Sharif Digital Repository

A large number of structures and substructures, such as piles, have damaged or even yielded the entire structure during seismic loading. The kinematic interaction of piles under seismic loading has been widely studied from analytical, experimental, and numerical perspectives. In numerical modeling, most existing literature relies on simplified approaches to describe the soil-pile interaction, which leads to the need for more reliable and comprehensive research. In this research, the seismic response of the soil-pile system was investigated through a fully nonlinear three-dimensional numerical analysis in the time domain using the FLAC3D program. This model simulates the dependence of soil... 

Determination of soil bearing capacity has been a subject for both geotechnical engineers and designers for a long time and a variety of relationships have been proposed to determine the ultimate bearing capacity of homogeneous soils. One of the most primitive equations in bearing capacity of foundations, which was Based on prandtl's (1920) bearing capacity, with some modifications, was proposed by Terzaghi. In many lands, the soft clay layer Located in a low depth of subsurface soil profile. Either the foundation should be laid in greater depth on the stiff clay or a layer of compacted sand can be used to improve the ultimate bearing capacity. Most of the recent works, which have done so... 

The direct technique in which response of the soil and the structure is obtained using numerical methods like finite element is not an appropriate method for seismic analysis of soil-structure interaction of buildings. For this reason, the effects of the foundation and retaining walls are considered for a building with underground floors. Interaction models include a concrete moment frame with ten stories and zero to five underground floors in which constructed on a specific soil and analyzed in FLAC software. Three types of accelerograph Tabas, El-Centro, and Luma are used for time history analysis. Indeed, for a model with a rigid foundation, a ten stories moment frame without an... 

Cemented and cohesive sandy soils are found in many places around the world, including Tehran and Karaj. Therefore, determining the bearing capacity of these soils is important. In this research, some relationships have been established based on geotechnical parameters for drilled shafts in cohesive sandy soils. For this purpose, FLAC software is used for modeling. The elastoplastic Moher-Coulomb constitutive law is used. The verification of the model is done by both experimental and numerical results of other researchers in the sand and clay.The results of modeling show that undrained clayey soils have the greatest effect on the tip and side resistance of drilled shaft. In the clay, the... 

In recent years, due to the development of cities and population growth, the number of underground floors and the depth of excavations have increased. Sustainability of excavation and control of deformation due to excavation process has always been considered as one of the important issues in geotechnical engineering. One of the most commonly used systems for deep excavation, especially in urban areas, is the soldier pile wall with tiebacks. This system consists of anchoring on soldier piles that are performed at horizontal distances around the excavation range. The cables have two parts. Unbond and bond length that, when pretensioned, have the task of transfering load out of the wedge of... 

Liquefaction is an important phenomenon in geotechnical engineering which can cause severe damages to structures. Liquefaction-induced lateral spreading is defined as the lateral displacement in mild slopes or level grounds ending in free faces (such as quay walls) triggered by liquefaction in subsurface soil layers. During recent years, extensive studies have been conducted around the world documenting liquefaction induced lateral spreading and its effects on deep foundations. In the present study, a series of shaking table experiments which were previously conducted at Sharif University of Technology are numerically simulated using the three dimensional finite difference based program,... 

Numerous structures which are involved in seismic soil-pile-structure interaction have been destroyed. Considering complexities which exist in soil-pile interaction problems and lack of precise methods without imperfect bases, it is necessary to use numerical methods for analyzing soil-pile interaction problems. In this research, three-dimensional modeling and studying the effect of changing soil and pile parameters on the behavior of pile under earthquake loading is performed using finite difference software, FLAC3D. The soil in this model has a softening behavior. Real earthquake spectrum has been applied into the model as the acceleration time history at the bedrock level. The results of... 

Geothermal piles are being used to serve dual purposes: transfer the structural load to the ground and act as heat exchanger elements to harvest and reject heat from and to the ground. Thermal loading can change the mechanical performance and bearing capacity of the geothermal piles during heating and cooling cycles. Therefore the thermo-mechanical responses of the geothermal piles should be comprehensively studied. In this paper the thermo-mechanical performance of a geothermal pile was analyzed using a 3D finite difference model in FLAC. The energy pile tests performed at Lambeth College, London were simulated using the developed numerical model. Comparison of both thermal strain and... 

In recent years, due to urban expansion and population growth, number of floors and excavations depth has increased. Stabilization of excavations is one of the most important issues in geotechnical engineering. Today, one of the most widely used methods that is used in deep excavations is brace soil by steels and pretension them. In this thesis tries to evaluate static behavior of flexible supporting structures with pretension anchors by using PLAXIS2D, FLAC3D and GEOSTUDIO softwares. The objective of this modeling is better understanding the static behavior of walls, comparing the two and three dimensional modeling and the effect of corners of excavation on deformation. The results shows... 

