有限变形理论的深厚冲积层冻结壁变形特性分析

Finite strain analysis on deformation characteristics of frozen soil wall in deep alluvium

冻结壁的变形及其影响因素是冻结凿井工程,特别是深厚冲积层冻结法凿井工程中急需研究解决的技术课题。基于有限变形理论,利用冻土有限变形本构关系及其蠕变参数,对深厚冲积层(超过400m)冻结壁进行了有限元分析,表明冻结壁井帮径向位移在段高内的分布是不均匀的,一般是上下小、中间大,并且冻结壁内部径向位移比井帮径向位移小;得出了冻结壁井帮的最大径向位移与冻结壁厚度、冲积层厚度、开挖段高、开挖段井帮暴露时间和井筒开挖半径关系表达式,并得到了现场实测验证。

FEM analysis of frozen soil wall is performed with ANSYS software in which the finite strain constitutive equation of frozen soil and the parameters of creep in the equation are incorporated. The regularity of the radial displacements on the surface of frozen soil wall and in inner frozen soil wall is revealed. The factors of influencing on the displacement distribution of frozen soil wall are analyzed. A formula is proposed for expressing the relationship of the maximum radial displacement of frozen soil wall with the thickness of frozen soil wall, the thickness of frozen alluvium, excavating segment height, exposure time of frozen soil wall, excavating radius of shaft. The results obtained from the formula are consistent with the data measured in situ.