AMIRKABIR
Year:2007 | Volume:17 | Issue:65-C|Papers Count:12

Siahu, Sarchahan and Faraghun formations in Fars and Bandar-Abbas regions have been studied with different geochemical methods for evaluated their role in gas generation in the study area. On the basis of Rock-Eval result, Siahu formation in Kuh-e Faraghun cannot be as a suitable source rock because of its low percent of organic matter and high maturation. This formation with shaly lithology has mixed of terrestrial and marine organic matter and deposited in anoxic to oxic conditions. Sarchahan formation only in Kuh-e Faraghun area has a good quality and relatively suitable organic matter. The Study of different parameters of biomarker also shows that Sarchahan formation has deposited in suboxic to oxic condition in marine environment and has shaly-carbonate lithology. Rock-Eval result in well samples indicates that Sarchahan formation only in Kuh-e Siah well has enough qualities and quantities in order to generate hydrocarbon. Rock-Eval and vitrenite reflectance of Faraghun formation also show that this formation in well Kuh-e Siah- 1 is able produce hydrocarbon and can be introduced as the probable source rock of hydrocarbon in this area.

Asynchronous excitation of supports is important in large structures such as dams, suspension bridges and cable-stayed bridges and lifelines. The effects of soil shear velocity and length of main span on structural response of suspension bridges are discussed in this study. Four bridges with different main span length are designed based on AASHTO-89 code. The designed bridges are subjected to ground motion records, which are chosen based on different shear velocities. Four shear velocities are used in this study and for each of them three records are considered. The response of the structure due to each group of records is the maximum response of these three records. ANSYS software Ver.7.0 is used for time history analysis of models and the total runs are 96. After applying the records to the models in main directions and performing time history analysis by taking into consideration large deflection, the response of structures is compared to each other for the cases of asynchronous and synchronous excitation. The results show that the effect of asybchronous excitation of supports is decreased with increasing the length of main span and soil shear wave velocity.

Cyclic Loading produced by earthquake can induce liquefaction in saturated loose sands containing fines. In this investigation, the effect of plastic fines on the liquefaction strength was studied by considering both sand and fines. The tests were performed by implementing a cyclic triaxial apparatus.Tests results reveal that increasing the fines content to 20 percent (PI=4) decreases the liquefaction strength. By increasing the fines content to more than 20 percent the liquefaction strength increases so that for the specimens containing 40 percent (PI=7), the liquefaction strength is about the value clean sand. The results indicate that the presence of fines content does not increase the liquefaction strength and conversely decreases it significantly. Thus, using conventional methods of evaluating liquefaction potential such as SPT are not conservative if sand contains plastic fines.

Underground voids can be created by different reasons such as tunneling, mining, water and gas networks and old conduits. The existence of above factors can affect the bearing capacity of shallow foundations. To study the behavior of strip foundation located above a continuous void in sand, a new physical model was developed in K.N.Toosi University of Technology. The experiments were performed in a test tank, which accommodates the soil with desired density, model void and footing. A series of different tests were carried out to study the effect of relative density of soil, embedded depth of void and eccentricity of footing against the void. The results of the tests indicate that, there is a critical region under the footing. Only when the void is located within this region, the stability and bearing capacity of  the footing will be significantly affect by presence of the void and the magnitude of this effect must be consider.

In this paper, three-dimensional scattering of plane harmonic SH, SV and P waves by alluvial valleys is investigated by using a boundary element method in frequency domain. It is shown that in order to achieve real responses, problem must be analyzed and modeled three-dimensionally. Also, for exact evaluation of surface ground motions in alluvial valleys all key parameters such as layering shape, material and geometrical characteristics, wave type, angle and azimuth of incidence, reflection and refraction effects must be taken in to account altogether.The accuracy and efficiency of the proposed formulations for the computation of surface displacement field amplification are demonstrated by solving a number of problems.

Dynamic Relaxation is an iterative technique, which is used as an equation solver. In this paper, a new time step will be formulated for Dynamic Relaxation method. The suggested technique is based on the minimization of residual force in each iteration. Mathematical theories and numerical examples are used to verify efficiency of the formulation. By using optimum time step, mathematical convergence rank of DR algorithm will be infinite and two in linear and nonlinear analyses, respectively. To investigate the capability of the proposed formulation, isotropic plates and frame structure by linear and geometrical nonlinear behaviors are analyzed. This study shows that optimum time step reduces number of convergence iterations.Therefore, the cost and the computational time will be reduced. As a result, the suggested formulation for optimum time step has higher mathematical and numerical efficiency than other common methods, such as constant time step. Therefore, the convergence rate of DR iterations will considerably improve.

