فصلنامه مهندسی معدن
پیاپی 16 (پاییز 1391)

Pseudo geological map is one of the main products of airborne geophysical data. In such maps، lithology boundaries and structural properties like lineaments features could be identified using integration of airborne geophysical data، while rock type will not be identified. However، it would be possible to label the maps with the field studies. In this paper، pseudo geological map of some areas of 1:100،000 Alut geological sheet is drawn using clustering of Helicopter-Borne DIGHEM data by K_Means and Fuzzy K_Means methods. Comparison between the drawn map and Alut''s 1:100،000 geological map confirms the validation of prepared pseudo map. Meanwhile various sets of Helicopter-Borne data were used as clustering input data in order to find the best set for clustering. The results showed that among different data sets، combination of {radio elements with their ratios} and {resistivity for different frequencies with analytical signal of total magnetic} results generated more reliable pseudo geology maps.

This work deals with the geostatistical simulation of mineral grades whose distribution exhibits spatial trends within the ore deposit. Such trends can be reproduced via the definition of conditioning data. These conditioning data can be available from hard data or some soft data، which are produced from the result of cokriging. The conditioning process forces its realizations to conform these data and therefore، their local properties، in particular the local mean (trend)، could be reproduced. In fact، soft data can compensate the lack of hard data in sampled areas with insufficient data and force the realizations to reproduce the trend in the study area. The proposed method was applied on obtained data، located at 1850 m، from exploration boreholes of Sungun mine. The study area was divided into two rock type domains: Sungun Porphyry (SP) and Dyke (DK) and it was shown that the incorporation of soft and hard conditioning data improves the modeling of the uncertainty in the actual copper grades and decreases the conditional variance of simulation significantly.

In order to achieve maximum information hidden in raw geophysical data and to enableing accurate interpretation consistent with geological data، geophysical inverse modeling has been devised and routinely employed by explorationists. However in some cases due to both complex nature of most earththe earth systems and influence of some parameters unrelated to the sought mineralization، this methodology has resulted in unsatisfactory results. A crucial case is encountered in the joint interpretation of Resistivity and Induced Polarization (RS/IP) datasets. Usually combined RS/IP method plays important role in most porphyry copper exploration programs. However drillings has revealed that high IPs corresponds to high pyritic zones with low copper content therefore misleading the exploration program. In the present study RS/IP data are were integrated with the corresponding lithology، alteration and assay data from drilling dataand followed by applying discriminant function analysis was applied to separate high from low grade copper zones at Chahfirouzeh porphyry copper deposit، Iran. Through employing lithological and alteration data، the performance of discriminant function analysis has been improved considerably compared to the case where only IP and RS data were used. The final model has yielded a linear statistical model by which high copper grade zone can be discriminated from zones with high IP and low Cu contents. Validation through the drillings has confirmed that 90% and 87% correct classification is achieved for discriminating high and low grade ore zones respectively.

Grate and its specification can significantly affect the performance of ball mills، semi-autogenous grinding (SAG) and fully autogenous grinding (FAG) mills equipped with this type of discharge mechanism. The grate design، open area and grate aperture size affect grinding throughput. In SAG and FAG mills، the inadequate design of discharge grate can lead to inefficiency of comminution device and creation of a slurry pool which practically stops particles'' breakage. In optimization projects، investigation on discharge grate and its effect on grinding process is critical due to particle size classification at mill exit، which necessitate the effect of grate to be considered in process modeling and simulation. In this project، discharge grates of Esfordi and Gol-e-Gohar plant ball mills and their effect on mill performance were investigated in details to make sure that the modeling and simulation and subsequent optimization studies are accurate as much as possible. To study and determine the effect of the discharge grate، samples were collected from mill feed and discharge streams when the circuits were under steady-state operation. After mass balancing، the discharge streams were simulated by BMCS®. Then the observed and simulated PSD of output were compared. The obtained results showed that the grate inside Esfordi ball mill does not affect the particle size distribution of mil output. In Gol-e-Gohar pilot plant ball mill the grate behaves like a fine screen which should be considered in mill mathematical modeling and simulation.

In a copper heap leaching process in a heap، copper oxide soils are leached by sulfuric acid. The acid dissolves the copper and drains off the bottom of the heap through a drainage system consisting of slotted polyethylene pipes and some granular soil layers. Permeability coefficient of a granular soil affects the performance of the drainage system significantly. This coefficient، based on which the thickness of the draining layer is designed، is usually measured in the laboratory according to ASTM-2423 using water. But، in heap leaching structures، the fluid is a pregnant leach solution (PLS) of different the density and viscosity of which are different from those of water. In this study، three granular soil samples and one sample of a PLS were taken to the laboratory from heap leaching structure No. 2 of Sarcheshmeh copper project، Kerman. The density، PH pH and viscosity of the acid and water، and the soil samples’ particle size distribution were determined at a temperature of c before starting the permeability tests. The samples were then poured into three separate cells and their permeability coefficients were measured against water and PLS at the same temperature. (a comparison of the Rresults showeds that the coefficients are were not the same for the three soil samples). Next، the permeability coefficients of the samples were determined theoretically and the outcomes were compared with those of the experiments. It is، therefore، recommended that، when designing the drainage system of a heap leaching structure، the permeability coefficient of the soil be measured using the PLS. On the basis of this research، the drainage system of a real case (Sarcheshmeh heap leaching structure No. 4) has been designed and presented in this paper.

