scholarly journals Crack coalescence and strain accommodation in gypsum rock

2020 ◽  
Vol 14 (52) ◽  
pp. 247-255
Author(s):  
Chiara Caselle ◽  
Sabrina Maria Rita Bonetto ◽  
Daniele Costanzo
Keyword(s):  
Crack Coalescence ◽  
Gypsum Rock

Investigation of Dynamic Crack Coalescence Using a Gypsum-Like 3D Printing Material

2016 ◽  
Vol 49 (10) ◽  
pp. 3983-3998 ◽  
Author(s):  
Chao Jiang ◽  
Gao-Feng Zhao ◽  
Jianbo Zhu ◽  
Yi-Xin Zhao ◽  
Luming Shen
Keyword(s):  
3D Printing ◽  
Crack Coalescence ◽  
Dynamic Crack

The Use of Closely Spaced Vickers Indentations to Model Erosion of Polycrystalline α-Al2O3

2004 ◽  
Vol 843 ◽  
Author(s):  
Adolfo Franco Júnior ◽  
Steve G. Roberts
Keyword(s):  
Grain Size ◽  
Impact Velocity ◽  
Erosive Wear ◽  
Significant Loss ◽  
Crack Coalescence ◽  
Good Correspondence ◽  
Mean Grain Size ◽  
Static Indentation ◽  
Α Al2o3 ◽  
Wear Maps

ABSTRACTArrays of closely spaced quasi-static indentation were made on specimens of polycrystalline α-Al2O3, mean grain size G=1.2, 3.8 and 14.1 μm. The critical indentation spacing to produce crack coalescence between indentations, and thus significant loss of material from the surface, was determined. These data are compared to results for low-impact-velocity wet erosive wear on the same materials; a good correspondence is found. The indentation data can be used to produce “wear maps”, which provide a guideline for predicting the low-impact-velocity erosive wear resistance of brittle materials.

scholarly journals Bacterial Life and Dinitrogen Fixation at a Gypsum Rock

2004 ◽  
Vol 70 (12) ◽  
pp. 7070-7077 ◽  
Author(s):  
Gudrun Boison ◽  
Alexander Mergel ◽  
Helena Jolkver ◽  
Hermann Bothe
Keyword(s):  
Nitrogenase Activity ◽  
Dinitrogen Fixation ◽  
Molecular Techniques ◽  
Low Light ◽  
Light Intensities ◽  
Bluish Green ◽  
Reductase Gene ◽  
Gypsum Rock ◽  
Microaerobic Conditions ◽  
Reduced Light

ABSTRACT The organisms of a bluish-green layer beneath the shards of a gypsum rock were characterized by molecular techniques. The cyanobacterial consortium consisted almost exclusively of Chroococcidiopsis spp. The organisms of the shards expressed nitrogenase activity (C2H2 reduction) aerobically and in light. After a prolonged period of drought at the rock, the cells were inactive, but they resumed nitrogenase activity 2 to 3 days after the addition of water. In a suspension culture of Chroococcidiopsis sp. strain PCC7203, C2H2 reduction required microaerobic conditions and was strictly dependent on low light intensities. Sequencing of a segment of the nitrogenase reductase gene (nifH) indicated that Chroococcidiopsis possesses the alternative molybdenum nitrogenase 2, expressed in Anabaena variabilis only under reduced O2 tensions, rather than the widespread, common molybdenum nitrogenase. The shards apparently provide microsites with reduced light intensities and reduced O2 tension that allow N2 fixation to proceed in the unicellular Chroococcidiopsis at the gypsum rock, unless the activity is due to minute amounts of other, very active cyanobacteria. Phylogenetic analysis of nifH sequences tends to suggest that molybdenum nitrogenase 2 is characteristic of those unicellular or filamentous, nonheterocystous cyanobacteria fixing N2 under microaerobic conditions only.

Correlation between the mineral composition and strength properties of sulfate rocks

2021 ◽  
pp. qjegh2020-173
Author(s):  
Mohammad Reza Rahimi ◽  
Seyed Davoud Mohammadi ◽  
Alireza Taleb Beydokhti
Keyword(s):  
Mineral Composition ◽  
Failure Mode ◽  
Strength Properties ◽  
Shear Mode ◽  
Rock Cores ◽  
Strength Tests ◽  
Engineering Problems ◽  
Gypsum Rock ◽  
Under Construction ◽  
First Time

The literature review confirms that the effect of mineral composition on the strength properties of rocks has rarely been studied. One of the most problematic sedimentary rocks is sulfate rocks, which cause engineering problems in the infrastructure sites such as reservoir dams. In this paper, for the first time, the effect of mineral composition on the strength properties of sulfate rocks was investigated. The rock blocks were collected from the Gachsaran Formation outcrops at the four under construction reservoir dam sits in Iran. After preparing, drying and saturation the rock cores samples (329 samples), uniaxial compressive strength tests were performed in accordance with ASTM and ISRM standards. The results of this study confirmed that firstly, there is a correlation between the mineral composition and the strength properties of the sulfate rocks, but the obtained relationships do not have the necessary certainty to be used as predictive equations. Secondly, by increasing the amount of anhydrite or microcrystalline carbonates in a gypsum rock, its strength properties are increased. Thirdly, in a dry condition the dominant failure mode in gypsum and anhydrite rocks is a shear and dilatation mode, respectively, but after saturation, the failure mode tends to shear mode.

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