土石围堰中混凝土防渗墙设计方案的数值优化

doi:10.13278/j.cnki.jjuese.20190095

摘要/Abstract

摘要： 土石围堰中防渗墙的结构对坝基渗流量及坝体稳定性具有重要的影响，因此优化防渗墙的尺寸十分有必要。本文以珠江流域某水利枢纽工程施工中的土石围堰为例，采用有限元法，对防渗墙的厚度和嵌入弱风化层基岩的深度进行了优化研究，分别模拟了有防渗墙和无防渗墙两种情况下围堰的防渗效果，共设计了33种计算方案。将坝基单宽渗流量、防渗墙后作用水头、防渗墙底部和坝脚溢出点的水力比降分别与其允许值进行了对比分析，提出了防渗墙的优化尺寸。研究结果表明：防渗墙厚度的变化对防渗效果影响较小；增大防渗墙的入岩深度，可以有效控制本围堰工程的单宽渗流量和防渗墙后作用水头；防渗墙底部水力比降的变化与防渗墙入岩深度有关，当入岩深度在0~8 m时，水力比降随入岩深度的增大而减小并呈先快后慢的趋势，当入岩深度在8~12 m时，水力比降随入岩深度的增大而增大，超过10 m时水力比降骤增。考虑经济因素和施工的方便性，满足防渗设计要求的防渗墙最优设计参数为厚度0.8 m、嵌入弱风化层基岩深度2 m。

关键词: 土石围堰, 混凝土防渗墙, 优化设计, 水力比降, 渗流量

Abstract: It is necessary to select an optimal scheme of cutoff wall for earth-rock cofferdams, because the structure of the cutoff wall in the earth-rock cofferdam has an important influence on the seepage flow and the stability of cofferdam. In this paper, the optimal design of the thickness and depth of cutoff wall is studied by finite element method (FEM) taking as an example of a certain earth-rock cofferdam for construction, which is located in the Pearl River basin. The seepage fields based on 33 types of cutoff wall scheme which is composed of no concrete cutoff wall and 32 types of concrete cutoff wall about its thickness and its embedded depth within the weakly weathered rock were simulated. Then the control index, such as the seepage per unit width of cofferdam, the water head behind the cutoff wall, the hydraulic gradient at the bottom of cutoff wall and the cofferdam foot, were calculated and compared with the allowable value. Finally, the optimized anti-seepage scheme of cutoff wall was obtained. The conclusions made are as follows:1) Comparing with the thickness of cutoff wall, increasing the embedded depth within the rock can control more effectively the seepage per unit width of cofferdam and the height of the water head behind cutoff wall. 2) The change of hydraulic gradient at the bottom of cutoff wall is related to the depth of cutoff wall within the weakly weathered rock. Increasing the depth of cutoff wall from 0 to 8 m, the hydraulic gradient will decrease and will change from fast to slow. When the depth increases from 8 to 12 m, the hydraulic gradient will increase with the embedded depth and there is a significant increase after 10 m. 3) The cutoff wall with 0.8 m in thickness and 2 m in embedded depth within weakly weathered rock is regarded as the optimal anti-seepage scheme for this project after considering the project input and construction convenience. The results not only provide a basis for the design of the earth-rock cofferdam, but also provide a reference for the anti-seepage system of proposed earth-rock cofferdam projects under the same geological conditions.

Key words: earth-rock cofferdam, concrete cutoff wall, optimal design, hydraulic gradient, seepage flow

中图分类号:

TV223.4

王常明, 鲁鋆, 马栋和. 土石围堰中混凝土防渗墙设计方案的数值优化[J]. 吉林大学学报(地球科学版), 2020, 50(3): 857-865.

Wang Changming, Lu Yun, Ma Donghe. Numerical Optimization of Design Schemes for ConcreteCutoff Wall in Earth-Rock Cofferdam[J]. Journal of Jilin University(Earth Science Edition), 2020, 50(3): 857-865.

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