凝灰岩の26年間のクリープ試験

抄録

Understanding the time-dependent behavior of rock is crucial in rock engineering and geoscience for tasks such as long-term stability assessments of underground structures and to elucidate long-term deformation of the crust. Creep tests, which are used to investigate time-dependent deformation under constant stress, have been used extensively in studies on rocks. However, most previous creep tests were conducted over periods of less than a few weeks, and only a few tests have been performed over several years. The authors initiated a uniaxial compression creep test with tuff submerged in water at a creep stress of 30% of its strength on May 23, 1997, and have continued this test for more than 26 years. This paper provides an overview of this creep test, including the methodology employed and long-term maintenance. Although slight changes in creep stress, temperature, and humidity have affected the recorded creep strain, its long-term trend can be approximated by a power function of time and is similar to the trends of creep strains observed at higher creep stresses. Compared to previous bending creep tests conducted with dry granite for 30 years, the creep test in this study showed minimal differences in creep stress level and strain rate, despite differences in rock type, loading conditions, and test environment. The current creep test with tuff will be continued for as long as possible.