为解决土压平衡盾构穿越富水砂层时，因渣土改良效果不佳而面临的排渣障碍、喷涌、刀盘刀具磨损加剧及掌子面压力调控困难等难题，构建一套融合渣土流塑性、抗渗性、摩擦性及压力传递特性的渣土改良综合评价指标体系，实现渣土改良效果的快速定量评估与参数优化。泡沫、膨润土泥浆和砂土混合改良后，对渣土进行坍落度、加压渗透、十字板剪切及盾构模型土舱压力传递特性等试验，分别得出理想渣土的坍落度值、细颗粒质量分数、不排水剪切强度及压力传递系数，并结合现场实测数据和盾构土舱模型试验验证该套指标的可靠性。结果表明富水砂层理想渣土应符合的关键指标如下： 1）渣土坍落度值S维持在150~200 mm，能确保渣土具备优异的流动性和顺畅的排渣能力； 2)渣土细颗粒质量分数需大于10%，以增强渣土在高水压环境下的抗渗性，有效预防喷涌问题； 3)渣土不排水剪切强度Su控制在3~7 kPa，可平衡渣土的低摩擦性与良好的压力传递特性； 4)渣土压力传递系数K0在0.70~0.85时，渣土才能确保将盾构推力有效传递至掌子面及盾体外侧超挖区域，维持压力平衡，避免掌子面失稳及地层过度沉降。
Inadequate soil conditioning poses substantial challenges for earth pressure balance shields operating in water-rich sandy strata, including mucking obstruction, muck spewing, accelerated cutterhead tool wear, and difficulties in regulating tunnel face pressure. To address these challenges, a comprehensive evaluation system for soil conditioning is established. This system integrates the plasticity, impermeability, friction, and pressure transmission characteristics of conditioned muck, enabling the rapid, quantitative assessment and parameter optimization of soil conditioning performance. After soil conditioning using foam, bentonite slurry, and sand mixtures, a series of laboratory tests is conducted, including slump, pressurized permeability, vane shear, and pressure transmission characteristic tests using a shield model soil chamber. Key parameters of ideal conditioned muck, including the slump value, fine particle content, undrained shear strength, and pressure transmission coefficient, are determined. The reliability of these indices is further verified through field measurements and model experiments using a shield soil chamber. The results indicate that ideal conditioned muck should satisfy the following criteria: (1) a slump value S of 150－200 mm to ensure excellent flowability and smooth muck discharge; (2) a fine particle content exceeding 10% to enhance impermeability under high hydraulic pressure and effectively prevent spewing; (3) an undrained shear strength Su of 3－7 kPa to balance low friction with favorable pressure transmission properties; and (4) a pressure transmission coefficient K0 of 0.70－0.85 to ensure effective transfer of shield thrust to the tunnel face and over-excavation zones, thereby maintaining pressure equilibrium and preventing tunnel face instability or excessive ground settlement.
