Year:2006 | Volume:40 | Issue:1 (95)|Papers Count:11

In this method by using seismic attributes, petrochemical parameters are obtained along a seismic section. First of all seismic attributes are extracted from the trace passing the well bore and used as input of neural network; petrochemical parameters measured along the well bore are used as output of neural network. The network has been trained by mentioned input and output and seismic attributes has been extracted from each of the traces along the seismic section. By applying them to the network, respected petrochemical parameters has been estimated along the seismic line.

Estimating the future conditions is necessary for planning, and this is possible only with forecasting. Enterprises need to forecast the price of the products, for production planning, economic analyses of projects, study for new development investment, etc. In this paper the price of the copper is estimated from 1995 to 2004 using Moving Average (MA), eighted Moving Average (WMA), Exponential Smoothing (ES) and Justified Exponential Smoothing (JES) methods. The results are, then, compared with real prices, and validity of forecasts is evaluated using Mean Average Deviation (MAD) and Tracking Signal (TS) indicators. The result of study shows that forecasting by Justified Exponential Smoothing (JES) method, with parameters: α= 0.9 and β= -0.2 has the least deviation from real prices, and the expected price of the copper for 2005 is estimated 117.37 cent per pound.

Scope of this paper is the application of Krief’s method to petrochemical interpretation of an oil/gas reservoir in southwest of Iran. The base of this method is via shear and compress ional waves. Recent development in oil industry and full-waveform sonic tools have renewed interest in the interpretation of the velocities of compress ional and shear waves and their relationship to the litho logy and the petrochemical parameters of formation. As we know, original researches, such as the Wyllie and the Raymer equations, are currently used in a petrochemical interpretation of formations. But these equations deal only with the compress ional wave. In this paper the Krief’s method would be reviewed and applied to an oil/gas research in southwest of Iran. This method is based on a relationship between the squares of the velocities of the compress ional and shear waves and porosity of a formation, which is derived half theoretically and half empirically. A cross plot of the squares of the velocities of the compress ional and shear waves shows the quasi-linear relationship between the squares of the velocities.

Magnetite and hematite concentrates are produced in Chadormaloo mineral processing plant in three parallel lines. Apatite as gangue of iron ore is now removed by mechanical flotation method using sala cells. In order to reduce more apatite from hematite concentrate, the replacement of mechanical floatation with column floatation cell was investigated. For this purpose, a lab column cell was used with diameter and height of 74 and 1535 mm, respectively. In this research, for the optimization of type and dosage of reagents (depressant and collector-frother) in hematite  flotation at rougher stage, several reagents  were applied including Asame, Atrac 1580, Flo_G30, Asame+Atrac, as collector-frother and also sodium silicate, dextreen+starch, as depressant. Therefore, Asame+Atrac and sodium silicate were selected as suitable collector-frother and depressant, respectively. In the next stage, reagent dosage was also optimized as follows: Asame+Atrac: 150 g/t, ratio of Asame/Atrac: 70/30, sodium silicate: 800 g/t. Under these conditions, separation efficiency was obtained 56%.

In civil and mining, the design of some structures, such as pillars in mines and bridges, requires the knowledge of the effect of the relative size of dimensions (shape effect) on the strength of the structure. Therefore, to assess the effect of shape on the uni-axial strength of rocks, laboratory tests were conducted on samples of 3 different types of rocks (namely; Isfahan dolomite, Bookan limestone and Gadouk sandstone) with various sample relative dimensions. Analyzing the data of these tests resulted in an overall relationship as σc =k σc√ D/L where D, L and σC1  are the diameter, length and the uni-axial compressive strength of a sample with D/L=1 and K was obtained to be 1.14, 1.21 and 0.96 for the 3 rock types relatively. Also, as D/L and confining pressure affect uni-axial compressive strength and tri-axial compressive strength similarly, 3 axial tests, in various confining pressures, were conducted on the samples of the same rocks with D/L=0.5. Graphs of  σ -3σc and  σC - D/L were compared.  After omitting the term  σC from these formulas the overall relationship of ) σ3=A(D/L)-B was obtained. Finally, for the 3 type of rocks, a single formula as…σ3= 8.7515 D/L-6.3789 with coefficient of determination of 0.9534 was introduced. By applying the simulation proposed in this study, within the limit of the results, the costly time consuming tri-axial tests can be replaced with uni-axial ones.

