Search for: unsaturated-soil
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    Collapsible Behavior of Gorgan Loess Using Odeometer

    , M.Sc. Thesis Sharif University of Technology Zamani, Atefeh (Author) ; Haeri, Mohsen (Supervisor)
    In nature, there are types of soils that when goinging under stress at constant moisture, or increase of moisture at constant stress, or change of both characters, they show a sudden and high level decrease in their volume. These type of soils are named as Collapsible soils. Iran is one of the countries that at some parts of its land collapsible soils are found. In this research by using of laboratory equipments, the volume change behavior of collapsible loess soils of Gorgan plain (North of Iran) is evaluated under increase of water content and inundation stress. In these experiments, the usual odeometer cell has been used for exploring the behaviour of collapsibility and volume change of... 

    A large plasticity deformation of unsaturated soil for 3d dynamic analysis of lower San-Fernando dam

    , Article Asian Journal of Civil Engineering ; Volume 12, Issue 1 , 2010 , Pages 1-25 ; 15630854 (ISSN) Khoei, A. R ; Anahid, M ; Zarinfar, M ; Ashouri, M ; Pak, A ; Sharif University of Technology
    In this paper, a large plasticity deformation finite element modeling is presented for three-dimensional dynamic analysis of unsaturated soils with special reference to the failure of lower San Fernando dam under the 1971 earthquake. The finite element method is applied to the governing equations for the spatial discretization, followed by a generalized Newmark scheme used for the time domain discretization. Time stepping scheme is used in the fully implicit coupled method and a direct solution procedure is used for the coupled equation system. The framework of generalized plasticity is presented and the numerical results of unsaturated soils are demonstrated based on the Pastor-Zienkiewicz... 

    Implementation of plasticity based models in dynamic analysis of earth and rockfill dams: A comparison of Pastor-Zienkiewicz and cap models

    , Article Computers and Geotechnics ; Volume 31, Issue 5 , 2004 , Pages 384-409 ; 0266352X (ISSN) Khoei, A. R ; Azami, A. R ; Haeri, S. M ; Sharif University of Technology
    Elsevier BV  2004
    In this paper, a unified finite element formulation associated with saturated and unsaturated soils is presented. The finite element method is applied to the governing equations for the spatial discretization, followed by a generalized Newmark scheme used for the time domain discretization. Time stepping scheme is used in the fully implicit coupled method and a direct solution procedure is used for the coupled equation system. The framework of generalized plasticity is presented and the numerical results of three saturated-unsaturated earth and rockfill dams are demonstrated. A comparison is performed between the Pastor-Zienkiewicz and cap plasticity models through the dynamic analysis of... 

    Numerical Modeling of the Bahavior of Unsaturated Soils with the BBM in the FLAC Software

    , M.Sc. Thesis Sharif University of Technology Mohammadi, Hojjat (Author) ; Pak, Ali (Supervisor)
    Although unsaturated soils exist all around the world, civil engineers are not familiar with unsaturated soil behavior; consequently, the soil structures they design may neither be safe nor economical. Thus, implementing unsaturated soil constitutive models to practical computer softwares can be very beneficial for geotechnical engineers. Geotechnical engineering softwares normally consider soil in saturated or dry conditions. So, their built-in constitutive models do not usually consider unsaturated soils. In this study, Barcelona Basic Model (BBM), which is developed using critical states soils mechanics principles, is implemented to the FLAC2D software. This model can simulate complex... 

    Numerical Modeling of Unsaturated Soils Behavior (Wheeler Model) in Flac Software

    , M.Sc. Thesis Sharif University of Technology Foroughi, Sina (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    The mechanical behavior of unsaturated soils is much more complex than saturated soils and the effective stress principle cannot be initially applied to them. The soils found in most parts of Tehran, Iran, are unsaturated and this underlines the importance of having access to softwares capable of analyzing such soils; despite the fact that most available softwares are unable to do so. This thesis aims at adding one of the common unsaturated soil models to a geotechnical software and use that to model and analyze earth structures such as earth dams, foundations, embankments, etc. The Wheeler model (2003) for unsaturated soils is used in this study. This model takes advantage of two... 

