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Influence of CaO on structure and permeability of clayey soil
Pastyriková, Zdeňka ; Boháč, Jan (advisor) ; Frankovská, Jana (referee) ; Sněhota, Michal (referee)
The aim of this study was to determine the effect of quicklime (1 - 8% CaO) and maturation time (1 - 540 days) on the structure of clayey soil compacted at optimum moisture content by Proctor standard energy and whether expected change in structure affects the long - term permeability. The change of pore space of compacted loess with 1-8% lime (CaO) was studied by mercury porosimetry (MIP) for a long period of maturation (from 1 to 540 days). Development of pozzolanic reactions were monitored by measuring the pH. The development of new mineral phases (calcium silicate hydrates, calcium aluminate hydrates and calcium aluminate carbonate hydrate) in the treated soil was investigated by using X-Ray diffraction. The MIP indicated that 2% of CaO were sufficient for long term pozzolanic reaction. The threshold value is below the initial consumption of lime determined from the pH measurements (Eades and Grim, 1966). The alteration of the voids of the lime treated soil is noticeable, but the pH value can not drop below 11.7. At 4% of CaO, at 8% of CaO respectively, the macroporosity kept decreasing due to increasing mesoporosity for 360 curing days, for 540 curing days respectively, due to the new mineral phases. At 2% of CaO, the decrease of the macroporosity stops after 120 days. Below 2% of lime, the...
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Quasi-overconsolidation pressure of Brno Tegel determined by the oedometer test.
Černíková, Monika ; Boháč, Jan (advisor) ; Fiala, Radek (referee)
The present Diploma Thesis deals with overconsolidation of Brno Neogene Clay (Brno Tegel). It investigates whether the yield pressure pm' determined by the oedometer test is a direct measure of the overconsolidation of the soil or rather a combination of overconsolidation and diverse effects of ageing. Further it looks at the problem of determining the original thickness of Brno Tegel (depth of the erosion). The yield pressure was determined by standard oedometer tests on undisturbed specimens. In order to assess the effect of ageing on the structure of the clay, the concept of "intrinsic" properties from the literature was used, which was based on "Critical state soil mechanics". The additional testing and investigations needed for soil characterisation included the determination of consistency limits, grading curve, and the density determination by weighing under water. Clay minerals in selected specimens were determined by X-Ray diffraction analysis. The literature review clarified some geotechnical aspects of the development of postsedimentation structure of Brno Tegel.
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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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Secondary compression of Brno Tegel
Pavlová, Martina ; Boháč, Jan (advisor) ; Král, Jan (referee) ; Rozsypal, Alexandr (referee)
Observation and measurement of long-term volumetric deformation of clay are important in tackling different geotechnical and geological issues. The area of interest is the northern part of Vienna Basin, where Miocene clays sedimented. It is locally known as Brno Tegel. The Thesis deals with the secondary compression of clays, which can be defined by the Cα/Cc concept. The one-dimensional creep can be determined using the numerical values of the coefficient of secondary compression Cα and subsequently the thickness of overburden of sediments can be estimated. The two different theories, known as Hypothesis A and B are also discussed, which have been used to interpret the effect of creep during the primary consolidation phase. The laboratory measurements of long-term oedometric tests are presented for two undisturbed samples and one reconstituted sample of Brno clay. A nonstandard behaviour in uniaxial creep is also discussed, namely the observed diffusion collapse. Powered by TCPDF (www.tcpdf.org)
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Analysis of peak and critical strength of remoulded clay from Jiři mine
Mužík, Vlastimil ; Boháč, Jan (advisor) ; Hudek, Jiří (referee)
This Thesis deals with the determination of the critical and peak strength of clay fill soils from open mine Jiří. The strenght of clay was determined by conventional triaxial apparatus and triaxial apparatus with frictionless specimens, and two types of direct shear box: translational and ring shear box. The results of laboratory tests are discussed and compared with data of geotechnical investigation of landslide in mine Jiří.
