富水砂卵石地层地铁联络通道冻结试验研究

Field Test of Artificial Ground Freezing for Subway Cross Passage in Water-rich Sandy Gravel Stratum

联络通道是地铁区间的重要结构,冻结法凭借封水性好和适应性强等优势成为复杂环境条件下建造联络通道的核心工法。依托北京地铁19号线草桥站-右安门站区间3#联络通道冻结工程,通过现场实测研究地层温度场和泄压孔压力的发展规律,分析冻结帷幕的交圈情况,以保证联络通道冻结施工顺利推进。结果表明:盐水去回路温度和测温孔温度均经历快速降温、缓慢降温和持续降温3个阶段,冻结壁外侧温度高于内侧,迎水面侧温度高于背水面侧,应重点关注迎水面冻结壁外侧的交圈情况。泄压孔压力经历保持平稳、压力增长和压力释放三个阶段,冻结28 d后,泄压孔压力增长趋缓,冻结壁交圈良好。冻结37 d后,测温孔的平均温度均低于-10 ℃,泄压孔压力降为0 MPa,冻结壁已基本不再发展。

The cross passage is an important structure in the subway.The artificial ground freezing method has become a significant method for the construction of cross passage in complex environmental conditions due to its advantages such as good water sealing and adaptability.Based on an artificial ground freezing project of 3#connecting passage between Caoqiao Station and You'anmen Station of Beijing Metro Line 19,ground temperature and pressure of depressurization holes were studied through field measurement,and the intersection of freezing curtain was analyzed,so as to ensure the safe construction of cross passage.The results show that brine and ground temperature go through three stages:fast cooling,slow cooling and continuous cooling.The temperature on the outside of the freezing curtain is higher than that on the inside,and the temperature on the upstream side is higher than that on the downstream side.It should be paid more attention to the outer circle of the freezing wall on the upstream surface.The pressure of depressurization holes go through three stages:keeping steady,increasing pressure and releasing pressure.After freezing for 28 days,the pressure of depressurization holes increase slowly and the freezing curtain intersected well.After freezing for 37 days,the average temperature of each temperature hole is lower than-10℃,the pressure of depressurization holes dropped to 0 MPa,and the freezing curtain was basically no longer developed.