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liquefaction
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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) ; Kavand, A ; Rahmani, I ; Torabi, H ; Sharif University of Technology
2012
Abstract
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...
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) ; Ghasemi Fare, O ; Pak, A ; Sharif University of Technology
2012
Abstract
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...
Evaluation of variation of permeability in liquefiable soil under earthquake loading
, Article Computers and Geotechnics ; Volume 40 , 2012 , Pages 74-88 ; 0266352X (ISSN) ; Pak, A ; Taiebat, M ; Jeremić, B ; Sharif University of Technology
2012
Abstract
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...
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) ; Pak, A ; Sharif University of Technology
2010
Abstract
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...
Numerical investigation of the effects of soil densification on the reduction of liquefaction-induced settlement of shallow foundations
, Article Scientia Iranica ; Volume 16, Issue 4 A , 2009 , Pages 331-339 ; 10263098 (ISSN) ; Pak, A ; Sharif University of Technology
2009
Abstract
The liquefaction phenomenon is usually accompanied by a large amount of settlement. Based on the observations made in past earthquakes, ground improvement by densification is one of the most useful approaches to reduce the liquefaction-induced settlement. Currently, there is no analytical solution for evaluation of the amount of settlement and tilting of footings that are constructed on densified ground surrounded by liquefiable soil. A number of factors, such as underlying soil properties, dimensions of the footing and earthquake loading characteristics, cause the problem to become complicated. In this paper, the dynamic response of shallow foundations on both liquefiable and...
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) ; Shahir, H ; Pak, A ; Sharif University of Technology
2007
Abstract
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...
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) ; Khalili, A ; Sadati, N ; Sharif University of Technology
2006
Abstract
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...
Steady state and liquefaction characteristics of gravely sands
, Article Geotechnical and Geological Engineering ; Volume 23, Issue 2 , 2005 , Pages 141-156 ; 09603182 (ISSN) ; Hamidi, A ; Sharif University of Technology
2005
Abstract
Liquefaction of loose and saturated soils during earthquakes and strong ground motions has been a major cause of damage to buildings and earth embankments as well as other civil engineering structures. In order to evaluate the liquefaction potential and steady state characteristics of gravely sand of south west Tehran, a subsoil exploration program conducted dividing the region into 10 zones. In each zone of 500 m × 500 m a borehole of 20 m deep was drilled. SPT was performed at one meter intervals in each borehole and a total of 200 samples were recovered. Soils of similar grain size distribution have been considered to have similar steady state characteristics,therefore consolidated...
Risk analysis of liquefaction potential in South West Tehran
, Article Amirkabir (Journal of Science and Technology) ; Volume 15, Issue 58 D , 2004 , Pages 521-534 ; 10150951 (ISSN) ; Haeri, S. M ; Shirazi, A ; Olyaei, M. N ; Bakhshi, A ; Sharif University of Technology
2004
Investigation of Effects of Successive Liquefaction Occurrence on Piles Located in Level Ground With an Inclined Base Layer with Using Stone Cloumns – a Physical 1g Shake Table and Laminar Shear Box Model
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen (Supervisor)
Abstract
Lateral spreading is defined as finite lateral displacement of mildly sloping grounds or those ending in free faces induced by liquefaction. The phenomenon of lateral spreading caused by liquefaction in coastal areas and mildly sloping grounds has caused significant damage to deep foundations of engineering structures such as bridge and buildings in severe earthquakes. Since earthquake is unavoidable, therefore, it is necessary to provide appropriate solution to reduce the effects of liquefaction induced lateral spreading. Despite conducting various laboratory and field studies by previous researchers, there is still no comprehensive approach to evaluate the effects of lateral spreading on...
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 ; Haeri, Mohsen (Supervisor) ; Kavand, Ali (Co-Supervisor)
Abstract
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...
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 ; Haeri, Mohsen (Supervisor)
Abstract
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...
Design and Optimization of Helium Extraction and Liquefaction Cycle from Natural Gas by Direct Method
, Ph.D. Dissertation Sharif University of Technology ; Afshin, Hossein (Supervisor)
Abstract
Helium is known as a strategic material due to its unique properties and applications in the development of advanced industries. Currently, natural gas is the only source from which helium can be produced economically. The United States, Qatar, Algeria, and Russia have the largest share of helium production, respectively. In this research, the process of helium extraction from natural gas and its liquefaction, independent of LNG production based on helium in South Pars gas of Iran, which is the largest helium reservoir in the world, were designed and simulated.In the helium liquefaction section, the speed and accuracy of the process simulation were improved by developing a home code based on...
A Numerical Model Development for Cryogenic Spiral Wound Heat Exchanger Design Considering Temperature dependent thermo-physical properties, Heat Leakage, and Longitudinal Heat Conduction
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor)
Abstract
Cryogenic temperature is below than 123 Kelvin and any physical study that occurs below this temperature is Cryogenic science. Cryogenic has varaiety of application in medical, industry, food, oil and gas etc. Based on this paper and its relavant source spiral wound HE is one of the most optimum HE for cryogenic application specially for helium liquification cycle. In order to liquefy helium in helium cycle efficiency of spiral wound HE shall be over than 85 percent. For this reason and special fluid behavour in low temperature considering property variation, heat in leak and axial conduction is vital for calculating efficiency in cryogenic temperature of helium liquification cycle. In this...
Numerical Investigation of Nitrogen Condensation in a Two-phase Vortex Tube
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
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....
Effects of Lateral Spreading on Two 2×2 Pile Groups (with and Without Lumped Mass) Using Shaking Table and Laminar Shear Box
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen (Supervisor)
Abstract
Lateral spreading is the downstream movement of mild slopes or free fronts occurring due to soil liquefaction during a dynamic loading such as an earthquake. The magnitude of this movement can be from a few centimeters to tens of meters depending on parameters such as slope length, soil type, cyclic loading intensity, etc. Large displacements caused by this phenomenon can cause severe damage to some structures and infrastructures located in the direction of their movement. Numerous articles and reports of damage caused by the lateral spreading of soil have been presented during several earthquakes. Understanding this phenomenon and observing and testing its effective parameters can help...
Investigation of Mixed Refrigerant Behavior in Multistream Plate-Fin Heat Exchangers
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Hassan (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
Abstract
Multistream plate-fin heat exchangers are used to supply the energy required by process units in the oil and gas industry. improving their performance is very important to reduce operating costs. In many applications, mixed refrigerants have replaced to improve the performance of plate-fin heat ecxhangers; Because the greater adaptability of the mixed refrigerant to the required refrigeration conditions that reduces the exergy losses. The Prico liquefaction cycle is one of the most commercial and commonly used liquefaction cycles. One of the most important parameters in designing a Prico liquefaction cycle is the molar percentage of the mixed refrigerant components. Proper determination of...
Probabilistic Evaluation of Seismic Soil Liquefaction in Sands Using Cone Penetration Test (CPT)Data
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
More than half a century has passed since the start of research on seismic liquefaction phenomenon in cohesionless soils, and various researchers has proposed different correlations for liquefaction prediction based on in situ tests. However, there still exists a great uncertainty in liquefaction prediction correlations, and liquefaction still occurs in different parts of the world. Hence, the main objective of this research is to reduce uncertainty in seismic liquefaction initiation correlations. While the technical literature indicates that soil resistance can alter due to liquefaction and shaking events and soil resistance after the liquefaction is not necessarily indicative of it prior...
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 ; 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...
Assessing Liquefaction Potential Based on Cone Penetration Test Results
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
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...