Sharif Digital Repository

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... 

This study aims to propose a new correlation between in-situ horizontal stress and cone tip resistance in soils. Knowing the field in-situ stress state condition has an important role in stability assessment and stress-deformation analysis in a common geotechnical system. Although vertical stress could be measured easily, horizontal stress is still known as challenging work. Due to the difficulty in sampling undisturbed sand specimens, in-situ tests have been proposed in the previous literature to investigate the different characteristics of this soil. Cone Penetration Test (CPT) is one of the most used and accepted soil methods for soil investigation, identifying different soil parameters... 

Shallow geothermal energy is a renewable and sustainable form of energy that has the potential to help alleviate the growing climate and energy crisis. The most common system used to extract shallow geothermal energy is the ground source heat pump (GSHP) system. The concept of using underground structures in exploiting shallow geothermal energy for space heating and cooling has received increasing attention. This study focuses on the use of geothermal tunnels as a means of extracting shallow geothermal energy.This research examines the effects of different heat transfer mechanisms, and highlights the effects of this phenomenon by focusing on the effects of natural convection around the... 

Determination of ultimate bearing capacity of shallow foundations has been discussed since long time ago in many books and papers. Although this is not generally a new problem, there are still some problems which may be interesting to be investigated in detail using suitable computer programs and by application of appropriate soil models. Comprehensive surveys on bearing capacity coefficients of different foundations have been done by utilizing FLAC software. The failure of soil is governed by the Elasto-Plastic Mohr-coulomb criterion. New graphs and equations have been developed for determining the coefficients. The equations achieved in this study by numerical methods, have been compared... 

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... 

There are several factors affecting the behavior and response of a pile under lateral loads. These factors can be divided into two main categories: geometrical factors (e.g. dimensions of the pile, soil, and mesh scheme) and material properties (e.g. shear modulus, bulk modulus, soil elasticity, soil density, and shear strength). Studying the effects and importance of these factors in the final response of the pile (i.e. ultimate forces and displacements) can help design engineers in optimization of their designs. Given the importance of the subject and the possibility of using numerical methods and computer technology to evaluate the behavior of piles, this research attempts to use finite... 

It has been realized that the raft (mat) foundations are capable of bearing very large loads when they are assisted with a pile group. The contribution of both raft and piles to carry the surcharge loads is taken into account, considering the stiffness and strength of involved elements in the system, i.e. piles, raft and surrounding soil. Piles are usually required to ensure the stability of the foundation and to act as settlement reducers especially for high rise buildings. The present study focuses on both kinematic and inertial effects of piled foundations and piled raft foundations under earthquake loading. The Finite Element Method (FEM) via ABAQUS will be used as an appropriate tool to... 

The main purpose of designing machine foundation is to limit its motion to such an amount that not to prevent the perfect workability of machine, not to let the foundation strains exceed the elastic limit and also not to disturb the persons working around the machine. The key note in successfull design of machine foundation, is to precisely analyse the response of foundation to dynamic loads induced by machine operations.The numerical study of shallow foundations response to vertical harmonic loads induced by machinaries have been discussed in this investigation.To aim this purpose, FLACD3D has been utilized in order to 3 dimensionally analyse a continuum medium comprising soil-foundation or... 

Regarding the existing contrary in the literature in relation to the effect of plastic fine on sand liquefaction behaviour, we decided to study this effect. Amounts of 5, 15, and 25 percent of two types of plastic fine, Kaolinite with PI=19 and Bentonite with PI=116 added to Firoozkooh Sand and 68 stress controlled tests were conducted using cyclic simple shear apparatus. In all teste the frequency of shear loading and consolidating vertical effective stress were constant and 0.1 Ht and 100 kPa respectively. Reaching excess pore water pressure ratio to the maximum value (r_u=Max) and reaching double amplitude shear strain to the value of 5% have been considered as liquefaction critera. In... 

Behaviour of piled-raft foundation on clayey soils have been analysed and assessed by the numerical methods. In this study; emphasis is made on assessment of the settlement distribution and the decrease of differential and average settlement for piled raft foundation. in these type of foundations adding piles are primarily as settlement reducers. In order to study the behaviour of pile raft foundations, numerical modelling with FLAC 3D have been carried out by using the elastic structural elements encoded in the software. In this modelling, the behaviour of soil is assumed Elastoplasts and was modelled by the Mohr-colomb constitutive medel. In this survey, the effects of different... 

Ground vibration during pile driving is one the most important factors that limits usage of this kind of piles. It is of great importance to estimate the level of vibration prior to the beginning of pile driving to avoid structural damage or disturbance of building occupants. In this study, an axisymmetric finite element model that utilises an adaptive meshing algorithm has been introduced, using the commercial code ABAQUS, to simulate the full penetration of a pile from the ground surface to the desired depth by applying successive hammer impacts. The model has been verified by comparing the computed particles velocity with those measured in the field. The results indicate that the peak... 

In-situ tests are strongly recommended in site investigations, since laboratory studies are not sufficient for precise determination of soil parameters. Effects of soil disturbance on laboratory studies questions the validation of obtained soil parameters. In the in-situ tests, soil experience less disturbance and these tests are conducted in stress levels resembling to soil initial horizontal and vertical stresses. Also more volume of soil is tested by in-situ tests in comparison to laboratory studies. Pressuremeter instrument was invented by Menard (1954). In this test, a flexible cylinder is expanded in the cavity under fluid pressure and the volume and stress changes of the cavity are... 

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... 

The estimation of soil parameters in geotechnical practice is always an important and challenging task for the geotechnical engineer. Obtaining undisturbed samples from sands is generally very difficult and expensive, and in some cases impractical. A good prediction of sands parameters from insitu tests such as Cone Penetration Test (CPT) is one of the most challenging problems in geotechnical engineering. Using Calibration Chambers, a soil with predefined parameters is tested by cone penetrometer and some relationships are developed between CPT results and soil parameters. Using these relationships, in-situ results are interpreted.
In this thesis, after introducing previously developed... 

Soil nailing is a method of in situ reinforcement utilizing passive inclusions. It can be used to retain excavations and stabilize slopes by creating in situ, reinforced, soil retaining structures. This method has been used widely in recent years. Construction of a soil nail wall is performed in vertical steps, with construction starting at the top of the excavation and proceeding down. Once an excavated step is reinforced with soil nails, a permanent or temporary facing is then applied to retain the soil. Stepped soil nail wall is formed by setting a platform in the middle part of a typical soil nail wall.In this Thesis, behavior of a soil nail wall and a stepped soil nail wall are studied... 

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... 

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... 

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... 

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... 

The importance of rainfall pattern in assessing embankment stability and deformation is widely known. However, many studies have examined an embankment with simple rainfall patterns or used average and maximum ones. The importance of diverse rainfall patterns has also been overlooked in the study of divergent soil stability in the previous study. Therefore, the hydraulic properties of a natural soil with and without salinity potential and the stability analysis of the railway embankment located on this type of soil under various rainfall patterns are investigated. The study area is part of the Zahedan Chabahar National Railway Project, which is located on divergent soil and has high...