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Start Over Subject sandstone rocks

2. Slope failures around the rock castle Drábské Světničky, Czech Republic

Creator:
Jan Rybář, Stemberk, Josef, and Hartvich, Filip
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, pískovcové skály, sandstone rocks, landslide inventory, landslide susceptibility mapping, slide, spread, fall, dilatometric measurements, pseudocarst, 7, and 551
Language:
English
Description:
Stability conditions in a wider surrounding of the rock castle Drábské Světničky (Drábské Rooms) near the town of Mnichovo Hradiště were investigated. The area which has been intensively disturbed by large old as well as present slope movements is located in the north-western part of Příhrazy Platform. Solid, thick bedded sandstones, well resistant to weathering, are lying on claystones apt to plastic deformations. Marginal sandstone blocks separate, move down on the slope and sink into the plastic bedrock. As a result, block fields with many crevasses develop. In rock walls that separate individual blocks, rockfalls originate and central, as well as lower parts of the slopes develop large landslides. A zone comprising up to 400 m wide rim of the high and exposed platform has been subject to a process of loosening. A local group of tower-like sandstone blocks was used in the 15th century to build a small rock castle called Drábské Světničky. An extensive landslide that destroyed a substantial part of the village of Dneboh in June 1926, reached in its separating zone up to the toe of marginal rock towers belonging to the complex of Drábské Sv ě tni č ky with the result of local movement activation. Marginal zones of the flat land behind display fresh linear, as well as oval depressions and sinks. Fissure and pseudocarst caves develop. Present activity of the movements has been evidenced by dilatometric measurements on two selected rock objects where movement rates reached 1 to 2 mm per year in average., Jan Rybář, Josef Stemberk and Filip Hartvich., and Obsahuje bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Vyšší princip pískovcový

Creator:
Michal Filippi and Jana Schweigstillová
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Věda. Všeobecnosti. Základy vědy a kultury. Vědecká práce, pískovce, pískovcové skály, eroze (geologie), sandstones, sandstone rocks, erosion, 12, and 00
Language:
Czech
Description:
Weathering and erosion of sandstone landscapes often results in many amazing landforms such as arches, alcoves (rock shelters), pedestal rocks and pillars. Long-term research has produced numerous contrasting ideas for the origin of these landforms. The presence of salt and/or occurrence of freezing water and/or similar potential weathering/erosion processes at site are common causes of these landforms. The effect of gravity loading stress has been overlooked or assumed to increase the landform’s weathering rate. Research at the Institute of Rock Structure and Mechanics is based on field observations of locked sands and cemented sandstones and on physical experiments, followed by a numerical modelling. This may be the first time that the landforms cited above were reproduced in laboratory experiments. The Institute interpreted its findings by a novel mechanical model called “the concept of locus of fabric instability.” The results clearly show that an increase in stress within the landform (fabric interlocking) reduces weathering and erosion. Material with insufficient loading is rapidly removed by that weathering process and the remaining load bearing landform structure is protected by the fabric interlocking mechanism. The Institute concludes that its research that planar discontinuities in sandstone and negative feedback between stress and weathering/erosion processes are sufficient conditions to create landforms. and Michal Filippi, Jana Schweigstillová.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public