Sharif Digital Repository

In previous studies, effect of certain parameters such as soil K0 on piled raft load sharing ratio α_pr was not considered. Here, α_pr is ratio of pile group load to total load. In this study, we consider the effect of pile length (L), pile spacing (s), raft thickness (t), raft modulus of elasticity (Er), pile modulus of elasticity (Ep), coefficient of lateral earth pressure, and pile concentration. Soil is undrained clay with typical properties. Raft is made of concrete and piles are cast in-place. Modeling is done in FLAC 3D. To determine the effect of these parameters we calculated load sharing ration of piled raft at 10 cm settlement which is typical for design. Based on the results of... 

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... 

Piles are usually used in groups. The complicated interaction between piles on the one hand and between piles and their surrounding soil on the other hand, have made it difficult to recognize mechanisms that influence the pile group behavior and analyze it accurately. In this research, three dimensional models in ABAQUS software were used to investigate response of single piles and pile groups under lateral loading in clayey soils. Configuration of piles in a group, connection of piles to the pile cap, pile spacings, and pile cross section were taken into consideration as some important factors affecting response of pile groups. All the modeled piles were categorized as long piles. In order... 

In recent years, growth of industries has led to consistent increase in energy consumption around the globe. On the other hand, non-renewable energy sources are the most consumed ones in the world. Therefore, governments and companies have tried to introduce budgets to facilitate the use of renewable energy sources and make their use cheaper. One of the renewable energy sources is geothermal energy which one economical way to havest it is thermal energy exchange between the building foundation and the ground. Therfore, thermal piles , by the use of a heat exchanger fluid, transfer the heat on the surface to the ground in warmer seasons and in cold seasons, they transfer the heat from the... 

The phenomenon of lateral spreading occurs as a consequence of earthquakes induced liquefaction in grounds with mild slopes or ending to an opening. This phenomenon has caused many damages to deep foundations and associated structures. Therefore, it is necessary to study and estimate the forces which may be induced by lateral spreading to these structures. Due to the complex mechanism of the effect of lateral spreading on the piles, various tests have been carried out in the form of shaking table as well as centrifuge tests. According to the results of these tests, the forces applied to the piles are significant and can cause crucial damages to deep foundations. On the other hand, because... 

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 ... 

Heat exchanger piles are innovative technologies used to harvest heat from shallow ground. Heat exchanger pile, also known as energy pile, transfers mechanical (structural) loads to the ground while acting as a heat exchanger. Heat extraction in winter and heat rejection during summer changes the pile, pile-soil interaction and the surrounding soil temperature. Therefore, pile temperature increments have been recognized as a new factor of controlling the behavior of energy piles in recent decades. Besides, thermal cyclic loadings may affect the serviceability and geotechnical performance of heat exchanger piles. Physical models provide an affordable experimental medium through which new... 

Nowadays, pile usage in construction of deep foundations has increased significantly, instead of shallow foundation in areas that shallow foundations doesn’t provide enough bearing capacity and measuring the velocity and acceleration due to pile driving is very important. Because, all responses of building and individuals located near the pile driving site influenced by these three parameters: pile vertical displacement, peak particle acceleration (PPA) and peak particle velocity (PPV). One can estimates these important parameters by numerical analysis of pile driving process in different distances and depths to determining the effect of pile driving. Compared values obtained from numerical... 

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.... 

Energy piles couple the structural support role of conventional piles to the heat exchanger role of shallow geothermal systems for any built environment. So, they are subjected to both mechanical and thermal loads. The use of these piles can be useful in reducing greenhouse gas emissions and reducing fossil fuel consumption. With this in mind, this study is conducted to evaluate the thermomechanical behavior of heat exchanges group piles. For this porpuse, a physical model has been constructed in the Advanced Soil Mechanics Laboratory of the Civil Engineering Department at Sharif University of Technology. In this physical model, four closed-end aluminum pipes with a diameter of 20 mm and a... 

This study highlights an important distinction between heat transfer mechanism in dry and saturated soil. Soil temperature data recorded during model tests, soil thermal response predicted using finite difference and analytical methods are compared with finite element models. In recent years, due to the industrial development of human societies, the energy consumption has been increased worldwide. On the other hand, the most commonly used energy resources are non-renewable energies. Therefore, governments and industries aimed to develop a technology which provides economical use of renewable energy sources. One of the renewable energy sources is the geothermal energy of the Earth. In this... 

Based on the large number of interacting cells and their abundant connections, human brain is a complex system able to produce interesting collective behaviors. Studying these collective behaviors needs special tools that potentially could be found in the context of the statistical physics of critical phenomena, as these tools are specifically developed for understanding the large-scale properties of physical systems. Starting with the introduction of the self-organized criticality in the late 80s, a number of physicists have tried to utilize this concept for explaining some aspects of the brain properties, such as memory and learnig. The observation of the neuronal avalanches in the early... 

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... 

The phenomenon of soil liquefaction has caused significant damage to deep foundations of engineering structures such as bridges and buildings in past earthquakes. In recent years, many researchers have studied the effects of soil liquefaction on the pile response, but there are still many unknowns that require further research and study. The present study is part of a comprehensive research that involves several Ph.D. and master students at Sharif University of Technology (SUT). In this study, the effects of soil liquefaction on two pile 2×2 groups (one with a lumped mass and another without) in a level ground with a sloping bed were investigated. A surface non-liquefied layer was also... 

Regarding the issue that significant amount of energy consumption in the world is dedicated to heating and cooling of the buildings, by using traditional methods of heating and cooling, the environment is facing serious problems like green house gases. There were various techniques for decreasing the amount of contaminants stem from this process. Heat-exchanger energy piles are one of the most common methods that will result in economic usage of energy resources. Assessing the long-term behavior of the energy piles requires comprehensive understanding of the complex interaction between soil and pile subjected to mechanical and thermal loadings. Several numerical and analytical methods have... 

Bearing capacity of piles depends on many factors among which geometrical properties of piles, soil type, and strength properties of soil are of great importance. Based on these parameters, several approaches have been developed in order to overcome the uncertainty in the prediction of pile bearing capacity. Studies carried out in this area or research can be divided into two main categories: first, laboratory based approaches, and second, numerically based approaches. The research followed in the present study is based on numerical modeling. In this study, a single pile is initially modeled in the axisymmetric configuration and its bearing capacity is determined. The results of the model... 

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... 

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.... 

The seismic behavior of pile-supported systems has been an active area of research over the past decades. However, focus has mostly been on evaluating the seismic response of structures embedded in either dry or fully saturated, especially liquefying soil conditions. In this study, a series of dynamic centrifuge tests have been conducted to investigate the effects of soil’s degree of saturation on the seismic behavior of pile-supported superstructures. The scaled physical model tests were carried out on two distinct pile-mass systems embedded in uniform sand layers. A steady state infiltration technique was used to control matric suction profiles in the sand layer prior to shaking. The... 

Lateral spreading due to liquefaction and resulting destruction of buildings is important in Iran because of high seismicity and important infrastructure near south and north coasts of Iran. Lateral spreading is vast lateral movement of sloping ground or level ground ending in an opening like river which is caused by earthquake inducedliquefaction. For considering the effects of lateral spreading during design of deep foundations of structures in a susceptible area, one needs to determine the lateral loads on piles under lateral spreading. Present study investigates the behavior of a 3x3 pile group against lateral loads due to lateral spreading with numerical methods using OpenSees software....