大直径公路隧道圆形联络通道的冻结加固设计与实践

人工冻结技术是软土地层中联络通道加固的常用方法,而联络通道结构形式是影响冻结加固设计和施工的重要因素。依托上海沿江通道工程,针对江底大直径隧道的工程特点和地质条件,介绍了圆形冻结加固体的设计方法和施工过程,分析了地层温度和隧道变形的变化规律。获得以下结论:水土压力作用下,圆形冻结壁内部不会出现拉应力,可以充分发挥冻结壁抗压强度高的优势;沿联络通道轴线平行布置的双圈冻结孔布置形式,使形成的冻结壁更均匀,而管片内表面敷设的冷排管的加强冻结方式,也可以避免冻结壁内部出现薄弱环节。圆形冻结壁结构形成过程中产生的冻胀作用,对两侧大直径隧道影响较小,可以保证隧道的安全和稳定。研究结果表明,圆形联络通道冻结加固形式较传统直墙拱形断面具有明显的优势,研究成果可供类似地层的联络通道冻结设计和施工时参考。

Design and Practice on Freezing Reinforcement of Circular Connecting Channel in Large Diameter Highway Tunnel

Artificial freezing technology is a common method for strengthening the connection channel in soft soil stratum,and the structure form of the connection channel is an important factor affecting the design and construction of freezing reinforcement.Relying on the channel projects along river in Shanghai,and based on the engineering characteristics and geological conditions of the large diameter tunnel under the river,the design method and construction process of the circular freezing reinforced body are introduced,and the variation rules of stratum temperature and tunnel deformation are analyzed.The following conclusions are obtained that there is no tensile stress inside the circular frozen wall under the action of soil and water pressure,which can give full play to the advantage of high compressive strength of the frozen wall.The layout form of double-loop freezing hole along the axis of the connecting channel can make the formed freezing wall more even,and the strengthened freezing mode of the cold discharge pipe laid on the inner surface of segments can also avoid the weak links in the freezing wall.The frost heaving effect produced during the formation of the circular frozen wall structure has little influence on the large diameter tunnels on both sides,which can ensure the safety and stability of the tunnel.The study results show that the frozen strengthening form of circular connection channel has obvious advantages over the traditional straight-wall arch section.The study results can be referred for the freezing design and construction of connecting channels in the similar stratums.