AMIRKABIR
Year:2008 | Volume:18 | Issue:67-C|Papers Count:15

This experimental research work was aimed at investigating the possibilities of bulging organic clay compounds in heterogenic suspension system of clay minerals and in the presence of natural substances. Moreover, the role of clay mineral in forming clay complexes was investigated to find a way of describing the formation of a clay mineral humic acid system.In the conducted experimental work, acids and humic acid precursors were extracted from soil samples and these extracts were allowed to react with different clay minerals. Various experimental approacpes (e.g. IR spectroscopy, Conductivity, X-ray Diffraction, Ultra sound technique, Cation- Exchange capacity) were employed to demonstrate the formation of stable clay/organic complexes. The experimental findings show that the formation of these complexes occurs under the catalytic influence of the organic substances. Based on experimental result the formation of clay organic compounds under mild conditions can be described two consecutive stages. First, the humic acid precursors are fixed between layers of clay.Then, other humic substances are attached to the fixed humic substances by intermolecular forces at the edges of clay mineral particles. Accordingly, a model is proposed to describe the conditions of natural soils and different phases of clay organic compounds formation.

Calculation of loads on TBM (Tunnel Boring Machine) shield is extremely important in TBM type selection and estimation of support system. Two main ground loading components on TBM consist of loading on TBM cutter head from the tunnel face and loading on the TBM shield from the tunnel surrounding rock mass. In weak rock masses, where convergence rate is high or TBM maintenance take long time, the ground convergence fills the gap between shield and surrounding rocks, which leads to TBM jamming or stoppage. Thus, TBM needs to overcome two forces excreted from ground. In this research, loads on TBM and tunnel lining segments are evaluated using three-dimensional continuum - discontinuum numerical analysis in Ghomrod tunnel. It is founded that; at first, continuum analysis results are different from discontinuum ones, which is due to heavily jointed rock masses condition. Secondly, calculated tunnel convergence with new information is higher than predicted convergence using preliminary data from geotechnical investigation (before tunnel excavation). Several records of TBM jamming confirm these results. Finally, load on tunnel lining cause to segments instability. Evident such as cracks on installed lining segments at tunnel walls verify the numerical analysis results.

Despite the fact that kerogen decomposition has not been yet very well understood, it is possible to obtain kinetic parameters which correlate with both empirical and natural geologic data by pyrolysing samples in closed and open systems. In this study, in order to determine hydrocarbon source rocks kinetic parameters, synthetic maturation by using open pyrolysis system (Rock-Eval) was used. In order to determine the equation of the real pyrolysis temperatures, the Rock-Eval pyrolysis oven was calibrated against three standard samples. Three source rock samples from three well known Iranian source rock formations namely Pabdeh, Garu and Kazhdumi were anafyzed at temperature rates of 25, 15, 10 and 5°c/min and their kinetic parameters including activation energy distribution, Arrehnus coefficient and the amount of generated hydrocarbon were determined.

Geochemical exploration, using the stream sediment method, involves two components which control the oncentration of elements in the samples: syngenetic and epigenetic. The epigenetic component is the useful component for exploration. However, usually as the syngenetic component is stronger, it dwarfs the effect of epigenetic component. There are several methods that are used to eliminate the effect of syngenetic component on geochemical data; for example, separation of upstream rock groups, principal component analysis (PCA) and fuzzy c-means clustering method (FCM). The effect of the syngenetic component, from stream sediment samples obtained from North of Takab, was removed, using the fuzzy clustering method. Then results from this method were compared to results obtained from the separation of upstream rock groups method. Based on this comparison, FCM distinguished new anomalies and removed weak and virtual anomalies in some place. Furthermore, the software that was created for this purpose was explained.

Golgohar iron mining Company which is one of the major suppliers of the raw material for Iran's steel industries produces 5 million tons of iron concentrate which is 33 percent of the concentrate production of iron in 2006. The feed of wet magnetic separators is supplied by three ball mills. The classification of the feed by hydrocyclone and the rejection of particles less than 100 microns and avoiding wet magnetic separator's middling from entering the ball mills increases the production capacity of the ball mill circuits by 33% removed of particles -125 mm from ball mill feed, reduces the production of particles -63 mm (which cause problems in low intensity wet magnetic separators) by 2 percent. By eliminating one mill from the circuit it is possible to reduce power consumption and the costs of depreciation, maintenance of ball charge and lubrication by 30 percent.

