Experimental Study on Permeation of Composite Grout with Multi-Particle-Size Distribution: Comparative Analysis with Nano-Silica Sol and Cement Grout

The low injectability and strong permeation of micro-fractures in argillaceous rock masses significantly impair the impermeabilization and reinforcement performance of conventional cement-based grouting materials. This study first develops a highly injectable and high-strength nano-silica sol-based composite grout. Then, the characteristics of silica sol, cement grout, and composite grout in argillaceous fractured rock masses are analyzed and compared. The permeation mechanism of the composite-grout grouting in these rock masses is preliminarily elucidated, and the grouting process is described in detail, showing its application prospects. The research results indicate the following: (1) The electrical conductivity and stone-formation rate of granular pulp can reflect the characteristics of pulp filtration. Silica sol is a grouting material with nanometer particles, and the stone rate and gel strength are weakly affected by rock mass infiltration. (2) A large amount of water cannot be combined into the gel network and separated during the cement slurry percolation process, resulting in a significant reduction in the stone rate and compressive strength of deep rock mass. The minimum stone rate decreased to 45.19%, and the minimum compressive strength decreased to 2.29 MPa. This reduces the sealing and reinforcement effect of cement grouting on deep rock masses. (3) Rock permeation primarily affects the compressive strength of the formed stones, with minimal impact on the stability and stone-formation rate of the composite grout. As permeability decreases, the position of rock permeation shifts closer to the rock surface, while the sealing of deeper rock masses is less affected, enabling the composite grout to achieve dual functions of superficial reinforcement and deep sealing. This study provides theoretical support for the practical application of composite-grout grouting in reinforcing argillaceous rock masses.