双线冻结隧道下穿车站冻胀特性模型试验与工程实测

Experiment and Engineering Measurement of Frost Heave Characteristics of the Frozen Double-track Tunnel Underpass an Operation Station

近年来,中国城市轨道交通大规模建设,新建地铁隧道采用人工冻结法下穿地面建筑等工程数量逐年增加。冻结过程中,人工冻土冻胀容易引发上覆地表和相邻建筑物出现不均匀变形,造成上覆结构损坏。为保证双线隧道冻结施工中上覆结构安全,需要研究冻结下穿过程中的冻胀规律以选取最优施工方案。基于上海地铁18号线双线隧道冻结下穿地铁10号线国权路运营车站工程,开展冻结隧道下穿上覆车站相似模拟试验,并采用传感器对上部10号线国权路车站底板变形进行自动化监测,研究了上覆车站底板在全长冻结和分段冻结2种模式下的冻胀抬升规律,得出了工程施工过程中上覆车站底板变形规律。结果表明:分段冻结模式对上覆结构产生的最大抬升量为20.5 mm,出现在下行线隧道冻结期间,小于全长冻结模式产生的最大抬升量30 mm。车站底板在分段冻结模式下出现整体抬升,下行线隧道在积极冻结期间的抬升速度为0.12 mm/d,大于上行线隧道冻结时的抬升速度0.08 mm/d。采用分段冻结、分段开挖方案时,冻胀抬升和开挖沉降交替产生,车站底板抬升位移曲线呈锯齿状。实际工程中采用分段冻结、取土卸压等方法降低冻胀量,实测车站底板最大抬升量为25.41 mm。试验得出车站底板抬升规律与施工数据呈现较好的一致性,有效地指导了工程施工。

In recent years,with the large-scale construction of urban rail transit in China,the number of new subway tunnel construction projects that use the artificial ground freezing method to underpass ground buildings has increased year by year.The freezing process of artificially frozen soil can easily cause uneven deformation of the upper-structure surface and adjacent buildings.To ensure the safety of overlying structure in the frozen double-track tunnel,it is necessary to get the frost heave law caused by different conditions in advance to select the optimal construction scheme.Taking the double-track tunnel of Shanghai metro line No.18 passing down the running station of the No.10 line as the research object,a similar simulation experiment was carried out.The law of frost heave uplift of the overlying station floor in two modes segmental freezing and the simultaneous freezing mode was studied.The deformation law of the upper station base slab during the construction process was obtained.The results showed that the upper structure’s maximum lift value generated by the segmental freezing occurred during the freezing period of the downline tunnel,and the lift value was 20.5 mm,which was less than the value of the simultaneous freezing mode.The base slab of the station was lifted as a whole mode of the segmental freezing mode,and the lifting speed of the second frozen tunnel during active freezing was 0.12 mm/d, which was greater than that of the upline tunnel when it was frozen by 0.08 mm/d. When the tunnel was in the construction of segmental freezing and segmental excavating, frost heave uplift and excavation settlement occurred alternately, and the displacement curve of the station floor was zigzag. In the actual project, methods such as coring were used to reduce frost heave, and it was concluded that the maximum lift value of the base slab was 25.41 mm. The base slab lift law obtained from the similar simulation experiment was in good agreement with the construction project data, which guided the construction of the project effectively.