Search for: soil-water-retention
0.004 seconds

    Use of Bio-Cementation for Reducing Land Subsidence

    , M.Sc. Thesis Sharif University of Technology Abed, Mahrooz (Author) ; Khosravi, Ali (Supervisor) ; Pak, Ali (Supervisor) ; Ghobadi Nejad, Zahra ($item.subfieldsMap.e)
    Land subsidence is a gradual settling or sudden sinking of the land surface from changes that take place underground. There are different causes of land subsidence; most notably, groundwater overdraft and severe weather conditions. Subsidence of the land surface due to ground water overdraft is caused by an increase in the intergranular pressure in unconsolidated aquifers, which results in a loss of buoyancy of solid particles in the zone dewatered by the falling water table and accordingly compaction of the aquifer. In this study, an experimental approach was developed to examine applicability of Microbially induced carbonate precipitation (MICP) for land subsidence control under... 

    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... 

    Development of a New Analytical Model based on Soil-water Retention Curve Microstructure Considering the Effects of Osmotic Potential

    , M.Sc. Thesis Sharif University of Technology Golaghaei Darzi, Ali (Author) ; Sadeghi, Hamed (Supervisor)
    The soil-water retention curves (SWRC) is an unsaturated soil mechanics hydro chemical state surface, which expresses the relationship between the soil suction and water content. The soil-water retention curve could describe the water adsorption and desorption process that happened in soils. The difference between the desorption or drying retention curve and the adsorption or wetting retention curves in a specific soil specimen indicates the hydraulic hysteresis phenomenon. Generally, the amount of water remaining in the drying process is greater than the amount of water adsorbed in the wetting process at a certain amount of suction. Suction due to the combined effects of capillary and... 

    In-situ Stabilization of Collapsible Soil Using Grouting

    , M.Sc. Thesis Sharif University of Technology Sharifimanesh, Mohamad Javad (Author) ; Haeri, Mohsen (Supervisor)
    The aim of this study is to investigate the feasibility of in-situ stabilization of collapsible soil using grouting. Collapsible soils are a type of problematic soils that are found mostly in arid and semi-arid regions. Loess is stable in its natural unsaturated state, but when it is inundated under a sufficient stress, it will suffer a severe volume reduction due to reduction in matric suction and dissolution of its cementious bonds in water. So, finding a method for in situe remmediation of such a soil is very important especially for the built environments. The collapsible soil used in this study is a loessial soil sampled from the northeast of Golestan province, Iran. The undisturbed... 

    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... 

    A semi-empirical shear strength model for infilled rock fractures with infills in an unsaturated state

    , Article Geotechnical Frontiers 2017, 12 March 2017 through 15 March 2017 ; Issue GSP 280 , 2017 , Pages 529-538 ; 08950563 (ISSN) Khosravi, A ; Mousavi, S ; Khosravi, M ; Brandon T. L ; Valentine R. J ; 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
    Based on the results of recent studies, 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 paper describes a semi-empirical equation to interpret the effects of wall-roughed nature of the fractures and presence of partially saturated fine materials within the fractures on the behavior of infilled rock fractures during shear. The proposed equation incorporates the soil-water retention curve parameters as... 

    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... 

    Hysteresis of soil water retention and shrinkage behaviour for various salt concentrations

    , Article Geotechnique Letters ; Volume 11, Issue 1 , 2021 , Pages 21-29 ; 20452543 (ISSN) Sadeghi, H ; Nasiri, H ; Sharif University of Technology
    ICE Publishing  2021
    Laboratory investigation on the influence of solute concentration on the soil water-retention curve (SWRC) and volumetric behaviour of expansive soils has received much attention in recent years due to increasing environmental pollution. However, most studies only considered applying wetting or drying path with almost no attention to hydraulic hysteresis. Furthermore, these studies have focused on examining expansive soils and only marginal effort has been devoted to collapsible soils. Therefore, the main objective of this study is to systematically explore the SWRC and shrinkage characteristics of an artificially made collapsible soil at various molar concentrations. The tests were... 

    A Micro-structural Study on Hydro-mechanical Behavior of Loess

    , Ph.D. Dissertation Sharif University of Technology Sadeghi, Hamed (Author) ; Jafarzadeh, Fardin (Supervisor) ; W. W. NG, Charles (Supervisor)
    Loess soil layers in semi-arid to arid areas have been deposited through the accumulation of aeolian sediments, resulted in a special metastable and open structure being usually unsaturated in nature. Since naturally occurred loess is widespread, it has been recently considered as a promising resource for constructing earth-fill structures. However, due to different microstructures of intact and recompacted loess, different responses to hydraulic and mechanical loading would be expected. Up to now, the hydro-mechanical behavior of loess from different perspectives has not been linked to its microstructural characteristics. The current research, therefore, aims to provide insight into the... 