In this research the application of external potential to reduce the amount consumption of depressant in a copper- molybdenite flotation circuit was studied. Control of the pulp in electrochemical flotation can be carried out by changing the electrochemical parameters like Eh، pH and oxidation and reduction reactions. One of the electrochemical flotation methods is application of external potential in which the flotability of minerals is considered. In this paper the feasibility of chalcopyrite removal from a copper-molybdenite concentrate is presentedinvestigated. The rResults showed that usage ofing external potential can be consideredbe considered as an alternative method for reducing the other depressants usageconsumption.

Many models have been proposed to predict the mechanical behavior of rock joints، but precise evaluation of effective roughness coefficient has been the most important limitation of these models. Geometry of asperities greatly influences the joint mechanical behavior، and these effects must be estimated by reliable and applicable methods. This paper deals with a method، which characterizes the rock joint surface in terms of roughness based on multi-scale decomposition using wavelet theory. Wavelet decomposition allows for distinguishing the small-scale and large-scale components of a wave. Here، joint geometryies is considered as a wave، and its roughness and undulation are regarded attributed to as the small-scale and large-scale components، respectively. Different scales of upper and lower joint surface roughness have been combined to produce the composite surface having asperities characteristics of both joint surface. Thus، the contribution of two surface components of the joint was considered separately in the shear strength criterion. It was found that peak shear strength is mainly influenced by both roughness and undulation، but the residual shear strength and dilation are mainly influenced by the undulation. The proposed shear model is capable ofhas capability to quantifying tative consideration of the roughness and undulation and helps to well understanding and modeling of the shear mechanism. The experimental test results verified the shear model predictions. results are well verified by comparison with experimental test results.

The deformation modulus of a rock mass is an important input parameter in any analysis of rock mass behavior for geotechnical projects such as dams. The determination of this parameter by in situ tests are time consuming and expensive. Therefore، different researchers have proposed empirical relationships for estimating the value of rock mass deformation modulus. This work has been done by using rock mass classification systems and data collections from in situ tests in different places. Based on data collected from a large number of dilatometery tests conducted in seven dam sites located at southwest Iran، a new nonlinear multi-variable empirical equation (logistic function) was developed using the GSI index and the rock elasticity modulus (Ei) to estimate the rock mass modulus of deformation (Ed).

Since، in geomechanical evaluation of rock masses، many parameters affect the rock mass behavior simultaneously، rock engineering classifications are suitable approaches for studying and prediction of rock mass behaviors. Classic classifications in rock engineering have suffer from some practical limitations، particularly. These limitations are more obvious in when classification is made near the boundaries. y conditions. In this study in order to increase the abilities and expending the applications of rock mass drillability index (RDi)، fuzzy theory has been used. For this purpose، six parameters of the rock mass which are used in RDi classification، including uniaxial compressive strength (UCS)، joints dipping، Mohs hardness، joints aperture، joints spacing and grain size have been used. Then، some fuzzy functions have been defined on these parameters and finally the class of each rock mass has been identified. In order to compare the results of classic classification with results of fuzzy classification، a case study was done on rock masses of limestone mine of Shahrood cement factory. The results show that the fuzzy logic based classification produces clearer better results than classic system especially in rock masses with boundary condition. During this research، a software was prepared for doing theto calculate the RDi scoresions and classifying the rock mass. Theis program has been written by coded in Visual C++ and has a contains a graphical main window thatinterface with all input parameters which are related (rock mass characteristics) and also the out output parameters of the program (which are RDi score and class of rock mass). are illustrated in it.

Uncertainties are an inherent part of any exploration and resource development activities. Mining projects، due to their variable nature، are always faced with many kinds of uncertainties. Substantial amount of investment and complexity in design and execution in mining industry، cause the mining projects being categorized as activities with high level of risk. Feasibility studies facilitate a better identification of uncertainties sources and present more efficient risk management in these projects. These uncertainties will also affect the time scheduling and resource allocation in the feasibility studies procedures. In this research، the effects of time and cost uncertainties on the process of feasibility studies are assessed. In order to illustrate the role of these uncertainties، their effects on scheduling and costing is depicted by using Monte Carlo simulation method. Also the associated risks of these uncertainties are evaluated in a probabilistic approach. The result confirms the significant impacts of these uncertainties on the project implementation، while it shows that considering the uncertainties lead to more reliable results. The outcomes of this research help a better and more realistic understanding of the effects of time and cost uncertainties on the design and implementation of feasibility studies. Besides it proposes more efficient plans for managing these uncertainties and the related risks.