Performance and mechanism of modified backfill grouting materials prepared from EPB shield fine-grained waste soil for resource utilization

The construction process of the shield generates a considerable quantity of discharged soil. The residual fine-grained waste soil resulting from the discharge soil screening process is now classified as a new solid waste for disposal. In order to optimize the utilization of fine-grained waste soil, it is proposed that it be employed in the preparation of shield backfill grouting materials in-situ. However, utilizing fine-grained waste soil does possess certain disadvantages, including poor fluidity, low strength and protracted setting time. To surmount these deficiencies, polymers have been developed with the specific purpose of modifying the grouting material. This study investigates the feasibility of preparing modified backfill grouting materials through the resource utilization of fine-grained waste soil. The fresh and hardened properties and micro-characterized of the grouting materials were tested under different mixture ratio. The results demonstrated that the incorporation of polymer into the grouting material can enhance initial fluidity, strength and improve other properties. The modest dosage of polymer can facilitate the hydration reaction, whereby the hydroxyl functional group on the polymer chain reacts with free Ca2 + to form a complex mesh structure, achieving the combination of organic and inorganic to complete the modification. The water/solid mass ratio exerts the most significant influence on the diverse properties of the grouts. This study proposes a method for the utilization of fine-grained waste soil, following the screening of shield discharge soil, which is both feasible and effective. The method has been demonstrated to have a positive effect on low-carbon green tunnel construction.