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1 
BEHAVIOR OF UNSATURATED SOIL AND ITS INFLUENCE ON SOIL  SOIL INTERACTION AT AN INTERFACE.TOUFIGH, MOHAMMAD MOHSEN. January 1987 (has links)
The interface failure between caps and natural soil in trenches containing buried low level nuclear waste material was investigated in this study. The Casa Grande Highway Farm (CGHF) soil was used for the entire investigation. This soil is described as being a silty sand with approximately 23% by weight passing sieve No. 200. Other preliminary testing was performed on the same soil. Isotropically consolidated drained (CID) tests were performed on the laboratory compacted samples at different degree of saturation including fully saturated specimens. Suction pressure was measured in the laboratory by adopting pressure plate extractor and compared with determined effective suction in triaxial testing. A generalized failure equation, in term of strength parameters and suction pressure, was defined for all degrees of saturation. The consideration of unsaturated soil sets the current modified model apart from previous bounding surface which only allows use of fully saturated cohesive soil. The saturated material constants associated with the model are identified. These new constants are obtained from a generalized failure equation. The model was then verified by comparing predictions with other laboratory tests which are not used in the calibration. Generally a good agreement between the model and test results was found for stressstrain, stress path and volumetric strain response at different degrees of saturation. Extensive interface tests were performed in the conventional direct shear machine with some modification. Similar to trench cap soil and natural soil in the field, the test specimens were prepared at different degrees of saturation and density (compaction effort). Comparisons were made for the effects of magnitude of normal load, degree of saturation, density, compaction effort, moisture migration and dissimilar bodies density. An interface element and the modified bounding surface model and elasticity model was used in a finite element program to predict the interface response for the laboratory results and actual field problems. Material parameters related to the interface were identified and good predictions were observed for the interface behavior.

2 
SPATIAL VARIATION MODELING OF REGULARLY SPACED SOIL PROPERTY DATA IN ONE DIMENSION (TIME SERIES ANALYSIS)Southworth, Roger Kevin, 1961 January 1986 (has links)
No description available.

3 
Development and implementation of a hypoelastic constitutive theory to model the behavior of sandCollins, Steve Alan 05 1900 (has links)
No description available.

4 
Dilatancy effects on the constitutive modeling of granular soilsSalahuddin, Mohammed, 1959 January 1988 (has links)
Unique features of behavior of granular materials make constitutive modeling of these materials a challenge that has not yet been answered completely. Because volume changes are so important for the type of behavior exhibited by frictional materials, it is important to correctly incorporate them in constitutive models, both in terms of their rate of development and their magnitude. In this study a number of consolidated drained triaxial tests are performed to find those features of sand behavior that can be considered "material parameters" and can be used for constitutive modeling of granular soils. Special attention is given to those features of material behavior that are related to dilatancy. A number of published experimental data are also analyzed and useful trends of soil behavior are found.

5 
NONASSOCIATIVE PLASTICITY MODEL FOR COHESIONLESS MATERIALS AND ITS IMPLEMENTATION IN SOILSTRUCTURE INTERACTION.HASHMI, QUAZI SARWAR EHSAN. January 1987 (has links)
A constitutive model based on rateindependent elastoplasticity concepts is developed and used to simulate the behavior of geologic materials under arbitrary threedimensional stress paths. The model accounts for various factors such as friction, stress path and stress history that influence the behavior of geologic materials. A hierarchical approach is adopted whereby models of progressively increasing sophistication are developed from a basic isotropichardening associative model. Nonassociativeness is introduced as correction or perturbation to the basic model. Deviation of normality of the plastic strain increments to the yield surface F is captured through nonassociativeness. The plastic potential Q is obtained by applying a correction to F. This simplified approach restricts the number of extra parameters required to define the plastic potential Q. The material constants associated with the model are identified, and they are evaluated for three different sands (Leighton Buzzard, Munich and McCormick Ranch). The model is then verified by comparing predictions with laboratory tests from which the constants were found, and typical tests not used for finding the constants. The effect of varying initial density of a material on the stressstrain and volumetric response is investigated. An empirical relation is proposed, whereby one parameter is modified based on the initial density, such that improved predictions can be obtained without increasing the total number of parameters. Implementation of the nonassociative model in a finite element program to solve boundary value problems leads to a nonsymmetric stiffness matrix. Besides, using a nonsymmetric solver, three numerical schemes are investigated. The idea of the schemes is to modify the stiffness matrix such that a symmetric equation solver can be used. Prediction of stressstrain, volumetric response and CPU time for different schemes are compared with the predictions obtained using the nonsymmetric solver. The nonsymmetric equation solver used less CPU time and the solutions were more accurate. Based on the above findings, a soilfooting system is analyzed using the finite element techniques. The associative and nonassociative models are used to predict the behavior. For the nonassociative model, solution is obtained by using a nonsymmetric solver. Results obtained from both models are compared with a model footing test performed in the laboratory.

