|
|
Salt precipitation in subsurface zone of sandstone and other porous rocks and simulation of water transport and evaporation
Sommerová, Anna ; Bruthans, Jiří (advisor) ; Filippi, Michal (referee)
The main goal of this thesis was to find and compare salt-forming ions from samples of a subsurface zone of sandstone and other porous rocks. The surveyed samples came from different environments (humid and arid climate) from different locations in the Czech Republic, Jordan and the United States of America. Identification of various types of salt was based on evaluation of chemical analyzes of leached samples. Furthermore a laboratory experiment in which I used a fluorescein dye to observe the capillary rise and evaporation in unsaturated samples of sandstone was carried out. The salt content in the Czech Republic humid environment locations is generally lower than the one in foreign arid climate locations. Halit dominates in the locations Petra and Crystal Peak. In the other locations sulphate minerals dominate. The salts containing aluminum - alums were determined in the Czech Republic in the area of Czech Paradise and the surrounding. Relatively high concentrations of nitrate mineral nitratine were identified in the Devil's Pulpit location in Pilsen, the Czech Republic. From the observation of capillary rising experiments performed with artificially created honeycombs, I conclude that the height of the capillary rise is crucial for the transport of solution, and at a certain capillary height,...
|
|
|
Comparison of hydraulic characteristics of cavernous weathering rocks forming tafoni and honeycombs
Studencová, Alžběta ; Bruthans, Jiří (advisor) ; Sněhota, Michal (referee)
Forms of cavernous weathering - tafoni and honeycombs - belong to long-term investigated and discussed phenomena in geology. The reason for the difference in size between few centimetres- long honeycombs and the several-metres-long tafoni has not been yet studied. In my master thesis I compared the hydraulic properties of rocks with developed honeycombs and tafoni. The research consists of field measurements (measurement of suction pressures and capillary water absorption using Karsten tube) and laboratory measurements on tafoni and honeycomb samples (retention curve measurement, capillary water absorption, water vapour diffusion rate and saturated hydraulic conductivity). I have been studing honeycombs from various sites in the Bohemian Cretaceous Basin and tafoni from three different sites: Carbon Arkoses near Kralupy nad Vltavou, Cambrian Sandstone in Petra (Jordan) and Tunnel Spring Tuff in Crystal Peak (Utah). The measurements showed that values of suction pressure are far higher inside tafoni than inside honeycombs. This observation corresponds to different retention curves of studied rocks: steeper retention curve for honeycomb's quartz sandstone than for fine-grained arkosic sandstones to arkoses with tafoni. In the other part of my research I have compared the properties of hydrophobic...
|
|
|
Moisture and its transport in shallow subsurface of quartz sandstone
Svobodová, Eliška ; Bruthans, Jiří (advisor) ; Schweigstillová, Jana (referee)
The thesis deals with moisture transport in porous medium of quartz sandstone. Capillary water and its movement is crucial for processes such as salt and frost weathering, growth of organisms and development of honeycombs and tafone. However, moisture transport is still not well described. I focused particularly on two new methods applied to sandstone investigation. In the laboratory I studied moisture transport in sandstone samples by means of repeated injection of uranine solution. I observed the evolution of evaporation front based on the changes in solution concentration indicated by difference in color of uranine solution. Additionally I investigated moisture content in the shallow subsurface of sandstone outcrops in the field using suction pressure and moisture content measurements by microtensiometers and TDR in three locations in the Bohemian Cretaceous Basin. Uranine proved to be an excellent tracer for visualization of the evaporation front geometry and its evolution in time. The results suggest that moisture transport is considerably affected by the presence of biofilms which are hydrophobic and retain moisture transport to surface. In addition, the values of suction pressure measured in honeycombs and a tafone are in agreement with the salt weathering model proposed by Huinink et al. (2004).
|
guest ::
