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Elastic anisotropic behaviour related to crack distributions in two gneisses
Full text linkStress-strain response of foliated rocks shows that mechanical behaviour and degree of anisotropy are influenced by the spatial arrangement of phyllosilicates. But the anisotropy of these rocks is essentially due to the characteristics and distribution of cracks aligned with mica beds. At the laboratory scale, the elastic symmetry can be represented by the transverse isotropy, with the lowest elastic modulus perpendicular to the plane of aligned microcracks. These issues are discussed with reference to experimental data obtained for two gneisses of the same geological formation. The gneisses show a quite similar strength behaviour, but very different deformabilities. The measures of dynamic and static deformabilities under loading prove the influence of the progressive closure of open cracks on the compliance tensors of both gneisses. The relationship between the elastic parameters and the characteristics of the crack distributions is discussed in the framework of non-interacting crack models. Assuming the presence of two different sets of cracks, crack densities have been estimated. The different deformabilities of the two gneisses can be ascribed to their different microcrack distributions. The degree of anisotropy due to cracks reduces as stresses increase, differently for the two gneisses
Rock Laboratory Tests
No full textLaboratory tests are carried out to determine rock properties. Since rock properties are a key input for rock mechanics design in civil, mining and petroleum engineering, the present chapter is mainly based on documents by the International Society for Rock Mechanics (ISRM). The ISRM Commission on Testing Methods since 1974 has published the ISRM Suggested Methods (SMs) covering different aspects of rock mechanics. The SMs are collected in books (‘yellow’ book, Brown 1981; ‘blue’ book, Ulusay and Hudson 2007; ‘orange’ book, Ulusay 2015). A complete list of ISRM SMs is included in the ‘orange’ book. The content of the present entry does not presume to provide detailed instructions on the test procedures or to be exhaustive of the rock laboratory tests. The reader is invited to refer to the above-mentioned ISRM books. Moreover, not only are rock laboratory tests numerous, but the work of the ISRM Commission on Testing Methods is always in progress and further SMs on different tests or updated procedures will be published
Multiscale physical and mechanical characterization of a sandstone used as armourstone
No full textThe suitability of a sandstone from Central Italy as armourstone source was investigated both at the specimen and block scale. Once the physical properties were determined, the rock material was subjected to ultrasonic pulse, mechanical and wear/durability tests. The results were linked to the petrographic features observed at the optical and scanning electron microscope. Possible defects in blocks were investigated through drop tests and by comparing wave velocities measured on specimens and blocks. The rock has good physical, mechanical and durability index properties, whilst its wear resistance addresses the use of blocks in moderately stressing conditions (e.g. internal harbour areas). Blocks can be downgraded if affected by diffuse oxidation, as it is associated to a reduction of physical and mechanical properties. © 2024 The Author(s)
Analisi delle condizioni di sicurezza di una cava in esercizio con modelli del discontinuo. Memorie Gruppo Naz. Ing. Geotec
No full textEvoluzione delle deformazioni di una frana di scivolamento in calcari con interstrati, periodicamente riattivata dalle precipitazioni
No full textCaratterizzazione dell’ammasso roccioso di fondazione di una diga in presenza di discontinuità con riempimento
No full textAnalisi del comportamento di alcune gallerie (SS 106 Jonica) in corso di scavo in terreni a grana fina
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Analisi delle condizioni di sicurezza di una cava in esercizio con modelli del discontinuo
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