Microstructure in linear elasticity and scale effects: A reconsideration of basic rock mechanics and rock fracture mechanics

Exadaktylos, GE; Vardoulakis, I

dc.contributor.author	Exadaktylos, GE	en
dc.contributor.author	Vardoulakis, I	en
dc.date.accessioned	2014-03-01T01:16:45Z
dc.date.available	2014-03-01T01:16:45Z
dc.date.issued	2001	en
dc.identifier.issn	0040-1951	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/14194
dc.subject	Brittle geomaterials	en
dc.subject	Elasticity	en
dc.subject	Fracture mechanics	en
dc.subject	Microstructure	en
dc.subject	Rock mechanics	en
dc.subject	Size effect	en
dc.subject.classification	Geochemistry & Geophysics	en
dc.subject.other	deformation	en
dc.subject.other	elasticity	en
dc.subject.other	fracture	en
dc.subject.other	rock mechanics	en
dc.subject.other	scale effect	en
dc.subject.other	structural geology	en
dc.title	Microstructure in linear elasticity and scale effects: A reconsideration of basic rock mechanics and rock fracture mechanics	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/S0040-1951(01)00047-6	en
heal.identifier.secondary	http://dx.doi.org/10.1016/S0040-1951(01)00047-6	en
heal.language	English	en
heal.publicationDate	2001	en
heal.abstract	An account on the role of higher order strain gradients in the mechanical behavior of elastic-perfectly brittle materials, such as rocks, is given that is based on a special grade-2 elasticity theory with surface energy as this was originated by Casal and Mindlin and further elaborated by the authors. The fundamental idea behind the theory is that the effect of the granular and polycrystalline nature of geomaterials (i.e. their microstructural features) on their macroscopic response may be modeled through the concept of volume cohesion forces, as well as surface forces rather than through intractable statistical mechanics concepts of the Boltzmann type. It is shown that the important phenomena of the localization of deformation in macroscopically homogeneous rocks under uniform tractions and of dependence of rock behavior on the specimen's dimensions, commonly known as size or scale effect, can be interpreted by using this 'non-local', higher order theory. These effects are demonstrated for the cases of the unidirectional tension test, and for the small circular hole under uniform internal pressure commonly known as the inflation test. The latter configuration can be taken as a first order approximation of the indentation test that is frequently used for the laboratory or in situ characterization of geomaterials. In addition, it is shown that the solution of the three basic crack deformation modes leads to cusping of the crack tips that is caused by the action of 'cohesive' double forces behind and very close to the tips, that tend to bring the two opposite crack lips in close contact, and further, it is demonstrated that the fracture toughness depends on the size of the crack, and thus it is not a fundamental property of the material. This latter outcome agrees with experimental results which indicate that materials with smaller cracks are more resistant to fracture than those with larger cracks. (C) 2001 Elsevier Science B.V. All rights reserved.	en
heal.publisher	ELSEVIER SCIENCE BV	en
heal.journalName	Tectonophysics	en
dc.identifier.doi	10.1016/S0040-1951(01)00047-6	en
dc.identifier.isi	ISI:000170090600007	en
dc.identifier.volume	335	en
dc.identifier.issue	1-2	en
dc.identifier.spage	81	en
dc.identifier.epage	109	en