Search for: liquefaction
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    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.... 

    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... 

    Investigation the Effect of Content and Plastisity of Plastic Fines on Liquefaction Resistance of Sand Using Cyclic Simple Shear Tests

    , M.Sc. Thesis Sharif University of Technology Hassani, Mehrdad (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    Regarding the existing contrary in the literature in relation to the effect of plastic fine on sand liquefaction behaviour, we decided to study this effect. Amounts of 5, 15, and 25 percent of two types of plastic fine, Kaolinite with PI=19 and Bentonite with PI=116 added to Firoozkooh Sand and 68 stress controlled tests were conducted using cyclic simple shear apparatus. In all teste the frequency of shear loading and consolidating vertical effective stress were constant and 0.1 Ht and 100 kPa respectively. Reaching excess pore water pressure ratio to the maximum value (r_u=Max) and reaching double amplitude shear strain to the value of 5% have been considered as liquefaction critera. In... 

    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... 

    Assessment of Effectivness of Compaction Improvement for Liquefaction Mitigation of Saturated Sand Deposits Based on Performance Levels of Shallow Foundations

    , Ph.D. Dissertation Sharif University of Technology Shahir, Hadi (Author) ; Pak, Ali (Supervisor) ; Ghannad, Mohammad Ali (Supervisor)
    Settlement and tilt of structures due to liquefaction of subsoil layers is a major cause of damage during earthquake. One of the main approaches to reduce terrible effects of liquefaction on shallow foundations is ground improvement. Among the variety of ground improvement methods, the densification-based methods have been more paid attention for liquefaction mitigation. For liquefaction hazard mitigation using densification methods, three basic values should be determined i.e. depth, lateral extent, and degree of improvement (percent increase in Dr). In the current design practice, the need for ground improvement is usually decided based on the semi-empirical methods for assessment of... 

    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... 

    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... 

    Evaluation of variation of permeability in liquefiable soil under earthquake loading

    , Article Computers and Geotechnics ; Volume 40 , 2012 , Pages 74-88 ; 0266352X (ISSN) Shahir, H ; Pak, A ; Taiebat, M ; Jeremić, B ; Sharif University of Technology
    Liquefaction phenomenon is usually accompanied by large amounts of settlement owing to disruption of soil structure. In addition to that, large settlement also occurs by a significant increase in soil permeability during seismic excitation. To properly simulate the post-liquefaction settlement, it is important to take the compressibility properties of the liquefied sand as well as the permeability increase into account. Using initial permeability coefficient in the course of simulation of liquefaction leads to underestimation of settlement. In addition to that, using unrealistic values for permeability may cause erroneous predictions of other aspects of soil behavior. Therefore, an accurate... 

    Prediction of lateral spreading displacement on gently sloping liquefiable ground

    , Article Geotechnical Frontiers 2017, 12 March 2017 through 15 March 2017 ; Issue GSP 281 , 2017 , Pages 267-276 ; 08950563 (ISSN) Ghasemi Fare, O ; Pak, A ; Geo-Institute (G-I) of the American Society of Civil Engineers; Industrial Fabrics Association International (IFAI) ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2017
    A fully coupled numerical analysis using Biot's theory with u-p formulation considering variable permeability during liquefaction is used in this study to simulate liquefaction induced lateral spreading phenomenon. A centrifuge test performed on liquefiable soil at Rensselaer Polytechnic Institute is simulated using the developed model. The numerical results are in good agreement with experimental observations. A number of numerical simulations under different geometric, site-specific, and ground acceleration parameters have been carried out in the course of this study. Based on the statistical analysis conducted on the results of 31 different models, a new relation is proposed for... 

    A Neuro-Fuzzy model for prediction of liquefaction-induced lateral spreading

    , Article 8th US National Conference on Earthquake Engineering 2006, San Francisco, CA, 18 April 2006 through 22 April 2006 ; Volume 13 , 2006 , Pages 8001-8008 ; 9781615670444 (ISBN) Haeri, S. M ; Khalili, A ; Sadati, N ; Sharif University of Technology
    Lateral spreading generated by earthquake induced liquefaction, is a major cause for significant damage to the engineered structures, during earthquakes. Knowing the amount of displacement which is likely to occur due to the lateral spreading, will lead to better construction policies, and will reduce unexpected damages. A Neuro-Fuzzy model based on subtractive clustering is developed to predict the amount of lateral spreading expected to occur due to an earthquake. A large database containing the case histories of observed lateral spreading during seven major earthquakes of the past is used for training and evaluating the models. The results of this study show that Neuro-Fuzzy method serves... 

