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

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...

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Bibliographic Details
Published in:Rock mechanics and rock engineering 2003, Vol.36 (1), p.27-38
Main Author: KEMENY, J
Format: Article
Language:English
Subjects:
Applied sciences
Bridges (structures)
Buildings. Public works
Cohesion
Computation methods. Tables. Charts
Degradation
Discontinuity
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Engineering geology
Exact sciences and technology
Failure
Fracture mechanics
Geotechnics
Land bridges
Mathematical models
Rock
Rocks
Sliding
Slope stability
Soil mechanics. Rocks mechanics
Structural analysis. Stresses
Studies
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Summary: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.[PUBLICATION ABSTRACT]
ISSN:0723-2632
1434-453X
DOI:10.1007/s00603-002-0032-2