坝基防渗中灌浆帷幕与排水作用的探讨

Approach to Effects of Grouting Curtain and Drainage in Seepage Control of Dam Foundation

文章主要探讨不同渗透特性的坝基中，灌浆帷幕和排水的作用与效益。提出：对于不同渗透系数的坝基所设置的帷幕深度，必须进行具体分析和计算；帷幕与坝基渗透系数的相对值，是确定帷幕防渗效果的主要参数，而且在弱透水层中帷幕的作用是很小的；坝基排水的作用是缩短渗径、增大渗透坡降，而使扬压力迅速消散于排水中；虽然坝基的强弱透水性不同，但其排水降压效果是相同的，只是所要求排走的流量不同，强透水基础要求排走的流量多，而弱透水基础要求排走的流量少，因此，合理设计排水孔尺寸和布置是保证排水孔降压效果所必需的。在实际工程中，坝基防渗设施中总是考虑帷幕与排水的组合作用，但对不同透水性的基础，帷幕的深度及排水布置应分别对待，以尽量缩短帷幕长度，又能保证最佳的降低扬压力和防渗效果为前提。

The author discusses mainly the role and effects of grouling curtain and drainage in dam foundation wilh various permeability properties. It is necessary to analize and calculale the depth of curtams set for dam foundation with different coefficients of permeability. The author conclutles that the main parameter determining the seepage control effect of grouting curtain is the relative value between curtain depth and coefficienr of permeability, and the role of grouting curtain is rather small in weakly permeable layer. The role of drainage for dam foundation is to shorten the seepage path and increase the seepage gradient, thus dissipating rapidly the uplift pressure during drainage. No matter the dam foundation is weakly or slrongly permeable , the effect of drainage in lowering the pressure is just the same. For strongly permeable foundation it is required to drain more flow, while less for weakly permeable foundation. Hence to ensure the effect of draomage in lowering the pressure, it is necessary to design rationally the size and layout of drain holes. Practically, the combined role of grouting curtain and drainage is always taken in to account in seepage control facilities. For dam foundation with different per,eability properties, the depth of curtain and layout of drainage should be varied so as to both shorten the length of curtain as far as possibic and ensure the best results of seepage control and lowering the uplift pressure.