IRANIAN JOURNAL OF MINING ENGINEERING (IRJME)
Year:2010 | Volume:4 | Issue:8|Papers Count:15

The commonly used failure criterion based on stress intensity factors is compared with new developed stress based failure criterion to predict crack growth trajectory and the advantages and disadvantages of both criteria are discussed using some examples. To obtain displacement vector and strain and stress tensors, the element free Galerkin method (EFGM) is used. The visibility criterion is applied to model cracks and the M-integral method is employed to calculate the stress intensity factors. Two examples are considered to evaluate the mentioned failure criteria. The stress intensity factors obtained from EFGM show good agreement with the results of finite element and analytical solutions. The failure criterion based on stress intensity factors only can predict the initial crack trajectory however the stress based failure criterion can predict the complete crack growth path and its predictions coincide very well with numerical and experimental results.

Nowadays, using GIS in exploration of mineral deposits is among the important, and of course, indespensible methods. Accordingly, the algorithm of Weights of Evidence in GIS has been employed in this paper for integrating data from geological, exploration and mining sources in order to detect and discriminate areas bearing high potential of minerals in Irankoh of Isfahan as a case study.In order to obtain and complete some evidential layers the remotely sensed digital imagery from multi-spectral satellites including Landsat ETM+ and Aster sensors of the region were processed in the first stage. Other evidential layers such as geophysical, geochemical, Barite outcrops, surficial ore indications and known deposit training sites were created using information available in many exploratory reports and maps.Using weights of evidence approach, the weights for above eight separate evidential layers including geophysical, geochemical, faulting, dolomitization, baritization, ore indications, oxidation and hydroxylation layers were calculated and in the mean time, the conditional independencies were evaluated using chi-square statistical test.  The final favorability map for further follow-up priorities in the frame of systematic exploration was drawn, and based on this map the regions with ranked prospectivities were identified. The results show that parts of Roomarmar region, areas to the west of Gooshfil mine, east of Tappeh-Sorkh mine, north of Kolahdarwazeh mine and lastly west of Tappeh-Sorkh mine with lowest prospectivity are respectively areas to be considered for further exploration programs.

Hydrocyclone is the most effective classification unit in mineral processing practices. This device is very sensitive to the operational parameters. Due to the short residence time of material in the hydrocyclone, its monitoring has a great effect on the circuit performance. Two criteria are normally used to evaluate the cyclone performance, namely, cut size and water recovery to underflow. In this research, first, underflow discharge angle was measured using image processing technique. Then, statistical method was used to evaluate the effect of operational parameters on the underflow discharge angle. Empirical models were fitted to the data, relating the underflow angle to the variables. It was shown that this method can be used to control, the hydrocyclone performance.

Convergency measurement is one the most utilized methods to analyze the behavior of underground openings. In this research, the extraction effects of the coal stopes "245 advance" and "245 regressive" on the gallery Post no. 5 of Pabedana coal mine are considered. This gallery has experienced difficult loading conditions which are caused many stability problems like high deformation and yielding of steel sets. Convergences are recorded for about 1 year implementing tape extensometer and 3-point convergence monitoring arrays. Results of analyzing the recorded convergences of 12 stations showed that more than 92% of displacements are occured behind the stope face. Critical displacements occur under the gob zone, i.e. between 7-22m behind the stope face. Also, it is concluded that the rate of coal extraction in longwall stopes has a key role on stability of gallery.

