异形加强冻结管在管幕冻结法中的冻结效果及使用方法研究

港珠澳大桥珠海连接线拱北隧道工程口岸暗挖段的超前预支护体系采用管幕冻结法,该工法将3种功能不同的特殊冻结管内置在顶管内进行冻结封水。其中异形加强冻结管主要起到减少或是抵消由于开挖和施作衬砌引起的热扰动以抵御冻土弱化的作用。结合管幕冻结法大型物理模型试验,重点分析异形加强冻结管的冻结效果及其使用方法。结果表明:1)异形加强冻结管降温效果明显,能抵御开挖和施作衬砌带来的热扰动;2)提前开启异形加强冻结管,形成良好的冻土帷幕后开挖更安全。

Study on Freezing Effect and Operation of Profiled Enhancing Freezing-tube in Freeze-sealing Pipe Roof

Gongbei tunnel on Zhuhai Link of Hong Kong Zhuhai Macau Bridge is to be constructed by “Freeze sealing Pipe Roof” (FSPR) method. FSPR, serving as a forepoling system, consists of three types of freezing pipes with special functions. Profiled enhancing freezing tube is aimed at minimizing the influence of the excavation disturbance and lining placement on the frozen soil. Based on the model experiment of FSPR, the effect of profiled enhancing freezing tube is presented. Conclusions drawn are as follows: 1) Using profiled enhancing freezing tube can weaken the thermal disturbance arising from the excavation and lining placement; 2) The safety of the excavation is improved because of the better frozen soil achieved by opening the profiled enhancing freezing tube in advance.