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Gravity survey of the highway route D3
Kohout, Milan ; Blecha, Vratislav (advisor) ; Mrlina, Jan (referee)
The aim of this thesis was to determine if in the area lying west of the town Jílové u Prahy occur old mine galleries, that could pose a risk for the future construction of the highway D3. The problem was solved by microgravity measurements carried out in an area of 310 x 50 m on the five profiles. There were 3 parallel profiles P15, P1 and P-15 and 2 profiles P9290 and 9180 which were perpendicular to them. The measured data were then quantitatively and qualitatively interpreted in the programs Surfer and GM-SYS. The survey located four areas of potential occurrence of galleries or tectonics lines that also appear in the area of study. Quantitative interpretation excluded the presence of the galleries in three sections. In one area was not possible to recognize if the negative anomaly in caused by old mine gallery or by the fault. Based on the interpreted data there was marked one potential risk area with possible occurrence of the old mine gallery. For more accurate information it would be necessary to make more detailed microgravity survey supplemented by electrical resistivity tomography.
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Geophysical survey of subsurface voids at locality Letonice
Bartášková, Lucie ; Blecha, Vratislav (advisor) ; Skácelová, Zuzana (referee)
The Větrníky national nature reserve, located in the South Moravian region north of the village of Letonice, is one of the largest steppe reserves in Southern Moravia. This whole area is characterized by the presence of both stable and active landslides, and the occurrence of suffosion sinkholes has been monitored there in the long-term. The aim of the thesis was to investigate whether it was possible to observe subsurface phenomena, caused by the washing out of fine rock particles by ground water, by means of geophysical methods. This phenomenon is known as suffosion. The measurements took place in the areas where the suffosion manifestation was very distinctive, that is around two sinkholes that were visible on the surface. In order to identify the suffosion structural-geological causes and their manifestations at a given location, the gravimetric and electrical resistivity tomography (ERT) methods were used in the first stage of the research. Measured data was further processed and geologically interpreted. The gravimetric method has proved suitable when identifying rocks affected by suffosion, in which case we assume that their density is lower than the density of the surrounding rocks. Using the ERT method, it was possible, in the vertical profile, to distinguish the sandy-gravelly sediments...
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Complex interpretation of gravity data focused on tectonic structure assessment and environmental projects
Mantlík, František ; Kobr, Miroslav (advisor) ; Blecha, Vratislav (referee) ; Pašteka, Roman (referee)
3 Abstract Gravimetry is an enormously expanding geophysical exploration method during the last decade. Unfortunately the gravity inversion ambiguity problem introduces the necessity to constrain gravity model parameters by other independent data. Overview of gravity data processing and interpretation is presented. All stages of the project lifecycle are discussed with emphasis to the methodological aspects and new challenges introduced by common use of modern digital zero-length spring gravimeters. Special attention is drawn on approaches used in the presented case histories projects. Description of the interpretation stage of the project concentrates on constraining of gravity model parameters with a complex of geophysical and geological data in order to reduce ambiguity of the inversion process in gravimetry. In addition, approaches used for delineation of tectonic structures, an important aspect of the interpretation stage, are described. Three case histories examples are presented to demonstrate methodological aspects of the interpretation of gravity data. They are focused on environmental problems and tectonic structure assessment. The first project represents an attempt to use micro-gravity for determination of internal structure of an undocumented sealed landfill. The second project demonstrates...
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Magnetic survey in Pruhonice park
Bartášková, Lucie ; Kletetschka, Günther (advisor) ; Blecha, Vratislav (referee)
The aim of the thesis was to get acquainted with the measurement of the magnetic field of the earth on a concrete example, in Průhonice Park, where the geological structures are covered pond, and there is direct access to rock. It was also proposed vessel for measuring the magnetic field on the surface of the water. The measurement result was compared with existing geological maps and interpreted in terms of magnetic sources. On the basis of familiarity with the course of magnetometric data acquisition and processing the earth was proposed procedure for measuring the magnetic field of the planet Mars. Powered by TCPDF (www.tcpdf.org)
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Gravity and magnetic survey of the east tectonic boundary of Cheb sedimentary basin
Buřičová, Pavla ; Blecha, Vratislav (advisor) ; Beneš, Vojtěch (referee)
Region of West Bohemia and the neighbouring German area Vogtland is characterized by its recent seismic activity. For better understanding of the distribution and origin of earthquake swarms it is necessary to know in detail the shallow as well as deeper geological structure of this area. This thesis deals with the geological and tectonic situation between villages Kopanina and Nový Kostel. In this area Mariánské Lázně Fault, which represents - from our point of view - the eastern marginal fault of the Cheb basin, is crossed with the fault zone Počátky - Plesná. The greatest amount of earthquakes hypocenters on the territory of Czech Republic have been registered in this region. The aim of this thesis is not only to find the eastern marginal fault of the Cheb basin, but also to define its course in the terrain and to determine its slope. Geophysical methods gravimetry, magnetometry and conductometry have been applied to identify these fault parameters. Geophysical methods were measured on three paralel profiles in August 2010 and in June 2011. The data from these profiles were consequently processed and geologically interpreted. During interpretation it was shown that contribution of magnetometry to recognition of different rock types and to identification of tectonic features was poor. On the...
