|
|
Swelling soils in the Czech Republic
Fencl, Michal ; Boháč, Jan (advisor) ; Kostkanová, Vladislava (referee)
This thesis deals with swelling soils and tries to determine their occurrence in the Czech Republic. Swelling of soils is a process in which the soil either increases its volume and/or exerts the swelling pressure, and thereby typically causes considerable problems in buildings and other structures. Volume changes affect all soils, depending on the degree of saturation, the stress level and its chenges, and on the soil mineral composition. Based on the literature review the thesis describes the basic principles of swelling. It deals with the general description of clay minerals, mostly smectite, and their role in the phenomenon of swelling and in the identification of potentially swelling soils Finally the published data on swelling pressures of soils from selected sites in the Czech Republic are summarised.
|
|
|
Horizontal stress in Brno Clay determined by oedometer test
Krupička, Martin ; Boháč, Jan (advisor) ; Mašín, David (referee)
This Thesis deals with the determination of horizontal effective stress in-situ the clay massif in the city of Brno. To determine the value of the horizontal in-situ stress was at first established value of the coefficient of earth pressure at rest K0, which captures stress conditions in the massif and which is a main part of this Thesis. To determine the value of K0 was used the method of the ratio of the horizontal to vertical preconsolidation pressure. Pseudo-preconsolidation pressure used to calculate K0 was determined by using standard oedometer compression tests of oriented undisturbed samples. Research part of the Thesis deals with the issues of evolution of K0 during secondary compression and results of previous published data. The results obtained from own experiments are discussed and compared with the results of previous published data.
|
|
|
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.
|
|
| |
|
|
Spolehlivá správa času pomocí TSC na platformách s nestabilním TSC
Boháč, Jiří ; Kosina, Jiří (advisor) ; Bureš, Tomáš (referee)
Some SMP hardware architectures (including x86_64) have unsynchronized Time Stamp Counters (TSC) between individual CPUs. This implies that TSC can't be used reliably to implement a fast gettimeofday() system call in a straightforward way. The current Linux kernel implementation uses synchronized (but significantly slower) hardware time sources on these architectures. The primary aim of this thesis is to perform a detailed analysis of how TSC could be used for reliable and accurate approximation of current time, so that it could be used as a trustworthy and fast time source. A working implementation based on the outcome of the analysis is expected.
|
|
|
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.
|
|
|
Foundation of traffic embankments on clayey landfills of SHR
Mužík, Vlastimil ; Boháč, Jan (advisor) ; Kudrna, Zdeněk (referee)
Title Foundation of traffic embankments on clayey landfills of SHR Abstract This Bachelor thesis was worked out for Faculty of Science of Charles University in Prague led by Ing. J. Boháč. The thesis deals with motorway embankment over the landfill A. Zápotocký, which is part of motorway strech D8-0807/I. The thesis compiles research results, monitoring of trial embankments and monitoring performed by the own construction motorway embakment. Based on these data is determined the creep portion of the total settlement.
|
|
| |
|
|
Properties of alluvial sediments at Albertov, Prague
Chvílová, Martina ; Boháč, Jan (advisor) ; Lešner, Jeroným (referee)
Bachelor thesis deals with the sediments of river terraces in Prague, Albertov. On these sediments from the deep drill hole J6 in campus Albertov area I made eight grain measurements, processed grain curves and normatively classified terrace soils with classes S1, S2, S3 and F3, F4. They are sandy soils partly containing fine gravel or fine fraction admixture. I also performed the grain analysis on soils 1,5m deep in near morphological distance from the drill hole on which bases I searched for analogy between sediments on campus Albertov building site. They are recent soils of local and foreign digged material. In documented terrace material with S2 character was observed that with content of fine- grained fraction under ca. 5% the increase of the proportion of fine-grained admixture elevates the angle of sands natural slope.
|
|
|
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...
|
guest ::
