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Title Formation and interpretation of dilatant echelon cracks
Creator/Author Pollard, D.D. ; Segall, P. ; Delaney, P.T.
Publication Date1982 Dec 01
OSTI IdentifierOSTI ID: 6151146
Other Number(s)CODEN: BUGMA
Resource TypeJournal Article
Resource RelationGeol. Soc. Am., Bull. ; Vol/Issue: 93:12
Subject580300 -- Mineralogy, Petrology, & Rock Mechanics-- (-1989); CRACK PROPAGATION-- STRESS ANALYSIS;ROCKS-- CRACK PROPAGATION; COMPRESSION STRENGTH;DATA ANALYSIS;GEOLOGIC FISSURES;GEOMETRY;ORIENTATION;ROCK MECHANICS;TENSILE PROPERTIES
Related SubjectGEOLOGIC STRUCTURES;MATHEMATICS;MECHANICAL PROPERTIES;MECHANICS
Description/Abstract The relative displacements of the walls of many veins, joints, and dikes demonstrate that these structures are dilatant cracks.^It is inferred that dilatant cracks propagate in a principal stress plane, normal to the maximum tensile or least compressive stress.^Arrays of echelon crack segments appear to emerge from the peripheries of some dilatant cracks.^Breakdown of a parent crack into an echelon array may be initiated by a spatial or temporal rotation of the remote principal stresses about an axis parallel to the crack propagation direction.^Near the parent-crack tip, a rotation of the local principal stresses is induced in the same sense.^Incipient echelon cracks form at the parent-crack tip normal to the local maximum tensile stress.^Further longitudinal growth along surfaces that twist about axes parallel to the propagation direction realigns each echelon crack into a remote principal stress plane.^Thus, many echelon cracks grow from a single parent because the work done in creating the array, as measured by its surface area, decreases as the number of cracks increases.^The geometry of dilatant echelon cracks may be used to infer spatial or temporal changes in the orientation of principal stresses in the earth.^43 references.
Country of PublicationUnited States
LanguageEnglish
FormatPages: 1291-1303
System Entry Date2001 May 13

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