红谷隧道围堰塑性混凝土防渗墙抗渗性能分析

Analysis of Anti-seepage Performance of Plastic Concrete Wall Used in Cofferdam of Honggu Tunnel

为探讨运行环境下塑性混凝土防渗墙工作性能,获取合理的设计参数取值,以红谷隧道围堰工程为背景,结合典型断面建立渗流数值模型,分析塑性混凝土防渗墙渗透系数k和厚度d以及围堰水头hr变化下共11种工况的围堰渗流性状。结果表明:随着渗透系数k的减小,围堰内单宽渗流量Q随之减小,且变化速率逐渐降低,而防渗墙内水力坡降峰值Js基本保持不变;随着防渗墙厚度d的增大,围堰内Q值和Js值均随之减小,且变化速率逐渐降低;随着围堰水头hr的下降,围堰内Q值和Js值均随之线性降低。分析得到兼具良好防渗能力和经济效益的渗透系数k和厚度d的设计取值,并提出满足设计要求的塑性混凝土施工配合比。最后,通过高密度电法和围堰内外水位动态监测对塑性混凝土防渗墙的防渗效果进行检测和评价,验证设计和施工参数的合理性。

The seepage numerical models of typical sections of cofferdam of Honggu Tunnel are established; and cofferdam seepage properties under 11 kinds of construction conditions when the permeability coefficient k and thickness d of the cutoff wall and the weir head hr varying, are analyzed. The results indicate that ： 1 ） The cofferdam seepage flow per unit width Q reduces with the permeability coefficient k decreases ; and the variation velocity of Q reduces gradually ; the peak of hydraulic grade Js remains stable in cutoff wall. 2 ） The Q and Js reduce with the cutoff wall thickness d decreases ; and the variation velocities of Q and Js reduce gradually. 3 ） The Q and Js reduce linearly with the weir head hr decreases. The design values of k and d with good anti-seepage ability and economic benefits are obtained; furthermore the mixing proportions of corresponding plastic concrete which can meet the design requirements are presented. The anti-seepage performance of plastic concrete wall is detected and evaluated by high density resistivity method and monitoring of water levels inside and outside cofferdam.