砂卵石地层盾构带压开舱泥膜闭气能力研究  

Study on Airtightness of Filter Cake during Hyperbaric Intervention in Shield under Sandy Gravel Stratum

作　　者：孙金鑫 钟小春[1] 孙鹤明 张书香 葸振东 Sun Jinxin;Zhong Xiaochun;Sun Heming;Zhang Shuxiang;Hui Zhendong(School of civil engineering and transportation,Hohai University,Nanjing,210098,P.R.China;China first highway engineering Co.,Ltd.,Beijing,101102,P.R.China)

机构地区：[1]河海大学土木与交通学院,南京210098 [2]中交一公局集团有限公司,北京101102

出　　处：《地下空间与工程学报》2021年第2期445-452,460,共9页Chinese Journal of Underground Space and Engineering

基　　金：国家自然科学基金面上项目(51678217);国家自然科学基金面上项目(51378176);国家重点基础研究发展计划(“973”计划)项目(2015CB057800)。

摘　　要：本研究在考虑非饱和土内的水、气渗透系数随饱和度变化的基础上通过Geostudio Air/w数值模拟,分析了开舱气压、泥膜厚度和泥膜干裂等因素对泥膜的闭气能力的影响。结果表明:1)当开舱气压小于泥膜进气值与地下水压之和时,泥膜具有良好的闭气能力;当开舱气压大于泥膜进气值与地下水压之和时,压缩空气将进入泥膜,排出孔隙内水分,泥膜内部逐步形成贯穿孔隙,闭气能力下降,开始漏气。2)增加泥膜厚度能大幅度降低开挖面空气逃逸流量,显著提高泥膜的闭气能力。3)泥膜干裂后,开舱气压产生小波动时(小于5 kPa),空气逃逸量可能突增几个数量级,泥膜丧失闭气能力。基于以上认识,成都轨道交通17号线一期TJ07标的带压开舱工程中设置的开舱压力为300 k Pa,成功地在砂卵石地层完成了带压换刀作业。This paper studied the airtightness of filter-cake,considering factors such as air pressure,thickness of the filter-cake and fractures on the filter-cake,via Geostudio Air/w numerical simulation analysis based on the change of water and gas permeability coefficient in unsaturated soil with saturation.The results show that:(1)when the air pressure is lower than the sum of the air-entry value of filter-cake and the groundwater pressure,the filter-cake has good ability in preventing air escaping;when the air pressure is higher than the sum of the air-entry value of filtercake and the groundwater pressure,the air enters the filter-cake to discharge the water in the pore until the inside of the filter-cake forms a penetrating pore,and the filter-cake fails and loses its ability to keep air.(2)Increasing the thickness of the filter-cake can greatly reduce the air escape flow rate on the excavation face and significantly improve the ability of keeping air of the filter-cake.(3)When there is a fracture on the filter-cake and only a small fluctuation in the air pressure(less than 5 k Pa),the air escape may increase by orders of magnitude and the filter-cake suddenly loses its ability to hold the air.Under the guidance of this paper,the TJ07 of the first phase of Chengdu Rail Transit Line No.17 completed safely the knife changing operation in the sandy gravel stratum during hyperbaric intervention in shield tunneling by setting the air pressure as 300 k Pa.

关 键 词：带压开舱 进气值 泥膜厚度 泥膜干裂 闭气能力 砂卵石地层 

分 类 号：TU94[建筑科学—建筑技术科学]