Search for: liquefaction
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    Design and Optimization of Helium Extraction and Liquefaction Cycle from Natural Gas by Direct Method

    , Ph.D. Dissertation Sharif University of Technology Ardeshir Larijani, Morteza (Author) ; Afshin, Hossein (Supervisor)
    Helium is known as a strategic material due to its unique properties and applications in the development of advanced industries. Currently, natural gas is the only source from which helium can be produced economically. The United States, Qatar, Algeria, and Russia have the largest share of helium production, respectively. In this research, the process of helium extraction from natural gas and its liquefaction, independent of LNG production based on helium in South Pars gas of Iran, which is the largest helium reservoir in the world, were designed and simulated.In the helium liquefaction section, the speed and accuracy of the process simulation were improved by developing a home code based on... 

    A Numerical Model Development for Cryogenic Spiral Wound Heat Exchanger Design Considering Temperature dependent thermo-physical properties, Heat Leakage, and Longitudinal Heat Conduction

    , M.Sc. Thesis Sharif University of Technology Beheshtikhoo, Amir (Author) ; Afshin, Hossein (Supervisor)
    Cryogenic temperature is below than 123 Kelvin and any physical study that occurs below this temperature is Cryogenic science. Cryogenic has varaiety of application in medical, industry, food, oil and gas etc. Based on this paper and its relavant source spiral wound HE is one of the most optimum HE for cryogenic application specially for helium liquification cycle. In order to liquefy helium in helium cycle efficiency of spiral wound HE shall be over than 85 percent. For this reason and special fluid behavour in low temperature considering property variation, heat in leak and axial conduction is vital for calculating efficiency in cryogenic temperature of helium liquification cycle. In this... 

    Effects of Lateral Spreading on Two 2×2 Pile Groups (with and Without Lumped Mass) Using Shaking Table and Laminar Shear Box

    , M.Sc. Thesis Sharif University of Technology Zangeneh, Milad (Author) ; Haeri, Mohsen (Supervisor)
    Lateral spreading is the downstream movement of mild slopes or free fronts occurring due to soil liquefaction during a dynamic loading such as an earthquake. The magnitude of this movement can be from a few centimeters to tens of meters depending on parameters such as slope length, soil type, cyclic loading intensity, etc. Large displacements caused by this phenomenon can cause severe damage to some structures and infrastructures located in the direction of their movement. Numerous articles and reports of damage caused by the lateral spreading of soil have been presented during several earthquakes. Understanding this phenomenon and observing and testing its effective parameters can help... 

    Investigation of Effects of Successive Liquefaction Occurrence on Piles Located in Level Ground With an Inclined Base Layer with Using Stone Cloumns – a Physical 1g Shake Table and Laminar Shear Box Model

    , M.Sc. Thesis Sharif University of Technology Dehghanpour Farashah, Ali (Author) ; Haeri, Mohsen (Supervisor)
    Lateral spreading is defined as finite lateral displacement of mildly sloping grounds or those ending in free faces induced by liquefaction. The phenomenon of lateral spreading caused by liquefaction in coastal areas and mildly sloping grounds has caused significant damage to deep foundations of engineering structures such as bridge and buildings in severe earthquakes. Since earthquake is unavoidable, therefore, it is necessary to provide appropriate solution to reduce the effects of liquefaction induced lateral spreading. Despite conducting various laboratory and field studies by previous researchers, there is still no comprehensive approach to evaluate the effects of lateral spreading on... 

    Swirl intensity as a control mechanism for methane purification in supersonic gas separators

    , Article Journal of Natural Gas Science and Engineering ; Volume 83 , 2020 Ghorbanian, K ; Amini Magham, M ; Sharif University of Technology
    Elsevier B.V  2020
    Supersonic gas separator is proposed for methane purification. One-dimensional analysis is performed to examine the design aspects associated with the converging-diverging nozzle and the liquid separation chamber. The results indicate that at low swirl intensities, the separation chamber length is about 100 times of the nozzle throat. Increasing the swirl intensity would lower this length sharply and it will be less than 10 for swirl intensity of unity which is equivalent to a swirl angle of 45°. In addition, a sensitivity analysis of the separator performance to the inlet conditions like the temperature, pressure, and composition of the mixture is carried out. It is observed that increasing... 

    Numerical investigation of the effects of soil densification on the reduction of liquefaction-induced settlement of shallow foundations

    , Article Scientia Iranica ; Volume 16, Issue 4 A , 2009 , Pages 331-339 ; 10263098 (ISSN) Shahir, H ; Pak, A ; Sharif University of Technology
    The liquefaction phenomenon is usually accompanied by a large amount of settlement. Based on the observations made in past earthquakes, ground improvement by densification is one of the most useful approaches to reduce the liquefaction-induced settlement. Currently, there is no analytical solution for evaluation of the amount of settlement and tilting of footings that are constructed on densified ground surrounded by liquefiable soil. A number of factors, such as underlying soil properties, dimensions of the footing and earthquake loading characteristics, cause the problem to become complicated. In this paper, the dynamic response of shallow foundations on both liquefiable and... 

