Engineering Properties Of Taklamakan Desert Sands And Their Application In Exploration Of The Application Of Buffer Materials In Waste Repositories

As the final engineering barrier of the deep geological repository for radioactive waste,the buffer material wraps the radioactive waste tank tightly and is in close contact with the surrounding rock and soil,playing a key role in blocking the escape of radioactive elements to the external environment and the intrusion of groundwater into the waste tank causing erosion.During the service period of the disposal bank is subject to water-force-chemical-thermal multi-field coupling,the buffer material made of pure bentonite is difficult to meet the property requirements of its long-term stable operation.Considering that most of the repositories are built in the desert(mainly desertification),the production process of repository buffer materials can greatly save the project cost if the desert sand is used locally instead of river sand.In this paper,we propose to use Taklamakan desert sand mixed with bentonite to make mixed soil buffer materials with different sand mixing ratios and degree of compaction,and conduct experimental research on the anti-seepage,swelling,shear strength and thermal of mixed soil buffer materials to comprehensively evaluate the feasibility of using desert sand as buffer materials for repositories and to determine the suitable sand mixing ratio and degree of compaction for engineering applications.The main research of this paper is as follows:1)Select representative Taklamakan desert sands and conduct field samples to carry out relevant physical and mechanical tests to reveal their geotechnical properties.A 150 mm large diameter flexible wall infiltration test was conducted using mixed soil buffer materials with different desert sand blending ratios and degrees of compaction to explore the anti-seepage of the mixed soil buffer materials and reveal the influence of sand blending ratio and degree of compaction on the anti-seepage property.2)The swelling rate and swelling force tests were conducted on the mixed soil buffer material to investigate the swelling property of the mixed soil buffer material and to analyze the characteristics of the sand mixing ratio and degree of compaction on the swelling rate and swelling force.At the same time,a direct shear test was conducted on the mixed soil buffer material to investigate its shear strength under different vertical loads and to study the characteristics of shear strength change under different sand mixing ratio and degree of compaction.3)The thermal conductivity test was conducted with the mixed soil buffer material to find out the thermal conductivity of the mixed soil buffer material and to reveal the mechanism of the influence of sand mixing ratio and degree of compaction on the thermal conductivity.The properties of anti-seepage,swelling,shear strength and thermal are integrated to propose a more suitable configuration of buffer material for repository based on the application of desert sand.