多冷媒联合冻结技术在盾构抢险中的应用

Application of Multi-Refrigerant Combined Freezing Technology in Shield Rescue

为解决地层冻结加固工程加固时间长、加固效果不足的问题,提出多冷媒联合制冷的新型技术,并以珠江三角洲水资源配置某盾构刀盘更换工程为案例背景,对液氮+盐水双冷媒联合冻结方案进行介绍。从地质条件、方案设计、数值计算验证和应用效果等方面入手,对多冷媒联合冻结技术的可行性进行分析。主要结论如下:1)液氮冻结速度快但均匀性欠佳,盐水冻结速度慢但均匀性较好,二者联合冻结可以有效完成高风险地层中的盾构开舱换刀;2)液氮冻结会造成掌子面工作环境温度偏低,本案例中开挖掌子面温度低于-40℃,环境温度约-13℃,作业人员应注意低温防护;3)为保证施工效率,盾构换刀冻结工程施工应在冻结壁交圈后及时清空土舱泥浆,防止泥浆冻结。

The artificial ground freezing has disadvantages such as long reinforcement time and insufficient reinforcement effect.Therefore,a novel technology of multi-refrigerant combined refrigeration is proposed.Meanwhile,a case study is conducted on a shield cutterhead replacement project in the Pearl River Delta water resources allocation,and a combined freezing scheme of liquid nitrogen+brine double-refrigerant is presented.Moreover,the feasibility of the multirefrigerant combined freezing technology is analyzed from four aspects:geological conditions,program design,numerical calculation verification,and application effect.Some conclusions are drawn as follows:(1)The liquid nitrogen freezes quickly with poor uniformity after reinforcement,and the brine freezing freezes slowly with good uniformity,thus the combined freezing of liquid nitrogen and brine can provide conditions for shield chamber opening in high-risk strata.(2)The liquid nitrogen freezing lowers the working environment temperature of tunnel face.In this case,the temperature of the tunnel face is lower than-40℃,and the ambient temperature is approximately-13℃,thus lowtemperature protection measures should be applied.(3)To ensure construction efficiency,the slurry in shield chamber should be cleaned after freezing wall intersection to prevent mud frozen.