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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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Frost weathering of sandstones: mechanisms and laboratory experiments
Dvořák, Matěj ; Bruthans, Jiří (advisor) ; Schweigstillová, Jana (referee)
Frost weathering of sandstones: mechanisms and laboratory experiments This thesis studies and compares different mechanisms of frost weathering, and further describes the characteristics of the rock material and the external environment, which affect this process. The effects of frost action were related to sandstones. The thesis consists of a literature review and practical experiments. The literature review indicates, that frost weathering of sandstones is due to their characteristics (higher porosity, grain structure) rather influenced by mechanisms based on water migration through the pore space of freezing rock. Beside the properties of the sandstone material, also the water content, the final temperature of freezing and the rate of the temperature fall are important. The experiments were performed on samples of Cretaceous sandstones (thick-bedded and argillaceous sandstones of Bohemian Paradise) and Carboniferous arkoses of Syřenov formation. Samples were subjected to repeated cycles of freezing at - 20 řC and thawing in distilled water. The weathering progress was monitored by measuring the weight loss and damage description. Selected samples were further compared to samples weathered under the influence of tensile stress (3 kPa). Based on the experiments, the frost resistance (from the most...
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Origin of karst conduits and caves in Jizera Formation in Turnov.
Slavík, Martin ; Bruthans, Jiří (advisor) ; Schweigstillová, Jana (referee)
Aim of this study is to characterize the processes responsible for evolution of open conduits and caves in Jizera Formation near Turnov, in particular to distinguish if the main factor acting in enlargements of conduits is dissolution and the conduit system can be called karst, or if the process is caused by erosion of weakly cemented sandstone without contribution of dissolution. An important part of the study is to introduce the concept of self-organization. Based on results from accelerated simulation of dissolution of twenty rock samples, SEM analysis and drilling resistance, I have proved that rocks in Jizera Formation near Turnov dissolve in an acidic environment and their strength characteristics does not enable direct erosion by flowing water. Samples from localities of "Bartošova pec", "Slepé údolí Podhorčí", "Rozsedlinové ponory pod Drábovnou", "Šetřilovsko", "U Kačeny" and "Semikraska" dissolve, but behavior of samples from "Sudoměř - rybník" and "Sudoměř - Skalský potok" is in an acidic environment very similar to samples from Teplice Formation "Skalní pískovcový výchoz u Podhorčí" and "Valdštejn".
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Sapping- its field features and studies focused on detail description of the process
Soukup, Jan ; Bruthans, Jiří (advisor) ; Schweigstillová, Jana (referee)
The study discuss about groundwater sapping erosion, whereas is upon process looked from various points of view. In small scale it observes difference between sapping drainage network and network formed by surface runoff. Further forms of the sapping weathering are described and are mentioned examples of sapping valleys from different places around the world. Partially are mentioned actual knowledge in evolution of deep incised valleys on the Mars surface, which are obviously also formed partly by sapping. In the second part, study describes some experiments focused on evolution of sapping valleys in laboratory environment.
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Frost weathering of sandstones: mechanisms and laboratory experiments
Dvořák, Matěj ; Bruthans, Jiří (advisor) ; Schweigstillová, Jana (referee)
Frost weathering of sandstones: mechanisms and laboratory experiments This thesis studies and compares different mechanisms of frost weathering, and further describes the characteristics of the rock material and the external environment, which affect this process. The effects of frost action were related to sandstones. The thesis consists of a literature review and practical experiments. The literature review indicates, that frost weathering of sandstones is due to their characteristics (higher porosity, grain structure) rather influenced by mechanisms based on water migration through the pore space of freezing rock. Beside the properties of the sandstone material, also the water content, the final temperature of freezing and the rate of the temperature fall are important. The experiments were performed on samples of Cretaceous sandstones (thick-bedded and argillaceous sandstones of Bohemian Paradise) and Carboniferous arkoses of Syřenov formation. Samples were subjected to repeated cycles of freezing at - 20 řC and thawing in distilled water. The weathering progress was monitored by measuring the weight loss and damage description. Selected samples were further compared to samples weathered under the influence of tensile stress (3 kPa). Based on the experiments, the frost resistance (from the most...
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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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Effect of compression on salt weathering rate of sandstone
Vaculíková, Jana ; Bruthans, Jiří (advisor) ; Schweigstillová, Jana (referee)
The aim of this study was to investigate whether the uniaxial compression have any influence on the rate of salt decay. Tests were performed on several types of rocks, mainly sandstones from the Czech Republic and the USA. The first tests were made on Strelec sandstone blocks that were loaded with a mass of 6-24 kg, slowly saturated by solutions of NaCl, CaSO ₄. H ₂ O and KAl(SO ₄) ₂. 12 H ₂ O and dried at room temperature. Because the weathering rate was too low, another method was used for other rocks. Cubes cut fromrock were compressed by steel frame with a torque wrench to 0.75 Nm, which corresponds approximately to the uniaxial compression of 1.2 MPa. These compressed samples were tested according to a modified standard EN 12370, saturated by solution of Na2SO4 and subsequently dried in an oven. The cycle was repeated until the complete decay of the sample or until the residual weight of samples fall below 10 grams. Weight of the samples was plot over numbes of cycles. Approximately after first two cycles increase in weight due to the salt crystallization within samples was observed. In following cycles the samples begun to lose weight. All compressed samples wistand more cycles than their non-compressed counterparts. The experiment continues to find out how many cycles will the compressed...
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Origin of karst conduits and caves in Jizera Formation in Turnov.
Slavík, Martin ; Bruthans, Jiří (advisor) ; Schweigstillová, Jana (referee)
Aim of this study is to characterize the processes responsible for evolution of open conduits and caves in Jizera Formation near Turnov, in particular to distinguish if the main factor acting in enlargements of conduits is dissolution and the conduit system can be called karst, or if the process is caused by erosion of weakly cemented sandstone without contribution of dissolution. An important part of the study is to introduce the concept of self-organization. Based on results from accelerated simulation of dissolution of twenty rock samples, SEM analysis and drilling resistance, I have proved that rocks in Jizera Formation near Turnov dissolve in an acidic environment and their strength characteristics does not enable direct erosion by flowing water. Samples from localities of "Bartošova pec", "Slepé údolí Podhorčí", "Rozsedlinové ponory pod Drábovnou", "Šetřilovsko", "U Kačeny" and "Semikraska" dissolve, but behavior of samples from "Sudoměř - rybník" and "Sudoměř - Skalský potok" is in an acidic environment very similar to samples from Teplice Formation "Skalní pískovcový výchoz u Podhorčí" and "Valdštejn".
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Sapping- its field features and studies focused on detail description of the process
Soukup, Jan ; Bruthans, Jiří (advisor) ; Schweigstillová, Jana (referee)
The study discuss about groundwater sapping erosion, whereas is upon process looked from various points of view. In small scale it observes difference between sapping drainage network and network formed by surface runoff. Further forms of the sapping weathering are described and are mentioned examples of sapping valleys from different places around the world. Partially are mentioned actual knowledge in evolution of deep incised valleys on the Mars surface, which are obviously also formed partly by sapping. In the second part, study describes some experiments focused on evolution of sapping valleys in laboratory environment.
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