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Microgravity survey and monitoring of subsurface inhomogeneities
Spěšný, Marek ; Mrlina, Jan (advisor) ; Blecha, Vratislav (referee)
Marek Spěšný - abstract This thesis has the nature of a survey report of a specific area. The task was to localize with the help of microgravimetry anomalous places in an area of a by-pass road construction, where subsurface inhomogeneities may possibly exist due to subsurface and surface historical mining of ceramic clay. The gravimetrical measurements were carried out with a relative gravimeter Scintrex model CG-5 AUTOGRAV. After the first stage of the gravimetrical measurements and following two weeks of recultivation works our assignment was to verify the success of the first measurements by the means of repeated microgravimetric control measurements. The results from both stages of measurement were processed into a 4D gravimetrical form. The results of the 4D gravimetry displayed that contrary to the expectations, the measured gravity of most of the area of interest decreased as much as by 30 ?Gal. We conclude that this is due to the drainage of injected material beyond the recultivated mining area, which washed and carried away a portion of the existing material. Our proposition was also supported by results of repeated leveling, which discovered subsidence of the road at times by up to 3 centimeters.
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Geophysical survey of undermined area in Lukavice near Chrudim
Slavíčková, Michaela ; Blecha, Vratislav (advisor) ; Dohnal, Jiří (referee)
Lukavice village is located in Eastern Bohemia and it is known for its historical pyrite mining. The first mention of mining comes from the beginning of 17th century. The mines were abandoned in 1892 due to a significant depletion of the upper parts of the deposit and also because of the competition of cheaper pyrite from abroad. Old mine workings were often backfilled incompletely and their exact location is unknown. The occurrence of empty mine workings under the roads in the village centre could cause a collapse of the ground under the weight of heavy trucks which carry through Lukavice village aggregate from the nearby quarry. The aim of geophysics was to determine the thickness of dump material (seismics), subsidence monitoring in the village centre (repeated levelling) and the principal aim was to locate old mine galleries and shafts (gravity survey). Gravity measurements did not prove the presence of empty mine workings under the main road at the village centre. Most pronounced negative Bouguer anomaly, which occurs in the vicinity of Bartolomějská jáma schaft, may be caused by higher degree of alteration of underlying porphyroids. According to historical maps and photos we determined approximate location of the former water pit Vilemina. For the determination of the exact position of the...
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Gravity response of deformation zones around subsurface cavities
Šifnerová, Kristýna ; Blecha, Vratislav (advisor) ; Gürtler, Richard (referee)
The main purpose of this diploma thesis was to determine whether the deformation zone, which arises above intact mining workings in soils, has a measurable gravity effect and influences the interpretation of gravity measurements. The railway tunnel in Březno u Chomutova has been chosen as a test site. We have progressed so that the geotechnical model of the geological environment above the tunnel was calculated first. The model was constructed on the base of two core wells, which were drilled near the tunnel especially for this purpose. The geotechnical model of deformation zone was converted into a density model and its gravity response was calculated. This model was compared with the gravity effect of the tunnel in rock environment without any deformation zone. The difference between effects of these two models gives the gravity response of the deformation zone. We found out that the gravity effect of the deformation zone is insignificant and does not affect the gravity interpretation in the environment of stiff tertiary clays, where the Březno tunnel is excavated. We compared the results of our modeling with the field gravimetric measurements results above the tunnel in Březno. The measurement was realized on three parallel profiles, which reach the tunnel in various depths. The results of...
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