摘要(英) |
bentonite is used to buffer material in an engineered barrier system for isolation of high-level radioactive wastes(HLW) in a repository. After emplacement of the buffer material, groundwater begins to be taken from the rock by the buffer. And the buffer becomes saturated gradually.
The resaturation of the buffer is considered a hydro-process occurring at elevated temperatures in the near-field of a repository. it is mainly affected by Thermal, Hydro and Mechanical factors, called T-H-M coupling effect.
In order to understand the thermal-hydraulic-mechanical coupling behavior of buffer materials at different dry densities. Through parameter test to obtain thermal conductivity, hydraulic conductivity and soil water characteristics curve with dry density 1,400 kg/m³, 1,500 kg/m³ and 1,600 kg/m³. And use water intake test, temperature distribution test and numerical simulation analysis to verify whether the actual thermal-hydraulic-mechanical coupling behavior is consistent with the numerical simulation results.
The test result shows that the thermal conductivity increases with the increase of density and temperature. At the same temperature, thermal conductivity of the dry density specimen 1,600 kg/m³ is higher than the dry density 1,400 kg/m³. At the same density, the thermal conductivity of the 60°C specimen is higher than that of the 25°C specimen. The swelling pressure of bentonite increases with the increase of dry density. Saturated hydraulic conductivity decreases with increasing dry density. Unsaturated hydraulic conductivity estimated by Abaqus model is higher than vG-Mualem model. There is no obvious difference between the close range photogrammetry and wax coating method in the volume correction result of the vapour equilibrium technique. Temperature affects the radius of the capillary tube and the pore radius of the air-water surface. Soil water characteristics curve decreases with increasing temperature. Comparing numerical simulation and temperature distribution test, the numerical simulation of temperature overestimates the actual temperature. Comparing the results of water intake test and hydraulic-mechanical parameter coupling. The numerical model sets the unsaturated relative hydraulic conductivity of the Abaqus model to overestimate the actual water content distribution.The numerical model sets the unsaturated relative hydraulic conductivity of the vG-Mualem model to underestimate the actual water content distribution |
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