In the course of a 7-km-long railway tunnel, which is situated mainly in weathered chalk marl, covered by Tertiary over a length of about 500 m, the tunnel traverses a transition zone of chalk marl, weathered chalk ma...
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ISBN:
(纸本)0415408229
In the course of a 7-km-long railway tunnel, which is situated mainly in weathered chalk marl, covered by Tertiary over a length of about 500 m, the tunnel traverses a transition zone of chalk marl, weathered chalk marl and Tertiary. In a specific area with a length of 100 m, the deformation during tunnel drive did not cease and exceeded the predicted values considerably About one year after the installation of the primary lining, cracks occurred in the shotcrete lining of the invert. Many different geotechnical models have been discussed to explain this special ground behaviour and the failure. numerical calculations based on extensive geotechnical investigations were performed, aiming at detecting the cause of this failure. It was only when the real ground behaviour and reasons of failure had been understood that the secondary lining could be designed in an optimised way.
Analysis of many geotechnicalengineering phenomena is a complex problem due to the heterogeneous nature of soils and the participation of a large number of factors involved. During the past few years artificial neura...
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ISBN:
(纸本)0415408229
Analysis of many geotechnicalengineering phenomena is a complex problem due to the heterogeneous nature of soils and the participation of a large number of factors involved. During the past few years artificial neural networks (ANNs) have been the most widely used pattern recognition techniques in modeling of complex geotechnicalengineering problems;however they suffer from a number of drawbacks. In this paper the application of a new evolutionary polynomial regression (EPR) method to a number of geotechnicalengineering problems is presented. Like ANN, this method can operate on large quantities of data in order to capture the nonlinear interaction between variables of the system. In addition, it provides a structured representation of the data, which allows the user to gain additional information on how the system performs. Capabilities of the EPR methodology are illustrated by application to a number of complex practical geotechnicalengineering problems which are difficult to solve or interpret using conventional approaches. the merits and limitations of the proposed method are discussed in detail.
this paper focus on numerical analysis of strain and stress holding stage realized during a pressuremeter test. the aim of this study is to highlight the effect of the viscous behavior of soft clay on the response of ...
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ISBN:
(纸本)0415408229
this paper focus on numerical analysis of strain and stress holding stage realized during a pressuremeter test. the aim of this study is to highlight the effect of the viscous behavior of soft clay on the response of the soil during this kind of tests. In this way different simulations are performed using to model implemented in the finite element code Plaxis: the soft soil model, which is an elastoplastic model, and the soft soil creep model which is an extension of the soft soil model that take into account creep behavior of the soil. the effects of consolidation and creep on the tests results are pointed out.
For the design of a deep excavation, different methods were applied in order to investigate the deformation behaviour and the stability of the structure. Especially the uncommon geological situation with a layer consi...
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ISBN:
(纸本)0415408229
For the design of a deep excavation, different methods were applied in order to investigate the deformation behaviour and the stability of the structure. Especially the uncommon geological situation with a layer consisting of gravel underlain by a soft clay layer and a groundwater table close to the ground surface and its lowering during excavation required comprehensive geotechnical analyses. the ground failure mode was investigated by using different models, namely the finite element method with PLAXIS and the limit equilibrium method. In the finite element method the stability of the excavation support was investigated by means of the phi/c-reduction method. Special attention was paid to the dimensions of the jet grouting body and the prestressed anchors, respectively. the effects of varying the depth and the width of the retaining wall and the prestress forces were studied in detail.
the influence of system and boundary conditions on the earth pressure acting on the vertical stem of a L-shaped retaining wall is analysed with a numerical model. It is found that only in rare cases, namely with very ...
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ISBN:
(纸本)0415408229
the influence of system and boundary conditions on the earth pressure acting on the vertical stem of a L-shaped retaining wall is analysed with a numerical model. It is found that only in rare cases, namely with very high wall and subsoil stiffnesses, is the design load due to German regulations reached. In most cases the earth pressure is significantly lower than the average of active earth pressure and earth pressure at rest. A connection is found between the average rotation of the vertical wall stem and the magnitude of the earth pressure load. On this basis a concept for a more sophisticated, but still simple-to-use new design method is outlined.
