多元结构堤基半封闭式防渗墙概化模型研究

Study on generalized model of the semi-closed cutoff wall of multi-structure levee foundation

为了确保洞庭湖区堤基安全,根据堤基地质特点,建立了多元结构堤基的垂直防渗概化模型;并采用渗流有限元法对影响半封闭式防渗墙防渗效果的各种因素进行了较为全面系统的研究,分别得到了天然弱透水覆盖层、第二层强透水层、防渗依托层、依托层下伏强透水层的厚度、渗透性对堤内和堤脚附近最大渗透坡降的影响曲线.计算结果表明,防渗依托层的厚度、渗透性对堤内、堤脚附近最大渗透坡降的影响程度远远大于其他因素,其对半封闭式防渗墙防渗效果起决定性的作用;在所有次要因素中,天然弱透水覆盖层的厚度、渗透性对堤内最大渗透坡降的影响较其他因素大,尤其对堤脚附近渗透坡降的影响比较明显.本文的研究成果既可用于定量研究半封闭式防渗墙的防渗机理,也可以为垂直防渗墙的设计提供可靠的理论依据.

In order to ensure the safety of the levee foundation in Dongting Lake region,a generalized model of the semi-closed cutoff wall of multi-structure levee foundation is established according to the geologic characteristics of the levee foundation.The factors of influencing the anti-seepage result of the semi-closed cutoff wall is systemically and comprehensively studied by seepage FEM,and the influencing laws of the thickness and permeability of less permeable covering layer,the second strongly permeable layer,anti-seepage supporting layer and the strongly permeable layer under anti-seepage supporting layer on the maximal seepage gradient inside the levee and near the levee toe,are presented.The numerical results indicate that the thickness and permeability of anti-seepage supporting layer are main influencing factors and have the greatest effects on the maximal seepage gradient inside levee and near the levee toe,they determine the anti-seepage effect of semi-closed cutoff wall.The thickness and permeability of less permeable covering layer have greater effect than other secondary factors on the seepage gradient inside the levee,especially near the levee toe.These numerical results can be used for the quantitative study of the anti-seepage mechanism of the semi-closed cutoff wall and provide theoretical basis for the design of the vertical cutoff wall.