拱北隧道管幕冻结施工中限位管的冻结效果控制研究

港珠澳大桥珠海连接线拱北隧道采用管幕冻结法施工。为了获取合适的冻结施工参数,采用原型试验研究限位管的冻结效果控制作用。试验结果表明:当管幕冻结施工过程中实顶管正上方冻土发展较快时,可通过在限位管循环热盐水来控制冻土发展,其中,限位管温度为8℃比2℃时能更好地控制冻土厚度;但是,若实顶管与空顶管之间的冻土及空顶管上方的冻土仍需要发展时,可采用2℃盐水,此时,冻土帷幕厚度继续增加,但幅度减小。因此,采用限位管控制冻土帷幕发展是可行的。

Case Study on Control of Freezing Effect by Installing Limiting Tubes in Freezing-sealing Pipe Roof in Gongbei Tunnel

Gongbei tunnel of Zhuhai Link Road of Hongkong Zhuhai Macao Bridge is proposed to be constructed by freezing sealing pipe roof method. In the paper, the effect of limiting tubes is studied by means of prototype experiment so as to obtain the rational parameters for the freezing sealing pipe roof scheme. Conclusions drawn are as follows: 1) When the frozen soil wall above the pipe filled with concrete is growing at a relatively high rate, the method of circulating warm brine in the limiting tubes can be used to control the over growth of the frozen body. Considering the brine temperature in the brine tube for limiting the over growth of the frozen body, the temperature of 8 ℃ is more effective than the temperature of 2 ℃. 2) When the frozen soil between the pipe filled with concrete and that without concrete filled and the frozen soil above the pipe filled with concrete need further freezing, the brine temperature of 2 ℃ can be adopted, the frozen soil wall is still growing, however at a lower speed. The result of the prototype experiment proves the effect of the limiting tubes.