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"The transportation or railway system constructors usually, wherever possible, build the transportation system on the ground surface and avoid the necessity of underground tunnelling. However, this is not always possible. In many locations, such as mountainous area, hilly area or urban area, the underground tunnelling have to be built. The main problem of underground tunnelling is the soil stability around the tunnel, and the problems continue to mount for long and big tunnel. Therefore in recent years, engineers try to find the method to predict and solve all aspect of ground responses induced by excavating and tunnelling.

For the past 30 years, the research for estimating an accurate prediction of ground deformation caused by tunnelling processes, have been a major engineering challenge all around the world. A good prediction of ground deformation due to tunnelling excavation and advancement is highly necessary to ensure that no damage will occur in the existing buildings and services at the surrounding area.

In this study, the excavation and advancement of tunnelling excavation in Tunnel TGV of Tartaiguille, France is modeled and analyzed using the numerical program in order to simulate the ground response due to the construction processes. On the other hand, CETU (Centre d'Etudes des Tunnels) had set out an instrumentation in sections of the tunnel in order to analyze the loading of the support of the tunnel and obtained the displacement of surrounding ground responses. The numerical simulation will take into account the visco plastic behavior of the soil. And then the result of numerical simulation will be compared to the field measurement data.

The constitutive model used in this study is an elasto-plastic constitutive model called CJS 2EC which has been developed by Ecole Centrale de Lyon. To lake into account the time-dependent behavior of the soil, the visco-plastic constitutive model has been embedded in the CJS 2EC model.

Hopefully with this study, we are getting one step ahead in estimating the ground responses in tunneling. The more realistic behavior of the soil around the tunnel, which include the time dependent behavior of the soil will be examined and gives an accurate prediction of ground response due to tunnelling excavation.

Observation of the results and comparison with the measurement data demonstrate that the time dependent behavior of soil cannot be neglected in the analysis of the tunnelling excavation."

"ABSTRACTThe development and extension of large cities creates a need of multiple shallow tunnels in the soft ground of built areas. Excavating a tunnel generates ground displacements and deformations which can affect existing buildings and services in urban sites and can lead to unacceptable damages. Prediction of the ground settlement caused by the tunnel excavation has been a major engineering challenge. A numerical simulation using finite element method was implemented in the aim of developing a procedure for forecasting the movement induced by tunneling. This study describes the modelling procedure, comparing one procedure in a complete stages of modelling (called phases modelling) taking into account different phases simulating the different kinds of interaction between the tunnel and the soil (deconfinement, lining installation, pore pressure applied on the lining, and weight of the lining) and one in a simple way called `deconfinement modeling', simulating the excavation using a stress decrease vector exerted on the excavation boundary in the opposite to the initial ground stress described by a scalar parameter A. (the deconfinement rate). A shallow lined tunnel is analyzed in a two dimensional analyses, and observations are made for the settlement at the surface and at the tunnel crown, the deformations of the tunnel opening, and the stress path around the tunnel. Comparison is conducted using two soil models : the Mohr-Coulomb model and the CJS model. Observations of the results and comparison with the experimental data demonstrate that the deconfinement modeling is adequate for the analyses of settlement induced by tunneling only if a good modeling of the soil behavior is considered."

"The bearing capacity of footings on level ground can be predicted by different calculation methods, using the results of laboratory or in situ tests. In the other side the effects of proximity to a slope are poorly understood.This study was performed as a research on the bearing capacity of foundation on slope, in particular the influence of the internal angle of. friction (Φ), the cohesion (c) of the soil and the eccentricity of the load applied have been analyzed.The study was conducted using a numerical method that is based on the Finite Difference Method. Building the problem in this numerical method was studied first, then the validation of the code was obtained by comparison to experimental results available. Further the influence of the particular parameters was then studied and analyzed.The model used is the Mohr-Coulomb model as an approach to the behavior of soil with parameters very easy to define from laboratory tests.The analysis of the result was performed with making a comparison to the theory or the experimental results available."

"This thesis presented a numerical study of the improvement of soft soil using columnar inclusions. Review of analytical studies has been concentrated to British Standard BS8006, modified Terzaghi theory, and arching theory. Numerical model in this study is using FLAC3D code to generate 3D model. The materials properties uses in this model refer to typical values. Some of important design variables have been considered in our parametric study. The most efficient platform thickness is lm for loading 30kPa or more, in point of view to minimize the proportion stress on soft soil or to maximize ratio of load transferred to columns. Optimal area ratio A, is in range from 5% to 10% its depends on the considered parameters, but 10% is acceptable for most parameters. Study of stress distribution on column indicates that the negative friction will act on top part of column in any level of loading. Due to the mechanism of stress distribution, inclusion system could settle as a group. The maximum of stress reduction ratio Sr and stress concentration ratio Er is obtained for the same value as Terzaghi analysis."

"ABSTRACTNowadays, the ways, how to solve the mass transportation problem in the big city become the major problem for the government. Some difficulties come when the mass transportation facilities can't be build at the ground surface because many buildings and services will be disturbed. For avoiding that, the mass transportation facilities usually are built in the underground. It means that we have to excavate the underground to make a tunnel. Excavating a tunnel generates ground displacements and deformations, which can affect the existing buildings and services in urban sites and can lead to unacceptable damages. To predict and to solve the all affects of excavating and tunneling have been a major engineering challenge.A numerical analysis by using the finite difference method was implemented in the aim of developing a procedure for forecasting the all affects induced by tunneling. The influences of the strain-softening of the soil in the tunneling were discussed in this study. To take into account these behaviors, the Mohr-Coulomb criterion with strain-softening behavior were applied and as the comparison data we used the Mohr-Coulomb criterion without strain-softening behavior. We defined a new approximation for defining the strain-softening model. Two new constants obtained from the triaxial test, were used for defining this model. In this definition, the strain-softening behavior of the soil will depend on a;, and the peak values of cohesion and friction angle of the soil. This study presented also the implementation of convergence-confinement method by using the deconfinement modeling and the Sequential Excavation Method (SEM). For deconfinement modeling, we analyzed in two dimensional with plane strain condition. And for the Sequential Excavation Method, we analyzed in axisymmetric condition and in three-dimensional condition. The finite difference software, Fast Lagrangian Analysis of Continua (FLAC), was used for simulating all the problems."

"ABSTRACT

The finite element method has been applied to the study the behavior of vertically loaded single micro pile, the nine piles in a close group, the three piles in a row group in a homogeneous non linearly behavior medium, that is cohesion less soil.

Bidimensional and axis metric elements have been used in the analysis to determine the stress and the strain state in the soil around the piles and the deformation of the pile due to the grouting pressure of the micropiles.

This paper uses Mohr Coulomb model with a parameter controlling dilatancy.

The effect of grouting pressure in the soil around the member of piles group at three-diameter spacing are presented and analyzed. The efficiency of each piles and piles group at two until five spacing diameter, at 10% up to 50% deformation of pile are shown and studied. Those efficiency graphs are compared with the efficiency of driven pile group and bored pile group.

The effect of dilatancy to the deformation of pile at different grouting pressure is presented.

Using super positioned method that efficiency graph can be used for evaluating the efficiency of bigger micro piles group.

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