فصلنامه مهندسی معدن
پیاپی 22 (بهار 1393)

From economical point of view، identification and quantification of grade uncertainty have a great importance. For uncertainty quantification، conditional simulation techniques، appropriate to uncertainty quantification can be applied. These techniques are effectively implemented for single element deposits; but in the multi elements deposits in which spatial correlation is of great importance، can rarely be employed. For this purpose، other techniques such as conditional co-simulation (CCS)، stepwise conditional simulation (SCT)، principal component analysis (PCA(and min/max autocorrelation factors (MAF) can be utilized. In the recent years، MAF technique considering various merits to the aforesaid approaches has successfully been applied for simulating multi elements deposits. MAF can effectively be used in such deposits with more than one spatial structure. Also، using this technique، de-correlation can be done for all lag distances and accordingly can well reproduce the correlations. In this research، MAF was applied for simulation of a multi-element porphyry Copper deposit. On basis of the obtained results، it was considered that MAF can effectively be utilized for reproducing the correlations.

Performance of a column flotation cell depends on the hydrodynamic conditions (gas holdup، density of the collection zone and density of the froth zone) of the process. Present work has been carried out to observe the effect of column operating variables (gas flow rate (0. 78-1. 3 cm/s)، wash water rate (0. 1-0. 2 cm/s)، feed flow rate (0. 39-0. 91 cm/s) and froth height (45-65cm)) on hydrodynamic conditions in a batch flotation column (400cm height & 10cm diameter) using the zinc rougher concentrate of Irankooh plant. Response Surface Methodology (RSM) was used to design and analysis of experiments as well as process modeling. Results showed that Gas holdup increased and density of collection zone decreased with increasing feed flow rate، gas flow rate، wash water rate and froth height. Also، with increasing wash water rate and gas flow rate، density of froth zone increased and it decreased with increasing feed flow rate and froth height. Froth height and wash water rate were the most significant factors affecting gas holdup and density of collection zone responses. Feed rate and wash water rate were the most significant factors affecting froth zone density. When wash water rate increased from 0. 1-0. 2 cm/s، gas holdup changed from 15. 01-19. 97% and density of collection zone changed from 0. 88- 0. 79 g/cm3. Also gas holdup increased from 15. 85-19. 13 and density of collection zone changed from 0. 86- 0. 81 g/cm3 when hieght froth increased from 45-65 cm. Froth zone density decreased from 0. 47- 0. 3 g/cm3 with increasing in gas rate from 0. 39-0. 91 cm/s. When wash water rate increased from 0. 1-0. 2 cm/s، froth zone density increased from 0. 34 to 0. 44 g/cm3. Two linear and a quadratic models were derived for prediction of gas holdup، density of collection zone and froth zone density.

In this research، effects of the presence and variations of dam lakes water level on block toppling failure of rock slopes facing the lakes have been investigated. First، a brief history of the researches carried out on toppling failures is presented. Then، a theoretical model is proposed، for different impounding states، for rock slopes facing dam lakes and having a potential of block toppling failure. Next، on the basis of the proposed model، a new approach is presented for the stability analysis of such rock slopes. Since this analysis is very time consuming we first، using the proposed relationships، prepared a special computer code (in MATLAB environment) that receives، from the user، the data of the slope and predicts its stability against block toppling failure for different impounding states of the dam lake. Finally، as a case study، the slope facing the headrace tunnels of Moshampa dam، in Zanjan province، Iran، was analyzed and assessed using the model and code proposed in this paper.

One ofthe most fundamentalgoalsin the interpretation of geomagnetic dataisestimatingthe depth of magneticanomaly. The Eulermethodis a procedurethatis usedto estimate thedepth، but level ofconfidenceinthis method، depends on the right choice of thestructuralindex. Sourceparameter imaging method (SPI) isanother procedure to calculate thedepth which does notdepend on the magnetic properties. These two methods were applied on artificial data and excellent results were obtained from the SPI method. The results from the Euler method for the index 0. 5 were excellent too. In this paper، the data taken from the Gol-e- Gohar area was interpreted. The return to pole، upward continuation and analytic signal filters were applied to magnetic anomaly and then the anomaly depth was estimated about 30 to 40 meters by using SPI method. This estimation was verified by drilling results.

Addition of flocculants to a dilute stable suspension creates bridges between particles، which then results in formation of flocs. Estimation of flocs size is of prime importance in solid-liquid separation studies but this task is challenging because flocs have complex and irregular shapes. Feret''s diameter، minimum Feret''s diameter، mean Feret''s diameter، equivalent area diameter، and equivalent perimeter diameter are commonly used to describe flocs sizes. The flocs sizes formed in the tailings of the Gol-E-Gohar magnetite processing plant were estimated. The accuracy of aforementioned parameters were evaluated by determining the calculated settling velocities and comparing with the settling velocities of particles obtained in the batch settling tests. Image processing methods were used to measure flocs sizes and densities which were needed to calculate the settling velocities. The mean Feret''s diameter and equivalent area diameter were found to be the appropriate parameters with the relative errors of 16 and 17%، respectively. Mean Feret diameter and settling velocity of flocs formed in a pulp containg 5% solids with 10 g/t flocculant were estimated to be 338 µm and 67 cm/min، respectively. In this condition، the experimental settling velocity obtained was 57 cm/min. Whereas the floc size and settling velocity were estimated to be 304 µm and 54. 5 cm/min when the average of mean Feret’s diameter and equivalent area used as the floc size. When the average of mean Feret’s diameter and equivalent area used as the size to calculate the settling velocities the relative error reduced to 4. 3%.