부산대학교 도서관

• Temperature-controlled steady state water permeability tests and gas injection tests were conducted. • Intrinsic (water) permeability, gas permeability and breakthrough pressures at temperatures were obtained. • Intrinsic permeability of GMZ bentonite ranges between 3.2 E-20 and 5.83 E-20 m2, and increases as temperature increases. • Measured effective gas permeability slightly fluctuates with time and increases with temperature increases. • Measured gas breakthrough pressures are much higher than the snap-off pressures. Determination of parameters for description of gas migration in saturated bentonite is of great importance for the design and construction of artificial barriers in the geological repository for the disposal of high-level radioactive nuclear waste. In this paper, temperature-controlled gas injection tests were conducted on initially water-saturated bentonite specimens using the residual capillary pressure (RCP) technique. Effective gas permeabilities in low injection pressures and the gas breakthrough pressures at temperatures 20, 40 and 60 °C were obtained. Results show that: (i) for all the temperatures tested, the intrinsic water permeabilities (k i n) range between 3.2 × 10−20 and 5.72 × 10−20 m2, furthermore, those values increase with rising temperature. Meanwhile, the intrinsic water permeabilities derived from the steady state tests are lower than those obtained from the non-steady state tests; (ii) for all the temperatures tested, the effective gas permeabilities (k e f f) corresponding to the viscous gas flow before gas breakthrough range between 4.81 × 10 - 24 and 2.74 × 10 - 22 m2, with slight fluctuations with time. The maximum effective gas permeabilities measured at the occurrence of gas breakthrough on the initially water-saturated bentonite specimens extend from 2.27 × 10 - 18 up to 3.32 × 10 - 17 m2 and increase as temperature increases, while the time required for gas breakthrough decreases as temperature increases; (iii) for all the temperatures tested, the gas breakthrough pressures measured on the initially water-saturated bentonite specimens vary from 2.74 to 4.08 MPa, while the residual capillary pressure differences, also denoted as snap-off pressures (P snap-off), range from 0.2 to 0.38 MPa. Additionally, the gas breakthrough pressures and the residual capillary pressures decrease as temperature increases. [ABSTRACT FROM AUTHOR]