为研究衡盾泥在带压开舱时的闭气保压效果，通过室内试验及理论计算的方法对衡盾泥的泥膜气密性进行分析。结果表明： 1）3 d龄期的衡盾泥泥膜中自由水所占比例约为10％； 2）在0.292 MPa压力下，改良黏土浆体泥水质量比为1∶2、塑化剂掺入质量比为1/20、成膜龄期为3 d的衡盾泥泥膜，仅1.7％的孔隙可能出现渗气； 3）衡盾泥泥膜渗气系数为10-8~10-7 cm3/s,换算到直径为6 m的隧道开挖断面上，泥膜的渗气量为2~3 m3/h，盾构开舱时配置的空压机完全满足补气条件。

The airtightness of filter cake of Paste HDN when opening the chamber under pressure is analyzed by laboratory test and theoretical calculation. The analytical results show that: (1) The proportion of free water in the filter cake of Paste HDNwith 3day age is about 10%. (2) Under the pressure of 0.292 MPa, 1.7% of the pore size of the filter cake of Paste HDN with 1∶2 of mudwater ratio of improved clay slurry, 1/20 of plasticizer injection amount and 3day of filming age may leak. (3) The are permeation coefficient the filter cake of Paste HDN rangesfrom 10-8 cm3/s to 10-7 cm3/s, which is 2-3 m3/h when converting to tunnel excavation crosssection with diameter of 6m; and the air compressor can fully meet the airsupply requirements.