    Impact of Changes in Matric Suction on Dynamic Properties of Unsaturated Silty Soil from Small to Large Strain During Drying Path

    , M.Sc. Thesis Sharif University of Technology Banar, Shaya (Author) ; Haeri, Mohsen (Supervisor) ; Khosravi, Ali (Supervisor)
    Shear modulus and damping ratio are of the most important parameters for geotechnical structures during dynamic and seismic loading. Secant shear modulus is the slope of hysteresis shear stress-shear strain loop, and damping ratio is indicative of dissipation of waves energy during propagation in the soil. These parameters mainly depend on void ratio, stress state, and shear strain of the soil. Climate changes cause some drying and wetting process which changes the soil state from saturated to unsaturated form. Previous researches indicated that the shear modulus and damping ratio change with the amount of matric suction. During the drying process, the matric suction increases,therefore,... 

    Evaluation of the Behaviour of Collapsible Soils in Saturated and Unsaturated Oedometer Tests – Case Study of Gorgan Loess

    , M.Sc. Thesis Sharif University of Technology Khorshidi, Morteza (Author) ; Haeri, Mohsen (Supervisor)
    Collapsible soils are kinds of problematic soils which are susceptible to large and sudden reduction in volume upon wetting. A manifest kind of these soils is loess; catastrophic settlement of structures which are built upon it has been observed when the soil becomes wet. In this investigation the collapse potential of samples of loess taken from Gorgan, Golestan, Iran, has been studied by using unsaturated odometer tests under controlled matric suction. To this end, two modified odometer apparatus with the capability of controlling the matric suction, have been designed and developed. Undisturbed samples of soil have been tested under K0 condition, while the matric suction, volumetric... 

    Evaluation of Improvement of Collapsible Soils with Adding Lime in Conventional and Suction Controlled Oedometer tests– Case study of Gorgan Loess

    , M.Sc. Thesis Sharif University of Technology Roohparvar, Hamid Reza (Author) ; Haeri, Mohsen (Supervisor)
    Collapsible soils such as loess, sustain large stress under dry condition but they show a high level and sudden decrease in their volume by increase of moisture. So they are not suitable for construction works. This research present the utilization of different percent of lime for stabilization of gorgan loess. To this end several simple oedometer tests performed on stabilized loess and collapse potential was obtained. Also several unsaturated oedometer test performed for found the effect of matric suction on unsaturated stabilized loess. These tests were performed under constant matric suction and varring vertical stress and also constant vertical stress and varring matric suction. The... 

    Study of Stability of Unsaturated Railway Embankment Founded on Saline and Desalinated Loess

    , M.Sc. Thesis Sharif University of Technology Kolahdooz, Ali (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    Loess with a dispersion potential is one of the problematic soils of Iran. This study aims to investigate the impact of dispersion potential on the water flow in a three-phase medium and determine the effect of salinity on the stability of an unsaturated railway embankment by employing the soil-water retention curves of the materials. To satisfy this objective, the natural dispersive loess of the Chabahar region is desalinated in this study and the hydraulic properties of both saline and desalinated soils are comprehensively investigated. First, the soil-water retention curves of the materials are measured through the filter paper test method. Afterward, the saturated hydraulic conductivity... 

    Investigating the Behavior of the Group Energy Pile in Unsaturated Silty Sand Soil Using Physical Modelling

    , M.Sc. Thesis Sharif University of Technology Fardin Jafarzadeh (Author) ; Jafarzadeh, Fardin (Supervisor)
    A physical model has been developed in the advanced soil mechanic lab of the sharif university of technology. This model has been used to investigate the thermo-hydro-mechanical behavior of the group energy pile, which was embedded in the unsaturated silty sand soil. This model contains a steel soil box, 4 aluminum piles, strain gauges, the total pressure cells, the thermocouples, and the mechanical load. Three sets of tests were conducted on these piles. In the first the thermal cycles were applied on 1 pile and in the second and third tests, the number of the energy piles was 2 and 3, respectively. The result has shown there was a permanent settlement at the end of the thermal cycles.... 