Studies on less than 12 mm product due to crushing and sizing plant of Gol-e-Gohar Iron Ore Co. showed that this material contains significant amount of valuable iron ores. Based on the carried out experimental studies, the processing flow sheet designed to upgrade iron content. This plant is known as the first hematite iron ore enrichment plant that has used dry medium intensity magnetic separators (3500 gauss) which are manufactured by Fakoor Sanat Tehran Company. The purpose of the plant is production of fine with iron content mote than 60.5% and recovery by weight more than 55% from the feed with iron content of 54%. In this plant, material at first are classified by a single deck screen (6mm), then screen oversize are separated at one stage by magnetic separator, while screen undersize at two stage. Based on experimental result, a product with iron content of 59.3% and recovery by weight 73% produced.Practically, the iron content has enhanced by increasing speed of magnetic separators and little decreasing recovery by weight to more than 60.5%. Finally, economical investigations showed that annual proceeds would be 17.8 millions dollar that time of capital return would be 13 day.

Iju porphyry copper deposit is located in southern part of Orumieh-Dokhtar volcano-plutonic belt, northwest of Shahr-e-Babak. The area is composed of an Eocene volcano-pyroclastic complex intruded by Oligo-Miocene diorite-quartzdiorite porphyries. The intrusive bodies contained several alteration mineralization producing phases. Minor potassic (biotite), phyllic, clay, propylitic and silicic alterations are observed in the area. Mineralization occurs as hypogene, secondary sulfide enrichment and oxide. Lithogeochemical data show that the main part of the Iju deposit was destroyed due to surficial processes. Average salinity for the two-phase liquid-rich fluid inclusions studied in quartz grains is 24.6 wt% NaCl equivalents. Average homogenization temperature for the fluids was 296.8°C and the emplacement depth is calculated as being about 500 meters. Combination of mono-phase gas and multi-phase fluid inclusions indicating boiling as well as low average of Cu content imply that the initial ore-forming fluid was poor in Cu and it would be unlikely to find copper at deeper parts of the deposit.

Geoelectrical surveys were carried out in Khenadareh-bala area, Sarband district, Markazi province, Iran for exploration of the graphite veins. In Sarband region, there are some potential areas for graphite mineralization, but most of them are not economical. Geoelectrical surveys were designed in Khenadarehbala area based on the geological evidences and physical properties of graphite. At first, self-potential (SP) method was carried out along 10 N-S profiles with 2 m distance between measuring points. Then, mise-a-la-masse measurements were implemented over there. The prepared self-potential and equipotential maps confirm each other and prove the presence of graphite mineralization with north-northeast trend. After that, resistively measurements were performed over the same profiles using dipole-dipole array (AB=MN=4 m) for more investigation of graphite distribution in the depth. The apparent resistivity pseudo sections indicate that the graphite veins (p<20 Wm) are approximately extended to depth of 25 m where SP profile shows the amplitude about -200 mV. Some excavation such as exploratory pits, well, and trench dug in this surveying area, demonstrate that these veins are discontinuous, thin, and impure.

The electroleaching of Sar-Cheshmeh copper sulfide concentrate in aqueous sulfuric media has been investigated under the influential parameters as; current density, leaching time, sulfuric acid concentration and temperature. The experiments were carried out in batch conditions and static bed status. Based on the illustrated results, concentration of copper in leaching solution increases strongly when electric current is applied. At the above-mentioned conditions the concentration of copper decreased while the electrical current is increased toward the maximum. On the other hand, the concentration of Fe2+ in leach liquor increases with increasing the current density. So, the irregular increasing of current density is not convenient to electroleaching of copper concentrate. The results showed that both anodic and cathodic reactions during the leaching process caused the copper concentration decreases at the long period of times, but iron concentration increases rapidly. It is also suggested that the deposition of copper on cathode surface during the leaching process "as a reduction reaction" causes the decreasing of the copper concentration in the solution. Decomposition of copper sulfides is an endothermic reaction, so the copper concentration of solution increases with increasing the temperature up to 80°c. increasing the temperature from 60°C to 80°C decreases the iron extraction during the process.

