Paper contribution

Estimation of long-term behavior of rock from short-term creep tests

Kimihiro Hashiba; Katsunori Fukui

Proceedings
EUROCK 2026
Pages
337-342
Submitted
28 January 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

Creep tests under constant stress are essential for investigating the time-dependent deformation and failure of rock. The strain rate of a rock specimen under a constant high stress level gradually decreases, reaches a minimum, and increases until the final failure occurs in a relatively short period of time. Here, the stress level means the ratio of creep stress to short-term strength. That is to say, the creep deformation of rock under a constant high stress level is composed of decelerating and accelerating parts. In contrast, the strain rate of a rock specimen under a constant low stress level gradually decreases and apparently approaches nearly zero, and hence it is quite difficult to complete the creep test until the final failure occurs. To estimate the long-term creep deformation and failure of rock under low stress levels, the authors developed a new test method in which axial stress is increased, kept constant for a while at a predetermined stress level, increased again, decreased in the post-peak region, and kept constant at the same stress level until the final failure occurs. This test method provides both the beginning part of decelerating creep and the ending part of accelerating creep of a single specimen in a short period of time. By interpolating the decelerating and accelerating creep curves, we can estimate a complete creep curve and hence the time to final failure. In this study, this test method was applied to two types of Japanese rocks, tuff and andesite, in uniaxial compression under dry conditions, and the long-term creep deformation and lifetime were estimated under stress levels of between 30% and 80% of the short-term strength. The new test method is promising for investigating the long-term creep behavior of rock under low stress levels.

Contributors

Authors

  1. Kimihiro Hashiba The University of Tokyo, Japan
  2. Katsunori Fukui The University of Tokyo, Japan

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References

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