    Coupled effects of suction and degree of saturation on large strain shear modulus of unsaturated sands

    , Article Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 ; Vol. 2, issue , July , 2014 , p. 1559-1564 ; 978-1-138-00150-3 Jafarzadeh, F ; Ahmadinezhad, A ; Sadeghi, H ; Sharif University of Technology
    Predictions of soil behavior in response to dynamic loads require an understanding of dynamic properties of soil. Studies on dynamic properties of unsaturated soils at large-strains are quite limited, while some dynamic loadings, like earthquakes, are in the medium to large-strain ranges. A cyclic simple shear apparatus was developed to measure large-strain shear modulus and damping ratio under different matric suction or degree of saturation. Six cyclic tests, with referring to the soil-water retention curve, were conducted on clean medium sand. Results indicated that shear modulus slightly increases when suction varies from zero up to the air entry value. Approaching the residual value, a... 

    Hydro-mechanical behavior of collapsible soils in unsaturated soil mechanics context

    , Article 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015, 9 November 2015 through 13 November 2015 ; November , 2015 , Pages 25-40 Haeri, S. M ; Association for Disaster Prevention Research; et al.; Fukuoka Convention and Visitors Bureau; Japan Society for the Promotion of Science - Grant-in-Aid for Publication of Scientific Research Results; Kyushu Regional Planning Association; The Maeda Engineering Foundation ; Sharif University of Technology
    Asian Regional Conference on Soil Mechanics and Geotechnical Engineering  2015
    This paper is related to the studies taken place during last decade to understand the intact behavior of a Collapsible Loess subjected to loading and wetting at Advanced Soil Mechanics Laboratory of Sharif University of Technology, Tehran, Iran. In this regard intact block samples are carefully taken from Hezar Pich Hill in the city of Gorgan, Iran, and various tests are performed on undisturbed specimens recovered from the intact block samples. In this way three automated unsaturated oedometer are built and a conventional triaxial apparatus is upgraded to a fully automated unsaturated triaxial device to accommodate rigorous and different stress and wetting path with continuous data... 

    Pressuremeter test in unsaturated soils: a numerical study

    , Article SN Applied Sciences ; Volume 3, Issue 4 , 2021 ; 25233971 (ISSN) Keshmiri, E ; Ahmadi, M. M ; Sharif University of Technology
    Springer Nature  2021
    The paper presents a numerical analysis of pressuremeter test in unsaturated cohesive soils. In practice, pressuremeter is commonly expanded up to 10–15% cavity strains. At these strains, limit pressure is not usually reached, and its value is estimated by extrapolation. Accordingly, authors suggest using cavity pressure at 10% strain (P10) for the interpretation of pressuremeter test rather than limit pressure. At this strain, it is also assured that plastic strain occurs around the cavity, which is crucial for the interpretations. In unsaturated soils, the moisture at which a soil is tested has a noticeable influence on the pressuremeter cavity pressure, and consequently, on the magnitude... 

    Combination of water head control and axis translation techniques in new unsaturated cyclic simple shear tests

    , Article Soil Dynamics and Earthquake Engineering ; Volume 126 , 2019 ; 02677261 (ISSN) Ahmadinezhad, A ; Jafarzadeh, F ; Sadeghi, H ; Sharif University of Technology
    Elsevier Ltd  2019
    A cyclic simple shear device was modified for testing coarse-grained soils at unsaturated conditions. A combined methodology of controlling suction for the practical range of coarse-grained soil water retention curves was adopted. Water head control method was used to accurately control suction within capillary and transition zones of such soils. The axis translation technique, on the other hand, was employed as a complementary approach to reach higher suction values within residual zone. In order to evaluate the performance of the new setup, independent cyclic tests were carried out at various initial suctions including all key points and zones along the primary drying path. The analyses of... 

    A Semi-Emperical Model for Small Starin Shear Modulus of Unsaturated Low Plasticity Soils

    , M.Sc. Thesis Sharif University of Technology Gheibi, Amin (Author) ; Khosravi, Ali (Supervisor)
    The shear modulus of soils is a key material quantity which is frequently used in the evaluation of wave propagation through soil layers in dynamic response analyses for many geotechnical systems. The shear modulus, G, is defined as the slope of the shear stress-strain hysteresis loop and is significantly influenced by the shear strain amplitude induced in a soil specimen. Of particular interest in geotechnical engineering, the value of shear modulus for strains less than 10-6 defined as the small strain shear modulus, Gmax. The early experimental studies on the shear modulus of water-saturated or dry soil showed that shear modulus is highly dependent on mean effective sress, p´, and void... 