    Investigation of the Effects Of Microbially-Induced Calcium Carbonate Precipitation on the Soil-Water Retention Curve and Changes of Small Strain Shear Modulus of Unsaturated Sand During Drying Path

    , M.Sc. Thesis Sharif University of Technology Jahanbakhsh, Yashar (Author) ; Pak, Ali (Supervisor) ; Khosravi, Ali (Supervisor) ; Ghobadi Nejad, Zahra (Supervisor)
    Microbially-induced calcium carbonate precipitation is a low-cost, environmentally friendly, novel ground improvement technique that has received much attention in recent years. Most studies on biological soil stabilization have investigated the mechanical and hydraulic behavior of soils in dry and saturated conditions. However, the behavior of soils stabilized by this method in the unsaturated state should be of immense concern through the extent of unsaturated soils in nature. Therefore, this study aims to investigate the effects of microbially-induced calcium carbonate precipitation on the soil-water retention curve and changes of small strain shear modulus of unsaturated cemented and... 

    Laboratory Investigation of the Effects of Sodium Chloride Concentration on Soil Water Retention Curve and Volumetric behavior Using an Unsaturated Automatic Oedometer

    , M.Sc. Thesis Sharif University of Technology Nasiri, Hamed (Author) ; Sadeghi, Hamed (Supervisor)
    Laboratory studies to investigate the effects of different saline concentrations (such as sodium chloride or calcium chloride) on the soil water retention behavior of clayey soils and their volumetric changes have received much attention recently. However, many previous studies have investigated these effects in only one path of the SWRC (wetting or drying path) and the effects of saline concentration on hydraulic hysteresis have not been considered. In addition, researchers have frequently studied these effects on SWRC on clay samples, and little research has been done on collapsible soils. Therefore, the most important purpose of this study is to investigate the effects of increasing... 

    Study of the Shear Stress Effect on the Behavior of Collapsible Soils and Introducing an Innovative Consecutive Model: “Three linear Stages” to Predict Behavior of Gorgan Loess

    , M.Sc. Thesis Sharif University of Technology Saberi, Saeed (Author) ; Haeri, Mohsen (Supervisor)
    In all five continents, existence of collapsible soils such as Loess has been reported. These kinds of soils have mutual properties such as open structure, high void ratio and low dry density. Collapsible soils are always at risk of experiencing significant reduction in volume due to increasing water content or degree of saturation. Hence, this kind of soil can lead to serious problems including reduce of load bearing capacity, excessive deformation and failure of foundations.Collapsible soils exist in several regions of Iran. Consequently, researching their properties is a key point of geotechnical studies in our country. Hence, in past 10 years, several studies have been conducted by... 

    A Microstructural Investigation on the Influence of Pore Fluid Osmotic Potential on Volume Changes and Soil Water Retention Curve, Low Plasticity Clay

    , M.Sc. Thesis Sharif University of Technology Heydari, Ali (Author) ; Sadeghi, Hamed (Supervisor)
    Understanding many issues related to environmental geotechnics and soil sciences such as: instability and collapse of soil slopes, sinkholes, leakage from landfills and isolation of nuclear landfills, and optimization Agricultural processing depends on our knowledge of the behavior of unsaturated soils and their volume changes. To better understand the behavior of unsaturated soils, it is important to study the soil-water retention curve (SWRC) and the factors affecting it. These include factors such as porosity, grain size distribution, soil minerals, pore size distribution, and pore water chemistry, which affect soil-water retention curves and volume changes. Since the simultaneous effect... 

    Numerical Modeling of Stability and Transport of Soluble Contaminants in Tailings Dams under Coupled Hydro-Chemical Processes (A Case Study of Sarcheshmeh Tailings Dam)

    , M.Sc. Thesis Sharif University of Technology Anbarestani, Mona (Author) ; Sadeghi, Hamed (Supervisor)
    The instability and contamination leakage through tailings dams is one of the major problems of them. These dams are usually constructed through self-consolidation with minimum compaction effort, so special attention must be given to the stability of these structures. In addition, tailings dams contain considerable amounts of metals and chemically soluble contaminants resulting from mining processes in their reservoirs, making them more likely to leak contamination from the dam's foundation and body, causing pollution downstream. The infiltration of various chemical contaminants into the soil may alter its hydraulic and resistance properties. Laboratory studies have shown that pore solution... 

