复杂地层旁通道冻结施工过程的模拟与实测分析

采用FLAC3D模拟分析了在复杂地质条件下,采用冻结法修建上海地铁旁通道时,土体的冻胀和融沉的现象。将模拟得到的地表位移与现场实测值进行了对比,结果表明:(1)积极冻胀阶段:地表竖向位移主要发生在旁通道的正上方,随着向两边的延伸,距离隧道中心的距离越大,垂直冻胀量越小。(2)维持冻结阶段:测点因为开挖过程中的继续冻胀位移值随开挖步距先略有增加而后随着开挖量的增加沉降量随之逐步的增大,最终地表发生了明显的变形。(3)融沉阶段:施作完衬砌结构以后进行60天自然解冻过程中,实测位移和计算位移较为一致,研究表明建立的数值分析模型合理、结果可靠。

Numerical simulation and measurement of freezing method applied to connected aisle of subway tunnels under complex conditions

FLAC3D was applied to simulate frost-heave and thawing settlements during the whole construction process of a connected aisle in Shanghai metro under a very complex geologic condition. By comparing the numerical solution with the field test values,several main conclusions were obtained as follows：First,in active freezing stage the vertical ground settlement emerged over the connected aisle,and decreased gradually in the lateral directions. Second,during maintain freezing stage,the vertical surface displacement had a small increase due to the continuing frost-heave at first,then the surface began to gradually subside as the increase of excavation volume. At the end of this stage,the surface subside could be obvious. Third,a process of naturally thawing was last for 60 days after finishing the lining structure,during this period,the numerical solution and measurement showed a same tend and the error between them was very small. Altogether,the hypotheses for 3-D numerical simulation in this paper were reasonable and the calculation result was also reliable.