6 
NONLINEAR ANALYSIS OF POROUS SOIL MEDIA AND APPLICATION (PORE PRESSURE, TIME INTEGRATION, FINITE ELEMENTS).GALAGODA, HERATH MAHINDA. January 1986 (has links)
The behavior of porous media subjected to any arbitrary loading is a complex phenomenon due to the coupled nature of the problem. Proper understanding of this coupled behavior is essential in dealing with many of the geotechnical engineering problems. A very general threedimensional formulation of such a coupled problem was first reported by Biot; however, a twodimensional idealization of the theory is used here with extension to nonlinear material behavior. A finite element computer code is developed to analyze the response of coupled systems subjected to both static and dynamic excitations. The code can also be used to solve problems involving only solid media by suppressing the presence of fluid. The generalized anisotropic hardening model is implemented into the finite element procedure to characterize nonlinear material behavior throughout the realm of its deformation process. Both drained and undrained conditions are considered in order to verify the performance of the model in capturing material behavior. Three different materials are considered for this purpose. The predictions obtained using the anisotropic model for both drained and undrained condition yield satisfactory comparison with observed behavior. The finite element procedure is verified by solving several problems involving undrained, consolidation and dynamic responses of coupled system. Good agreements are found between numerical and analytical results. Further verification of the computer code and the material model is performed by solving two boundary value problems. For this purpose, a laboratory pressuremeter test subjected to quasistatic loading condition and a building foundation system subjected to rapid earthquake excitation were analyzed. The results of this research have provided an improved understanding of coupled behavior of porous media. The procedure developed here can be effectively used under a wide range of loading conditions varying from very slow quasistatic to very rapid earthquake excitations.

7 
THREEDIMENSIONAL NONLINEAR SOILSTRUCTURE INTERACTION ANALYSIS OF PILE GROUPS AND ANCHORS.MUQTADIR, ABDUL. January 1984 (has links)
Analysis and design of structures supported by geological media pose various complexities such as nonlinear behavior of supporting media, nature of loading, irregularities in geometry and boundary condition, and the interaction effects. It is extremely difficult to find closedform solutions for such problems. So often, numerical techniques such as finite difference, finite element and boundary integral methods are used. In this research two soilstructure interaction problems are analyzed using the finite element method involving fully threedimensional idealizations. In order to incorporate nonlinear behavior of a soil, a nonlinear elastic (hyperbolic model), and generalized single surface plasticity model including hardening are implemented in the finite element program for analysis of a pile group foundation, and an anchor in sands, respectively. The parameters required to define these models are determined from comprehensive laboratory stressstrain data obtained by using a multiaxial testing device. Typical stress paths are back predicted using the generalized plasticity model to verify that it is capable of predicting those paths, and is found to be satisfactory. In order to include the interaction effects resulting in relative slip and debonding or crack and openings at the junction between two dissimilar materials, the thinlayer element model is implemented. Load deformation behavior, force and stress distributions in various components of pile group foundation, and the anchorsoil system are predicted by using the numerical procedure. The predictions are compared with results from a model test for the pile group and field observations for the anchor problem; the comparisons are found to be satisfactory. The effects of soil nonlinearity and interface behavior are also delineated and it is found that their inclusion, particularly in case of anchors analysis, can substantially effect the behavior of the system. Detailed analysis of the results permits an increased understanding of the stress deformation mechanisms of the threedimensional problems.

8 
CONSTITUTIVE MODELLING FOR ANISOTROPIC HARDENING BEHAVIOR WITH APPLICATIONS TO COHESIONLESS SOILS (INDUCED, KINEMATIC, NONASSOCIATIVENESS).SOMASUNDARAM, SUJITHAN. January 1986 (has links)
A constitutive model based on rateindependent elastoplasticity concepts is developed to simulate the behavior of geologic materials under arbitrary threedimensional stress paths, stress reversals and cyclic loading. The model accounts for the various factors such as friction, stress path, stress history, induced anisotropy and initial anisotropy that influence the behavior of geologic materials. A hierarchical approach is adapted whereby models of progressively increasing sophistication are developed from a basic isotropichardening associative model. The influence of the above factors is captured by modifying the basic model for anisotropic (kinematic) hardening and deviation from normality (nonassociativeness). Both anisotropic hardening and deviation from normality are incorporated by introducing into the formulation a second order tensor whose evolution is governed by the level of induced anisotropy in the material. In the stressspace this formulation may be interpreted as a translating potential surface Q that moves in a fixed field of isotropic yield surfaces. The location of the translating surface in the stressspace, at any stage of the deformation, is given by the 'induced anisotropy' tensor. A measure to represent the level of induced anisotropy in the material is defined. The validity of this representation is investigated based on a series of special stress path tests in the cubical triaxial device on samples of Leighton Buzzard sand. The significant parameters of the models are defined and determined for three sands based on results of conventional laboratory test results. The model is verified with respect to laboratory multiaxial test data under various paths of loading, unloading, reloading and cyclic loading.

