长距离液氮冻结加固高承压富含水层温度实测研究

结合杭州庆春路过江隧道盾尾刷更换工程，给出了在高承压富含水层地层中采用长距离液氮冻结加固封水的冻结参数和工艺，并进行了冻结温度场实测研究。监测分析结果表明：长距离液氮冻结去路温度应保证在到达工作面时液氮温度为 - 100℃ 以下，经循环后出口温度应保持在 - 50℃ ～ - 70℃ ；采用 3 层 1 cm 厚的聚乙烯保温材料和 3 层密封薄膜交替包裹保温效果明显，温度回升为 0.070℃/m ，最长可用于 1000 m 的远距离液氮冻结；冻土体发展速度从大到小依次为圆砾层 > 粉细砂层 > 粉质黏土层；管片中的温度受外界影响较大，盾壳 - 管片界面温度在盾尾刷焊接前、焊接时及焊接后分别为 5.4℃ ～ - 3.2℃ 、 19.3℃ ～ 8.7℃ 、 12.7℃ ～ 4.8℃ ，确保了冻结壁不融化和焊接质量；强制解冻仅需 2 d 即可达到盾构继续推进的条件，本工艺总工期为 23 d ，解决了承压含水层中封水更换盾尾刷的难题。

Temperature measurements of long-distance liquid nitrogen freezing in high-confined aquifer reinforcement

Based on the Qingchun Road cross-river tunnel of Hangzhou,frozen parameters and process of long-distance liquid nitrogen freezing in high-confined aquifer are obtained,and field measurements of freezing temperature are performed.The results show that the long-distance liquid nitrogen freezing temperature should be guaranteed in the way when the temperature reaches the working liquid nitrogen below-100℃,and the exit temperature after cycling should be held between-50℃～-70℃.By using three 1 cm-thick layers of polyethylene insulating materials and three layers of sealed film alternately,the heat preservation effect is obvious,the package temperature has a rise of 0.070 ℃ / m,and the longest distance for the liquid nitrogen freezing can reach 1000 m.The development speed of permafrost from large to small order is gravel layer> silt sand layer> silt clay layer.The temperature of segment is affected by external environment,and the temperatures at segment-shield shell interface before,during and after welding of shield tail brushes are 5.4℃～-3.2℃,19.3℃～8.7℃ and 12.7℃～4.8℃ so as to ensure the thawing and welding quality of frozen walls.Compulsory thawing only needs 2 days to achieve the condition for the shield,and this procedure has a total duration of 23 days,which solves the problem of replacing shield tail brushes in confined aquifer.