New Rapid Evaluation for Long-Term Behavior in Deep Geological Repository by Geotechnical Centrifuge. Part 1: Test of Physical Modeling in Near Field Under Isotropic Stress-Constraint Conditions

The objective of this study is to evaluate the long-term geomechanical behavior of a geological repository for high-level radioactive waste disposal, using the centrifugal near-field model test. The model consisted of a sedimentary rock mass, bentonite buffer, and model overpack, and was enclosed within a pressure vessel. Tests were conducted with a centrifugal force field of 30 G under isotropic stress-constraint conditions with confining pressures of 5–10 MPa and injection of pore water up through a time period equivalent to about 165 years in the field. Our results showed that the measured values and the temporal changes in the displacement of the overpack, the soil pressure of the bentonite, and the strain of the rock mass were clearly dependent on the confining pressure. These data were not convergent during the test. Our data experimentally revealed that long-term behavior in the near field was changed by the geomechanical interaction between the deformation stress of the bedrock/disposal hole and the swelling behavior of the bentonite buffer.