    Development of Dynamic Simple Shear Apparatus for Small Strain Dynamic Tests on Unsaturated Granular Soils by Bender Element and ultrasonic Sensors

    , M.Sc. Thesis Sharif University of Technology Karimzadeh, Ali Akbar (Author) ; Jafarzadeh, Fardin (Supervisor)
    Shear modulus and confined modulus are important parameters for static and dynamic analysis in geotechnical applications. Elastoplastic and nonlinear constitutive models has been formulized by these parameters. Cyclic simple shear apparatus had been developed by mounting bender element and ultrasonic sensor to measure continuous shear wave and pressure wave velocities for determination of G_max and M.For this purpose two new pedestals have been fabricated on which HAE ceramic disc and sensors were mounted. A pressure control panel and a hanging column system have been designed to apply high and low matric suction with high accuracy.At first two small strain tests were conducted for... 

    Impact of Hydraulic Hysteresis on Hydro-mechanical Behaviour of Infilled Fractured Rocks in Unsaturated Condition

    , M.Sc. Thesis Sharif University of Technology Mousavi, Masoud (Author) ; Khosravi, Ali (Supervisor)
    Recent studies have shown that comprehensive characterization of the behavior of infilled rock fractures under saturated and unsaturated conditions requires knowledge of morphological details of fracture surface, as well as state of stress of infill materials and their initial innate conditions (e.g., void ratio, water content, degree of saturation and dry density). This study presents the details and typical results from a new testing approach to study the hydro-mechanical behavior of the infilled rock fractures under different stress states and saturation conditions. The new testing approach incorporates the axis translation technique for suction control, a flow pump for the measurement of... 

    Analytical Solution to Partial Differential Equations Derived from Thermo-Hydro-Mechanical Analysis

    , M.Sc. Thesis Sharif University of Technology Yazdani, Davood (Author) ; Pak, Ali (Supervisor)
    In this research an analytical and semi analytical solution to the differential eqautions derived from coupled analysis of heat transfer, moisture transfer and solid deformation in porous materials is presented. In first section, differential equations derived from Hydro-mechanical analysis of an unsaturated soil layer with limited thickness was considered and it is assumed that pore air pressure is equal to atmospheric pressure. To solve the system of equations laplace transform is used.In second section, the effect of daily changes in temperature on transient heat and moisture transfer in semi infinite layer is studied in three dimension. Energy conservation equation and pore liquid mass... 

    Investigation of Ardabil Plain Subsidence with Respect to Changes in Groundwater Level and Climate Fluctuations

    , M.Sc. Thesis Sharif University of Technology Fazel Mojtahedi, Farid (Author) ; Khosravi, Ali (Supervisor)
    The subsidence phenomenon in the past years has caused many problems and issues for the agricultural lands, roads, power transmission lines, energy etc., due to different reasons including over use of groundwater resources and changes in climate. This phenomenon has been observed in different plains of the country including the Khorasan, Kerman, Hamedan, Ghazvin and Isfahan plains and has caused many damages to infrastructure and agricultural products in the mentioned regions. In this research the main factors which have affected the subsidence phenomenon especially reduced ground water table and climate changes in Ardebil plain, are taken into account and some studies which comprise... 

    Assessing the Hydro-Mechanical Behavior of Undisturbed Collapsible Soils by Conducting Unsaturated Odeometer Tests Case Study: Northeastern Loess of Golestan Province

    , M.Sc. Thesis Sharif University of Technology Tavasoli, Iman (Author) ; Haeri, Mohsen (Supervisor)
    The deposits in many regions in Iran, particularly eastern zones like Golestan, Semnan, Yazd, Kerman, Hormozgan, Sistan and Baluchestan provinces consist of deposits of loess, which are categorized as collapsible soils. This kind of soil show sufficient shear strength and low deformability in dry or natural condition. However, if a structure is built on the soil and water seeps or infiltrates into the soil due to several reasons such as sewer leakage, water seepage or heavy precipitations in a way that its moisture reaches to a critical value, the interparticle bonds may break or the present suction in the soil may decrease in a way that the soil experiences sudden collapse, which may result...