The porphyry copper deposit (PCD) at Sungun is located in East Azarbaijan, NW of Iran. The Sungun porphyries occur as stocks and dikes ranging in composition from quartz monzodiorite through quartz monzonite and granodiorite to granite. The stocks are divided into two groups (1) Porphyry Stocks I and (2) Porphyry Stock n. Porphyry Stock n, hosting the copper ore, experienced intense hydro-fracturing leading to the formation of stockwork-type, veinlets and micro-veinlets of quartz, sulfides, carbonates, and sulfates. Three distinct types of hydrothermal alteration and sulfide mineralization are recognized at Sungun (1) hypogene, (2) contact metasomatic (skarn), and (3) supergene. Four types of hypogene alteration are developed at Sungun, potassic, propylitic, potassic-phyllic, and phyllic. Based upon their phase content, four types of fluid inclusions are common at Sungun (1) vapor, mono-phase (2) vapor-rich, two-phase, (3) liquid-rich two-phase, and (4) multi-phase. Halite is the principal solid phase. The distribution pattern, shape, and phase contents of fluid inclusions in quartz veinlets at Sungun are analogous to those from Bingham and Globe-Miami in western USA. We used multiphase inclusions to calculate the point pressure and hydrothermal fluid density. Four variables have been measured and calculated for forty seven separated samples, including the homogenization temperature, salinity, pressure and density. Histograms of variables represented that no variable could separate potassic and phyllic alterations lonely. In potassic alteration zone, the average of homogenization temperature is 413.6°C while in phyllic alteration, it is 375.9°C. As it is expected in potassic alteration, the temperature of hydrothermal is higher than that in phyllic zone, but there is not high difference between them. The salinity of the hydrothermal has a high coherency with homogenization temperature, so the average amount of salinity in potassic samples is 46.3 (w% NaCl) which is higher than phyllic samples. Based on the location of potassic alteration, it is expected that the lithostatic pressure is much more than the phyllic one, so it is realized that the average of pressure in the potassic alteration is -1195 (bar) while the average pressure in phyllic is -623 (bar). The amount of the density depends on the amount of the salinity of hydrothermal fluid, so the average density of the samples in potassic alteration is 1.124 (gr/cm3) which is higher than that in phyllic zone (1.083 gr/cm3).

The effect of aluminum content, austenitizing temperature and austempering time and temperature on the microstructure and mechanical properties of Fe-C-Al grey cast iron are investigated. Three alloys containing 1, 2 and 4 weight percent of a1uminumare provided. The tensile samples are austenitized at 850°C and 900°C for 2h, followed by and austempering process at 275°C for 1-120min.The results show that increase of austenitizing temperature from 850°C to 900°C in the alloys with 1wt% and 2wt% aluminum decreases the elongation and ultimate tensile strength. In the samples without aluminum and containing 4wt% aluminum increase in the austenitizing, temperature leads to increasing of ultimate tensile strength and elongation. Experiments carried out on austenitized samples at 900°C shows that in alloys with 1wt% and 2wt% of aluminum maximum strength and elongation appear after 30 minutes of austempering but in samples without aluminum or those containing 4wt% aluminum the maximum strength and elongation appear after 60 minutes.

For the purpose of manufacturing of the Cobalt-base superalloy of Co-Cr-Mo (ASTM F75-87) an appropriate mold has been made from silicon:-rubber, and subsequently melting and alloying procedure was carried out. For alloying in this study a vacuum induction melting (VIM) was used. After conducting tensile test on produced specimen, it was observed that mechanical properties of superalloy except ductility are in the standard range; therefore, solution treatments were carried out on the specimens.Specimens were preheated at 1130°C and afterward those were subjected to solution. Heat treatments at 1230°C for several times. When heat treatments completed, specimens were discharged from furnace and were quenched in water. As a result of heat treatment, elongation was enhanced considerably. It seems that the main strengthening mechanism stems from the solid-solution and carbide precipitates. Heat treatments cause the dissolution of carbides specially grain boundary carbides, thus increasing ductility and reducing hardness.

Solution phenomena and formation of intermetallic compound during contact of solid iron and aluminum melt was seen in the interface. In this study, the compositional recognition method was used in interface to find a better understanding of such phenomena. To this end, with using optical microscope and SEM, interface structure has been studied in immersion condition without turbulence in 750, 800 and 850 degrees centigrade. The results indicate the co-occurrence of solution and formation of intermetallics they showed also detachment and destruction of parts of compositional layer is one of the main mechanisms of entering iron atoms in aluminum melt. The solution phenomenon does not occur only with direct diffusion.