Active screen plasma nitriding (ASPN) is a promising surface modification technique that has many advantages over the conventional DC plasma nitriding (CPN). Behavior of 30CrNiMo8 Low-alloy steel has been compared under varying conditions of ASPN and CPN processes. The process variables included active screen setup parameters (top lid and screen hole size), treatment temperature (550 and 580°C), gas mixture (fixed for 75/25 of N2/H2) and treatment time (5h) in 500 Pa pressure for 5h. The structure and phases composition of the compound layer was studied by X-ray diffraction (XRD), microhardness tests, light optical microscopy and scanning electron microscopy (SEM). It was observed that ASPN treated sample surfaces for both screen and iron plate top lid consist of g¢ and e phases and while the temperature and/or hole size of screen setup increased, the intensity of e phase in the compound layer increased. The results show that ion transition via sputtering and recondensation mechanism of screen top lid on the sample surface can be affected on the hardness and layer thickness. It appears that the AS plasma nitriding process facilitated the formation of e phase in this test.

Research indicates that various hydrological parameters affect the transport of cyanide from tailing dam to groundwater including porosity of the soil, type of the soil, aquifer characteristics and effective velocity of groundwater. Cyanide is often used by chemical and mineral industries especially in gold, lead and zinc processing. The transport of cyanide to water recourses is one of the most important environmental issues due to the acutely toxic properties of many cyanide compounds to humans and acute life. The investigation of cyanide fate into the soil can help to predict the adsorption and transport of cyanide into groundwater. Tailing wastewater which contains about 250 mg/lit cyanide was obtained from Muteh gold mine factory. Three types of clays soils including a soil from around tailing dam, natural clay samples from Tehran and bentonite clay were used for the coefficient of permeability tests. The volumes of effluents, coefficient of permeability' and concentration of cyanide were measures at specific times. Cyanide concentration in effluents was determined by Rhodanine indicator solution regarding the standard titration method. The results indicate that very little of cyanide was absorbed along the column regardless the type of the clays soil which was employed in this research.

In this paper the effects of experimental parameters on cyanide degradation in wastewater of heat treatment units has been investigated. In this process, hydrogen peroxide and CU2+ are used as oxidizing agent and catalyst, respectively. In the First steep on the desired concentration of 100mg/l cyanide solution in alkaline condition at 25°c, the molarity of hydrogen peroxide and catalyst concentration were optimized. Experimental results show that in molar ratio of (H2O2 :CN-)9: 1 and CU2+concentration equal to 20mg/l, cyanide content decreases to less than 5mg/l in 30 minutes. The practical relevance of the laboratory degradation method is demonstrated for actual wastewater with 540 mg/l cyanide. In 100 minutes, the cyanide content of the wastewater was decreased to less than 5mg/l.

Deepening of Chadormalu Iron Mine pit is important from the planning point of view. This paper aims to re-evaluate the pre-designed slope angles of Chadormalu Open pit. In order to update the geological model of open pit and for determination of geological and mechanical properties of rock mass, geotechnical mapping was performed. After obtaining the updated vertical and horizontal planes of open pit, the stability of slopes was investigated using experimental, analytical and numerical methods. MRMR classification was first used for estimation of primary slope angles. Then, the resultant sections were analyzed using analytical methods. Finally, the stability of the slopes obtained from analytical method was re-evaluated by using a Finite Element Code. Results showed that the inter-ramp slope angle of 55 degrees is not stable in some parts of the pit. Depending on the rock type, the safe slope angles in Chadormalu pit are suggested between 30 to 55 degrees.

There are many chromite pods in the Sabzevar ophiolite but the high topography and mountainous condition and inability to trace the hidden lenses, many of them are not explored yet. A mathematical genetic model could be helpful to overcome the problem. So a very detailed investigation about the geology, mineralogy and petrology of the studied area has been done. The parameters that we need in the model are critical genetic factor (CGF) and critical reconnaissance criteria (CRC). Then with a linear combination of the factors, we have a function called intrinsic geological unit (IGU). By using characteristic analysis, the priority of each parameter would be defined. By running the model for Sabzevar area, a 3D space of lithological units would be highlighted which is called IGU. After running the program model, an area with a high precision of mineralization has been defined.