高水压高渗透砂性地层土压平衡盾构施工渣土改良技术研究

Study of Ground Conditioning Technology for Earth Pressure Balance( EPB) Shield Used in High Water Pressure and High Permeability Sandy Stratum

为防止福州地铁1号线上藤站—达道站区间土压平衡盾构在高水压高渗透砂性地层掘进时发生喷涌事故,采用纳基膨润土、CMC、聚丙烯酰胺等作为主要改良材料,开展系统渣土改良室内及现场试验工作,研究土压平衡盾构穿越高水压高渗透性地层渣土改良综合解决方案。结果表明:在单独使用某一种改良材料时,渣土改良效果并不明显;采用钠基膨润土-CMC混合浆液可改良渣土的和易性与渗透性,但在可用掺加比范围内无法满足坍落度要求;聚丙烯酰胺溶液与钠基膨润土-CMC混合浆液配合使用时,对过饱和中砂的和易性以及渗透性等改良效果显著;针对福州地铁区间段高水压高渗透砂性地层,可采用1∶10质量分数膨润土、5‰质量分数CMC混合浆液按照10∶2.5掺加比配合3%质量分数聚丙烯酰胺溶液按100∶5掺加比改良渣土,通过现场抽样检测,验证此渣土改良方案的有效性。

The Shangteng Station-Dadao Station on Fuzhou Metro Line No. 1 in high water pressure and high permeability sandy stratum is constructed by earth pressure balance( EPB) shield and prone to water gushing accidents.Therefore,the ground conditioning technology by taking sodium bentonite, carboxymethylcellulose( CMC) and polyacrylamide as the main materials is used to carry out laboratory test and site test and study the comprehensive ground conditioning method for EPB shield tunneling in high water pressure and high permeability sandy stratum. The study results show that: 1) The ground conditioning effect is not obvious when using single material. 2) The workability and permeability of the soil can be improved significantly by using mixed solution of sodium bentonite and CMC,while,the slump of the soil can not meet the requirement in available concentration range of solution. 3) The workability and permeability of the supersaturated medium sand can be improved significantly by using mixed solution of sodium bentonite-CMC cooperatively with polyacrylamide solution. 4) The solution of 100 ∶ 5 mixing solution of 3%polyacrylamide solution cooperatively mixed with 10∶2. 5 mixing solution of bentonite( with mass fraction of 1 ∶10) and5‰ CMC is adopted in Fuzhou Metro Line No. 1; and the conditioning effect is verified by sample test.