In situ resource reutilization of earth pressure balance (EPB) shield muck for the generation of novel synchronous grouting materials

Abstract

The utilization of large quantities of shield muck resources is a pressing issue that requires immediate attention and resolution. In this paper, an innovative approach that fully utilizes shield muck as an aggregate for synchronous grouting is introduced to realize the in situ resource utilization of this material. The newly formulated synchronous grouting grouts comprise shield muck and a solid waste-based cementitious material. The influences of components and compositions on the macroscopic performance of new grouts are investigated, and the formulation is optimized with a single-factor test and response surface methodology (RSM) analysis. The optimal formulation with a slurry specific gravity (SG) of 1.383 g/cm³ and a cementitious material (CM) content of 21.456% is determined. The microscopic characteristics of the grouts are revealed by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). Two main hydration products, namely AFt and C-S-H gel, are observed, exhibiting a crisscross growth pattern that contributes to the formation of a robust micronetwork structure. A full set of shield muck in situ pulping equipment is independently developed, thereby establishing an integrated grout production process. Considering the Suzhou Metro Line 6 as an engineering case, a field industrialization experiment is conducted, and the results demonstrate that the pulping system operates smoothly and can stably produce grouts. Compared with conventional cement-based finished grout, the newly developed synchronous grouting material with an optimal formulation exhibits significant superiorities in terms of surface deformation control (average reduction of 30∼40%), segment attitude control, and anti-seepage effect. The proposed approach effectively realizes in-situ resource utilization and source reduction of shield muck and can significantly reduce the cost of synchronous grouting. Aligned with the dual carbon strategy, the prospects for widespread adoption of this approach are promising, and the results of this study are highly significant.