Experimental Study on the Grouting Diffusion Process in Fractured Sandstone with Flowing Water Based on the Low-Field Nuclear Magnetic Resonance Technique

Due to the invisibility and complexity of underground engineering rock masses, it is extremely difficult to observe the diffusion process of dynamic water grouting. Therefore, studying the diffusion mechanism of grouting in underground fractured rock masses with flowing water is crucial in preventing water inrush and improving the rock mass tightness. In this study, a novel dynamic water grouting test system based on low-field nuclear magnetic resonance (LF-NMR) was developed to investigate the dynamic grouting diffusion process in fractured sandstone with flowing water. Then, the NMR characteristics of superfine cement-sodium silicate slurry and free water were compared, and the influences of water flow velocity, grout flow velocity and fracture apertures on the grouting diffusion characteristics of fractured sandstone with flowing water were systematically investigated. The test results show that the increase in the grout flow velocity and fracture aperture can effectively improve the dynamic water grouting efficiency, while the increase in the water flow velocity will reduce the dynamic water grouting efficiency. When the grout flow velocity is lower than the water flow velocity, the dynamic water grouting test cannot be successfully performed. Additionally, the slurry filling ratio of the pores peaks when the flow velocities of grout and water are identical. The findings in this paper can provide meaningful reference and guidance for grouting parameter selection in grouting engineering practice.