    The hydro-mechanical behavior of infilled rock joints with fill materials in unsaturated conditions

    , Article Geotechnical Special Publication ; Issue 231 , 3-7 March , 2013 , Pages 129-138 ; 08950563 (ISSN) ; 9780784412787 (ISBN) Khosravi, A ; Khosravi, M ; Meehan, C. L ; Sharif University of Technology
    The existence, nature, and frequency of discontinuities in a given rock mass typically govern the overall shear behavior of the rock. The presence of fine materials such as clay and silt within rock joints, whether the product of infilling or natural weathering processes, can have a significant effect on the shear behavior of the rock joint. When assessing the strength of filled rock joints, it is therefore necessary to determine the separate strengths of both the rock and the joint infill material, and to also have a good understanding of the interaction between the two for various joint geometries and levels of infilling. Much of the existing research on the shear strength of filled rock... 

    A numerical study on the effect of salinity on stability of an unsaturated railway embankment under rainfall

    , Article 4th European Conference on Unsaturated Soils, E-UNSAT 2020, 19 October 2020 through 21 October 2020 ; Volume 195 , 2020 Kolahdooz, A ; Sadeghi, H ; Ahmadi, M. M ; GDS; VJ Tech ; Sharif University of Technology
    EDP Sciences  2020
    Dispersive soils, as one of the main categories of problematic soils, can be found in some parts of the earth, such as the eastern-south of Iran, nearby the Gulf of Oman. One of the most important factors enhancing the dispersive potential is the existence of dissolved salts in the soil water. The main objective of this study is to explore the influence of water salinity on the instability of a railway embankment due to rainfall infiltration. In order to achieve this goal, the embankment resting on a dispersive stratum is numerically modeled and subjected to transient infiltration flow. The effect of dispersion is simplified through variations in the soil-water retention curve with salinity.... 

    Effects of initial suction and degree of saturation on dynamic properties of sand at large strain

    , Article Scientia Iranica ; Volume 28, Issue 1 , 2021 , Pages 156-174 ; 10263098 (ISSN) Jafarzadeh, F ; Ahmadinezhad, A ; Sadeghi, H ; Sharif University of Technology
    Sharif University of Technology  2021
    Soil deposits may experience different hydraulic states in terms of suction (φ) and saturation degree (Sr) while being subjected to large strain caused by dynamic loading during earthquakes. This phenomenon was investigated by considering the effects of initial φ, initial (Sr, sample preparation method, drainage condition, and cycle number (N) on dynamic properties. Shear modulus (G) and damping ratio (D) were specifically studied for unsaturated sand using a modified cyclic simple shear device for all zones of Soil Water Retention Curve (SWRC). Results revealed the relative significance of both φ and Sr in relation to SWRC on observed trends in G and D. Based on the analysis of some results... 

    Effect of Subsequent Drying and Wetting on Small Strain Shear Modulus of Unsaturated Silty Soils Using Bender Element

    , M.Sc. Thesis Sharif University of Technology Hashemi, Amir Hossein (Author) ; Khosravi, Ali (Supervisor)
    Evaluation of the seismic-induced settlement of an unsaturated soil layer depends on several variables, among which the small strain shear modulus, Gmax, and soil’s state of stress have been demonstrated to be of particular significance. Recent interpretation of trends in Gmax revealed considerable effects of the degree of saturation and hydraulic hysteresis on the shear stiffness of soils in unsaturated states. Accordingly, the soil layer is expected to experience different settlement behaviors depending on the soil saturation and seasonal weathering conditions. In this study, a semi-empirical formulation was adapted to extend an existing Gmax model to infer hysteretic effects along... 

    Assessing the Hydro-mechanical Behavior of Undisturbed Collapsible Soils by Conducting Unsaturated Odeometer Tests Case Study: Gorgan Loess

    , M.Sc. Thesis Sharif University of Technology Beigi, Majid (Author) ; Haeri, Mohsen (Supervisor)
    The deposits in many regions in Iran, particularly eastern zones like Golestan, Semnan, Khorasan, Yazd, Kerman, Hormozgan, Sistan and Baluchestan provinces consist of Aeolian 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... 

    Hydraulic Behavior of Infilled Fractured Rocks under Unsaturated Conditions

    , Article Joint Geotechnical and Structural Engineering Congress 2016, 14 February 2016 through 17 February 2016 ; 2016 , Pages 1708-1718 ; 9780784479742 (ISBN) Khosravi, A ; Mousavi, S ; Dadashi Serej, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE) 
    Slip along fractures or hydrothermal alternation may lead to formation of weak layers of soils intercalated between the existing rock layers. In this situation, characterization of the behavior of rock fractures requires consideration of a complicated interaction of mechanical properties and geometrical characteristics of the fracture, coupled together with the properties of infill materials. Of the most important parameters which may considerably affect the behavior of an infilled fractured rock are the hydraulic properties of the infill material. These properties reflect the water retention ability of the infill material and determine the meniscus arrangements between the particles. This...