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Laboratory research on stiffness of unsaturated soil in very small and small strain region
Mohyla, Tomáš ; Boháč, Jan (advisor) ; Herle, Ivo (referee) ; Panuška, Jakub (referee)
Unsaturated soils have come into focus of the geotechnical community in recent decades. They are commonly found in the interaction of structures with the geological environment. Laboratory tests are important to provide information on the behaviour of unsaturated soils and as a fundamental input for the design of engineering structures. Laboratory tests can also be used to design and calibrate numerical models describing the behaviour of unsaturated soils. One of the important input parameters of such models is the initial stiffness of the soil and its decrease with increasing strain. This thesis deals with a laboratory investigation of the stiffness of unsaturated soil in the regions of very small and small strains. The tested soil was a loess from the quarry near the village of Horky nad Jizerou, Central Bohemia, which represents a typical soil found in engineering practice. The soil was reconstituted for the purpose of laboratory tests. The maximum (initial) stiffness of the soil was determined from measurements using piezoelectric bender elements and the stiffness decay curves were measured using local strain transducers (LVDTs). The laboratory tests were carried out in a double-walled triaxial cell for unsaturated soils, mounted with a high air-entry value ceramic disc (HAEV). The triaxial...
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Suction in undisturbed samples of Brno Clay determined by filter paper method
Mohyla, Tomáš ; Boháč, Jan (advisor) ; Malát, Richard (referee)
Negative pore pressure (suction) in soils can be measured by various methods. Probably the most precise way is using the 'Imperial College suction probe', which is briefly described, was however not available. A simple alternative is represented by the filter paper method. It was used to determine the suction in the undisturbed samples of the overconsolidated Miocene clay from the town of Brno (Brno Tegel). However the capillary suctions determined by the filter paper were unrealistically high, and could not be used in estimating the in-situ horizontal stresses (at rest coefficient K0) in the Tegel. The reasons for the failure are discussed and possible future steps are suggested.
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Stiffness anisotropy of Brno Tegel determined by continuous loading in triaxial tests
Mohyla, Tomáš ; Boháč, Jan (advisor) ; Miča, Lumír (referee)
This Thesis deals with the determination of Young's modulus and Poisson's ratio from the measurement of small strains (10-3 - 10-5 ) in triaxial tests on the overconsolidated Miocene clay from Moravia (Brno Tegel). The tests were performed in a hydraulic triaxial chamber, fitted with submersible local LVDT sensors, which were fixed directly on the sample. The tests were carried out on undisturbed samples of standard height and diameter (76x38 mm). There were three types of tests - isotropic loading probe, axial loading probe and shear test to the failure. The measured data were analyzed and the results were discussed. The research part of the Thesis briefly describes previous works on stiffness of Brno Tegel and also some works on stiffness of similar material to Brno Tegel - London Clay.
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Stiffness anisotropy of Brno Tegel determined by continuous loading in triaxial tests
Mohyla, Tomáš ; Boháč, Jan (advisor) ; Miča, Lumír (referee)
This Thesis deals with the determination of Young's modulus and Poisson's ratio from the measurement of small strains (10-3 - 10-5 ) in triaxial tests on the overconsolidated Miocene clay from Moravia (Brno Tegel). The tests were performed in a hydraulic triaxial chamber, fitted with submersible local LVDT sensors, which were fixed directly on the sample. The tests were carried out on undisturbed samples of standard height and diameter (76x38 mm). There were three types of tests - isotropic loading probe, axial loading probe and shear test to the failure. The measured data were analyzed and the results were discussed. The research part of the Thesis briefly describes previous works on stiffness of Brno Tegel and also some works on stiffness of similar material to Brno Tegel - London Clay.
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Suction in undisturbed samples of Brno Clay determined by filter paper method
Mohyla, Tomáš ; Boháč, Jan (advisor) ; Malát, Richard (referee)
Negative pore pressure (suction) in soils can be measured by various methods. Probably the most precise way is using the 'Imperial College suction probe', which is briefly described, was however not available. A simple alternative is represented by the filter paper method. It was used to determine the suction in the undisturbed samples of the overconsolidated Miocene clay from the town of Brno (Brno Tegel). However the capillary suctions determined by the filter paper were unrealistically high, and could not be used in estimating the in-situ horizontal stresses (at rest coefficient K0) in the Tegel. The reasons for the failure are discussed and possible future steps are suggested.
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