Search for: liquefaction
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    Effects of Liquefaction on 2×2 and 3×3 Stiff and Flexible Pile Groups

    , M.Sc. Thesis Sharif University of Technology Goudarzi, Anahita (Author) ; Haeri, Mohsen (Supervisor)
    Liquefaction has a profound effect on buildings, bridges, buried pipes and other engineering structures. This phenomenon can lead to the sliding of huge earth masses, submersion and bending of substantial structures, uplift of buried light structures and collapse of retaining walls. In recorded earthquakes, liquefaction has caused major damage to structures and deep foundations, proving that pile foundations are not designed to withstand at liquefaction condition. Considerable damages in pile foundations due to liquefaction in destructive earthquakes has called for extensive study and research concerning the behavior and response of piles under the influence of liquefaction, resulting in... 

    Design and Construction of Large-scale Laminar Shear Box for Study of the Behavior of Deep Foundations Subjected to Lateral Loads due to Lateral Spreading using 1-g Shake Table Tests

    , M.Sc. Thesis Sharif University of Technology Kamali Zarch, Mohsen (Author) ; Haeri, Mohsen (Supervisor)
    Using appropriate box as an artificial boundary condition is one of the critical tasks in geotechnical physical modeling of the soil mass especially under cyclic loading such as earthquakes. In general there are two types of boxes which can simulate boundary conditions of scaled models as rigid or flexible conditions. Main purpose of this study is design and construction of a flexible box in a way that effects of boundary condition have been minimized during tests. Construction of this box is the first step of an investigation project which concern to evaluate the effect of lateral spreading as a result of liquefaction on deep foundations of bridges, piers, harbors by using shake table test... 

    An Investigation on the Effects of Liquefaction Induced Lateral Spreading on Deep Foundations and Development of Mitigation Measures Using 1g Shake Table Tests

    , Ph.D. Dissertation Sharif University of Technology Kavand, Ali (Author) ; Haeri, Mohsen (Supervisor) ; Rahmani, Iraj (Co-Advisor)
    Liquefaction induced lateral spreading is defined as the lateral displacement of mildly sloping grounds or those ending in free faces as a result of liquefaction in subsurface soil layers. Damages imposed by lateral spreading on pile foundations supporting different types of structures such as ports, bridges and buildings are usually observed in large earthquakes. These potential damages are of high degree of importance in southern and northern coastal areas of Iran where several ports and critical facilities are located. River banks all over the country where bridge piers exist are also among the areas prone to potential damages. Evaluation of the effects of lateral spreading on existing... 

    Linear and Non-linear Dynamic Analysis of Full Scale Shaking Table Laminar Shear Box to Study the Effects of Lateral Spreading Due to Liquefaction on Deep Foundations

    , M.Sc. Thesis Sharif University of Technology Kazemi Taskoh, Amin (Author) ; Haeri, Mohsen (Supervisor)
    Liquefaction-induced lateral spreading has imposed severe damages to many important structures supported on pile foundations during past earthquakes. As a result, evaluation of pile response to lateral spreading is an important step towards safe and resistant design of pile foundations against this destructive phenomenon. The boundary conditions for physical modeling in problems of earthquake geotechnical engineering have significant influence on the test results. In order to reduce the undesirable effects of boundaries on the model responses, the flexible containers are used. The flexible containers are those in which the shear stiffness of the walls is proportional to the soil inside. A... 

    Effect of Initial Static Shear Stress on Liquefaction Resistance of Babolsar Sand Using Cyclic Simple Shear Tests

    , M.Sc. Thesis Sharif University of Technology Pouragha, Mehdi (Author) ; Haeri, Mohsen (Supervisor)
    Initial static shear stress caused by slopes or nearby structures' foundations can affect the behavior of the soil which is concerned many investigators during previous three decade. In this investigation, the effect of initial static shear stress on the liquefaction resistance of Babolsar sand has been probed using cyclic simple shear tests. Three different initial relative densities (Dr0=20%, 40% and 60%) and three different initial normal stresses (σv0= 50, 150 and 250 kPa) were considered in tests and four various initial static shear ratios (α) ranging between 0.0 and 0.3 were applied which leads to more than 190 distinct experiments. All tests were conducted under constant volume and... 

    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... 

    Evaluation of the Steady State and Liquefaction Potential of Gravelly Soils By Static Triaxial Tests

    , M.Sc. Thesis Sharif University of Technology Payan, Meghdad (Author) ; Haeri, Mohsen (Supervisor)
    Gravelly soils are among the ones that can be found all over the world and have been investigated by many researchers in recent years. Although many investigations have been performed to clarify the behaviour of these soils, but still there are a lot of shortge of information about the steady state and liquefaction potential of them. In this research, to verify the behaviour of gravelly soils, static triaxial apparatus has been used. The tests performed in this research are devided into 2 groups: Consolidated Undrained tests (CU) and Consolidated Drainedtests(CD). In group 1 tests, all 4 parameters involving gradation, relative density, isotropic pressure and anisotropy of consolidation... 

