Abstract: In view of the grouting reinforcement requirements of argillaceous soft rock tunnel and the performance disadvantages of common single grouting materials, the nanosilica sol and aluminate cement is considered as the main agent, and a type of composite grouting material with silica sol/water/aluminate cement (100 mL/100 mL/120 g) is prepared. The preliminary study demonstrates that a simple combination of nanocolloidal silica-aluminate cement will lead to a low stone rate and cracks in the stone bodies. As a result, two admixtures of sodium silicate and Portland cement are chosen to study the influence of their dosage on the stone rate, 3day compressive strength, and gel time. On the premise that the stone rate reaches 100% and the 3day compressive strength and gel time are considered the main and auxiliary factors, respectively, the sodium silicate exhibits a better performance; its dosage is 1% of aluminate cement. Further, 1% sodium silicate is used as the conventional ratio for the subsequent tests. To solve the cracking problem, four admixtures of silica fume, magnesium oxide, calcium oxide, and redispersible latex powder are chosen to study the influence of their dosage on cracking, 3day compressive strength, and gel time. On the premise that cracks can be completely treated and the 3day compressive strength and gel time are considered as reference bases, the magnesium oxide has the best performance in cracking prevention, and the recommended dosage is 0.6% of aluminate cement. Finally, based on the theory of interface transition zone, the reinforcement effect of grouting material on the mudstone of the Xianglushan tunnel in Central Yunnan is evaluated. The results indicate that the average width of the magmatic interface transition zone is only 88.6 μm, the microhardness slightly decreases, and the interface between rock and grout is firm.

Key words: composite grouting material, nanocolloidal silica-aluminate cement, aluminate cement, stone rate, drying shrinkage cracking, argillaceous soft rock tunnel