砂–粘复合地层中泥浆渗透成膜特性的试验研究

Experimental Study on the Permeation and Membrane-Formation Characteristics of Slurry in Sandy-Clay Composite Strata

摘要: 随着大直径泥水盾构在复杂地质环境中的广泛应用，软硬交互砂粘复合地层中泥浆成膜稳定性已成为维持开挖面支护效果的关键技术难题。该类地层的显著非均质性导致泥浆渗透行为与均质地层存在本质差异。为深入揭示复合地层中泥浆渗透的宏–细观作用机制，本研究自主研发了高压泥浆渗透柱试验系统，开展了系列砂–粘复合地层泥膜形成试验，并引入参数化修正模型对非均质渗流场进行定量表征。研究结果表明：(1) 砂与粘性介质渗透性的显著差异引起渗流场出现明显“偏流”现象，实测复合渗透系数普遍高于理想并联模型的理论预测值，且该偏差随粘土含量增加而加剧；通过引入偏流放大系数，可有效修正有效过流面积的评估偏差；(2) 渗透性演化规律差异显著：纯砂地层表现为由初期颗粒重排主导的“瞬时陡降–快速平衡”模式，而复合地层则呈现“缓滞衰减–持续致密”模式，其渗透性在观测期内受深层堵塞机制驱动保持准稳态下降趋势；(3) 泥膜具有时效增强特性：复合地层内部的非均质结构增强了泥膜的抗破坏能力，其局部击穿时间较单一砂层显著延后，表现出更优的时效稳定性。

Abstract: With the widespread application of large-diameter slurry shields in complex geological environments, the stability of slurry membrane formation in soft-hard interbedded sandy-clay composite strata has become a critical technical challenge for maintaining excavation face support. The pronounced heterogeneity of such strata leads to fundamental differences in slurry penetration behavior compared to homogeneous ground. To deeply investigate the macro-micro mechanisms of slurry penetration in composite strata, this study independently developed a high-pressure slurry penetration column test system, conducted a series of slurry membrane formation tests in sandy-clay composite strata, and introduced a parameterized correction model to quantitatively characterize the heterogeneous seepage field. The findings indicate that: (1) The significant difference in permeability between sandy and clayey media leads to a noticeable “flow deviation” phenomenon in the seepage field. The measured composite permeability coefficient is generally higher than that predicted by the ideal parallel model, and this deviation increases with clay content. By introducing a flow deviation amplification factor, the evaluation bias of the effective flow area can be effectively corrected. (2) There are distinct differences in permeability evolution patterns: pure sandy strata exhibit an “instantaneous sharp decline-rapid equilibrium” mode dominated by initial particle rearrangement, while composite strata show a “gradual attenuation-persistent densification” mode, with permeability maintaining a quasi-steady decline driven by a deep clogging mechanism during the observation period. (3) The slurry membrane exhibits time-dependent strengthening characteristics: the heterogeneous internal structure of composite strata enhances the anti-damage capacity of the slurry membrane, resulting in a significantly delayed local breakthrough time compared to single sandy layers, demonstrating superior temporal stability.