The time-dependent reduction of sliding cohesion due to rock bridges along discontinuities: A fracture mechanics approach

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99 Citations (Scopus)

Abstract

In this paper, a fracture mechanics model is developed to illustrate the importance of time-dependence for brittle fractured rock. In particular a model is developed for the time-dependent degradation of rock joint cohesion. Degradation of joint cohesion is modeled as the time-dependent breaking of intact patches or rock bridges along the joint surface. A fracture mechanics model is developed utilizing subcritical crack growth, which results in a closed-form solution for joint cohesion as a function of time. As an example, a rock block containing rock bridges subjected to plane sliding is analyzed. The cohesion is found to continually decrease, at first slowly and then more rapidly. At a particular value of time the cohesion reduces to value that results in slope instability. A second example is given where variations in some of the material parameters are assumed. A probabilistic slope analysis is conducted, and the probability of failure as a function of time is predicted. The probability of failure is found to increase with time, from an initial value of 5% to a value at 100 years of over 40%. These examples show the importance of being able to predict the time-dependent behavior of a rock mass containing discontinuities, even for relatively short-term rock structures.

Original languageEnglish (US)
Pages (from-to)27-38
Number of pages12
JournalRock Mechanics and Rock Engineering
Volume36
Issue number1
DOIs
StatePublished - Jan 2003

Fingerprint

fracture mechanics
cohesion
Fracture mechanics
sliding
discontinuity
Rocks
rock
time dependent behavior
Degradation
rock block
degradation
Crack propagation
crack

Keywords

  • Joint cohesion
  • Joint friction angle
  • Rock bridge
  • Rock fracture
  • Rock fracture mechanics
  • Rock joint
  • Slope stability
  • Subcritical crack growth
  • Time dependent

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Geotechnical Engineering and Engineering Geology

Cite this

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title = "The time-dependent reduction of sliding cohesion due to rock bridges along discontinuities: A fracture mechanics approach",
abstract = "In this paper, a fracture mechanics model is developed to illustrate the importance of time-dependence for brittle fractured rock. In particular a model is developed for the time-dependent degradation of rock joint cohesion. Degradation of joint cohesion is modeled as the time-dependent breaking of intact patches or rock bridges along the joint surface. A fracture mechanics model is developed utilizing subcritical crack growth, which results in a closed-form solution for joint cohesion as a function of time. As an example, a rock block containing rock bridges subjected to plane sliding is analyzed. The cohesion is found to continually decrease, at first slowly and then more rapidly. At a particular value of time the cohesion reduces to value that results in slope instability. A second example is given where variations in some of the material parameters are assumed. A probabilistic slope analysis is conducted, and the probability of failure as a function of time is predicted. The probability of failure is found to increase with time, from an initial value of 5{\%} to a value at 100 years of over 40{\%}. These examples show the importance of being able to predict the time-dependent behavior of a rock mass containing discontinuities, even for relatively short-term rock structures.",
keywords = "Joint cohesion, Joint friction angle, Rock bridge, Rock fracture, Rock fracture mechanics, Rock joint, Slope stability, Subcritical crack growth, Time dependent",
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AB - In this paper, a fracture mechanics model is developed to illustrate the importance of time-dependence for brittle fractured rock. In particular a model is developed for the time-dependent degradation of rock joint cohesion. Degradation of joint cohesion is modeled as the time-dependent breaking of intact patches or rock bridges along the joint surface. A fracture mechanics model is developed utilizing subcritical crack growth, which results in a closed-form solution for joint cohesion as a function of time. As an example, a rock block containing rock bridges subjected to plane sliding is analyzed. The cohesion is found to continually decrease, at first slowly and then more rapidly. At a particular value of time the cohesion reduces to value that results in slope instability. A second example is given where variations in some of the material parameters are assumed. A probabilistic slope analysis is conducted, and the probability of failure as a function of time is predicted. The probability of failure is found to increase with time, from an initial value of 5% to a value at 100 years of over 40%. These examples show the importance of being able to predict the time-dependent behavior of a rock mass containing discontinuities, even for relatively short-term rock structures.

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