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    Numerical investigation into the effects of geometrical and loading parameters on lateral spreading behavior of liquefied layer

    , Article Acta Geotechnica ; 2013 , Pages 1-13 ; 18611125 (ISSN) Pak, A ; Seyfi, S ; Ghassemi, A ; Sharif University of Technology
    2013
    Abstract
    Numerical simulation of liquefaction-induced lateral spreading in gently sloped sandy layers requires fully coupled dynamic hydro-mechanical analysis of saturated sandy soil subjected to seismic loading. In this study, a fully coupled finite element model utilizing a critical-state two-surface-plasticity constitutive model has been applied to numerically investigate the effects of surface/subsurface geometry on lateral spreading. Using a variable permeability function with respect to excess pore pressure ratio is another distinctive feature of the current study. The developed code has been verified against the results of the well-known VELACS project. Lateral spreading phenomenon has been... 

    Comparison of liquefaction evaluation based on SPT and geophysical tests (case study: Mahabad dam, Iran)

    , Article 5th International Conference on Geotechnical and Geophysical Site Characterisation, 5 September 2016 through 9 September 2016 ; Volume 1 , 2016 , Pages 657-661 ; 9780994626110 (ISBN) Shahrabi, M. M ; Jafarzadeh, F ; Akbari Garakani, A ; Eskandari, N ; Banikheir, M ; Jahromi, H. F ; Sharif University of Technology
    Australian Geomechanics Society 
    Abstract
    Standard Penetration Test (SPT) is the most commonly used insitu test for soil characterization, including the liquefaction resistance. Many studies have sought to correlate SPT number to cyclic resistance ratio (CRR) as a frequently-used approach for assessment of liquefaction potential. However, it has been shown that SPT has major deficiencies (e.g., inaccuracy in coarse sands and clays) which have given rise to development and utilization of new characterization methods such as geophysical tests (e.g., down-hole and cross-hole). In this paper, a comparison is made between the results of SPT and geophysical tests in three boreholes through the body and foundation of Mahabad Dam (located... 

    A performance-based approach for design of ground densification to mitigate liquefaction

    , Article Soil Dynamics and Earthquake Engineering ; Volume 90 , 2016 , Pages 381-394 ; 02677261 (ISSN) Shahir, H ; Pak, A ; Ayoubi, P ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    In performance-based geotechnical earthquake engineering, the required degree and spatial extent of ground densification for mitigation of liquefaction beneath a structure should be determined based on the acceptable levels of performance of foundation. Currently, there is no solution for evaluation of the amount of settlement and tilt of footings constructed on a densified ground which is surrounded by a liquefiable soil. This implies the need for numerical procedures for simulation of seismic behavior of shallow foundations supported on both liquefiable and densified subsoil. In this paper, the dynamic response of shallow foundations on a densified ground is studied using a 3D fully... 

    Evaluation of variable permeability model in simulation of seismic behavior of uniform level and gently sloping sand layers

    , Article Earth Sciences Research Journal ; Volume 24, Issue 3 , 2020 , Pages 328-336 Ghassemi, A ; Seyfi, S ; Shahir, H ; Sharif University of Technology
    Universidad Nacional de Colombia  2020
    Abstract
    In this study, a fully coupled dynamic finite element model was employed for numerical simulation of the response of level to gently sloping saturated sand layers subjected to cyclic loading. This model utilized a critical state two-surface-plasticity constitutive model to simulate the cyclic behavior of sandy soil. Moreover, a recently proposed variable permeability function was implemented in the numerical model to reflect the effects of soil permeability variations during the liquefaction phenomenon. The numerical model was validated by simulating a number of well-documented geotechnical centrifuge tests with different relative density of sand, base acceleration time history, and surface... 

    Design and Simulation of Cryogenic Spiral Heat-exchanger for Gas Liquefaction Plant

    , M.Sc. Thesis Sharif University of Technology Rajabi, Vahid (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Heat exchangers are one of the most important components used in liquefaction cycles and overall efficiency of the cycle mainly depends on the heat exchangers effectiveness. It has been shown that the effectiveness of these equipments should be high enough to be able to liquefy a gas. Spiral heat exchangers are used frequently in cryogenic industry and specially in Helium liquefaction industry due to their specific characteristics, however according to literature review it turns out that little study is done in the field of simulation and geometrical parameter investigation of these kind of heat exchangers, so in this study the design and simulation of these cryogenics heat exchangers are... 