Heap leaching structure is the primary unit of the hydrometallurgy process in heap leaching method. In this method, copper oxide soil with a stepped height ranging from 5 m to15 m with a total height of 80 m to 100 m are placed on the sloped gravelly drainage layer. Potential instability of these structures may induce heavy economical and environmental damage. Thus, in order to prevent heap instability, steeply sloping sections are leveled out prior to placing the permeable layer of sand, compacted cushion and geo-membrane along the base of the structure. Given that the overall area of the structure is around 1 km2, an attempt at reducing the overall slope will prove to be a costly procedure. Therefore it is of great importance to carefully study the area to be leached and determine exactly which blocks in the structure require slope reduction as well as the amount of slope reduction necessary. The methods used to date for slope stability analysis in soil only provide that mass stability safety factor. However, the data neither allows the determination of the amount of slope to be reduced in each block of the structure nor potential failure location can be detected. In this paper, a new approach entitled: “Blockto- Block Stability Analysis” is presented. The method is based on a combined effect of passive, active and inert processes. In this method it is assumed that there is an upward force which acts between sliding block masses. The relations obtained and used were derived from the heap leaching structure, and the results obtained were studied. Using these results in practical scenarios it is possible to determine exactly which block in the structure requires slope reduction as well as the amount  of slope reduction necessary, easily and efficiently. The second advantage to this approach in comparison to already existing methods is that one can determine the admissible acid levels for each block in the structure as well as regions of heap leaching tension cracks within the leaching structure.

The concept of subsidence in mining is defined as the occurrence of differential ground surface elevation due to mining processes. Long wall mining is one of the commonly used methods in underground mining. In this paper, using mathematical modeling, two methods for subsidence prediction occurring due to coal mining are presented. Effects of parameters such as length of long wall, angle of influence and internal friction angle of roof strata have been evaluated. The results indicate that the amount of subsidence increases due to a decrease in the angle of influence and also due to an increase of parameters such as long wall length, thickness of extracting coal seams and internal friction angle. However, this increase is linearly proportional to the thickness of extracting coal seams while maintaining a nonlinear relationship with the latter parameters. The increase of subsidence with respect to increasing length of long wall has a limit, beyond which the amount of settlement remains unchanged even though the length of long wall is increased.

Problems associated with conventional pillar design methods has led to the extensive use of numerical methods in pillar design. In this research work, the FLAC-2D code was employed to evaluate the rock pillar strength as a function of applied loads. The commonly used elasto-plastic Mohr-Coloumb model is not suitable for expressing pillar behavior, and thus, more advanced material models such as various strain-softening models should be used. In this study, in order to assess the pillar strength the modified Hoek-Brown parameters were used to determine the softening parameters of pillars of varying geometries. Comparing the obtained results with published field data, the analysis results show that the use of modified Hoek-Brown parameters enables a realistic evaluation of pillar strength.

The introduction of mechanized tunneling with full face boring machines necessitates a better understanding of mechanical and petrography characteristics of rocks. Evaluating the abrasiveness and drill ability of rock, are prerequisites for choosing suitable boring instruments and machines. Compressive strength, hardness and abrasiveness are among parameters currently tested in this respect. Unfortunately the petrography characteristics of rock, such as texture, are rarely considered. In this paper, the relation between the cerchar abrasiveness Index (CAI) and texture coefficient of rock is studied. The results of tests on samples of five groups of building stones of Iran show a weak correlation between CAI and texture coefficient, whereas a good correlation exists between the average of CAI and the average of texture coefficient of different rock groups.

Theoretically, increase of steepness in natural or artificial slopes; raise the potential of instability. Zonation mapping, based on the statistical analysis of different slope classes, in northwest Iran (Khalkhal-Koloor region), showed that the percentage of unstable areas in the steepest slopes are less than slopes of medium or low steepness. This phenomena, causes a systematic error in the results of zonation mapping, which is normally based on the percentage of unstable areas in different classes of data layers. Following a slope rupture, the average gradient of slope decreases and slipped materials move to a flatter area compared to the initial slope. This final gradient is usually used to rank the slope parameter. On the other hand the map area of working units is less than their actual area, especially in steeper slopes. This also causes systematic error in ranking slope gradient and other parameters. Assessment of slope instability concentrations in eight directions in studied area, shows that landslides facing north and north-east are more frequent and those facing west and southwest are less frequent than the average slope instability concentration in the entire region. Present paper discusses some methods to overcome the mentioned pitfalls.

In this article at first some models of penetration rate prediction were reviewed then a Neuro Network was created for prediction of penetration rate. The Neuro Network inputs are UCS, RQD, normal force on disc cutter, diameter of disc cutter and quartz content. With elimination of quartz content and RQD from input parameters, the response of Neuro Network was investigated. Neuro Network response Compared with Garaham Model, and ability of Neuro Network in penetration rate prediction and prediction penetration rate of Gavoshan Tunnel's TBM were discussed in the latest part of article.