Sharif Digital Repository

Pile foundations suffered severe damages during the past earthquakes in all around the world. These damages were more severe in laterally spreading grounds and they mostly have been observed in gently sloping grounds and coastal areas. In these cases, Pile foundations not only are subjected to structures inertial loads and kinematic loads of liquefied soil but also lateral spreading intensifies damages. Thus, in the recent decade, several researches have been conducted to investigate the behavior of pile foundations in liquefiable and laterally spreading grounds, however, some uncertainties still remain in modeling of soil-pile interaction. In this study, the effects of liquefaction- induced... 

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... 

Initial static shear stress caused by slopes or nearby structures' foundations can affect the behavior of the soil which is concerned many investigators during previous three decade. In this investigation, the effect of initial static shear stress on the liquefaction resistance of Babolsar sand has been probed using cyclic simple shear tests. Three different initial relative densities (Dr0=20%, 40% and 60%) and three different initial normal stresses (σv0= 50, 150 and 250 kPa) were considered in tests and four various initial static shear ratios (α) ranging between 0.0 and 0.3 were applied which leads to more than 190 distinct experiments. All tests were conducted under constant volume and... 

In this research, the effects of Rayleigh waves on the response of typical three-dimensional concrete faced rock-fill dams (CFRDs), considering dam-foundation interaction and spatial variability of earthquake ground motion are investigated. The time history of Loma Prieta earthquake (Gilroy 1 station) is used as input excitation. The dam is considered to be located in a prismatic canyon with trapezoidal cross-section. A substructuring method, in which the unbounded soil is modeled by the scaled boundary finite-element method (SBFEM), is used to obtain scattered motion and interaction forces along the canyon. Non-linear model is used for rock fill... 

Soil liquefaction is a phenomenon in which soil loses much of its strength or stiffness for a generally short time but nevertheless long enough for liquefaction to be the cause of many losses. Thus, many researchers have worked on the factors which affect this phenomenon. Effects of initial static shear stress on liquefaction strength of loose and medium dense Babolsar sand specimens were investigated in this study. Babolsar sand is fine to medium uniform sand classified as SP in USCS. Tests were performed with cyclic simple shear and static triaxial devices. All tests were performed under consolidated undrained conditions. Cyclic simple shear tests were performed under constant vertical... 

Soil nailing is an in-situ technique of mechanically stabilizing soil masses which has been used in France, Germany, United states, and recently in Iran. A review of literature shows that Soil-Nailed walls have performed well during strong ground motions in comparison with the gravity retaining structures. After the 1989 Loma Prieta earthquake, minor signs of distress or corresponding deformation were found on the Soil-Nailed walls, indicating excellent performance of such structures during moderate and strong shakings. These observations indicate that Soil-Nailed walls have an inherent satisfactory seismic response. This has been attributed to the intrinsic flexibility of the Soil-Nailed... 

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... 

Gravelly soils are among the ones that can be found all over the world and have been investigated by many researchers in recent years. Although many investigations have been performed to clarify the behaviour of these soils, but still there are a lot of shortge of information about the steady state and liquefaction potential of them. In this research, to verify the behaviour of gravelly soils, static triaxial apparatus has been used. The tests performed in this research are devided into 2 groups: Consolidated Undrained tests (CU) and Consolidated Drainedtests(CD). In group 1 tests, all 4 parameters involving gradation, relative density, isotropic pressure and anisotropy of consolidation... 

Monitoring is of particular importance after impounding and during dam operation. In all large dams, by installation of the required instruments the pore pressure, soil mass pressure and displacement during construction, first impounding and operation are measured, then the performance of dam will be analyzed and evaluated. The aim of this study is to evaluate the performance of the "Gavoshan" dam, which has an important role on agriculture development and drinking water supply at west part of Country. To reach this, the values resulting from instruments have been implemented by FLAC software, using "Back Analysis" method. However, this assessment is complete when "back analysis" method is... 