    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)
    Abstract
    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... 

    Effect of different parameters on steady state and monotonic liquefaction of gravelly soils

    , Article Geotechnical Special Publication, 17 March 2015 through 21 March 2015 ; Volume GSP 256 , March , 2015 , Pages 2034-2048 ; 08950563 (ISSN) ; 9780784479087 (ISBN) Payan, M ; Ayoubi, P ; Mirmo'Azen, S. M ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2015
    Abstract
    In the current research, the main concern is to verify the behavior of gravelly soils. To that matter, with taking use of CU triaxial tests and variations in parameters of interest, gradation, relative density, isotropic pressure and anisotropy of consolidation during the tests, the effects on the steady state condition and monotonic liquefaction of gravelly soils are investigated. The test results indicated that as the isotropic pressure increases, percentage increase of steady state strength resulting from the increase of relative density will decrease. Moreover, with the increase of anisotropy of consolidation, the effect of relative density on steady state strength and built-up pore... 

    Investigation of effective parameters on the performance of the helium liquefaction cycle

    , Article International Journal of Heat and Technology ; Volume 37, Issue 4 , 2019 , Pages 1009-1018 ; 03928764 (ISSN) Larijani, M. A ; Eslami, M ; Afshin, H ; Sharif University of Technology
    International Information and Engineering Technology Association  2019
    Abstract
    Due to its unique properties, helium has wide application in different industries and scientific fields, which has turned it into a strategic material. Helium liquefaction plants include wide temperature range from 300 k to 4.2 k, so these plants have high energy consumption. A lot of studies have done to optimize the operation of these cycles. In this research, an exergy analysis is performed for a liquid helium production plant. The optimal performance of 3 and 4 stage cycles is extracted using parametric study and the results are compared with those of Collins dual-expander cycle. The results show that by increasing the number of cooling stages, not only the compressor optimum discharge... 

    Investigation of effective parameters on the performance of the helium liquefaction cycle

    , Article International Journal of Heat and Technology ; Volume 37, Issue 4 , 2019 , Pages 1009-1018 ; 03928764 (ISSN) Larijani, M. A ; Eslami, M ; Afshin, H ; Sharif University of Technology
    International Information and Engineering Technology Association  2019
    Abstract
    Due to its unique properties, helium has wide application in different industries and scientific fields, which has turned it into a strategic material. Helium liquefaction plants include wide temperature range from 300 k to 4.2 k, so these plants have high energy consumption. A lot of studies have done to optimize the operation of these cycles. In this research, an exergy analysis is performed for a liquid helium production plant. The optimal performance of 3 and 4 stage cycles is extracted using parametric study and the results are compared with those of Collins dual-expander cycle. The results show that by increasing the number of cooling stages, not only the compressor optimum discharge... 

    Requirements for soil-specific correlation between shear wave velocity and liquefaction resistance of sands

    , Article Soil Dynamics and Earthquake Engineering ; Vol. 57, issue , 2014 , pp. 152-163 ; ISSN: 02677261 Ahmadi, M. M ; Akbari Paydar, N ; Sharif University of Technology
    Abstract
    The application of the simplified method for evaluating the liquefaction potential based on shear wave velocity measurements has increased substantially due to its advantages, especially for microzonation of liquefaction potential. In the simplified method, a curve is proposed to correlate the cyclic resistance ratio (CRR) with overburden stress-corrected shear wave velocity (Vs1). However, the uniqueness of this curve for all types of soils is questionable. The objective of this research is to study whether the correlation between CRR and Vs1 is unique or not. Besides, the necessity of developing the soil-specific correlations is also investigated. Based on laboratory test data, a new... 

