فصلنامه مهندسی معدن
پیاپی 17 (زمستان 1391)

In resent years, dDrilling and blasting is the most applicable methods of excavation of underground structures. In tunnel blasting, the pattern design and the selection of type of explosive used, play a crucial role in achieving the desired results. In Iran, the common explosive used in tunnel blasting is dynamite, which is very expensive compare to ANFO. In this research, an investigation was carried out to substitute dynamite as a relatively expensive explosive but with high specific energy with ANFO as a relatively cheap explosive with low specific energy. Tests were carried out in Abasaleh Almahdi tunnel, a road tunnel, connecting Eghlid city to Yasooj city, Iran. At the first stage of the research, the existing pattern was modified (two tests) to improve the results obtained. HCF (Half-Cast Factor), Over Break (OB), Advance Rate (AR) and Specific Cost Factor (SCF) were used to do the quantitative assessment. In the second stage of the research, based upon the modification carried out, substitution of dynamite with ANFO was studied by 10 designed blast tests designed and the best dynamite-ANFO substitution option was suggested. The results obtained showed that by substituting dynamite with ANFO, as well as an AR of 95%, an OB of less than 5%, a HCF of more than 20% and a reduction in explosive costs up to 32% can be achieved.

Analysis of ventilation networks is one of the most important steps in mine ventilation. Hardy Cross method is one of the oldest and the most common methods of ventilation network analysis. This method is an iterative solution procedure and the equations are repeated until the error becomes negligible. The convergence rate of this method in the first stage depends on the preliminary theoretical values ​​of the branch air quantities and the correct choice of meshes. In addition, there are other factors which may affect the convergence rate. This paper focuses on the investigation and proof of those factors. First, if the summation of the branch air quantity and its relevant mesh errors are negative, the current directory must not be changed. Secondly, mentioned branch air quantity is considered with its algebraic sign in the denominator of the Hardy Cross equation in the next iteration. Then a hypothetical network is analyzed and the Newton- Raphson method was used to validate the results. Results from proven approach are in accordance with Newton- Raphson method results.

In this study, modeling of probability diagram method was used to calculate the residual component of gravity data at southwest of Zagros, Iran. The regional and residual components were separated based on the data analysis and evaluation of the various trends modeled on probability diagram. The first, second and optimum approximation of residual components were achieved based on different threshold values resulted from the modeled probability diagram. The regional and residual effects of the first and second approximations were not completely separated from each other in some parts of the study area. The 3D view of residual anomaly map of third trend surface, geological map together with the field investigations show that the optimum approximation map could remove the regional effects due to the deep geological structures from bBouguer anomaly values. Although not considered by the conventional anomaly separation methods, the proposed method takes into consideration the variation of the interested variable in the data set.

The Sungun Porphyry Copper Deposit is located in East-Azerbaijan province, 75km northwest of Ahar city. Due to mining activities, streams of this region (Sungunchay, Pakhirchay, Ilginechay and Zarnekabchay) are exposed to heavy metals contamination such as Cu, Mo, Pb, Zn and Ni. In this relation, to determine contamination degree caused by toxic metals, 27 sediment samples were analyzed and it was found that concentration of Cu, Mo, Pb, Zn and Ni are above permissible limits (local background of these metals). Elements Correlation coefficient indicates that Cu, Mo and Ni are correlated to Fe, while Pb and Zn are correlated to Mn. In addition, results from Enrichment Factor, Geo-accumulation Index, Contamination Factor and Pollution Load Index for sediment samples indicate that potentially toxic metals contamination exists.

Control and online optimization of a process could only be performed if the dynamic model of the system is available. In the case of grinding circuits, dynamic simulation provides substantial information on complex and sometimes non-linear interactions between the components of the system. In this paper, dynamic model of ball mill and cyclone are incorporated in MATLAB/SIMULINK platform and then the system is simulated in open and closed circuits. Such simulation showed that the selected platform is suitable for investigation of responses of the system to the changes in input variables such as flowrate or mean residence time. It was also observed that the transient state between two steady states could be well investigated by the ease of this platform.

Nowadays, acoustic emission tests based on the Kaiser Effect are increasingly used for estimating in-situ stress in laboratories. The present article proposes an automatic method based on pattern recognition methods, which accurately determines Kaiser Effect by combining the results of different common methods. The proposed method uses the signals obtained from uniaxial pressure tests on samples of pre-loaded sandstone samples sandstone. In the proposed new method, previous maximum stress in samples can be determined directly without analysis of waveform signals. Our results show that pattern recognition methods can be used for determining the point of Kaiser Effect. The developed method has a desirable level of precision for determining the Kaiser Effect point.

Due to the presence of large civil projects in the Zagros region, the engineering parameters of Asemari formation rock mass have attracted wide attention. One of the characteristics of this formation is the existence of cavities which based on their that related to the shape and position which can reduce strength and deformation parameters of rock mass. In first part of this research, laboratory modeling is used for evaluation of macro porosity effect on deformation modulus and strength of rock. Porous samples were created by plaster and spherical polystyrene granules with have 4 and 6 mm diameter. The range of porosity investigated was approximately 0-45% for uniaxial stengthstrength and 0-30% for elastic modulus. According to the results, uniaxial compression strength and deformation modulus decrease exponentially and by increasing the size of pores from 4 mm to 6 mm. This, decrease ing in the amount of uniaxial strength and elastic modulus is lower less than 7 percent. In the second part, with regard to thatsince the porous material can be considered as a special case of composite materials, effect of the amount of spherical pores on the elastic modulus was studied by micromechanics method and different homogenizing models. By curve fitting in range of 0-30% porosity, reduction of elastic modulus can be determined by exponential relation. The experimental results match well with models which considered the shape. In porosity of less than 15%, with regard to small differences in Eshelby, Self consistent, Mori-Tanaka and Lielens models, experimental results have good accordance with them. With increased porosity, experimental results tend to Selfself consistent and Eshelby model.