and pain severity was evaluated in first and after 20 minutes. Data was analyzed by presenting descriptive and inferential statistics with using SPSS version 15 software. Results: Results showed that there was a statistical different between mean score of pain severity before and after surface massage in intervention group (p <0.001) but this difference wasn't meaningful in control group (p=0.32). Conclusion: Considering surface massage as a safe and effective intervention, it could be used as an easy, cheap and executable method for treating pain in all medical health care centers and even at patient's home

Evaluation of the position of the posterior superior alveolar artery in relation to the maxillary sinus using the Cone-Beam computed tomography scans

The aim of the present study was to evaluate the diameter, relationship and position of the posterior superior alveolar artery and its relationship with the alveolar ridge, the medial wall of the maxillary sinus, the prevalence of pathologic conditions and the maxillary sinus septa on CBCT images. A total of 200 CBCT images (400 maxillary sinuses) of patients over 20 years of age were evaluated. The distances between the lower border of the artery and the alveolar crest and between the artery and the medial wall of the sinus and the diameter of the artery were measured. The position of the artery, the presence of pathologic conditions and septa were recorded in the posterior region in: a) males edentulous in the posterior region; b) males having teeth in the posterior region; c) females edentulous in the posterior region; and d) females having teeth in the posterior region. The mean distance between the artery and the alveolar crest, irrespective of groupings, was 16.17±1.63 mm, with significant differences between the groups (P<0.05). The mean distance between the artery and the medial wall of the sinus was 11.65±1.21 mm, with no significant differences between the groups (P=0.796). The mean diameter of the canal was 1.37±0.44 mm, with no significant differences between the 4 groups (P=0.570). The position of the artery was intraosseous in 73.2%, beneath the sinus membrane in 21.7% and external to the lateral wall of the sinus in 4.9% of the cases. The overall prevalence rates of pathologic conditions and septa in the maxillary sinus were 45.7% and 26%, respectively. CBCT technique is useful for such evaluations and for possible variations in maxillary sinuses and presence of septa and pathologic entities in maxillary sinuses

Environmental factors affecting agar extraction from Gracilaria corticata in the coastal areas of Persian Gulf, Bandar-e-Lengeh

The effects of environmental factors and season on agar extraction from Gracilaria corticata were investigated for the period 1993-94 in the coastal areas of Persian Gulf. Water temperature, water salinity and ammonia and phosphate ions were measured monthly. Mean temperature was found to be 27.8 centigrade, mean salinity was 36.38 PPT., mean ammonia ions was 0.154mg/l and mean phosphate ions was 0.029mg/l . After harvesting, Gracilaria were dried and weighed and subjected to the alkali agar extraction method. Maximum and minimum agar yield were obtained in August and December with 10.01% and 5.44% respectively. There was a significant correlation between agar yield, biomass and ammonium fertility. Results showed that the maximum agar yield from Gracilaria was obtained in March and August

Condition assessment criteria evaluation of asymmetric aged and fully aged silicone rubber insulators based on leakage current harmonics

The leakage current characteristic monitoring of transmission line insulators is considered a worthy technique for insulator state prediction. In this paper, the harmonic analysis of leakage current signals has been performed to analyze the composite insulator condition. Experimental studies of asymmetrically aged, fully aged, and virgin insulators have been conducted. The effects of different aging types, pollution, and humidity on leakage current components, such as harmonics and the phase differences with the applied voltage, have been investigated. The analysis of the results shows that the effect of asymmetric aging on leakage current components is non‐linear, and this non‐linearity increases with the degree of pollution. Also, the type of insulator aging can be determined by the ratio of the third‐ and fifth‐order leakage current harmonics. For instance, the classification of insulators into virgin, asymmetrically aged, and fully aged can be determined by examining the corresponding value ranges of 0–0.5, 0.5–0.9, and > 0.9, respectively. Similarly, the phase difference values of 15% indicate the clean and polluted operating conditions individually

Research paper: Psychometric properties of the Persian version of self-determination parent perception scale

Objectives: Self-determination is a significant skill in the proper transition from adolescence to adulthood. Parents play an important role in assessing the self-determination of their children. Currently, there is no valid instrument in Iran to assess parents' views about the self-determination of their adolescents. The present study was conducted to determine the psychometric properties of the Persian version of the Self-determination Parent Perception Scale (SDPPS) in an Iranian population. Methods: In this descriptive psychometric study, the original version of SDPPS was translated using the forward-backward method. The content validity index and content validity ratio of the questionnaire were confirmed by a panel of 15 experts, and its face validity was evaluated among 10 parents of the adolescents. Exploratory factor analysis was conducted on 125 parents of adolescents (aged 14-18 years) who were selected by convenience sampling with maximum variation. Its reliability and internal consistency were also assessed using test-retest and in a group of 17 parents, respectively. The obtained data were analyzed by SPSS V. 18. Results: The items were modified at the face validity stage and approved at the content validity stage. Five factors by explaining 54.14 of the variance and deleting four items were confirmed at the construct validity stage using exploratory factor analysis. A Cronbach's alpha of 0.93 was obtained for the total scale and 0.79 to 0.85 for the five subscales of the SDPPS. The intra-class correlation coefficient with 95 CI (0.82-0.98) was 0.83 indicating good reliability of the questionnaire. Discussion: The Persian version of SDPPS showed acceptable validity and reliability in explaining the self-determination of adolescents with and without disabilities based on the parents' perspectives and can be applied by professionals in rehabilitation centers and those studying on human behavior. © 2020 University of Social Welfare and Rehabilitation Sciences