    Dynamic behavior of pile foundations under cyclic loading in liquefiable soils

    , Article Computers and Geotechnics ; Volume 40 , 2012 , Pages 114-126 ; 0266352X (ISSN) Rahmani, A ; Pak, A ; Sharif University of Technology
    In this paper, a fully coupled three-dimensional dynamic analysis is carried out to investigate the dynamic behavior of pile foundations in liquefied ground. A critical state bounding surface plasticity model is used to model soil skeleton, while a fully coupled (u- P) formulation is employed to analyze soil displacements and pore water pressures. Furthermore, in this study, variation of permeability coefficient during liquefaction is taken into account; the permeability coefficient is related to excess pore water pressure ratio. Results of a centrifuge test on pile foundations are used to demonstrate the capability of the model for reliable analysis of piles under dynamic loading. Then, the... 

    Effects of membrane compliance on pore water pressure generation in gravelly sands under cyclic loading

    , Article Geotechnical Testing Journal ; Volume 33, Issue 5 , 2010 ; 01496115 (ISSN) Haeri, S. M ; Shakeri, M. R ; Sharif University of Technology
    The paper deals with an experimental study of the undrained cyclic behavior of a natural coarse sand and gravel deposit located in Tehran, a megacity situated on the continental side of the Alborz Mountain in Iran. Membrane compliance that plays a significant role in inhibiting redistribution of pore pressure and liquefaction in undrained cyclic triaxial tests performed on coarse granular soils is studied in this paper. Currently there is no or little satisfactory method for accounting for this phenomenon for gravelly soils, and thus the non-compliant cyclic loading resistanceof granular soils and the evaluation of the behavior of such material in natural and in situ state are not easily... 

    An Investigation on the Effects of Liquefaction-Induced Lateral Spreading on Deep Foundations Using Finite Difference Method

    , M.Sc. Thesis Sharif University of Technology Afzal Soltani, Sina (Author) ; Haeri, Mohsen (Supervisor)
    Liquefaction is an important phenomenon in geotechnical engineering which can cause severe damages to structures. Liquefaction-induced lateral spreading is defined as the lateral displacement in mild slopes or level grounds ending in free faces (such as quay walls) triggered by liquefaction in subsurface soil layers. During recent years, extensive studies have been conducted around the world documenting liquefaction induced lateral spreading and its effects on deep foundations. In the present study, a series of shaking table experiments which were previously conducted at Sharif University of Technology are numerically simulated using the three dimensional finite difference based program,... 

    Assessing Liquefaction Potential Based on Cone Penetration Test Results

    , M.Sc. Thesis Sharif University of Technology Pezeshki Najafabadi, Ali (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    This study aimed to model the cone penetration test using FLAC 2D software in order to investigate the silty soils that can be found in tailing dams. Additionally, the model of the direct simple shear test was built in the software to estimate the variation of liquefaction potential in these soils with in-situ conditions. It should be noted that the constitutive law used in this study was the NORSAND model which meets the requirements of modeling in both tests. After validating the models, several important parameters are considered as variables to examine their effects on the results of both experiments. Regarding the validation of the models, the constructed numerical models of the cone... 

    Effect of Initial Static Shear Stress on Liquefaction Resistance of Gravelly Soils Using Medium-Size Cyclic Triaxial and Simple Shear Tests

    , Ph.D. Dissertation Sharif University of Technology Nikoonejad, Khashayar (Author) ; Haeri, Mohsen (Supervisor)
    There are several case history records of liquefaction in gravelly layers with more broadly-graded particles than uniform sands which have been typically examined. Liquified deposits, in many cases, were subjected to initial static shear stress associated with the sloping ground condition or the adjacent shallow foundations prior to liquefaction. There are several graphs and recommendations for practitioners to consider the effects of the initial static shear stress on liquefaction resistance in design processes, developed based on the results of experiments on uniform clean sands. However, data for the effect of the initial static shear stress on the liquefaction strength of gravelly soils... 

    Effect of stress anisotropy on the pore water pressure generation of loose sand

    , Article 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability, 9 November 2015 through 13 November 2015 ; 2015 , Pages 401-406 Jafarzadeh, F ; Zamanian, M ; Sharif University of Technology
    Asian Regional Conference on Soil Mechanics and Geotechnical Engineering  2015
    It is well established that the main mechanism for the occurrence of liquefaction under seismic loading conditions is the generation of excess pore water pressure. The growth of the excess pore water pressure of saturated sand is dependent on several factors. Changing the inclination and magnitude of the major principal stress with respect to the depositional direction in most cases will increase the collapse potential and brittleness as well as reduce the shear strength and shear stiffness. An experimental program was carried out to study the variation of pore water pressure of cross-anisotropic deposits under anisotropic cyclic loading. A total of 30 undrained cyclic tests were performed... 

    Numerical investigation of the effects of geometric and seismic parameters on liquefaction-induced lateral spreading

    , Article Soil Dynamics and Earthquake Engineering ; Volume 89 , 2016 , Pages 233-247 ; 02677261 (ISSN) Ghasemi Fare, O ; Pak, A ; Sharif University of Technology
    Elsevier Ltd  2016
    The lateral movement of a liquefiable soil layer on gentle slopes is the most visible and devastating type of liquefaction-induced ground failure. Recent earthquakes have shown that this phenomenon causes severe damages to coastal structures, pier of the bridges and life-lines by exerting large lateral forces on the structures. In this paper coupled dynamic field equations of extended Biot's theory with u-p formulation are used for simulating the phenomenon and the soil behavior is modeled by a critical state two-surface plasticity model for sands. Furthermore, in this study variation of permeability coefficient during liquefaction is taken into account. The permeability coefficient is...