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Small strain stiffness of soils and methods of its measurement
Havlíček, Jaroslav ; Miča, Lumír (referee) ; Chalmovský, Juraj (advisor)
This thesis consists of theoretical and practical part. Firstly, the soil behaviour at small-strain range and its physical nature are described. Subsequently, the individual soil parameters affecting the value of small-strain shear modulus and the shape of the stiffness reduction curve with increasing shear strain are described. The individual methods of measuring the small-strain stiffness in the laboratory and in-situ with a more detailed explanation of the evaluation of measurements using bender elements are given in the last chapter of the theoretical part. In the practical part, a device for measuring small-strain stiffness using bender elements was put into operation. The used laboratory equipment is described first and then the parameters of tested soil are given. The main chapter is measurement and evaluation of the impact of software and hardware settings and the influence of effective stress of soil on the small-strain shear modulus that is compared with predictions of empirical expressions from the literature.
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Measurement of stiffness at small strains during oedometer test and detailed interpretation of output waves
Havlíček, Jaroslav ; Koudela, Pavel (referee) ; Chalmovský, Juraj (advisor)
This thesis has a theoretical and a practical part. The first part contains theoretical introduction to the phenomenon of increased stiffness at very small strains and possibilities of its practical applications. The available methods for evaluating initial shear modulus tests are described below. Increased attention is paid to the method of evaluation of test data in the frequency domain using the Fourier transform. The last chapter in this part describes an algorithm designed for automatic evaluation of measurements in the frequency domain. The practical part deals with measurement and evaluation of initial shear modulus for Brno clay as a function of vertical stress in oedometric test. Firstly, a device is presented that allows the extension of the oedometric test with sensors for measuring initial shear modulus of soil. This device was designed for the test in this thesis. Subsequently, the test plan is described including description of all soil samples. In this thesis, several types of soil samples from a single site were tested. Next, the results of the individual tests are evaluated by the selected methods. Examples are used for showing the differences in evaluation of the same data by other methods. At the end, the results of the individual tests for all sample types are compared with each other and with data from literature.
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Measurement of stiffness at small strains during oedometer test and detailed interpretation of output waves
Havlíček, Jaroslav ; Koudela, Pavel (referee) ; Chalmovský, Juraj (advisor)
This thesis has a theoretical and a practical part. The first part contains theoretical introduction to the phenomenon of increased stiffness at very small strains and possibilities of its practical applications. The available methods for evaluating initial shear modulus tests are described below. Increased attention is paid to the method of evaluation of test data in the frequency domain using the Fourier transform. The last chapter in this part describes an algorithm designed for automatic evaluation of measurements in the frequency domain. The practical part deals with measurement and evaluation of initial shear modulus for Brno clay as a function of vertical stress in oedometric test. Firstly, a device is presented that allows the extension of the oedometric test with sensors for measuring initial shear modulus of soil. This device was designed for the test in this thesis. Subsequently, the test plan is described including description of all soil samples. In this thesis, several types of soil samples from a single site were tested. Next, the results of the individual tests are evaluated by the selected methods. Examples are used for showing the differences in evaluation of the same data by other methods. At the end, the results of the individual tests for all sample types are compared with each other and with data from literature.
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Stiffness anisotropy of Brno Tegel determined by bender elements
Krupička, Martin ; Najser, Jan (advisor) ; Malát, Richard (referee)
This Thesis deals with the determination of shear moduli of Brno Neogene clay ("tegel") in various directions and the determination of its stiffness anisotropy. The basic measure of stiffness anisotropy in this thesis is considered to be the degree of anisotropy αG given by the ratio of shear moduli in the horizontal (Ghh) and vertical direction (Gvh). Measurements of shear wave velocity were performed on undisturbed vertically and horizontally oriented samples of the Brno tegel in triaxial cell using piezoceramic sensors, so-called bender elements. As an advanced method for determining the degree of anisotropy of the material, another pair of bender elements was used in the measurements, mounted horizontally on the side walls of the sample in the triaxial cell. Based on these measurements, the values of shear moduli Ghh and Gvh for different stress levels were determined. The ratio of shear moduli then determined the degree of anisotropy αG ≈ 1,43 for the given stresses, as the most reliable value based on performed experiments. Literature review part of the thesis briefly summarizes the existing findings from research of physical and mechanical properties of the Brno tegel.
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Small strain stiffness of soils and methods of its measurement
Havlíček, Jaroslav ; Miča, Lumír (referee) ; Chalmovský, Juraj (advisor)
This thesis consists of theoretical and practical part. Firstly, the soil behaviour at small-strain range and its physical nature are described. Subsequently, the individual soil parameters affecting the value of small-strain shear modulus and the shape of the stiffness reduction curve with increasing shear strain are described. The individual methods of measuring the small-strain stiffness in the laboratory and in-situ with a more detailed explanation of the evaluation of measurements using bender elements are given in the last chapter of the theoretical part. In the practical part, a device for measuring small-strain stiffness using bender elements was put into operation. The used laboratory equipment is described first and then the parameters of tested soil are given. The main chapter is measurement and evaluation of the impact of software and hardware settings and the influence of effective stress of soil on the small-strain shear modulus that is compared with predictions of empirical expressions from the literature.
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