Abstract:To explore the effects of synchronous grouting on tunnel structure uplift and ground settlement, this study proposes an improved grouting material to optimize construction performance. Microbubbles were introduced into the grout by adding an air entraining agent, endowing the grout with lightweight, elastic and compressible properties. A combination of laboratory experiments and field monitoring was employed to evaluate the influence of air entraining agent content on grout properties and construction performance. A lightweight, elastic, and compressible synchronous grouting material for shield tunnels based on the air entraining agent was developed. The study revealed that under identical grouting pressure and volume conditions, the lightweight grouting material effectively suppressed tunnel uplift during construction, reducing the average uplift from 8.7 mm to 0.1 mm. Additionally, ground settlement over 14 d decreased from 10.5 mm to 4.5 mm, a reduction of approximately 57%. The air-inducing effect of the air entraining agent enables grout lightweighting and enhances its performance, significantly mitigating tunnel uplift and ground settlement during shield tunnel construction. This provides an efficient grouting material solution for tunnel engineering projects.