Search for: liquefaction
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    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.... 

    Studying the Effects of Liquefaction Induced Lateral Spreading on Piles and Evaluation of a Remedial Measure Against Pile Damaging Due to These Effects with Shake Table Tests Using Laminar Shear Box

    , Ph.D. Dissertation Sharif University of Technology Rajabigol, Morteza (Author) ; Haeri, Mohsen (Supervisor) ; Kavand, Ali (Co-Supervisor)
    Liquefaction-induced lateral spreading is one of the most challenging problems in geotechnical earthquake engineering. This phenomenon may impose severe damages on deep foundations in large earthquakes. In this study, six physical modeling are designed, built and tested to investigate the effects of lateral spreading on deep foundations and also assess one mitigation method. The experiments were conducted using 1g shake table of Sharif university of technology. In this respect, a large laminar shear box with outer dimensions of 420, 240 and 180 cm was designed and constructed. The laminar shear box consisted of 23 steel laminates with inner dimensions of 306×172 cm. Four experiments were... 

    Correlation of shear wave velocity with liquefaction resistance for silty sand based on laboratory study

    , 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 794-799 Akbari-Paydar, N ; Ahmadi, M. M ; Sharif University of Technology
    Asian Regional Conference on Soil Mechanics and Geotechnical Engineering  2015
    Several methods have been used for the evaluation of liquefaction potential, among which the simplified method is mostly used. In this method, which is mainly based on standard penetration test (SPT), cone penetration test (CPT) and shear wave velocity (Vs) measurement, a boundary curve is provided to separate the liquefiable and non-liquefiable soil zones. Vs measurement is a good alternative method of penetration-based methods (SPT and CPT). This is especially true in micro-zonation of liquefaction potential. Although relatively large studies have been carried out to establish the correlation between Vs and liquefaction resistance for sands; there are uncertainties about the effects of... 

    A Performance-Based Approach to the Design of Shallow Foundations Resting on Heterogeneous Subsoil Prone to Liquefaction Hazards

    , Article 4th Geo-China International Conference: Innovative Technologies for Severe Weather and Climate Change, Geo-China 2016, 25 July 2016 through 27 July 2016 ; Volume 2016-January, Issue 264 GSP , 2016 , Pages 47-55 ; 08950563 (ISSN) Pak, A ; Ayoubi, P ; Shahir, H ; El-Badawy S ; Cheng D ; Arab M ; Chinese National Science Foundation; Geo-Institute (G-I) of the American Society of Civil Engineers (ASCE); Shandong Department of Transportation; Shandong University; University of Oklahoma ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2016
    Performance-based design (PBD) has become increasingly important in recent years, especially for the design of foundations rested on sub-soils that are susceptible to liquefaction at seismically active areas. Shallow foundations may fail due to excessive settlement because of liquefaction of the underlying loose saturated cohesion-less sands. Building codes usually do not address the issue of liquefaction-induced settlement of shallow foundations. In this paper, a framework is proposed for calculating the liquefaction-induced settlement of shallow foundations resting on heterogeneous two-layered liquefiable soil by conducting a series of 3D. hydro-mechanical dynamic analyses in a fully... 

    Effect of fines type and content of sand on correlation between shear wave velocity and liquefaction resistance

    , Article Geotechnical and Geological Engineering ; 2016 , Pages 1-20 ; 09603182 (ISSN) Akbari Paydar, N ; Ahmadi, M. M ; Sharif University of Technology
    Springer International Publishing 
    The use of shear wave velocity (Vs) measurements as an in situ test for evaluation of liquefaction potential has increased substantially due to its advantages. Relatively large numbers of studies have been performed to establish the correlation between Vs and liquefaction resistance (CRR) of clean sands. Usually, natural sands contain silt and/or clay, and previous studies have shown that both the amount of fines and their nature influence the values of CRR as well as Vs. Therefore, the CRR–Vs correlations may also be affected by fines content and type of sandy soils. However, effect of fines content and especially fines type of sandy soils on the correlation between Vs and CRR is... 

