Fracture and Stress Orientation.ppt
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Transcript of Fracture and Stress Orientation.ppt
7/25/2019 Fracture and Stress Orientation.ppt
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Fracture Analysis - 2
Fractures & Stress Orientation
7/25/2019 Fracture and Stress Orientation.ppt
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Fracture orientations relative to the
principal stress orientations• Stress = Gaya per satuan area yang
mengenai suatu bidang
• Kondisi stress yang mengenai suatuobjek misal batuan,memperlihatkan orientasi dan
besaran dari tiga stress, meruakan“principal stresses”
• !he principal stresses terorientasitegak lurus satu terhadap lainnya ,untuk ketiga bidang tidak ada shearstress yang mengenai
•
Suatu blok batuan dengan stress yang mengenainya, simbol "sigma#menunjukkan “compressi$e ortensile stress”
• !he principal stresses menunjukkan bah%a ' ( ) ( *
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Fracture orientations relative to the
principal stress orientations• +ompressi$e stress dan shortening
strain adalah sesuatu yang penting didalam “rock mechanics and structuralgeology” karena di bumi, ketiga“principal stresses” selalu bersiat“compressi$e” "kecuali disekitar“underground $oids” seperti ca$esatau karena dengan denganpermukaan
• -oints "e.tensional ractures#memperlihatkan pertentangan karenamerupakan salah satu kekar batuanalami, namun memerlukan suatu“eecti$ely tensile dri$ing stress”
"tensile stress = tegasan tarik#• !ekanan luida pori "/ore0luid
pressure# mendorong terbentuknya“tensile eecti$e stress” melalui“poroelastic loading o la%s” denganperingkat magnitude lebih besar daritipikal ractures
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Fracture orientations relative to the
principal stress orientations• -oints "G1223#• !he tip o a gro%ing joint is al%ays perpendicular
to * at the joint tip during propagation• +ur$ed joints indicate temporal and4or spatial
$ariations in the orientation o * during joint
gro%th• Faults "125#• 3e% aults in $irgin rock orm in each lithology
%ith an appro.imately constant acute angle bet%een ' and the t%o conjugate aultorientations !his angle ranges rom )67 to 897 but is normally about *97
• /re0e.isting discontinuities %ith a %ide range oorientations can be acti$ated as aults, pro$ided
they are not oriented perpendicular to aprincipal stress• 5eormation bands "aults %ith an anti0mode :
component# also tend to orm at *97 to ' but canorm at any angle ;<97
• Stylolites ">?2# and compaction bands "notsho%n# orm perpendicular to '
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Regional Fracture Orientations
@ Gambar ', ) and * menunjukkan tiga “regionalearth stress regimes” " Andersonian stressregimes#
@ erdasarkan “Andersonian regimes”, satu“principal stress” menunjukkan $ertikal, sedang
dua lainnya adalah horiBontal
http://www.naturalfractures.com/1.1.3.htm
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Regional Fracture Orientations
http://www.naturalfractures.com/1.1.3.htm