随着筑坝技术的发展,深厚覆盖层逐渐成为土石坝常选坝基方案,其中坝基渗流控制是需要解决的关键问题之一。采用有限元法,对深厚覆盖层上土工膜防渗堆石坝渗流场进行计算分析,重点研究悬挂式防渗墙深度、覆盖层深度和渗透性对坝基渗流特性的影响。结果表明:防渗墙深度、覆盖层深度和渗透性均显著影响坝基渗流特性;防渗墙深度变化或覆盖层深度变化下,大坝渗流量和相对防渗深度关系曲线基本重合,均呈现先线性缓慢减小后急剧下降的特点,防渗墙和覆盖层深度共同决定坝基渗控效果;采用悬挂式防渗设计时,为保证大坝渗流量控制率达到75%,相对防渗深度与覆盖层渗透系数之间呈强对数线性关系。研究成果可用于待建类似工程防渗墙深度的初拟或已建类似工程坝基覆盖层防渗效果的评价。
Abstract
Seepage control of dam foundation is a key issue that needs to be solved in dam construction with deep overburden. Finite element method is employed to analyze the seepage characteristics of geomembrane impervious earth-rock dam on deep overburden. The study focuses on the impact of the depth of suspended cut-off wall, the depth of overburden, and permeability on the seepage field of dam foundation. Results reveal that the seepage characteristics of dam foundation are significantly affected by these factors. Under varying depth of cut-off wall or overburden layer, the relation curves of seepage versus relative seepage control depth conincide in general, displaying a trend of slow linear decline before dramatic reduction. The depth of cut-off wall and overburden layer jointly affect the seepage control effect. When suspended cut-off wall is adopted, the relative anti-seepage depth should be in a good logarithmic linear correlation with permeability coefficient of overburden to ensure that the dam seepage control rate reaches 75%. This fitting relation can be used for preliminary design of cutoff wall depth for similar projects or effect evaluation of cutoff for existing projects.
关键词
土工膜防渗堆石坝 /
深厚覆盖层 /
渗流特性 /
相对防渗深度 /
渗流量控制率
Key words
geomembrane faced rockfill dam /
deep overburden /
seepage characteristics /
relative impermeable depth /
control rate of seepage flow
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基金
国家自然科学基金项目(51679073,51979089);国家自然科学基金联合基金项目(U2243244);江苏省研究生实践创新计划项目(SJCX21_0199)
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