泥水盾构带压开舱时泥膜性质对其闭气性的影响研究

摘要

For an underwater tunnel driven by a slurry shield machine, the formation of an airtight filter cake is key to the success of hyperbaric intervention under complex geological conditions. Great differences exist among filter cakes formed under different conditions, yet the effects on airtightness are unclear. In this paper, a forma-tion and airtightness test was performed on 9 different filter cakes by a self-made testing unit, and the effects of porosity and thickness of the filter cake on airtightness (airproof time and air pressure limit) were analyzed. The results show that: 1) porosity is the major influence affecting airtightness, and performance is better with less porosity; 2) filter cakes formed in the same stratum have similar porosities, and airtightness can be improved by increasing the thickness of the filter cake to acertain extent; 3) nearly 95% of the filtration water emerges from the compression of the filter cake, while the rest is generated by air penetrating the pores and stratum compres-sion; therefore the three stages of filter-cake compression, air penetration into pores and water flow into the filter cake are adopted to provide a better understanding of the process of the filter cake.%形成良好闭气性的泥膜是泥水盾构在江河底部等复杂地质条件下带压开舱成功的关键之一。不同条件下形成的泥膜性质差异较大，其对泥膜闭气性的影响尚不清楚。文章通过自制的泥膜闭气性试验装置，开展了9组不同泥膜的形成及闭气试验，分析了泥膜的孔隙比、厚度对其闭气性（闭气时间和极限气压值）的影响。研究结果表明：泥膜孔隙比是影响其闭气性的主要因素，孔隙比越小，泥膜的闭气性越好；在同一地层中形成的泥膜，孔隙比相近，增加泥膜厚度可以在一定范围内改善泥膜的闭气性；泥膜闭气过程中产生的滤水，约95%来自于泥膜压缩，其余由孔隙进气和地层压缩产生；泥膜闭气过程可分为泥膜压缩、孔隙进气、透气排水三个阶段。研究结果对带压开舱时泥膜闭气性的研究及闭气过程的理解有借鉴作用。