Development and engineering application validation of alkali-activated full-component shield tunnel spoil regenerated solid-waste grouting material

To address the issues of high disposal costs and low resource recovery efficiency of shield tunnel spoil (STS), this study proposes an Alkali-Activated Full-Component Shield Tunnel Spoil Regenerated Solid-Waste Grouting Material (AFS-RSWGM). Cement, fly ash, shield-sieved sand, and soil were used as raw materials, combined with synergistic alkali activation and the pozzolanic effect of fly ash. Key parameters, including water-binder ratio (A), binder-sand ratio (B), and shield tunnel spoil soil (STSS)-water ratio (C), were optimized using Response Surface Methodology (RSM). Rheological and mechanical tests assessed construction adaptability and structural stability, while Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and hydration heat analyses clarified alkali activation mechanisms. Alkali activation enhanced silico-aluminate dissolution in STSS, forming amorphous gels and ettringite (AFt). The fly ash pozzolanic effect released reactive SiO 2 and Al 2 O 3 continuously, refining the interfacial transition zone and reducing porosity. Optimal mix ratios (A=1.091, B=0.819, C=0.197) significantly improved compressive strength over conventional cement systems. Rheological analyses revealed reduced yield stress and enhanced shear-thinning behavior. Hydration heat demonstrated bimodal exothermic characteristics, confirming effective aluminosilicate activation and polymerization. Applied in Jinan Metro Line 4, AFS-RSWGM fully reutilized STS, achieving better ground settlement control without segment leakage. This low-cement-content approach combined with solid waste recycling technology provides a practical solution for green construction, carbon reduction, and resource recycling in underground engineering.