JOURNAL OF MINERAL RESOURCES ENGINEERING
Year:2017 | Volume:2 | Issue:2 |Papers Count:7

Nowadays, earth pressure balance tunnel boring machines (EPB-TBMs) are favorably used in urban mechanized tunneling projects. The availability of these machines is rather low, so their performance, time planning, maintenance scheduling and cost control may need further improvements. The reliability, availability and maintainability (RAM) of any machine could be analyzed by evaluating the actual performance of that machine or system and thereby minimizing maintenance costs. In current research work, RAM analysis of the electrical system of the EPB-TBM in line 1 of Tabriz metro in Iran is performed. For this investigation, failure and repair data were collected during about 26 months of machine operation. Statistical tests including trend and serial correlation tests indicated that the data are independently distributed, consequently the statistical technique was used for modeling. The data analysis also revealed that the time between failures (TBFs) and time to repairs (TTRs) data fit to the Lognormal (3P) and Gamma (3P) distributions, respectively. Reliability analysis showed that there is approximately 80.1% chance for the electrical system of TBM machine to be operational for 15 h without any failure. Moreover, the maintainability curve indicated that most of the failures have been repaired in less than 1 hour and that it is more likely that 80% of these failures would be repaired in 1.88h. Also the availability of electrical system of this machine is found to be equal to 97.8%.

The extraction of Pb from galena concentrate using fluoroboric acid media was studied and optimized as a potentially promising process to replace lead pyrometallurgical producing processes. The lead, zinc and iron content of the galena concentrate investigated were 57.66%, 5.50% and 1.55% respectively. Five control factors, including initial HBF4 concentration, the addition of iron and oxidizer agent, the reaction temperature and reaction time were considered in four different levels using Taguchi technique. L16 orthogonal array and analysis of variance (ANOVA) were applied to determine the optimum conditions and most significant factors affecting the overall lead extraction from galena concentrate. Analysis of variance indicated that the amount of oxidizer agent used and iron usage were the most influential leaching parameters respectively. According to former studies this result can be related to necessity of formation and presence of ferric fluoborate and also oxidation of ferrous ion to ferric in the system. The optimum dissolution condition to maximize lead extraction were; acid concentration = 5 mol/l, additive usage = 46.8 wt. %, oxidizer agent usage = 3 volume percent, temperature = 80oC and time = 6 hrs. Lead recovery efficiency in the optimum conditions predicted by Taguchi method successfully reached to 94.65%.

Foundation loading in mines typically occurs on pillars in underground mines which may not have necessarily a regular shape. The previous studied have mostly focused on the stress distribution within the pillar, rather than on the stresses induced in the underlying layers. In other words, a mining pillar has been mainly regarded as a column rather than a footing. The determination of foundation-induced stresses in rock and soil is of great importance when designing mine pillars. Hence, different methods have been presented to analyze the stresses induced in the ground due to the foundation loading. The influence chart is a graphical analysis method based on the elasticity theory which is capable of analyzing foundations with arbitrary shape. However, since this method suffers from difficulties associated with drawing and calculation, it has not been considered as an efficient method of foundation analysis. In this paper, a computer program is introduced and evaluated which determines the mining pillar-induced pressure using the influence chart method combined with image processing techniques. The software presents a graphical user interface which facilitates creating and editing of the foundation geometry. The developed program is capable of estimating the over-pressure value at given coordinates below the foundation. The modeling procedure in the developed software is much faster compared to other sophisticated numerical codes, while no discrepancy in results is observed. Hence, it would be considered as an efficient and handy numerical tool in preliminary studies.

In this study, the effect of thermal treatment on phase transformations and grindability of a low-grade manganese ore containing silica was studied. Thermal analysis (DTA/TG) and scanning electron microscope (SEM) are used to study the phase transformation and structural change of samples under thermal treatment. Thermal effect on grindability under various temperature and thermal duration time on mill feed was determined by standard Bond rod mill work index. Based on the results of thermal analysis, at 750oC dehydroxylation of montmorillonite and decomposition of calcite occured, and at 850oC decomposition of montmorillonite to silicate minerals were proved. SEM studies revealed that thermal treatment lead to some cracks with the size of 280´13 mm in the sample. For 60 min thermal treatment, while increasing temperature to 800oC, the amount of fine particles produced in a cycle (Gi) and the P80 of the mill product were increased to 90% and 10%, respectively and standard Bond rod mill work index was decreased from 20.06 Kwh/t to 14.35 Kwh/t.

The aim of the present study is to decrease the amount of unwanted gangue minerals to enter the cyanidation process. The flotation process was introduced for the beneficiation of the feed to the cyanide leaching stage. Selection of a proper procedure for gold processing needs the accurate characterization of the gold bearing minerals comprising the ore. Diagnostic leaching tests were conducted to specify the gold mineral phases and associated gold in Mouteh ore. Fire assay analysis showed gold grade equal to 0.85 ppm and 0.86 ppm for the two representative samples of Mouteh plant feed. In pyrite flotation tests, the recovery and grade of gold in concentrate were found to be 38% and 8ppm, respectively. The cyanidation of concentrate can lead to an efficient beneficiation process for the gold recovery. The optimized conditions was found to be: pH: 9, solid percent: 25, potassium xanthate (KAX) as collector: 150 gr/t, MIBC as frother: 25ppm, and conditioning time: 10 minute. EPMA analysis demonstrated that gold in Mouteh ore was associated with pyrite which would need more grinding for liberation. The size of liberated gold particles in EPMA pictures was found to be 3-4 microns. According to the diagnostic leaching experiments and silicates flotation tests, no gold was detected with silicates mineral. Following the flotation of quartz particles and elimination of 20 percent of feed by weight, it would be possible to reduce the feed of cyanide leaching. Therefore, Quartz flotation can also be an effective pre-concentration method prior to cyanidation process.

It is economically evaluated that building stone industry in Iran, among other industries has export comparative advantage. In order to improve this, it is necessary to plan and provide the infrastructure, thus effective advertisement and marketing are the primary and most important steps. One of the most important factors which causes the failure of Iran's stone is poor planning and organizing as well as failure in using effective methods of advertisement and marketing. In this research, major problems of marketing in the field of stone industry throughout the country have been studied. Afterward the main factors affecting the development of exports, have been presented. In this regard, as the guide patterns dealing with Iran's stone export, the experience and performance of advertising, marketing and export of progressive countries in the world stone trade (i.e. China, Turkey, Italy and India) have been evaluated.

Hierarchical cluster and principal component analysis are two statistical methods frequently used by geochemists to study the group of variables. In order to identify oil families in the Iranian sector of Persian Gulf, 33 oil samples were collected and analyzed by advanced gas chromatography, gas chromatography-mass spectrometry and Finnigan Delta Plus mass spectrometer. On the whole, 16 parameters were considered as the input data for Hierarchical cluster and principal component analysis. Four different oil families at least could be identified through the Iranian sector of Persian Gulf based on the results obtained. These families were categorized stratigraphically and regionally. Accordingly, oil families No. I and No. II in west and east of Persian Gulf respectively, are located in the Jurassic to early Cretaceous reservoirs, whereas oil families No. III and No. IV in west and east of Persian Gulf belong to Late Cretaceous to Tertiary reservoirs.