    Numerical Modeling of the Dynamic Behavior of Piles and Pile Groups Due to Liquefaction- Induced Lateral Spreading

    , M.Sc. Thesis Sharif University of Technology Pakzad, Amin (Author) ; Haeri, Mohsen (Supervisor)
    The phenomenon of lateral spreading occurs as a consequence of earthquakes induced liquefaction in grounds with mild slopes or ending to an opening. This phenomenon has caused many damages to deep foundations and associated structures. Therefore, it is necessary to study and estimate the forces which may be induced by lateral spreading to these structures. Due to the complex mechanism of the effect of lateral spreading on the piles, various tests have been carried out in the form of shaking table as well as centrifuge tests. According to the results of these tests, the forces applied to the piles are significant and can cause crucial damages to deep foundations. On the other hand, because... 

    , M.Sc. Thesis Sharif University of Technology Padash, Hadi (Author) ; Haeri, Mohsen (Supervisor)
    During the past earthquakes in all over the world, the piles have had serious damages in soils with liquefaction potential. During an earthquake, liquefaction occurs in some parts of ground with mild slope and saturated and soft granular soil. Afterwards lateral spreading induced by liquefaction incurs irreparable damages on structures and piles particularly. Observing these damages, the researchers and engineers have conducted more surveys and investigations to studying the behavior of piles in granular soils with liquefaction potential and also interactions between  soil  and pile.  In  these  researches,  they have  modeled  the  interactions between  soil  and pile.  However  there are ... 

    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... 

    3D Numerical Modeling of Dynamic Instability Induced by Liquefaction in Loose Sand Deposit when Earthquake Occurs Perpendicular to the Slope

    , M.Sc. Thesis Sharif University of Technology Nazari Tileki, Ali (Author) ; Pak, Ali (Supervisor)
    Soil liquefaction occurring in loose saturated sand deposits during seismic loadings is one of the most destructive earthquake-induced phenomena in the field of earthquake geotechnical engineering. Catastrophic destructions due to this phenomenon that have been observed in the earthquakes such as Kobe (1995), Chi-Chi (1999), etc. has led to extensive studies in this field. In case of soil slopes prone to liquefaction hazard, detailed analysis of this phenomenon requires considering soil-related factors (e.g. shear strength, relative density, permeability, slope geometry) on the one hand, and earthquake-related characteristics (e.g. amplitude, frequency, duration) on the other. Numerical... 

    Numerical Investigation of Nitrogen Condensation in a Two-phase Vortex Tube

    , M.Sc. Thesis Sharif University of Technology Mirjalili, Mohamad Reza (Author) ; Ghorbanian, Kaveh (Supervisor)
    The Ranque-Hilsch vortex tube (RHVT) has no moving parts through which a high-pressure fluid gains on rotational velocity by passing radially through the inlet nozzles and then enters the vortex chamber. Subsequently, the high-pressure fluid becomes divided into two relatively distinctive hot and cold axial flows. Today, while RHVT is of great industrial interest due to its simplicity in manufacturing and operation; however, the mechanism of energy dissociation, which is dominated by the complex coupled interaction of the viscous thermo-fluid characteristics and geometrical properties, is not fully understood and no clear theory has been proposed to explain the energy dissociation so far.... 

    CFD Modeling of a LNG Microchannel Heat Exchanger

    , M.Sc. Thesis Sharif University of Technology Mahdian, Ehsan (Author) ; Farhadi, Fathollah (Supervisor)
    In the present work, the possibility of using a cross flow microchannel heat exchanger in cryogenic service for natural gas liquefaction has been numerically investigated using 3D computational fluid dynamics approach. Microchannels of rectangular and triangular cross section with a hydraulic diameter of 0.667 and 0.472 mm respectively have been constructed in Gambit and Fluent is used as the solver of numerical simulations.For solver’s equations validation, the existing experimental data on flow of water through rectangular microchannels has been modeled by CFD. Comparison of CFD results with experimental data shows a good agreement.Both models are constructed of three distinct layers. In... 

    Investigating the Influence of a Silty Layer on the Liquefaction of Saturated Sandy Soils through Numerical Methods

    , M.Sc. Thesis Sharif University of Technology Moghaddam Ranjbaran, Babak (Author) ; Pak, Ali (Supervisor)
    One of the main geotechnical phenomena that causes severe damage during earthquake is liquefaction. This incident occurs due to the undrained behavior of loose sandy soils. In this occurrence, the interaction between the solid and liquid phases in a cyclic motion leads to an increase in pore water pressure and a decrease in interactive forces (effective forces) between grains in the solid grains. Therefore, shear strength decreases. Different aspects of the aforementioned phenomenon is investigated, namely, field, laboratory, and numerical; nevertheless, the study is largely focused on the numerical modelling. Most studies in this field are carried out on a one-layer saturated sand. However,... 

