Sharif Digital Repository

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... 

Soil Liquefaction is a phenomenon corresponding to earthquake in which granular soil loses most of its strength in seismic loading. In this study, cyclic simple shear tests were performed for evaluating the effect of non-plastic fines on liquefaction resistance of Firuzkouh sand. Firuzkouh sand is uniform and is classified as SP in USCS. Firuzkouh silt was used as Non-plastic fine. Tests were performed under constant vertical load and undrained conditions on cylindrical specimens 7 cm in diameter and 2.2 cm in height. Samples were prepared using wet tamping method. All specimens were saturated following the standard back pressure method until the Skempton B-value was at least 0.96. Samples... 

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... 

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... 

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... 

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... 

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... 

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... 

Cone Penetration Test (CPT) is one of the major in-situ tests used around the world. Obtaining undisturbed samples from sands is generally very difficult and expensive, and in some cases impractical. A good interpretation of CPT results can provide important soil parameters, and therefore the need for undisturbed sampling may be reduced. 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. CPT results can be used to evaluate different aspects: soil stratification, geoenvironmental characteristics, stress state and... 

Effect of utilizing Central Beam Column (CBC) structure on shallow, large span underground spaces excavation is studied. The CBC method focuses on increasing the overall rigidity of tunnel supporting system prior to full face excavation, in which central drift excavation is limited to the dimensions of the central beam and column to reduce disturbances. Constructing the central beam and column structure, the excavation is completed with NATM excavation method in a symmetric manner about centerline. In CBC method on each side of the centerline there is an arch structure composed of the initial lining resting on roof beam on top and bottom beam at the invert. The roof and bottom beams take the... 

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... 

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... 

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... 

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... 

Pile is used to transfer high loads from the structure by bearing on the hard soil layers or through the friction between the soil and the pile. Axial loads and transversal or lateral loads are the main loads apply on the piles. There are several different methods to investigate the pile behavior under lateral load: (1) Limit State method (2) Subgrade Reaction method (3) Elastic method (4) P-Y method (5) Evans and Duncan method (6) Numerical methods. Blum, Brinch Hansen and Broms methods are based on the Limit State method to determine the lateral capacity of pile. Although these methods are simple and the results can find quickly, they failed to calculate the soil resistance under lateral... 

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... 

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... 

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... 

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...