Relationship between Failure Process of Creep Test and Conventional Compression Test on Soft Rocks-- Studies on the creep mechanism under compressive load of rocks (Part-2) --

Abstract

For the rock engineering projects, it is necessary to correctly estimate the mechanical properties of the rock, namely, the stress-strain relations and strength properties, the time-dependent deformation properties and so on. In our previous studies, the drained creep tests under uni-axial compressive load were carried out on some soft rocks in Japan, such as Ohya-Ishi and Kimachi-sandstone. In these experiments, the axial and lateral strains and the acoustic emission activity were observed in the loading time intervals of several minutes ∼ one month. Also, the thin sections for microscope examination conducted on the specimens, which had loaded during the prescribed time or until some region of the creep process. In this study, the creep process and mechanism were discussed by using these experimental data, and the relationship between the failure process of creep loading and conventional uni-axial loading of rock were discussed by the specially planned testing programs of the experiment.by these results, it can be said that the residual compressive strength of the creep loaded rock specimen is almost the same as that of the intact rock, when the axial strain rate is in the decreasing condition, but the residual strength decreases the value when the axial strain rate passes the minimum value and in the increasing condition. Consequently, the failure process of the creep and conventional uni-axial loading are closely connected with each others；the changing point of the residual strength of the creep loaded rock which coincides to the minimum point of the axial strain rate, corresponds to the strength failure point of the rock under the conventional uni-axial compressive loading.