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Remedy of shallow slope slides by vegetation - using 'live poles'
Dašková, Barbora ; Boháč, Jan (advisor) ; Kudrna, Zdeněk (referee)
Slope instabilities (landslides) means hazard not only for structures, but also for human lives. This work describes one of the possible bioengineering methods which could prevent slope instability. The technique is called "Live Pole". It is an effectively, ecologically and economically undemanding method. However essential is the right choice of the plant species for the given site. Live Poles have a very positive influence on soil. Even with a small amount of roots the soil stability improves due to shear strength and dilatation increase anddue to root tensile effect. Also the amount of water in the soil decreases. The thesis also describes the use of "Live Pole" for the temperate zone and tropics (concretely for Malaysia). Keywords: Live Pole, slope stability, vegetation
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Mechanical behaviour of cemented fine-grained soils - simulation of undisturbed samples
Trhlíková, Jana ; Boháč, Jan (advisor) ; Herle, Ivo (referee) ; Miča, Lumír (referee)
The mechanical behaviour of natural clays is influenced by the degradation of the structure developed during and after deposition. In order to model the influence of structure artificially cemented specimens have been prepared. A series of one-dimensional compression tests of cement treated kaolin specimens were analysed. The effect of bonding and debonding on compression of the specimens was observed. The compression of cemented specimens was not monotonic, depending on disturbance of the structure. Cement content and curing period were found the main factors influencing the compressibility of cement treated kaolin clay. The possibility of using cement treated kaolin to model naturally cemented soil was confirmed. For the purpose of the research described in this dissertation, artificial cementation bonds were created in a model clayey material by adding 4% of Portland cement to kaolin clay. The mechanical behaviour of the model material at compression and shearing was compared with the behaviour of the pure reconstituted kaolin clay. Triaxial CIUP tests were carried out in determining the shear strength. Submersible LVDT's and bender elements were used for measuring of the shear modulus to identify the destructuration of the specimens. The experimental behaviour was successfully simulated by the...
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Effect of added lime on consistency limits of silty clay
Sotorník, Viktor ; Boháč, Jan (advisor) ; Kudrna, Zdeněk (referee)
This work looks into the effect of added lime on consistency limits of silty clay. It was carried out under the support of GAUK 62008 grant. In this work changes of consistency limits of a loessy soil from the borrow pit Horky nad Jizerou with amount of added quicklime (CaO) and curing time were observed. From the development of consistency limits the lowest amount of quicklime needed for the establishment of long - term (pozzolanic) reactions in the soil was determined. Consistency limits were determined following standardized procedures in an accredited laboratory. Determination of the liquid limit was conducted using the 80 g/30ř fall cone. Firstly sample heating caused by the exothermic nature of the slaking reaction CaO + H2O → Ca(OH)2 + heat and rapid soil flocculation after the lime addition were observed. Furthermore increase of the plastic limit, unpredictable behavior of the liquid limit and therefore influenced behavior of the plasticity index in agreement with findings stated in the research part were observed. The results showed finishing of the modification reactions within 48 hours after the lime addition too. Findings stated by Rogers et al. (1997) about the value of the lowest amount of quicklime determined by the consistency limits method being lower than the value determined by...
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Thickness of overburden and overconsolidation of Brno Clay
Pavlová, Martina ; Boháč, Jan (advisor) ; Mašín, David (referee)
Knowledge of the thickness of the overburden of sediments is important in tackling different geological and geotechnical issues. This Bachelor Thesis deals with the available methods for determining the original overburden thickness and with the possible errors from the point of view of the soil mechanics. The area of interest is the northern part of the Vienna Basin, in the vicinity of the town of Brno. The sediments in question are Miocene clays, known locally as Brno Tegel. Consequently the Thesis includes also a brief description of the geological origin of the Carpathian Foredeep.
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Slope stability of the Nová Ves clay pit
Šramota, Miloslav ; Boháč, Jan (advisor) ; Linhartová, Jitka (referee)
This bachelor thesis deals with clay quarry in west Bohemian locality Nová Ves II, where are mined Tertiary ceramic clays. Thesis summarizes available geological, engineering- geological and hydro geological information. Using ring shear apparatus, RTG analysis and silicate analysis were measured strength parameters and mineralogical composition for selected samples. Measurement and analysis showed very low readings angle of internal friction (φcr 12 - 13.6ř and φres 10 - 11.5ř). Using of only one measurement method prevented clear interpretation.
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