中文摘要：

泥膜的良好闭气性是保证泥水盾构带压开舱安全顺利实施的关键之一,要想提高泥膜的闭气性,首先应了解泥膜在带压开舱过程中的孔隙结构及渗透性变化。以南京纬三路过江通道在江底砂卵石地层中进行带压开舱为背景,在自制的试验装置中进行泥浆成膜和泥膜闭气试验,然后观测泥膜的孔隙结构和孔径变化,最后分析泥膜渗透系数的变化。研究结果表明：试验泥浆在0.2 MPa气压作用下6 h,在试验地层表面形成的泥膜厚度约为5.0 mm、孔隙率约为67%,在闭气过程中泥膜会发生压缩,且第一次单位压力引起的压缩量最大;随着闭气压力的增大,大孔隙组被优先压缩;泥膜基本单元体为骨架状结构,孔隙主要是粒间孔隙与架空孔隙,孔隙分布不连续、连通性差;孔径分布范围较广,其中在0.1～3.0μm的孔隙组占有绝对优势;本次试验中压缩后泥膜的渗透系数在10^-9 cm/s量级。研究结果有助于明确泥膜在闭气过程中的变化,对后续提高泥膜闭气性的研究有重要的参考意义。

英文摘要：

Good air tightness of filter membranes is necessary for opening excavation chamber under high pressure. To improve the value of air tightness, one should understand the pore structure and permeability change of filter membranes during chamber opening under high pressure. Taking the sandy cobble stratum of Nanjing Weisan Road river-crossing tunnel as an example, the air tightness tests are carried out for filter membranes formed under different pressures by a self-developed airtightness apparatus. Its pore structures and measured diameters are observed, and the changes of permeability coefficient are analyzed. The results show that the thickness of the filter membranes is 5.0 mm under 0.2 MPa for 6 hours, the porosity is about 67%, the filter membranes are compressed during the air tightness tests and at the first stage it is the largest. With the growth of the air pressure, the large pore group is preferentially compressed. The basic unit of filter membranes is a skeleton-like structure, and the pore structure is mainly inter-particle pore and overhead pore; furthermore, the pore is not continuous and poorly connective. The pore size has a broader distribution, and the group of 0.1～3.0 μm has an absolute advantage. The permeability coefficient in this experiment has a magnitude of 10^-9 cm/s. The results define the change of the filter membranes during air tightness, and it plays a significant role in improving the value of filter membranes during air tightness.