    Numerical investigation on the behavior of the gravity waterfront structures under earthquake loading

    , Article Ocean Engineering ; Volume 106 , September , 2015 , Pages 152-160 ; 00298018 (ISSN) Khosrojerdi, M ; Pak, A ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    Abstract Lateral Spreading, which usually occurs as a consequence of liquefaction in gently sloped loose saturated sand layers, is known to be a major source of earthquake-induced damages to structures such as quay walls, bridge piers, pipelines, and highway/railways. Therefore evaluation of the liquefaction potential and using appropriate methods for prediction of the adverse consequences of lateral spreading is of great importance. In this study, numerical modeling has been used to study lateral spreading phenomenon behind rigid waterfront structures. Coupled dynamic field equations of the extended Biot's theory with u-P formulation are used for simulating the phenomenon. A fully coupled... 

    Liquefaction evaluation based on CPTu soil classification chart

    , Article Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering: The Academia and Practice of Geotechnical Engineering, 5 October 2009 through 9 October 2009, Alexandria ; Volume 2 , 2009 , Pages 1028-1031 ; 9781607500315 (ISBN) Ahmadi, M. M ; Eslami, A ; Kangarani, M. R ; Sharif University of Technology
    Abstract
    Liquefaction is one of the most serious geotechnical hazards that may cause irreparable and financial damages. Based on in-situ testing results, several methods have been developed to evaluate the liquefaction potential. Due to continuous and repeated records, the piezocone (CPTu) has gained wide acceptance among other in-situ tests in geotechnical practice. In this paper, a new approach is proposed for liquefaction potential evaluation based on CPTu results. The new approach is verified by ten CPTu soundings (case histories) derived from different sites. By analyzing the liquefied sites, an area on the soil classification charts was introduced in this paper, showing the soil types which are... 

    Numerical Study on the Effects of Liquefaction Induced Lateral Spreading on Rigid Waterfront Structures

    , M.Sc. Thesis Sharif University of Technology Khosrojerdi, Mahsa (Author) ; Pak, Ali (Supervisor)
    Abstract
    Lateral Spreading, which usually occurs as a consequence of liquefaction in gently sloped loose saturated sand layers, is known to be a major source of earthquake-induced damages to structures such as bridge piers, quay walls, pipelines and highway/railway. Therefore, evaluation of liquefaction potential and using appropriate methods for prediction of the adverse events of lateral spreading is of great importance. In this study, numerical modeling has been used to study of lateral spreading phenomenon behind rigid waterfront structures. In order to perform a numerical modeling of lateral spreading and also designing the structures exposed to its effects, the interaction of the soil solid... 

    Numerical Simulation of Effect of Lateral Spreading Due to Liquefaction on Piles and Estimate Soil Lateral Displacement Pattern by Image Processing

    , M.Sc. Thesis Sharif University of Technology Sayaf, Hiva (Author) ; Haeri, Mohsen (Supervisor)
    Abstract
    In recent earthquakes piles have been severely damaged due to liquefaction-induced lateral spreading. Liquefaction causes lateral spreading in gently sloped saturated soft granular soils, leading to significant damage in structures and deep foundations. Although in recent years many studies have focused on different aspects of this phenomenon, the complex nature of the dynamic interaction between piles and liquefied soil is not yet fully understood. This potential damages are of high degree of importance in southern and northern coastal areas of Iran where several ports and critical facilities are located. The present study focuses on the behavior of a 2x2 pile group against lateral loads... 

    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)
    Abstract
    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... 

    The Effect of Fines Content and its Type on Shear Wave Velocity and Liquefaction Resistance of Sandy Soils

    , Ph.D. Dissertation Sharif University of Technology Akbari Paydar, Nima (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    Abstract
    Liquefaction is one of the most destructive geotechnical phenomena, and so the determination of soil liquefaction is very important. Shear wave velocity measurement is one of the methods of the soil liquefaction potential evaluation. The use of this method has increased substantially in recent years, due to its advantages compared to other methods, especially for microzonation of liquefaction potential. However, proposed curves for liquefaction evaluation which are based on the shear wave velocity measurement are more conservative than curves based on SPT and CPT, especially for sands containing fines. Local information from sites that have been liquefied previously and the shear wave... 

    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)
    Abstract
    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... 

    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)
    Abstract
    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... 

    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
    Abstract
    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
    Abstract
    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...