Sharif Digital Repository

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... 

The lateral movement of a liquefiable layer on gently slopes is the most visible and devastating type of liquefaction-induced ground failure. Occurrence of liquefaction in sloping ground causes large deformations on ground surface, which may lead to several meters in some cases. Recent earthquakes have shown that this phenomenon causes severe damages to coastal structures, piers of bridges and life-lines, by exerting large lateral forces. In this research, a fully coupled two-dimensional dynamic analysis has been used to simulate the lateral spreading phenomenon and to evaluate the magnitude of deformations occurred in liquefiable soils. The critical state bounding surface elastic-plastic... 

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... 

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. Thus more studies in this regard is inevitable. The present research focuses on the discussion and analysis of two large scale shaking table tests of 2x2 and 3x3 group piles. A three layer soil profile was used for the model, consisting of one... 

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... 

Separation of the effects of the initial horizontal stress and relative density on the cone tip resistance in the sandy soils has been a complicated issue for many years. On the other hand, there is no reliable method for determining the in-situ horizontal effective stress based on the piezocone measurements in the cohesive soils, and the empirical correlations suggested in the literature produce no more than a rough estimation.Considering the aforesaid issues, an attempt is made in this thesis to provide a new innovative solution for determining the in-situ horizontal (effective) stress in the sandy and clayey soils according to the CPT measurements. In this regard, at first, numerical... 

This study aims to numerically study the penetration process of piezocone (CPTu) in saturated intact clayey soils with emphasis on excess pore-water pressures (EPWPs) generated around the piezocone. It is well agreed in the literature that measurements of pore-water pressure during piezocone penetration tests can play an important role in assessing engineering parameters and characteristics of clays such as undrained shear strength (su) and stress history (overconsolidation ratio, OCR) of the soil. Due to the importance of role of these two parameters in analysis, design and construction in geotechnical projects e.g. slope stability and evaluation of ground settlements induced by... 

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...