The behavior of pile foundations under earthquake loading is an important issue that affects the performance of structures. Design procedures have been developed for evaluating pile behavior under earthquake loading; however, the application of these procedures to cases involving liquefiable ground is uncertain. The performance of piles in liquefied soil layers is much more complex than that of non-liquefying soil layers because not only the superstructure and the surrounding soil exert different dynamic loads on pile, but also the stiffness and shear strength of surrounding soil diminishes over time due to both non-linear behavior of soil and pore water pressure generation. In this... 

Collapsible soils such as loess, which are naturally found unsaturated, are kind of problematic soils that undergo sudden and noticeable decrease in volume under increasing stress at constant moisture, increasing moisture at constant stress, or increase in both of them. This kind of soil can be found in some parts of Iran such as plain of Gorgan. To fulfill the main purpose of this study, evaluating the effect of cementation on collapse behavior of loess of Gorgan, some oedometer tests under controlled matric suction were performed on reconstituted samples without and with lime. The lime was added for stabilizing of the collapsible materials and the amount was chosen to be %3 by weight of... 

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 ... 

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... 

The study of the behavior of gravelly soil in undrained condition has been a major topic for researchers for decades. Liquefaction in gravelly soils in recent earthquake has exposed the importance and necessity of investigation on undrained the behavior of gravely soils in earthquakes. In this research, undrained behavior of gravely soils and the effects of initial static shear stress on their behavior have been investigated. In this experimental research a gravelly soil (GP) performed and a triaxial apparatus is used. All tests are performed under consolidated undraiend condition and the specimens are prepared by wet tamping method. The diameter of the specimen was 10 cm and the height was... 

In the areas where the soil beneath the foundation is made of loose to semi-consolidated sand or noncohesive silts, Buildings and bridges are usually built on the pile foundations. One important issue that must be considered in the design of piles in saturated sandy soils, is liquefaction potential of saturated sandy soil under earthquake loads. During the earthquake, saturated sandy soil faces the sudden loss of shear strength in other word it liquifies . Liquefied Soil acts like a viscous fluid. This behaviour considerably increases the soil deformation and consequently the widespread disruption of soil layers, causes large deformation and applies great amount of forces on the piles... 

Liquefaction has a profound effect on buildings, bridges, buried pipes and other engineering structures. This phenomenon can lead to the sliding of huge earth masses, submersion and bending of substantial structures, uplift of buried light structures and collapse of retaining walls. In recorded earthquakes, liquefaction has caused major damage to structures and deep foundations, proving that pile foundations are not designed to withstand at liquefaction condition. Considerable damages in pile foundations due to liquefaction in destructive earthquakes has called for extensive study and research concerning the behavior and response of piles under the influence of liquefaction, resulting in... 

In this research, the effect of various parameters on the behavior of silty sands is evaluated under special loading conditions. To evaluate these parameters, the hollow cylinder apparatus of the Advanced soil mechanics at Sharif University is used. In this research the effect of principal stress directions, initial anisotropic consolidation, silt content, effective mean normal consolidation stress and intermediate principal stress are studied on the behavior of silty sands including the strength and pore water pressure. In order to evaluate these parameters, the specimens are made with wet tamping method with 0, 10, 20, 30 and 40 percent of silt. Before applying shear load to specimen, the... 

Foundation is the lowest load-bearing part of a structure and a part of underneath soil that is affected by the structure load. In fact, foundation transfers the loads from the superstructure to the substructure, preventing excessive settlement of soil or stresses exceeding soil bearing capacity. Indeed, almost all structures are placed on the ground, therefore the effects of soil and structure on each other, which is known as Soil Structure Interaction (SSI), is considered as a key factor in many important and engineered structures. In contrast to structures on a rigid footing, a flexible foundation may show stiffness degradation along with an increase of damping and natural period of the... 

Deformation induced by deep excavations is one of the most important factors in investigating function of retaining structure constructed in urban areas. Predicting content of deformation induced by deep excavations is a fundamental and important step in designing of retaining structures. A prestressed grouted ground anchor is a structural element installed in soil or rock that is used to transmit an applied tensile load into the ground. In this study, effective factors in deformation induced by deep excavation reinforced by method of anchoring is analyzed by application of numerical study based on finite element method by using PLAXIS software, and results are compared. The seismic... 

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...