9 
Cyclic triaxial testing of low to moderateplasticity siltsButlerBrown, Jason J. 04 June 2002 (has links)
This project report presents a laboratory investigation of the dynamic
behavior of saturated alluvial silty soils from sites in Oregon and Washington. The
focus of the study was to document the liquefaction susceptibility, post cyclic
strength, and volumetric strain behavior of the silt soils based on cyclic, undrained
triaxial compression testing. A cyclic triaxial testing apparatus with computer
control and data acquisition was assembled, calibrated, and used to perform
undrained cyclic triaxial testing and post cyclic testing on undisturbed and
reconstituted specimens. The results of this investigation are compared with the
undrained cyclic triaxial testing data on silty soils published by others. The
influence, of grainsize distribution, plasticity index, and overconsolidation ratio
(OCR) on the dynamic behavior was identified.
Several cyclic resistance curves were prepared that show the cyclic
resistance for the silts for OCR values of 1 to 2.5. The cyclic resistance curves
observed in the laboratory likely overestimate the insitu cyclic resistance of the
material due to sample disturbance during sampling, transport, and testing. It was
observed that OCR has a significant influence on the cyclic resistance of silt soils.
Cyclic resistance was observed to increase with increasing plasticity and percent
passing the U.S. Standard Number 200 Sieve and percent finer than 2 ��m. It was
observed that excess pore pressure measurements recorded at the transducer for
finegrained soils subjected to rapid loading may not accurately represent the actual
pore pressures of the soil. Therefore, it is proposed that strain criteria be used,
rather than excess pore pressure generation, to define initial liquefaction for finegrained
soils.
Post cyclic undrained strength test data shows that the silts are dilative
under compressive loading in the triaxial apparatus. Peak strengths were not
observed due to the dilative nature of the silty soil tested. Therefore, post cyclic
undrained strengths were strain based. The strain based strengths were compared
with relationships developed by Baziar and Dobry (1995) and Ishihara (1993) and
were found to have a higher residual strength than the sandy soils. Unusually high
S[subscript u]/p' ratios were also recorded for the silt soils. This observation highlights the
need to obtain postcyclic strength at a consistent strain.
The post cyclic volumetric strain data was compared with the findings of
Ishihara and Yoshimine (1992). Plots of volumetric strain versus maximum axial
strain were created. These plots were then used to establish a relationship between
post cyclic volumetric strain and the factor of safety against liquefaction. The
volumetric strain behavior of the silt was observed to be very similar to sand at
relative densities of 40 to 80 percent. / Graduation date: 2003

10 
Performance of an anisotropic clay under variable stressesMohamed, AbdelMohsen Onsy. January 1986 (has links)
In the true triaxial test procedure used for testing laboratoryprepared kaolinite clay samples, undrained (with constant mean stress) strength tests were conducted to study the yield and failure of the clays. The principle concern focussed around the influence of orientation of particle bedding plane on the development of yield and failure characteristics of the clay. As the true triaxial cell permits variations of the three principal stresses, it was possible to study the soil response in any chosen quadrant of the principal space. / As a consequence to what is mentioned above, two types of consolidated undrained true triaxial tests were conducted in this study. In the first type, specimens were trimmed from the block sample with 90, 60, 30 and 0 degree orientation angles of particle's bedding planes; these angles were measured with respect to the direction of the major principal stress axis. For each degree of inclination, specimens were tested with three confining pressures 207, 276 and 345 kPa, and for each value of confining pressure, the loading path was varied from compression to tension. / The degree of dissociation between the stress and strain increment vectors was seen to depend on both initial and stress induced anisotropy. / Most important of all, a constitutive relationship for anisotropic kaolinite clay was derived on the basis of the observed experimental behaviour of soil samples under loading. / Additionally, anisotropy is characterized by a double transformation technique. The first transformation accounts for the directional dependency whilst the second transformation concerns itself with anisotropy of the base vectors. The relative joint invariant principle is used to calculate the degree of dissociation during the loading process. The variation of the dissociation angle during the loading process can be considered as a measure of the evolution of the resultant anisotropy. The model has shown to provide viable predictions of the stressstrain relationships obtained from true triaxial tests on an anisotropic kaolinite clay for: (a) different inclinations of particle's bedding planes, (b) different stress paths in one sector, (c) different stress paths in other sectors, and (d) the failure surfaces for different inclinations of particle's bedding planes in the octahedral plane. (Abstract shortened with permission of author.)

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