Search for: liquefaction
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Total 93 records

    , M.Sc. Thesis Sharif University of Technology Boushehrian, Ahmad (Author) ; Haeri, Mohsen (Supervisor)
    Loads from laterally spreading ground have been a major cause of damages to pile foundations in past earthquakes. Analysis of case histories have shown that damages are particularly intense when a nonliquefiable surface crust layer spreads laterally over underling liquefied layers. In this research the effect of lateral spreading due to liquefaction on single piles embede in a gently sloping ground has been investigated. Finite element method using OpenSees is used to model the pile and embedded soil. The soil profile for all models consisted of a nonliquefiable crust layer overlying loose sand with Dr = 30-35% overlying dense sand with Dr = 70-80%. The effect of geometric properties such as... 

    Dynamic Analysis of Pile Foundations Embedded in Liquefiable Soils

    , M.Sc. Thesis Sharif University of Technology Rahmani, Amin (Author) ; Pak, Ali (Supervisor)
    The behavior of pile foundations under earthquake loading is an important issue that affects the performance of structures. Design procedures have been developed for evaluating pile behavior under earthquake loading; however, the application of these procedures to cases involving liquefiable ground is uncertain. The performance of piles in liquefied soil layers is much more complex than that of non-liquefying soil layers because not only the superstructure and the surrounding soil exert different dynamic loads on pile, but also the stiffness and shear strength of surrounding soil diminishes over time due to both non-linear behavior of soil and pore water pressure generation. In this... 

    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... 

    Dynamic Analysis and Liquefaction Evaluation of Earth Dams, Mahabad Dam case Study

    , M.Sc. Thesis Sharif University of Technology Fallah Moshfeghi, Sogol (Author) ; Jafarzadeh, Fardin (Supervisor)
    Liquefaction due to the earthquake loading is one of the most important threats in the earth structure. Analysis of liquefaction of structures such as dam/foundation systems utilizing numerical methods such as finite difference and finite element, can considerably determine the real response of the structures during strong ground motions. Mahabad rockfill dam, located in upper vicinity of Mahabad city, in North-West of Iran, completed and impounded in 1970. This embankment dam was designed as a zoned dam with a slightly inclined impervious clay core and 47.5 m in height. Studying such structures, which have been designed with simple methods in olden times, can recognize the potential risks... 

    Investigation on the Effect of Liquefaction-Induced Lateral Spreading on a Flexible Pile Group and Mitigation Measures for These Effects by Physical Modeling

    , M.Sc. Thesis Sharif University of Technology Raisianzadeh, Javad (Author) ; Haeri, Mohesn (Supervisor)
    Liquefaction-induced lateral spreading is a known cause of severe damages to deep foundations during past earthquakes. Lateral spreading often takes place in gently sloping grounds which consisted of saturated loose cohesionless soil deposits. Several researchers during recent years have been studying the behavior of piles and soil-pile interaction under lateral spreading but there are still many unknowns in this regard. Also with observing catastrophic damages during past earthquakes caused by lateral spreading, developing proper mitigation measures for existing vulnerable piles against this phenomenon is a necessary act. In the present research, the behavior of a 3x3 flexible pile group... 

    Effect of Non-Plastic Fine on Liquefaction Resistance of Sand Using Cyclic Simple Shear Test

    , M.Sc. Thesis Sharif University of Technology Shirasb, Atena (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    Soil Liquefaction is a phenomenon corresponding to earthquake in which granular soil loses most of its strength in seismic loading. In this study, cyclic simple shear tests were performed for evaluating the effect of non-plastic fines on liquefaction resistance of Firuzkouh sand. Firuzkouh sand is uniform and is classified as SP in USCS. Firuzkouh silt was used as Non-plastic fine. Tests were performed under constant vertical load and undrained conditions on cylindrical specimens 7 cm in diameter and 2.2 cm in height. Samples were prepared using wet tamping method. All specimens were saturated following the standard back pressure method until the Skempton B-value was at least 0.96. Samples... 

    Evaluate of Undrained Behavior of Uncompacted Gravely Soil With Triaxial Apparatus Under Anisotropic Condition

    , M.Sc. Thesis Sharif University of Technology Bozorgi, Arash (Author) ; Haeri, Mohsen (Supervisor)
    The study of the behavior of gravelly soil in undrained condition has been a major topic for researchers for decades. Liquefaction in gravelly soils in recent earthquake has exposed the importance and necessity of investigation on undrained the behavior of gravely soils in earthquakes. In this research, undrained behavior of gravely soils and the effects of initial static shear stress on their behavior have been investigated. In this experimental research a gravelly soil (GP) performed and a triaxial apparatus is used. All tests are performed under consolidated undraiend condition and the specimens are prepared by wet tamping method. The diameter of the specimen was 10 cm and the height was... 

    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... 

    Thermodynamic Aspect and Simulation of Oxygen Intravitreal Profile and its Effect on Cataract

    , M.Sc. Thesis Sharif University of Technology Safari Nore Eini, Hossein (Author) ; Abdekhodaie, Mohammad Jafar (Supervisor) ; Taghikhani, Vahid (Supervisor)
    Importance: Age related cataract is the major cause of blindness worldwide.in recent years several studies has been done with the aim of understanding the cataract process, but no attempts has been done for simulation and study of the vitreous aging and its effect on cataract.
    Objective: To investigation and determination of effective mechanism for increasing oxygen in vitreous humor and simulation the oxygen tension changes with vitreous degeneration with age or vitrectomy.Methods: Effects of changes in chemical composition of vitreous humor with age or vitrectomy on oxygen solubility is studied by thermodynamic relations. The posterior segment of the eye is modeled using transport... 

