In the design of rock structures such as tunnels and underground caverns, a continuity analysis considering the nonlinearity of rock has been used in many cases. On the other hand, the mechanical and hydraulic behavior of hard rock is governed by discontinuities of various sizes and numbers contained in rock mass. Therefore, the EDZ (excavation disturbed zone) assumed based on the result of the continuity analysis may differ from that of obtained by the analysis considering discontinuities explicitly. This means that the performance evaluation result of rock structures may change by evaluating discontinuity explicitly or not. In the performance evaluation of the high-level radioactive-wastes disposal facility and of the water-sealing type underground storage facility for gas and oil, it is necessary to examine a stress-fluid coupled behavior, because the requested performance to these facilities is greatly depending on the quality of sealing and water-tightness. In such examination, not only a mechanical stability but also a hydraulic performance such as extremely low permeability for long period is examined in detail. Here, the techniques concerning to stress-fluid coupling analysis which has been adopted up to now is reviewed and problems in the performance evaluation to important and highly reliable rock structures are examined.
A great earthquake disaster occurred in East Japan on March 11, 2011. Many structures such as buildings, roads, bridges, dikes and various manufacturing facilities were easily destroyed, though they should have been planned and constructed through many examinations which are relating to the safety and security. I am really sorry that there are so many victims. The author has engaged on the construction of underground structures such as tunnels and caverns for many years. And for him, this great disaster was large enough to realize that we must not make light of the natural force.
