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Report on survey of salinity of masonries under 3rd courtyard at Prague Castle
Slížková, Zuzana ; Náhunková, Pavla
In 2022, the characterization of the chemical composition and amount of salt efflorescence on archaeological constructions under Prague Castle was supplemented by two new locations (at the site of the foundations of the Chapel of St. Bartholomew and near the northern wall of zone III). In the results, carbonate minerals were not detected as in previous years (except for calcite in small quantities). Sodium sulfate was again the majority component in the efflorescences. Using thermal analysis, the presence of sodium sulfate in the form of mirabilite was confirmed in the samples taken in February. The high contamination of marlstone with nitrates and chlorides in today's crown of the chapel's masonry of St. Bartholomew and increased sulfate contamination in the plinth section was detected. Conversely, no risk values of water-soluble ions were detected in the mortar or the black bricks of the perimeter wall.
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The effect of the backfill on the integrity of a buried pipeline upon heavy-duty vehicle crossings
Gajdoš, Lubomír ; Šperl, Martin ; Slížková, Zuzana ; Drdlová, M.
The aim of this work was to determine stresses in the wall of a buried empty gas pipeline caused by the weight of backfill as well as by heavy-duty vehicles crossing the pipeline, and, on their basis to assess the applicability of protective sleeves. A buried pipeline with zero internal pressure of transported medium (empty pipeline) differs from an unburied pipeline by the vertical load due to the weight of the backfill which causes an ovalness of the circular cross section of the pipeline. This leads to the rise of through-wall bending stresses with the tensile stress at the outside surface at the 3 and 9 o´clock positions and compressive stress at the inside surface. At the 6 and 12 o´clock positions the stresses are tensile at the inside surface and compressive at the outside surface. The current depth of soil cover above gas pipelines is 0.5 m. For pipes DN500, t ~ 6.5 mm the through-wall bending stress is found to be σb ≈ ±10 MPa. In comparison with the yield stress of pipeline material, this stress is negligible. The situation is changed when heavy-duty vehicles cross the pipeline. For example, when a MAN truck with the mass load 3270 kg acting on a single wheel of the front axle crosses this pipeline, the pressure transmitted to the pipe will cause the through-wall bending stress σb ≈ ±76 MPa. This stress is superimposed to that of the backfill to give the total value ±86 MPa. When dead loads, imposed by backfill cover, together with live loads, caused by truck-wheel loads, are excessive a crushing of side walls of the pipeline and/or ring buckling of the pipe cross section can happen.
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Chemical and microstructural analysis of brick samples from the object of Zákupy castle horse stables
Frankeová, Dita ; Bauerová, Pavla ; Náhunková, Pavla ; Ševčík, Radek ; Mácová, Petra ; Slížková, Zuzana ; Vondráčková, Michaela
As part of the construction-technical survey, historical brick samples were characterized using thermal analysis (TGA), scanning electron microscopy (SEM/EDS), ion chromatography (IC), infrared spectrometry (FTIR) and physical tests. The results of the tests testify to the good production quality of the masonry elements used. Based on the analyzes carried out, it can be assumed that the observed damage to the bricks is caused by high wetting of the masonry in combination with frost cycles, as well as crystallization cycles of water-soluble salts present in the surface layer of some bricks.
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