The low grade oxide-sulfide lead-zinc ore sample taken from Changarzeh mine located in south of Natanz city in Isfahan province, containing 2.3% Pb and 1.91% Zn was concentrated by flotation and gravity methods. Studies were concentrated on producing Lead concentrate with maximum recovery. So, the effects of different parameters such as type and amount of collector, milling retention time, amount of sodium sulfur and its preparation time, application of sodium silicate, pH and solid content were investigated in relation to the metal contents of concentrates and flotation efficiencies. Experiments  in optimum condition  was carried out with 200 g/t KAX as collector, 2000 g/t Na2S, 500 g/t sodium silicate and 30 g/t MIBC at pH 10. A rougher concentrate with a recovery of 94% was produced through this condition and a lead concentrate with 70% Pb was produced as a result of 3 cleaning stages of flotation with a recovery of 40%. The process of rougher flotation was also analyzed kinetically and 18 minutes was determined as the optimum flotation time. Application of gravity methods for producing commercial product or a middle product for flotation was considered with a special attention to the effect of table slope and amount of water and for jig the effect of water and frequency. The result of one stage gravity separation by shaking table was a concentrate with a grade of 46% and a recovery of 80%. As a result, shaking table can be proposed for production of preconcentrate to be used as feed of flotation process. But since jig can be used for separation of coarse particles and the lead content of Changarzeh mine is in the form of fine particles, the results of jig were not considerable.

The Ghareh chaman area is located on Urumeih-Dokhtar zone in E-Azarbaijan, which is mostly, comprises of acid and intermediate volcanic rocks along with alluvium. Regional geochemical exploration was carried out in the area by 698 stream sediment sampling with the aim of optimizing different methods for obtaining reliable exploration model in the area. Hence a comparative studies of data processing using lithological unit's discrimination (L.U.D) method and Fuzzy C-mean clustering (FCMC) for eliminating syngenetic component was attempted.In FCMC method the normalized data was processed and the elements with higher percentage of sensord were eliminated and factor analyses on data were employed. Only one or two elements from each group were selected based on their factorial scores and then FCMC method on geochemical data was carried out on selected elements. The results revealed six optimized clusters. Using residual values for geochemical mapping the promising mineralized areas were detected. Application of  Fuzzy logic based FCMC on geochemical data reveal that, with membership of each sample in different clusters and estimating the residual values, the syngenetic effect is eliminated causing in detecting of  blind anomalies in the area. The comparative studies of different methods on stream sediments of Ghareh Chaman indicate that the employment of FCMC method has advantage of detecting anomalies precisely in a shorter period of time confirming the capability of this method in contrast to L.U.D particularly in regional scale exploration where the numbers of samples are enormously increasing.

Grade deviation between the feed and the consumption of concentration plant was a great debate from the beginning of the Sarcheshmeh copper mine operations until now. However, the ore dressing plant is designed in such a way to work optimally base on specific input feed. Therefore, the error identification of different sampling procedure and grade deviation investigation between the feed of the mine and the consumption of the concentrating plant is essential. With determination of limit allowance of adequate parameters in deviation variance and make use of them in daily product schedual, it is possible to reduce the grade deviation. In this research with utilizing the statistical and geostatistical implement an evaluation method of accurate grade deviation of concentrating plant feed is presented so that with the help of its result, possibility these deviations with the predicted deviations of feed of mine gets provided in terms of shift or daily scheduals. To apply this research in a particular day, 50000 ton feed compared with grade 0.89±0.05 that this grade lies within the limitation of predicted grade of 0.93±0.06 and limitation of operation grade 0.89±0.05 (at 95% confidence limit). Finally suggested that in order to reduce the grade deviation and to optimize the recovery of  the concentrating plant of Sarcheshmeh copper ore, no sampling should be done from the concentrating plant feed but instead the operation grade of  mine should be counted for the concentrating metallurgical calculations, provided from the 100 continuous days, 95 grade cases of concentrating plant feed should lie in the operation grade of confidence limit of the mine.

Basic in this paper in order to rank the lead and zinc reservoirs of Yazd province from view point of exploitation, some abandoned mines and mineral resources of lead and zinc have been studied. For this purpose, general information such as distance from main road and roads quality, previous mining works have been done, grade and mineralogy of ore and reserve, have been collected from 21 mines. Then for ranking of these mines, ELECTRE III as a multi criteria decision making method has been used. The results of this investigation show that Tajkooh, Drrezanjir and Mehrjerd have highest ranks of investmentability respectively.