Abstract: Residual muck from earth pressure balance shield tunneling, after screening, exhibits several challenges, including a low utilization rate, environmental pollution, and occupation of farmland. Therefore, a novel approach for the resource utilization of muck to prepare synchronous grouting materials is proposed. The grout is primarily composed of muck, cement, and water and is modified with a two-component waterborne polymer. A three-factor, five-evel central composite design based on response surface methodology (RSM) is employed to establish a quantitative relationship between mixing ratio and performance. Furthermore, the optimal grout mixing ratio is refined by combining the nondominated sorting genetic algorithm (NSGA-Ⅱ) with fuzzy decision-making within a multi-objective optimization framework. The results indicate the following: (1) the second-order polynomial models developed via RSM reliably predict grout performance, with both individual factors and their interactions significantly influencing the results; (2) the NSGA-Ⅱ algorithm produces a Pareto-optimal solution set for multi-objective optimization, and fuzzy decision-making identifies the optimal mixing ratio as a water-to-solid ratio of 0.852 2, a cement-to-muck ratio of 0.846 4, and a polymer-to-solid ratio of 0.014 6; and (3) life cycle assessment results show that, compared with conventional mortar, the proposed optimal muck grout reduces CO₂ emissions by 411.06 kg per ring and decreases cumulative material and muck disposal costs by CNY 466.25 per ring.

Key words: shield tunnel, muck, synchronous grouting material, mixing ratio optimization, life cycle assessment