Abstract: Muck discharge from shield tunneling induces resource waste and environmental pollution. To address these issues, a study on the replacement of traditional raw materials in synchronous grouting with a mixture of shield muck and ceramsite is conducted with the aim of realizing efficient resource utilization of shield muck and optimizing the construction performance of tunnel synchronous grouting. Based on an interval project of the Zhengzhou Metro, five mix proportions ranging from 10% to 50% are designed. The muck-ceramsite composite mixture is adopted to replace fly ash, bentonite, and fine sand in conventional grout. Laboratory tests are performed to investigate the physico-mechanical properties of the grout, including compressive strength, bleeding rate, and consistency. Digital image correlation （DIC） technology is used to analyze the deformation characteristics of the test specimens. In addition, indoor model tests are conducted to observe the diffusion patterns and solidification effects of modified and ordinary grout, and the internal force variations in the tunnel segment lining are monitored. The results indicate that: (1) as the mass replacement ratio of shield muck and ceramsite for fly ash, bentonite, and fine sand increases, the bleeding rate and consistency of the modified grout gradually decrease; (2) the modified grout significantly delays crack initiation and failure in specimens, thereby improving their deformation resistance. Furthermore, the modified grout diffuses uniformly and stably, forming a dense composite structure upon solidification, which effectively reduces the earth confining pressure on tunnel segments; and (3) the modified grout mixed with shield muck and ceramsite is suitable for synchronous grouting in metro tunnel projects. It significantly consumes shield muck, lowers construction costs, and improves the quality of grouting reinforcement.

Key words: shield muck, ceramsite, modified slurry, synchronous grouting, model test, resource utilization