异形加强冻结管外壁保温对管幕冻结效果影响试验研究

Experimental Study on Outer Insulation Influence of Profiled Enhancing Freezing Pipes on Effect of Freeze-Sealing Pipe Roofs

新型管幕冻结法冻结系统由充填混凝土的实顶管内布置圆形主力冻结管和限位管、未充填混凝土的空顶管内布置异形加强冻结管组成。为分析该新型管幕冻结系统中空顶管周围的冻结效果,通过拱北隧道管幕冻结现场原型试验,对空顶管中异形加强冻结管是否采取外表面保温措施展开研究,利用冻土帷幕厚度的变化对异形加强冻结管保温措施与不保温状态进行冻结效果对比分析。结果表明:异形加强冻结管保温不利于冻土帷幕的形成,随着冻结时间推移,冻土帷幕的发展会越来越慢;协同冻结模式下60 d后保温与不保温的冻土厚度之差约为冻结20 d的2倍。可以把空顶管作为“大冻结管”来考虑,利用异形加强冻结管对空顶管内部整体降温,更有利于顶管周围冻土帷幕的发展。

The freezing scheme of the freeze-sealing pipe roof method comprises circularmain freezing and limiting pipes arranged in a solid jacking pipe filled with concrete and a profiled enhancing freezing pipe arranged in an empty jacking pipe.To examine the freezing effect around the empty jacking pipe of this novel freezing system,an on-site prototype test is conducted in the Gongbei tunnel.The influence of external surface insulation of the profiled enhancing freezing pipe in the empty jacking pipe on the freezing-sealing effect is investigated based on the variation in the thickness of the frozen soil curtain.The results show that the insulation of the external surface of the jacking pipe is not conducive to the formation of the frozen soil curtain,and the formation rate of the frozen soil curtain decreases with freezing time.In addition,the thickness difference of frozen soil between the insulated and uninsulated cases at 60 days in the synergistic freezing mode is approximately twice that of 20 days of freezing.The empty pipe jacking can be considered as a"big freezing pipe",and overall cooling inside can be achieved using the profiled enhancing freezing pipe,which is more conducive to the formation of the frozen soil curtain around the jacking pipes.