Research on the Grouting Mechanism and Theoretical Models of Weathered Sandstone According to the Fractal Theory.

In the construction of tunnels, water conservancy, mining, and other engineering projects, the water-rich weathered sandstone with large porosity, strong permeability, and highly developed fissures is often exposed, which brings a great threat to construction safety. The method of grouting can greatly reduce the occurrence of such disasters, thereby improving the safety and reliability of related projects. Based on this, the paper considered the disorder and random uncertainty of sandstone fractures and established a theoretical model between sandstone hydraulic conductivity and fractal dimension based on fractal theory. Furthermore, a fractal model for the amount of grouting cement in weathered sandstone was established by considering the injectability of granular grout in fractures, effectively revealing the variation of grouting cement amount with fractal dimension under one- and two-dimensional flow states, respectively. Based on the relationship between cement dosage and hydraulic conductivity, three physically defined grouting areas were defined, that is, the hydraulic splitting zone, the normal grouting zone, and the micro-crack zone. Finally, the Qingdao Metro was selected as the site for verification. The on-site measured data were mainly located in the normal Pearl River area and less in the grouting area A, indicating that the grouting feasibility of this area was relatively good. Through the above work, some theoretical guidance can be provided for the construction of weathered sandstone engineering projects.