Reuse and Effect Analysis of Muck Slurry in Tail-void Backfill Grouting of Metro Tunnels

ObjectiveShield tunneling in metro construction generates a massive amount of waste muck that requires off-site disposal. Muck not only occupies ground construction space but also consumes significant manpower and material resources during transportation, causing resource waste and urban environmental damages. In response to the national "Dual Carbon" strategy (peak carbon dioxide emissions and carbon neutrality), it is essential to investigate recycling and reuse technologies for waste muck. MethodRelying on the shield tunneling project between Jinling Petrochemical Station and Qixiashan Station of Nanjing Metro Line 6, a muck slurry reuse technology with shield waste muck as the raw material is proposed. The case engineering overview is elaborated, and the preparation process of the muck-based slurry is introduced. In the initial implementation phase of the project, two sections are selected to apply commercial slurry (traditional single-liquid grout) and the muck slurry as synchronous grouting materials, respectively. Ground settlement, segment vertical displacement, and segment leakage locations of these two sections are analyzed to compare the application effects of muck slurry and commercial slurry. Result & Conclusion Due to its good properties, muck slurry can replace commercial slurry as a synchronous grouting material. In terms of both controlling ground settlement and segment floating, the muck slurry outperforms the commercial grout. Compared to commercial slurry sections, those utilize the muck slurry as synchronous grouting material can reduce ground settlement by approximately 40% and segment floating by about 56%. Preliminary calculations suggest that the project saves approximately 944,200 CNY in muck transportation costs and reduces slurry preparation costs by 400,000 CNY/km.