关键词: 盾构渣土, 碱激发材料, 壁后注浆材料, 固化剂, 现场试验

Abstract: To improve the utilization efficiency of shield muck in backfill grouting materials, shield tail mud and muck sand from a tunnel project in Guangzhou, China, are used as the main raw materials and slag-based alkali-activated materials as the binder to produce a full-muck-based backfill grouting material (FMBGM). The effects of the water-to-solid (W/S) ratio, dry sand-to-mud ratio, and binder dosage on the grout flowability, bleeding rate, setting and hardening characteristics, and mechanical strength of the FMBGM are systematically investigated. X-ray diffraction and scanning electron microscopy analyses are used to characterize the reaction products and microstructure of the FMBGM, followed by on-site grout preparation and field grouting tests for validation. The main results are summarized as follows. (1) The W/S ratio is the primary parameter affecting the flowability and stability of the grout. As the W/S ratio increases from 0.35 to 0.55, the interparticle free water content and surface water film thickness increase, leading to a 114.57% enhancement in flowability and a corresponding rise in the bleeding rate. (2) The dry sand-to-mud ratio primarily regulates the particle size distribution and skeleton structure of the grout. Specifically, the muck sand provides a rigid skeleton, whereas the fine fractions in the tail mud enhance the water retention and anti-dispersion properties through adsorption and filling effects. A dry sand-to-mud ratio of 7∶3 achieves the optimal balance of pumping flowability, water retention, and strength development. (3) The binder dosage has the greatest influence on strength development; the alkaline environment promotes the dissolution of the slag, leading to the formation of ettringite and amorphous calcium (alumino) silicate hydrate (C-(A)-S-H) gel as the main products. The muck sand mainly acts as a rigid skeleton to provide physical support, whereas the tail mud provides micro-aggregate filling and bound-water adsorption effects. Microstructural analysis reveals that the C-(A)-S-H gel and ettringite interweave and fill the pores of the muck sand skeleton, producing a dense structure. Based on the flowability, setting time, consolidation rate, and mechanical strength results, the optimal mix proportion comprises a dry sand-to-mud ratio of 7∶3, a W/S ratio of 0.45, and a binder dosage of 20%. Field validation tests show that the optimal FMBGM formulation meets the requirements for continuous preparation and synchronous grouting construction. Moreover, the FMBGM exhibits high early strength, and the segment floating in the trial section is reduced by 40% compared with that of conventional grouts, with no leakage or excessive deformation observed. These findings indicate that shield tail mud and muck sand can be successfully used to prepare FMBGMs that meet the performance requirements.

Key words: shield muck, alkali-activated material, backfill grouting material, binder, field test