Long-tenn behavior of a large underground cavern

In this paper, long-term behavior of rock at a large underground cavern which was excavated in hard rock was considered through measurement data, We especially focused on the slight change of rock strain measured by multiple stage extensometers at an underground power station which has passed approximately seven years since its excavation work was finished. From the result of consideration, it was found that relatively large increase of interval strain occurred in the vicinity of the boundary between failure zone and elastic zone after the end of excavation. This paper also shows the comparison between measurements and results of numerical analysis which applies a non-liner rheological model to the time dependent rock behavior.