Deep foundations using large diameter bored piles nowadays are applied widely to support heavy structures such as bridges, industry constructions and high rise buildings. the structural serviceability requirements can...
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ISBN:
(纸本)0415408229
Deep foundations using large diameter bored piles nowadays are applied widely to support heavy structures such as bridges, industry constructions and high rise buildings. the structural serviceability requirements can be fulfilled with relatively fewer piles in an economic manner. Although large diameter bored piles are successfully applied in most subground conditions, their behavior in moderately to completely weathered rock and in residual soils is not sufficiently clarified. the results of pile load tests for a bridge foundation using Osterberg-cell technique in weathered rock will be demonstrated. the conducted analyses to re-calculate the pile load tests and to simulate the behavior of the bridge foundation to consider the pile group action will be illustrated and discussed in detail.
A major concern related to the seismic design of a geo-structure, such as a municipal solid waste landfill, is to avoid a potential instability of its slopes under seismic loading, a phenomenon directly related to the...
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ISBN:
(纸本)0415408229
A major concern related to the seismic design of a geo-structure, such as a municipal solid waste landfill, is to avoid a potential instability of its slopes under seismic loading, a phenomenon directly related to the developed acceleration levels and the dynamic interaction of the geo-structure withthe underlying soil. the aim of this study is to examine the seismic response and the stability of a typical above-ground landfill founded either on rock or on an intermediate soil layer. Extensive numerical analyses have been performed in order to achieve a realistic assessment of the dynamic behaviour of the landfill, while simplified procedures have been utilized to estimate the effects of earthquake excitation on its slope stability by quantifying the induced displacements.
this paper studies how 2D numerical analyses maybe accurately used for simulating the truly 3D problem of the seismic response of improved sites. Specifically, parametric results are compared from pertinent 3D and 2D ...
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ISBN:
(纸本)0415408229
this paper studies how 2D numerical analyses maybe accurately used for simulating the truly 3D problem of the seismic response of improved sites. Specifically, parametric results are compared from pertinent 3D and 2D seismic ground response analyses and a methodology is proposed for replacing the time-consuming (and usually unavailable) 3D analyses with "equivalent" 2D analyses that closely simulate the results of the 3D analyses. Emphasis is put on replacement and solidification methods of soft (cohesive) soils and on three (3) improvement geometries: (a) an embedded soldier pile wall, (b) a grid of columns/piles and (c) a grid of closed square cells.
the design of geotechnical earth structures is, due to the use of new technologies and new materials, more and more sophisticated. this needs the development and the adaptation of the existing numerical models to take...
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ISBN:
(纸本)0415408229
the design of geotechnical earth structures is, due to the use of new technologies and new materials, more and more sophisticated. this needs the development and the adaptation of the existing numerical models to take into account the specificity and the particularity of the behaviour of each component of the structure. A coupling between Finite Elements Method and Discrete Elements Method was done in order to clarify the mechanical behaviour of embankments soil reinforced by piles and geosynthetics. the coupling of the two numerical models allows us to keep the main advantages of each method: use of a continuous model defined by the macroscopic parameters to describe the fibrous structure of the geosynthetic sheet and its interaction withthe soil, and use of a discrete model to describe the mechanisms of arching effect and transfer of load in the soil. Applications to embankments built on compressible soil and reinforced by piles and geosynthetic sheets are presented. Results given are the displacements and the deformations of the structure, the tensile forces acting in the armed directions of the geosynthetic and the efficiencies of piles, geosynthetic and supporting soil.
Diaphragms walls are often used to support deep excavations, especially in urban areas. their behavior is a critical point, taking into account the impact on the neighboring buildings. Design methods usually use limit...
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ISBN:
(纸本)0415408229
Diaphragms walls are often used to support deep excavations, especially in urban areas. their behavior is a critical point, taking into account the impact on the neighboring buildings. Design methods usually use limit equilibrium theory. these methods do not take into account the interaction parameters, some of them with great influence on the wall behavior, e.g. the relative wall - soil stiffness, the initial stress state in the ground, the wall - soil interface etc. A more reliable modeling can be obtained using the finite element method (FEM) which has been significantly improved over the past decade to model soil structure interactions. the paper presents the numerical modeling of a propped diaphragm wall. A parametric study is performed and the numerical results are compared withthose obtained using limit equilibrium methods.
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