    Liquefaction-induced settlement of shallow foundations on two-layered subsoil strata

    , Article Soil Dynamics and Earthquake Engineering ; Volume 94 , 2017 , Pages 35-46 ; 02677261 (ISSN) Ayoubi, P ; Pak, A ; Sharif University of Technology
    Elsevier Ltd  2017
    Geotechnical design codes have been shifted from classical limit equilibrium analysis toward the performance-based procedures. In foundation design, settlement is the most representative parameter for its performance. Settlement of shallow foundations subjected to earthquake loading and its consequences is one of the most outstanding issues which should be considered in designing different structures. In this study, settlement of shallow footing on two-layered subsoil strata under earthquake loading is of concern. The numerical study presented in this research by means of a 3D dynamic fully coupled u-p analysis, addresses the effect of different parameters on shallow foundation settlement... 

    Implementation of image processing technique for measuring membrane penetration in triaxial testing on gravelly soils

    , Article 19th International Conference on Soil Mechanics and Geotechnical Engineering, ICSMGE 2017, 17 September 2017 through 22 September 2017 ; 2017 , Pages 381-384 Haeri, S. M ; Shahcheraghi, S. A ; Sharif University of Technology
    19th ICSMGE Secretariat  2017
    The volume change that occurs due to membrane penetration into peripheral voids of gravelly specimens during hydrostatic compression test in a conventional triaxial apparatus is studied by performing a set of hydrostatic compression tests on gravelly specimens with different initial relative densities. During the isotropic loading on the specimens, the total volume changes of the specimens were determined by measuring the amount of water seeping out of the specimens at different loading steps. Image processing technique was implemented simultaneously to determine the skeletal volume changes of the specimens. In this regard specimens were compressed to isotopic pressures from 10 to 500 kPa... 

    Response of a group of stiff piles to liquefaction induced lateral spreading: numerical simulation of a shaking table experiment

    , Article 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019, 14 October 2019 through 18 October 2019 ; 2020 Haeri, S. M ; Afzalsoltani, S ; Sharif University of Technology
    Asian Regional Conference on Soil Mechanics and Geotechnical Engineering  2020
    During recent years, extensive studies have been conducted around the world documenting liquefaction induced lateral spreading and its effects on deep foundations. This study is aimed to numerically model a shaking table experiment, to investigate the effect of lateral spreading on piles and also to assess the capability of an advanced critical state two-surface plasticity model in predicting soil and pile responses to lateral spreading. Changes in permeability of the soil layers during the shaking are also accounted for using the software's built-in programming language, FISH. Numerical results showed that the onset of liquefaction occurs after just a few cycles from the beginning of the... 

    Study of pore pressure variation during liquefaction using two constitutive models for sand

    , Article Soil Dynamics and Earthquake Engineering ; Volume 27, Issue 1 , 2007 , Pages 60-72 ; 02677261 (ISSN) Taiebat, M ; Shahir, H ; Pak, A ; Sharif University of Technology
    Numerical analyses of liquefiable sand are presented in this paper. Liquefaction phenomenon is an undrained response of saturated sandy soils when they are subjected to static or dynamic loads. A fully coupled dynamic computer code is developed to predict the liquefaction potential of a saturated sandy layer. Coupled dynamic field equations of extended Biot's theory with u-P formulation are used to determine the responses of pore fluid and soil skeleton. Generalized Newmark method is employed for integration in time. The soil behavior is modelled by two constitutive models; a critical state two-surface plasticity model, and a densification model. A class 'B' analysis of a centrifuge... 

    , 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 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... 

    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... 

