National Repository of Grey Literature 19 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Porosity of different rocks in relation to capturing/moving of gases and liquids
Řimnáčová, Daniela ; Vöröš, Dominik ; Natherová, Vendula ; Přikryl, R. ; Lokajíček, Tomáš
Variability in the porosity of natural rocks and waste have been investigated in relation to the influence on the\npermeability of gases and water. The samples were of sedimentary or igneous rocks, carbon-rich rocks, and solid\nporous waste material after thermal conversion. Using mercury intrusion porosimetry, porosity values and pore\nsize distribution varied with the origin of materials. These results have been compared and a connection between\nthe origin and porosity of material was observed. Total porosity values of selected samples ranged from ca. 0.2%\nfor granite to 55% for waste porous material. Lower porosity values demonstrate the connectivity between\nmesopores or micropores and are related to the capturing of greenhouse gases, while higher porosity is caused\npredominantly by the presence of macropores and coarse pores, which serve as pathways for permeability of\ngases and liquids.
Laboratory study of 3D elastic anisotropy of rocks
Svitek, Tomáš ; Lokajíček, Tomáš (advisor) ; Fischer, Tomáš (referee) ; Pšenčík, Ivan (referee)
12 Abstract The presented work evaluates the significance of measuring acoustic S-wave velocities for determination of elastic anisotropy of rocks. The S waves are more sensitive to anisotropic properties of a medium than the P waves. Analyzing the S-wave splitting, it is possible to determine strength of anisotropy as well as the orientation of structures responsible for the anisotropic behavior of the medium. The S waves are necessary for determining the complete tensor of elastic parameters. In order to record the S waves, the measuring head of the present apparatus has been significantly adapted. Implemented innovations provided measurements of the P waves together with two orthogonally polarized S waves. The calibration performed on homogeneous isotropic materials proved that the recorded data are accurate and of high quality. The ultrasonic measurements on spherical samples under confining pressure and recording of the S waveforms significantly improved the accuracy of the retrieved elastic parameters compared to the measurements in standard use. The analysis of the S-wave records also required modifications of the processing software and a development of new algorithms. The proposed methods were tested on synthetic data. The tests evaluated the robustness of the inversion for anisotropy as a function...
Stanovení přetvárných charakteristik pískovce ultrazvukovou metodou : závěrečná zpráva
Živor, Roman ; Lokajíček, Tomáš ; Filler, Vlastimil
Dynamic deformational characteristics – modulus of elasticity, modulus of rigidity and Poisson‘s ratio were determined by the laboratory ultrasonic pulse method on samples of Cretaceous sandstone from Prague underground tunnelling. The characteristics were calculated from of P and S wave velocities found during ultrasonic propagation of rock samples.
Určení znaménka prvého nasazení a času příchodu u signálů akustické emise pomocí metody vyšších statistických momentů
Lokajíček, Tomáš ; Klíma, Karel
Application of high order statistic to determine arrival time and sign of ultrasonic and acoustic emission signals.

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