Announcements This week's lab: 1-3 PM with Andrew McCarthy. Please come prepared with specific questions. There will be no lecture this Wednesday! Please use the time to: 1) Study important terms/concepts listed at end of Powerpoint files 2) Study

Please download to get full document.

View again

of 22
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Information Report
Category:

Documents

Published:

Views: 0 | Pages: 22

Extension: PPT | Download: 0

Share
Related documents
Description
Announcements. This week's lab: 1-3 PM with Andrew McCarthy. ... 1) Study important terms/concepts listed at end of Powerpoint files ...
Tags
Transcript
Title: Announcements This week's lab: 1-3 PM with Andrew McCarthy. Please come prepared with specific questions. There will be no lecture this Wednesday! Please use the time to: 1) Study important terms/concepts listed at end of Powerpoint files 2) Study 1 AnnouncementsThis week's lab 1-3 PM with Andrew McCarthy. Please come prepared with specific questions.There will be no lecture this Wednesday!Please use the time to1) Study important terms/concepts listed at end of Powerpoint files2) Study the practice problems 3) Fault projectReminder Midterm Oct. 14 2 What is it? (quiz) 3 s1 s3 s1 s3 instantaneous strain ellipse 4 Stress and Deformation Part I(DR, 122-126 226-252) The goal for today is to explore the stress conditions under which rocks fail (e.g., fracture), and the orientation of failure with respect to the principal stress directions.1. Coulomb law of failure2. Byerlee's law 5 Experimental studies are fundamental in the study of rock failure 6 Common types of deformation experiments 7 Compressive strength tests The Goal 8 Compressive strength tests The Approach 3 2 1 9 Compressive strength tests The resultsLinear envelope of failure. The fractures form at angles of 25 to 35 degrees from s1- very consistent! 10 Coulomb's Law of Failure sc s0 tanf(sn) sc critical shear stress required for failures0 cohesive strengthtanf coefficient of internal friction (f 90 - 2q) sN normal stress 11 Tensile strength tests with no confining pressureApproach Similar to compressive strength testsResults (1) Rocks are much weaker in tension than in compression (2) Fracture oriented parallel to s1 (q 0) 12 Tensile Compressive strength testsResult Failure envelope is parabolic0 lt q lt 30 13 Failure envelopes for different rocks note that slope of envelope is similar for most rocks sc s0 tanf(sn) sc critical shear stress required for failures0 cohesive strengthtanf coefficient of internal frictionsN normal stress 14 Byerlee's Law Question How much shear stress is needed to cause movement along a preexisting fracture surface, subjected to a certain normal stress?Answer Similar to Coulomb law without cohesionFrictional sliding envelope sc tanf(sN), where tanf is the coefficient of sliding friction 15 Preexisting fractures of suitable orientation may fail before a new fracture is formed 16 (No Transcript) 17 What about pore fluid pressure? Increasing pore fluid pressure favors failure!-Also may lead to tensile failure deep in crustEffective stress sn fluid pressure 18 What is it? Tensile fracture filled with vein during dilation What is it?s1 is parallel to the structure. What does this suggest about the magnitude of effective stress?What mechanism may help produce this structure within the deeper crust? very low high fluid pressure to counteract lithostatic stress 19 What happens at higher confining pressures? Von Mises failure envelope- Failure occurs at 45 degrees from s1 20 Next Lecture Stress and Deformation II...A closer look at fault mechanics and rock behavior during deformation( DR pp. 304-319 126-149) 21
  • Important terminology/concepts
  • Uniaxial vs. axial states of stress
  • Coulomb law of failure known how it is determined and equation
  • q values for compression
  • q values for tension
  • Cohesive strength
  • Coefficient of internal friction
  • Byerlee's Law / frictional sliding envelope- know equation
  • Important role of pore fluid pressure
  • Recommended
    View more...
    We Need Your Support
    Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

    Thanks to everyone for your continued support.

    No, Thanks