    Parametric Study of Shallow Foundations Settlement Due to Liquefaction Phenomenon on a Two-Layered Soil

    , M.Sc. Thesis Sharif University of Technology Ayoubi, Peyman (Author) ; Pak, Ali (Supervisor)
    Settlement and tilt of structures due to liquefaction of subsoil layers is a major cause of damage during earthquake. Among different soil profile type, two layered soil is very common which was reported many times in differen earthquakes. Settlement of structures was measured by means of empirical methods before which were not viable because they do not consider different effective parameters. Consequently, different experimental studies performed to shed light on different aspects of liquefaction phenomena. In these studies, researchers consider some of the main parameters which have effect on the soil, otherwise, they neglected some important factors. So, numerical procedure is more... 

    , 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 ... 

    Comparison of Constitutive Laws for Numerical Simulation of Soil Liquefaction Phenomenon

    , M.Sc. Thesis Sharif University of Technology Iranmanesh, Mohammad Ali (Author) ; Pak, Ali (Supervisor)
    Liquefaction is one of the probable consequences of earthquake in soil layers of saturated loose sands. Various aspects of liquefaction have been investigated using different methods of field, laboratory, and numerical studies. Numerical simulation of liquefaction constitutes a major part of these researches. A proper constitutive law must be implemented in the numerical analysis for modeling the complicated behavior of saturated sands during dynamic loading. Simplicity of formulation, limited number of parameters and good performance are the main features of a proper constitutive law. In this study, Endochronic model for simulating liquefaction has been introduced. This model is implemented... 

    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... 

    Parametric Study and Numerical Simulation of Spiral Wound Heat Exchanger Performance at Cryogenic Temperatures

    , M.Sc. Thesis Sharif University of Technology Hosseinian Khorasgani, Mohsen (Author) ; Afshin, Hossein (Supervisor)
    Cryogenic is the study of physical phenomena at temperatures below 123 Kelvin. One of the applications of cryogenic science is the liquefaction of gases. In the liquefaction cycles of gases, such as helium liquefaction, fluidization occurs in the pressure reducing valve but temperature of the gas should be greatly reduced before it enters the pressure reducing valve. For this purpose, high-performance heat exchangers should be used. Spiral Wound is one of the heat exchangers that has ability to achieve over 90% efficiency due to its structure. Researchs in the field of design and simulation of spiral heat exchangers are limited and are done with a lot of simple assumptions such as constant... 

    Study of the behavior of pile groups during lateral spreading in medium dense sands by large scale shake table test

    , Article International Journal of Civil Engineering ; Vol. 12, Issue. 3 , 2014 , pp. 374-391 ; ISSN: 17350522 Kavand, A ; Haeri, S. M ; Asefzadeh, A ; Rahmani, I ; Ghalandarzadeh, A ; Bakhshi, A ; Sharif University of Technology
    In this paper, different aspects of the behavior of 2×2 pile groups under liquefaction-induced lateral spreading in a 3-layer soil profile is investigated using large scale 1g shake table test. Different parameters of the response of soil and piles including time-histories of accelerations, pore water pressures, displacements and bending moments are presented and discussed in the paper. In addition, distribution of lateral forces due to lateral spreading on individual piles of the groups is investigated in detail. The results show that total lateral forces on the piles are influenced by the shadow effect as well as the superstructure mass attached to the pile cap. It was also found that... 

    Investigation of the influence of permeability coefficient on the numerical modeling of the liquefaction phenomenon

    , Article Scientia Iranica ; Volume 19, Issue 2 , 2012 , Pages 179-187 ; 10263098 (ISSN) Rahmani, A ; Ghasemi Fare, O ; Pak, A ; Sharif University of Technology
    The soil permeability coefficient plays a key role in the process of numerical simulation of the liquefaction phenomenon. Liquefaction causes a considerable increase in soil permeability, due to the creation of easier paths for water flow. The work presented in this paper tries to investigate the effects of permeability coefficient on the results of numerical modeling of the liquefaction phenomenon. To do this, a fully coupled (u-P) formulation is employed to analyze soil displacements and pore water pressures. Two different versions of a well-calibrated critical state bounding surface plasticity model, which possesses the capability to utilize a single set of material parameters for a wide... 

    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...