Because of seismic flexibility, aesthetics, economic advantage and rapid construction of reinforced soil walls, application of these walls has raised tremendously since 1970’s. The early reinforced soil retaining walls used metallic srips to reinforce the soil with precast concrete panels as facing, however, since 1990’s using of geosynthetics to reinforce these walls with modular concrete block facing have replaced the old fashion. In this study, a finite difference code was developed in FLAC software. After verification of the numerical modeling procedure, a wall with 3.6m height reinforced by geosynthetics was simulated. In the course of numerical simulations the stage of counstruction,... 

Ground squeezing is defined as time-dependent shear displacement of rock mass that causes the decrease of the calculated excavation area of tunnels.Ground squeezing is one of the phenomenons that causes serious problems including the collapse of tunnels’ walls and TBM jamming during the construction of tunnels. Hence, the assessment of ground squeezing is an essential issue in tunneling. In this thesis, different ground squeezing potential prediction methods will be assessed. These methods consist of empirical, semi-emperical, analytical, and numerical methods. After assessing the ground squeezing potential, if it is evaluated high for a project, it will be required to consider the... 

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... 

Stability control of Rockfill dams during construction, first impoundment and during operation is of great importance. Increase in pore water pressure during construction and reservoir filling of rockfill dams with clay core can initiate or help the progress of the hydraulic fracture. Considering initiation of high excessive pore pressures while construction as an important causes of dam failure, precise estimation and analysis of It's variation will be necessary and will increase safety factor of dam stability.Horizontal and especially vertical displacements happening during Dam construction and reservoir filling and arching phenomenon in clay core while construction are the other factors... 

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... 

One of the most important conditions in weak rock masses with high overbuerden which causes problems in the tunnel construction, is squeezing condition. This is actually defined as increases in the shear deformation of the rock element, when the element is under constant deviatoric stress. Qomroud water tunnel with a length of 36 km and a drilling diameter of 4.5 meters deliveres water from the branches of the Dose to the Golpaygan and Qom. Because of a high overbuerden and existence of schist, slate, clay limestone zones, studing of squeezing potential,prediction of convergence of tunnel wall and lining pressure in this tunnel is very important.In this research, we stuied the 25th to 35th... 

In the recent years, in consideration with the developing of cities and increasing of population, the number of basement floors and associated depth of excavation, also, are increasing. Therefore, stabilization of the wall of these excavations is one of the most significant issues in geotechnical engineering. One of the most applicable methods in deep excavation is the use of soil anchoring by pre-stressed anchoring. This system is consisted of series of soldier piles to which, anchors, shot Crete or lagging walls, maintaining soil between piles, have been bolstered. Yet, there are lots of ambiguities about the static and the dynamic behavior of these structures. However, studies about... 

The use of public transportation in metropolises has developed due to the increase in the population and the need for within-city transportation. Among public transportation service, the use of city subways has attracted more public interest due to its speed, safety, and matching with the environment. Also, one solution for reducing the between-city transit distances,decreasing the accidents and above all, saving the time of the travel is building tunnels and underground lines. Design and construction of underground structures (tunnels),in comparison with surfacestructures, has more complex conditions and considerations that require special studies. One challenging problem fortunnel... 

The commercially available finite element software, FLAC, was used to provide better understanding of the static and dynamic behavior of tieback and anchored walls. Many of the codes dealing with the design of these structures use empirical methods to estimate the amount of deformation under static conditions. Therefore, in terms of static behavior, this thesis mainly focuses on the deformation patterns of the wall and the retained soil. Mohr-Coulomb elasto-plastic constitutive model was used; however, in elastic part the nonlinear Duncan-Change was implemented. The efforts made for better representation of soil behavior resulted in the suggestion of a modification to Duncan-Chang’s... 

In safe and economic designing of deep foundations for any structure, there are several factors affecting the behavior and response of a pile under seismic loads. These factors can be divided into three main categories: geometrical factors (e.g. Dimensions of the pile, soil, and mesh scheme), material properties (e.g. shear modulus, bulk modulus, soil elasticity, soil density, and shear strength) and earthquake load characteristics (e.g. frequency range, PGA, duration of excitation(. Studying the effects and importance of these factors in the final response of the pile (i.e. ultimate forces and displacements ) can help the design engineers of these foundations to optimize their designs....