    Liquefaction Effects on (a) Individual and Group of Capless Piles and (b) Group of three Piles under Real and Artificial Earthquakes

    , M.Sc. Thesis Sharif University of Technology Sabouri, Marjan (Author) ; Haeri, Mohsen (Supervisor)
    In the areas where the soil beneath the foundation is made of loose to semi-consolidated sand or noncohesive silts, Buildings and bridges are usually built on the pile foundations. One important issue that must be considered in the design of piles in saturated sandy soils, is liquefaction potential of saturated sandy soil under earthquake loads. During the earthquake, saturated sandy soil faces the sudden loss of shear strength in other word it liquifies . Liquefied Soil acts like a viscous fluid. This behaviour considerably increases the soil deformation and consequently the widespread disruption of soil layers, causes large deformation and applies great amount of forces on the piles... 

    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.... 

    Optimal Design of Cryogenic Heat Exchanger for Gas Liquefication Cycle

    , M.Sc. Thesis Sharif University of Technology Ebrahimi Ghalinghieh, Hamed (Author) ; Afshin, Hossein (Supervisor)
    Gas liquefication in low temperatures is one of the most challenging fields in engineering due to complexity of its thermodynamic analisys and fabrication of equipments. Heat Exchangers are one of the most important equipments in these prosseces. High prices of Heat Exchangers in these facilities makes their Optimal and cost effective design, of crucial importance. In this thesis three dimensional model of a Plate Fin Heat Exchanger is thoroughly investigated. Fistly, by means of Aspen Heat Exchanger design Software a counter flow Heat Exchanger is designed. This HX is to be placed in Collins cycle, so, working fluid in both hot and cold streams is Helium Gas. The HX then by means of ANSYS... 

    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,... 

    Effect of Initial Static Shear Stress on Cyclic Resistance and Undrained Behavior of Gravelly Soils under Low Confining Pressures Using Cyclic Triaxial Apparatus

    , M.Sc. Thesis Sharif University of Technology Raeesi, Ramin (Author) ; Haeri, Mohsen (Supervisor)
    Study on gravelly soils is one of the topics that Geotechnical Engineering researches have been concentrated on. Although several researches have enlightened the way to understand the behavior of gravelly soils, yet, there are some shortage of information about the dynamic behavior of this kind of soil in undrained condition. In this research, a series of cyclic triaxial tests have been performed using cyclic triaxial apparatus of Advanced Soil Mechanics Laboratory of Sharif University of Technology to study the effect of anisotropic consolidation (initial static shear stress) on dynamic behavior of a kind of gravel. The performed tests were divided into four groups with different initial... 

    , M.Sc. Thesis Sharif University of Technology Seyfi, Sahand (Author) ; Pak, Ali (Supervisor)
    Lateral spreading is a common mode of earthquake-induced failure that usually occurs as a result of liquefaction in gently sloped sandy layers. Numerical simulation of this phenomenon requires fully coupled analysis of displacement of solid sand particles and pore water pressure under seismic loading. Predicting occurrence of initial liquefaction and sub-sequent ground movement requires employing an efficient and robust constitutive model that can predict the undrained behavior of saturated sand under different conditions. In this study, a fully coupled finite element code “PISA” utilizing a critical state two-surface plasticity constitutive model, proposed by Manzari and Dafalias (1997),... 

    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... 

    Physical Modeling of Effect of Liquefaction-Induced Lateral Spreading on Single Piles

    , M.Sc. Thesis Sharif University of Technology Torabi, Hooman (Author) ; Haeri, Mohsen (Supervisor)
    Pile foundations suffered severe damages during the past earthquakes in all around the world. These damages were more severe in laterally spreading grounds and they mostly have been observed in gently sloping grounds and coastal areas. In these cases, Pile foundations not only are subjected to structures inertial loads and kinematic loads of liquefied soil but also lateral spreading intensifies damages. Thus, in the recent decade, several researches have been conducted to investigate the behavior of pile foundations in liquefiable and laterally spreading grounds, however, some uncertainties still remain in modeling of soil-pile interaction. In this study, the effects of liquefaction- induced... 

    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... 

    Study of Effective Parameters on Helium Liquefaction Cycle using Exergy Analysis

    , M.Sc. Thesis Sharif University of Technology Eslami, Mahdi (Author) ; Afshin, Hosein (Supervisor)
    Liquefaction of gases is one of the applications of cryogenic science. Among the gases, Helium has the lowest boiling point, which at a pressure of 1atm is approximately 4.2K. Liquid helium can be used to cool superconductors in transportation equipment, military radars, and medical imaging equipment. For helium liquefaction, various cycles are used; these cycles have different parameters in their structure such as of input mass fraction to expanders, heat exchanger effectiveness, expander arrangement and ... which their analysis for improving the performance of the cycle is important. In this research, the aim is to study 2, 3 and 4 expander cycle with various parameters and structure. For...