    Study of Phase Behavior and Economical Investigation on Transportation Of LNG and LPG Mixture

    , M.Sc. Thesis Sharif University of Technology Mashhadi Ebrahim, Amir (Author) ; Badakhshan, Amir (Supervisor) ; Taghikhani, Vahid (Supervisor) ; Ghotbi, Siroos (Supervisor)
    Many technologies should be applied for transportation or consumption of natural gas. There are many different ways for transporting natural gas from origin of production to the location of consumption which the simplest way is transportation via pipelines but for transportation of natural gas for long distances, we can not use this method in this way we should apply other technologies such as converting the natural gas to the liquid state. For using this method, first we should liquefy the natural gas up to -162 degree of centigrade at the atmospheric pressure and then transport it with large cargo ships. By using this method, the transportation costs are decreased in compared with the... 

    Investigation of the Effects of Successive Liquefaction Occurrence on Piles Located in Level Ground with an Inclined Base Layer-A Physical 1g Shake Table and Laminar Shear Box Model

    , M.Sc. Thesis Sharif University of Technology Moradi, Mohammad (Author) ; Haeri, Mohsen (Supervisor)
    The phenomenon of soil liquefaction has caused significant damage to deep foundations of engineering structures such as bridges and buildings in past earthquakes. In recent years, many researchers have studied the effects of soil liquefaction on the pile response, but there are still many unknowns that require further research and study. The present study is part of a comprehensive research that involves several Ph.D. and master students at Sharif University of Technology (SUT). In this study, the effects of soil liquefaction on two pile 2×2 groups (one with a lumped mass and another without) in a level ground with a sloping bed were investigated. A surface non-liquefied layer was also... 

    An Economic Approach To Study & Optimization of Helium liquefier

    , M.Sc. Thesis Sharif University of Technology Mahmoudabad Bozchelou, Mohammad Amin (Author) ; Afshin, Hossein (Supervisor)
    Gas liquefaction is one of the main applications of Cryogenics science. Due to the unique properties of Helium, it is a strategic product in the world. Therefore, appropriate and applicable analysis should be used to investigate and optimize the Helium liquefaction cycles. In the current study, the goal is to find the optimal point with the help of energy and exergy analysis based on economic criterion, for the various parameters of Collins’ cycle. In order to simulate the cycle, a computer code is developed. First, sensitivity analysis of different parameters affecting the exergy efficiency and liquid fraction of the cycle has been done. Then, Artificial Neural Network and Genetic Algorithm... 

    Effects of Static Shear Stress on Liquefaction Strength of Babolsar Sand Investigated under Cyclic Simple Shear and Static Triaxial Tests

    , M.Sc. Thesis Sharif University of Technology Mohammadi, Morteza (Author) ; Haeri, Mohsen (Supervisor)
    Soil liquefaction is a phenomenon in which soil loses much of its strength or stiffness for a generally short time but nevertheless long enough for liquefaction to be the cause of many losses. Thus, many researchers have worked on the factors which affect this phenomenon. Effects of initial static shear stress on liquefaction strength of loose and medium dense Babolsar sand specimens were investigated in this study. Babolsar sand is fine to medium uniform sand classified as SP in USCS. Tests were performed with cyclic simple shear and static triaxial devices. All tests were performed under consolidated undrained conditions. Cyclic simple shear tests were performed under constant vertical... 

    Numerical Simulation of Ground Displacement Induced by Lateral Spreading Phenomenon

    , M.Sc. Thesis Sharif University of Technology Ghasemifare, Omid (Author) ; Pak, Ali (Supervisor)
    The lateral movement of a liquefiable layer on gently slopes is the most visible and devastating type of liquefaction-induced ground failure. Occurrence of liquefaction in sloping ground causes large deformations on ground surface, which may lead to several meters in some cases. Recent earthquakes have shown that this phenomenon causes severe damages to coastal structures, piers of bridges and life-lines, by exerting large lateral forces. In this research, a fully coupled two-dimensional dynamic analysis has been used to simulate the lateral spreading phenomenon and to evaluate the magnitude of deformations occurred in liquefiable soils. The critical state bounding surface elastic-plastic... 

    Effect of Lateral Spreading Due to Liquefaction on Piles, Numerical Simulation with OpenSees

    , M.Sc. Thesis Sharif University of Technology Ghasemi Fard, Ali (Author) ; Haeri, Mohsen (Supervisor)
    Lateral spreading due to liquefaction and resulting destruction of buildings is important in Iran because of high seismicity and important infrastructure near south and north coasts of Iran. Lateral spreading is vast lateral movement of sloping ground or level ground ending in an opening like river which is caused by earthquake inducedliquefaction. For considering the effects of lateral spreading during design of deep foundations of structures in a susceptible area, one needs to determine the lateral loads on piles under lateral spreading. Present study investigates the behavior of a 3x3 pile group against lateral loads due to lateral spreading with numerical methods using OpenSees software....