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Influence of the stress field on weathering and erosion of sandstone landforms
Řihošek, Jaroslav ; Bruthans, Jiří (advisor) ; Mikuláš, Radek (referee) ; Válek, Jan (referee)
The influence of mechanical stress on weathering and erosion has been overlooked in works focused on sandstone landforms formation, although stress has been shown to be a key factor in the formation of a number of different sandstone landforms recently. The main goal of the doctoral thesis is to understand the relationship between mechanical stress and weathering or erosion in the formation and development of sandstone landforms. The influence of mechanical stress on the mode of weathering and the rate of disintegration of the material forming historical monuments in Petra, Jordan was investigated on the site and on samples in laboratory. A negative exponential dependence has been proven between the speed of salt weathering and the magnitude of uniaxial compression of Petra sandstone samples. The role of mechanical stress as a mechanism controlling the formation and development of the shape of sandstone forms was further studied in rock overhangs, sandstone arcades and rock gates in the Czech Republic and the USA. The doctoral thesis presents and verifies a method using Střeleč sandstone as a natural analogue in physical models simulating weathering and erosion of cemented sandstone. These physical models usually take the form of a reduced initial shape of a sandstone object created in situ from...
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Approaches to estimate wetland evapotranspiration and the evapotranspiration loss of groundwater from wetlands in the Liběchovka and Pšovka catchments
Pátek, Karel ; Bruthans, Jiří (advisor) ; Slavík, Martin (referee)
This work is dedicated to the study of evapotranspiration in wetlands. The theoretical part is an overview of methods that are used for estimation of evapotranspiration, especially in the wetland environment. The practical part is focused on measurement of evapotranspiration in the wetlands located in the upper part of the Pšovka and Liběchovka river watersheds. Periodical fluctuations of water table and water flow in the stream were observed there due to evapotranspiration. The role of evapotranspiration was dependent on the mean daily temperature and sunshine duration. For the warm sunny days the fluctuations indicated that in the studied wetland the maximal daily evapotranspiration can cause 32 % decrease of water flow in the stream. The evapotranspiration derived from stream flow oscilation reached 86 % of potential evapotranspiration based on Oudin method. Potential evapotranspiration in the Liběchovka wetlands in summer is capable to decrease the discharge of Liběchovka in similar way as groundwater abstraction.
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Groundwaters in vicinity of subway line A
Drábková, Jana ; Bruthans, Jiří (advisor) ; Kůrková, Iva (referee)
The main aim of bachelor's thesis was to process and assess data measured during groundwater monitoring in the surroundings of construction sites of the new subway line A (21/04/2010 - 31/08/2011). The data from 17 monitored objects (subhorizontal mine galeries, springs and hydrogeological wells), which, with few exceptions, drain mainly Cenomanian aquifer (1 object in Orovician shales a 2 objects in Quaternary aquifer). For outflows from galeries and springs, statistics of the following parameters was calculated: discharge, pH, electric conductivity and water temperature. Discharge of all studied objects shows very low time variation. pH is neutral waters and overall, pH values show very low variability. Mean conductivity of studied objects suggests lower to moderate mineralization of waters. Groundwater temperature does not respond significantly to temperature changes at the surface. Marked temporary declines in water table leveal were probably caused by tunnel construction in proximity of the wells. Chemical analyses of groundwater from all 17 objects demonstrated that groundwater in the studied area belongs to the Ca-HCO3 type. Waters from different objects differ in increased concentrations of chlorides, nitrates or sulphates. Water is undersaturated in gypsum. Water is undersaturated in...
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Sandstone moisture measurement: laboratory and field techniques
Sommerová, Anna ; Bruthans, Jiří (advisor) ; Schweigstillová, Jana (referee)
Summary: In my thesis I reviewed the most used methods for moisture measurements with the focus on sandstone exposures. Concerning direct methods, the gravimetric is used most commonly for the calibration of other methods. Concerning indirect methods I mention radiometric, microwave, resistive and capacity methods. The major part of thesis is dedicated to capacity device TDR (Time Domain Reflektometry), which emits electromagnetics pulses and measures the reflection time at the beginning and the end of the probe. This methodology is nondestructive and is widely used, mainly in pedology. In practical part of Theses I worked with drill cores of sandstone from natural exposures and I detected their mass water content using gravimetric method, their bulk density by laboratory measurements and from those values I calculated volumetric water content. Average value from measured mass water content is 3,3% and from volumetric water content 6,2%. At some localities the moisture content was measured by TDR was measured beside taking drill cores At places where it was possible to compare measurements using TDR with gravimetric method, TDR measurements show usually higher values (in average 1% higher) then gravimetric method. This fact is caused by calibration and accuracy of the device, generally though this TDR...
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Hydraulic conductivity of sandstone samples
Kobrlová, Alžběta ; Bruthans, Jiří (advisor) ; Ondovčin, Tomáš (referee)
Saturated hydraulic conductivity (k) describing the ability of the porous media to allow flow is defined by Darcy's low. Beside pore space properties it depends on the properties of liquid; therefore it is conventionally determined for water at 15 řC. Values of hydraulic conductivity vary between m/s and m/s for sands and sandstones and rises with increasing grain size and porosity. Hydraulic conductivity can be estimated by empirical formulas or measured by laboratory and field methods. Laboratory determination includes the constant head and the falling head permeameter tests. The constant head permeameter test is suitable for material with values of hydraulic conductivity ranging between m/s and m/s; the falling head test for values between m/s and m/s. Unsaturated hydraulic conductivity is a function of moisture (and pressure head). Retention curve describing the dependence of moisture on pressure head is the basic characteristic of each material. The unsaturated hydraulic conductivity can be calculated from the parameters of retention curve and the value of the saturated hydraulic conductivity using Van Genuchten - Mualem formula (1980). Fine grain rocks with small pores have higher values of hydraulic conductivity than coarse grain rocks in condition of significantly negative values of...
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Comparison of postoperative analgesia in ICU
Trojanová, Eva ; Bruthans, Jan (advisor) ; Pavlíček, Bohumil (referee)
The thesis deals with comparing the postoperative analgesia with a focus on pacients after hip replacement surgery at the intensive care units. The quantitative study realized at the Fakultní nemocnice v Motole and Nemocnice Třebíč during November 2012 and February 2013. The main task of the theoretical part is to analyze the current trends in the field of post- operativeanalgesia by the patients undergoing hip joint surgery as well as the explanation the basicconcepts of this issue and overviewing the international postoperative pain treatments. The practical part is an objective comparison the postoperative analgesia byselected patients at the Fakultní nemocnice v Motole and Nemocnice Třebíč determined by questionnaire. The results of the questionnaire are processed into graphical representation and subsequently evaluated. The work serves to clarify the overall issue of post-operative analgesia. The focus is mainly on ensuring the quality of postoperative analgesia, the financial requirements administered analgesics and the possible complications associated with the use of analgesic therapy. Key words: Analgesia, pain, hip surgery, visual analogue scale, analgesics
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