求解带自由面渗流问题移动网格法的改进及其工程应用

采用有限元固定网格和移动网格相结合的方法,求解带自由面的坝体稳定渗流问题。本方法是针对一般坝体的结构,在有限元网格生成之后,又自动生成了网格移动所需的信息,实现了网格在迭代计算中随自由面的变化自动均匀移动;讨论了网格奇异的不同类型,提出了避免单元形状怪异的移动网格方法;在欧拉空间中分区记录坝体不同的渗透性能,在网格移动到新位置后,自动识别网格所在的物性空间,从而确定单元在新位置上的渗流系数。本文将该方法应用到吉林丰满混凝土重力坝防渗加固的实际工程当中,在考虑大坝原有防渗措施的前提下,利用数值分析,研究了防渗芯墙对大坝渗流性能的影响。计算结果表明,加芯墙后坝体自由面位置明显下移,湿水部分大为减少,坝基扬压力没有明显提升,下游出水点位置没有明显下降。计算过程表明,本文方法及措施具有很好的收敛性与稳定性,且收敛性与自由面初始位置的选择无关。

Improvement of moving mesh method in solving seepage problem with free surface and its application

The steady dam seepage problem with a free surface was solved by using FEM with combined moving and fixed meshes.After data of the FEM meshes were prepared,information of moving meshes was generated according to general dam body's structure.Therefore,the automatic and homogenous moving meshes adapting to the free surface's shifting was implemented.Singular meshes of different styles were studied and the moving mesh method was proposed to avoid the monstrosity of the cells.After the meshes moved to the new position,recording zone by zone the dam body's different penetrability coefficients in Euler space,the physical spaces at which the meshes were located are identified automatically so as to ascertain the cells' penetrability coefficients in the new position.This method was applied to a practical project: Antiseep and Reinforcement of JiLin Fengman Concrete Dam.Considering the existing antiseep measures,the impervious performance of the dam before and after installing the impervious core was numerically simulated.The computational results show that(after installing the impervious core) the free surface descends greatly,the waterlogged parts of the dam body decrease significantly without increasing the dam foundation's lifting pressures,the head pressures of the spill points in the lower reaches do not decline obviously.The computational procedure shows that the method and the measures of this paper have good convergence property and stability,which is independent of selecting of the initial free surface.