| Summary: | 碩士 === 國立中央大學 === 土木工程研究所 === 93 === Most countries make choice of deep geologic disposal as the best method to achieve the isolation and retardation of nuclide migration by multiple barriers. In an underground disposal site, the radioactive wastes are encapsulated in containers surrounded by a buffer material and the excavation backfilled with a mixture of clay and sand. Bentonites serve as buffer material in an engineered barrier system for isolation of high-level radioactive wastes.
This research investigates the hydraulic behavior of the buffer material, in order to provide a basis for evaluating the thermal-hydro-mechanical (THM) coupling effects in a underground repository. Water uptake tests were conducted on bentonite specimens prepared at different densities to simulate groundwater intrusion to the buffer material. With these tests the degree of saturation (and void ratio) can be plotted as a function of the distance from the water inlet. The finite element program ABAQUS was used to perform numerical simulation of the hydraulic behavior of the buffer material. By comparing the experimental results and the numerical simulation, a model for describing the hydraulic behavior of buffer material was developed. In addition, material parameters suitable for Zhisin clay, a potential buffer material for Taiwan, are recommended based on the analysis.
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