防渗墙的弯矩计算

 在防渗墙设计时，较为关注的是防渗墙内力大小，特别是弯矩。借助有限元数值计算得到的往往是单元应力和节点位移，这就需要利用应力和位移信息间接计算防渗墙的弯矩。通过一防渗墙的计算分析，对上述问题进行探讨。研究结果表明，剪切闭锁对位移计算的影响不大，使用线性实体单元能够得到与二次单元相近的结果。位移计算结果对网格划分也不太敏感，所以防渗墙计算并不一定需要采用高次单元。用应力计算弯矩和用位移计算弯矩对防渗墙来说都是可行的，用应力计算弯矩需要在截面方向划分较多网格。位移计算弯矩需要的网格较少，但在一些情况下会出现振荡，而且对网格划分和单元类型比较敏感。即使得到的位移值很接近，利用位移得到的弯矩仍然会有很大差别。

BENDING MOMENT CALCULATION OF CUTOFF WALL

In the design of cutoff wall，it is important to get the wall¢s internal forces，especially the bending moment. Generally，the stresses and displacements with finite element method are obtained. So it is necessary to investigate the indirect calculation of bending moments with stress and displacement. The analytical results of a cutoff wall with different element types and mesh partitions show that shear locking is not so significant for the cutoff wall embedded in soil. First-order solid element and second-order solid element can get similar results of displacements；and the results are insensitive to mesh partition. Therefore，high-order elements are not always necessary in the computation. The bending moment can be well calculated both by stress and displacement. Enough grids are necessary across the cross-section if bending moment is calculated with stress. Computing bending moment with displacement needs fewer grids，but it sometimes results in fluctuation of the results. Additionally，the computed results of bending moment are sensitive to mesh partition and element type；i.e. the displacements can agree well with each other，whereas bending moments have great discrepancies with different element types and mesh partitions.