Abstract:
The deep geological storage has been widely adopted for long-lived high-level radioactive wastes. Compacted bentonite/sand mixtures have been recognized as suitable sealing materials in many countries, due to their favorable hydro-mechanical behavior. However, gas will be produced after closure of repository and thus the gas pressure will be accumulated, threatening the safety of sealing system. To investigate the HM-gas properties in bentonite/sand mixtures, compacted samples were firstly saturated under constant volume condition and the swelling pressure and hydraulic conductivity were measured. Then, gas injection was carried out and the gas breakthrough pressure and gas permeability were determined. Meanwhile, MIP test was performed to study the microstructural evolution during saturation and gas injection. It was found that the bentonite fraction and dry density had a significant influence on the HM-gas properties. Additionally, a heterogenous distribution of degree of saturation was observed in saturated samples, which was linked to the bentonite profile. It appeared that the two-phase flow was the dominant mechanism of gas transfer, with water drainage. Finally, based on experimental results, a model is being developed to simulate the HM-gas properties for the used sample and a complete sealing core in the repository.
Short bio:
Wenqing Cai obtained his master degree in Geotechnical engineering from Zhejiang University (China, 2022). He is now a PhD student at CERMES of Navier Laboratory, supervised by Prof. Yu-Jun Cui in collaboration with Andra (National Agency for the Management of Radioactive Waste) since 2022. His study aims to investigate the gas transfer and hydro-mechanical behavior of bentonite/sand mixtures, in both experimental and numerical aspects.