    Effects of intermediate principal stress parameter on cyclic behavior of sand

    , Article Scientia Iranica ; Vol. 21, Issue. 5 , 2014 , pp. 1566-1576 Jafarzadeh, F ; Zamanian, M ; Sharif University of Technology
    Soils have an anisotropic response, and changing the inclination (α) and magnitude of the major principal stress will affect collapse potential and brittleness, as well as shear strength and shear stiffness. In this paper, the effect of the stress path, with changes in intermediate principal stress, on the dynamic behavior of Babolsar sand, is studied. A series of undrained monotonic and cyclic tests on loose sand with induced anisotropy were conducted by using automatic hollow cylinder apparatus. Special attention was paid to the significant role of the intermediate principal stress parameter (b) in the deformation behavior of the sand during cyclic loading. Results show that at constant α,... 

    Response of a group of piles to liquefaction-induced lateral spreading by large scale shake table testing

    , Article Soil Dynamics and Earthquake Engineering ; Volume 38 , 2012 , Pages 25-45 ; 02677261 (ISSN) Haeri, S. M ; Kavand, A ; Rahmani, I ; Torabi, H ; Sharif University of Technology
    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. Current paper aims to study the response of a group of piles subjected to liquefaction-induced lateral spreading using a large scale 1-g shake table test. General test results including time-histories of accelerations, pore water pressures, displacements and bending moments are presented and discussed in this paper. In addition, distribution of lateral soil pressure on... 

    Estimating liquefaction-induced settlement of shallow foundations by numerical approach

    , Article Computers and Geotechnics ; Volume 37, Issue 3 , April , 2010 , Pages 267-279 ; 0266352X (ISSN) Shahir, H ; Pak, A ; Sharif University of Technology
    Occurrence of liquefaction in saturated sand deposits underlying foundation of structure can cause a wide range of structural damages starting from minor settlement, and ending to general failure due to loss of bearing capacity. If the bearing capacity failure is not the problem, reliable estimation of the liquefaction-induced settlement will be of prime importance in assessment of the overall performance of the structure. Currently, there are few procedures with limited application in practice for estimation of settlement of foundations on liquefied ground. Therefore, development of a general relationship is important from the practical viewpoint. In this paper, the dynamic response of... 

    Seismic behavior of a dolphin-type berth subjected to liquefaction induced lateral spreading: 1g large scale shake table testing and numerical simulations

    , Article Soil Dynamics and Earthquake Engineering ; Volume 140 , 2021 ; 02677261 (ISSN) Kavand, A ; Haeri, S. M ; Raisianzadeh, J ; Sadeghi Meibodi, A ; Afzal Soltani, S ; Sharif University of Technology
    Elsevier Ltd  2021
    The effects of liquefaction induced lateral spreading on the piles of a dolphin-type berth were investigated using 1 g large scale shake table testing accompanied by numerical simulations. For this purpose, various aspects of the response of the soil and the pile group to lateral spreading were considered. The results indicated that large bending moments were induced in the piles during lateral spreading and the downslope piles of the group received greater bending moments than the upslope one. The monotonic components of bending moments in the piles were reasonably predicted by the displacement based numerical approach using p-y springs when they were properly tuned for strength reduction... 

    Numerical-probabilistic modeling of the liquefaction-induced free fields settlement

    , Article Soil Dynamics and Earthquake Engineering ; Volume 149 , 2021 ; 02677261 (ISSN) Sadeghi, H ; Pak, A ; Pakzad, A ; Ayoubi, P ; Sharif University of Technology
    Elsevier Ltd  2021
    Liquefaction is a phenomenon through which saturated sandy soil loses its shear strength and turns into a liquefied state. One of the most detrimental consequences of liquefaction is the reconsolidation volumetric settlements after the earthquakes, which is due to the dissipation of excess pore pressure caused by earthquakes. Severe floods can follow these settlements in free fields such as grounds close to the sea or rivers. Several researchers studied this phenomenon using data obtained from experiments in the lab or observations in the fields. Previous works were mainly based on a limited number of experimental observations and considered loadings and boundary conditions that were... 

    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...