Field Grouting Test Study for High-Level Radioactive Waste Disposal at the Beishan Underground Research Laboratory

The safe disposal of high-level radioactive waste (HLW) is crucial for environmental protection and the sustainable development of nuclear energy. As the primary disposal method, deep geological disposal requires effective grouting to prevent radionuclide migration. To explore applicable grouting technologies for sealing fractures with water inflow in disposal repositories, this study investigates the rheological characteristics of low-pH cement-based materials (LPCM) composed of 60% Portland cement and 40% silica fume through laboratory experiments. Additionally, a three-dimensional single-fracture model was developed using COMSOL Multiphysics (version 6.2) to study the diffusion behavior of the slurry under different fracture apertures and grouting pressures, thereby providing theoretical support for field tests. The tests were carried out in the ramp of Beishan underground research laboratory (URL), successfully sealing fractures by implementing a grouting strategy that combined shallow holes, low pressure, short intervals, and an adjustable water-to-binder ratio for optimal sealing effectiveness. The permeability coefficient of the rock mass was reduced to 10−8 m/s after grouting, which significantly reduced the permeability and initially met the sealing requirements of the ramp. The results show that the grouting design is reasonable and effective, and the LPCM has a great sealing effect, which verifies the applicability of the previous materials developed in earlier research and provides theoretical support and practical experience for the grouting technology in the Beishan URL and HLW repository in China.