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Development and validation of a hypoplastic model for soft clays incorporating rate effects and strength anisotropy
Jerman, Jan ; Mašín, David (advisor) ; Blahůt, Jan (referee) ; Hrubešová, Eva (referee)
The thesis presents modelling framework for soft clays. Soft clays typically occur in marine environment, coastal areas and along rivers, soft clay deposits are also associated with the periglacial conditions. Soft clay seabeds are also prevalent in locations used as foundations of various energy sources (renewable and hydrocarbon). Growing world population increased demand for land, and this, consequently, leads to seaward land reclamation for urban development in coastal areas. Thus, construction on soft soil deposits has become increasingly important as soft clays occur in locations of construction projects for city infrastructure. The stress-strain behaviour of soils, especially clayey soils, is well-known to be rate- dependent. This fact is relevant for specific engineering projects, where the long-term performance of constructions is of interest. This is particularly important for soft clays as the very high degree of compressibility in primary compression and during creep makes rate-dependent soil behaviour an important factor for geotechnical problems. Moreover, the slow slope movements of slow-moving landslides and creeping slopes are controlled mostly by shear creep properties of the shear-zone soil and the effective stress state. Thus, for the case of creeping landslide modelling, a...
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Determination of erosion thickness of Brno Tegl
Malát, Richard ; Boháč, Jan (advisor) ; Hrubešová, Eva (referee) ; Miča, Lumír (referee)
The thesis deals with an application of the geotechnical numerical back analysis and several other geotechnical conventional techniques in estimating the thickness of eroded sediments. Investigated strata is the Lower Miocene marine clay, often called "Tegl" which was deposited in the Carpathian Foredeep in the eastern part of the Czech rep. Numerical back analysis is based on an assumption that erosion thickness of a soil can be derived from its stress sate represented by K0 coefficient (coefficient of earth pressure at rest). The erosion thickness given by the numerical back analysis is compared with two estimations using Baldwin-Butler's equation and Casagrande's concept of preconsolidation stress. The erosion thickness is also derived from K0 values given by two field probes: Flat dilatometer (DMT) and Push-in spade shaped pressure cell (PSPC). The numerical back analysis was applied to galleries and adits opened during site investigation of the Královo Pole Tunnels in Brno. Both the samples for laboratory analyses were taken and the field tests were carried out in area of Brno city. Discrepancy of the results is analyzed and the conclusion is that the results given by the four conventional mentioned techniques (Baldwin-Butler, Casagrande, DMT, PSPC) are strongly distorted if the investigated...
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Experimental investigation of shear strength of soils from the Dobkovičky landslide area and development of correlations between soil strength and their physical properties
Roháč, Jakub ; Mašín, David (advisor) ; Blahůt, Jan (referee) ; Hrubešová, Eva (referee)
Critical and residual states are key soil conditions relevant to slope stability. Evaluating the available shear strength in relation to these conditions is crucial for reliable stability analyses. The best way to determine the strength parameters is through properly selected laboratory tests of soil mechanics. However, in specific cases, these parameters can be estimated based on other material properties of soils. The work clarifies the applicability of various correlation equations from the literature and proposes new relationships, created from laboratory- determined results of strength and index parameters of soils from the Bohemian Central Mountains. It shows how different equations or different material properties of soils can predict the required value of strength. The work also describes how the residual strength of soils and its estimation can be affected. This is mainly caused by the clay fraction proportion and by the shear rate used in its laboratory determination. The results are applied to a specific geotechnical problem - to estimate the critical state and the residual friction angle of soils from the selected study area of the D8 motorway, which is well known thanks to the stability problems. Last but not least, various errors and misunderstandings are discussed, which are often...
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Determination of erosion thickness of Brno Tegl
Malát, Richard ; Boháč, Jan (advisor) ; Hrubešová, Eva (referee) ; Miča, Lumír (referee)
The thesis deals with an application of the geotechnical numerical back analysis and several other geotechnical conventional techniques in estimating the thickness of eroded sediments. Investigated strata is the Lower Miocene marine clay, often called "Tegl" which was deposited in the Carpathian Foredeep in the eastern part of the Czech rep. Numerical back analysis is based on an assumption that erosion thickness of a soil can be derived from its stress sate represented by K0 coefficient (coefficient of earth pressure at rest). The erosion thickness given by the numerical back analysis is compared with two estimations using Baldwin-Butler's equation and Casagrande's concept of preconsolidation stress. The erosion thickness is also derived from K0 values given by two field probes: Flat dilatometer (DMT) and Push-in spade shaped pressure cell (PSPC). The numerical back analysis was applied to galleries and adits opened during site investigation of the Královo Pole Tunnels in Brno. Both the samples for laboratory analyses were taken and the field tests were carried out in area of Brno city. Discrepancy of the results is analyzed and the conclusion is that the results given by the four conventional mentioned techniques (Baldwin-Butler, Casagrande, DMT, PSPC) are strongly distorted if the investigated...
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Numerical analysis of the colapse of an Nicoll Highway excavation in Singapore
Fabianová, Klára ; Mašín, David (advisor) ; Hrubešová, Eva (referee)
The diploma thesis dealt with collapse of deep excavation which occurred 20th April 2004 in the souhteast part of Singapore. The collapse of temporary retaining system was caused mainly by incorrect setting of Mohr-Coulomb material model in software called Plaxis. The collapse is analyzed by hypoplastic model for clays in this thesis. Hypoplastic model can simulate better behaviour of two main layers of local profile which are marine clay. The simulation of collapse of deep excavation, done by hypoplastic model, was realized in Plaxis software. The results were compared with measurement of inclinometers and also with simulation in witch Mohr-Coulomb model was used. Predictions of hypoplastic model mostly overestimate deformation of diaphragm walls of the excavation and results of Mohr-Coulomb model are very similar. It seems that final predictions of hypoplastic model are influenced mostly by strength than by nonlinearity of stiffness.
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