Feedback on work behavior of composite geomembrane in Wangfuzhou hydraulic project based on measured piezometric level
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摘要: 基于王甫洲水利工程近20 a的渗流监测资料,对复合土工膜的防渗工作性态进行反馈分析。首先对围堤土石坝整体渗流性态进行定性分析;然后选取典型断面建立测压管水位统计模型进行定量分析;接着采用正交设计-神经网络-数值计算相结合的方法,反演复合土工膜的渗透系数;最后对复合土工膜工作性态进行综合分析。研究表明,测压管实测水位仅在蓄水运行初期出现较大变幅,目前变化较平稳;典型GY5断面中3支测压管的实测水位和分离出的时效分量均呈逐渐减小的趋势;基于实测水位反演获得的复合土工膜渗透系数为1.11×10-10 cm/s;综合分析认为王甫洲水利工程复合土工膜经过约20 a的服役,防渗效果依然良好且没有明显的老化趋势。Abstract: The feedback analysis of anti-seepage behavior of composite geomembrane is performed based on nearly 20 years of seepage monitoring data from Wangfuzhou hydraulic project. Firstly, the qualitative analysis of the overall seepage behavior of the embankment earth-rock dam is carried out. Then a typical section is selected to establish the statistical model of piezometric level for quantitative analysis. Subsequently, the orthogonal design, neural network and numerical method are combined to invert the permeability coefficient of the composite geomembrane. Finally, the work behavior of the composite geomembrane is analyzed comprehensively. The results show that the piezometric level only changes greatly at the initial stage of water storage and operation, and the change is relatively stable at present. Additionally, it is found that the piezometric level and separated time-dependent components of three piezometers in the typical GY5 section decrease gradually. At the same time, the permeability coefficient of the composite geomembrane inverted by the piezometric level is 1.11×10-10 cm/s. The comprehensive analysis shows that the composite geomembrane of Wangfuzhou hydraulic project still has good anti-seepage behavior after nearly 20 years of service, and there is no obvious aging trend.
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表 1 复合土工膜与土工布的主要控制指标
Table 1 Main control indexes of composite geomembrane and geotextile
项目 一布一膜 两布一膜 土工布 单位面积质量(布)/(g·m-2) 200 200 200 厚度*(膜)/mm 0.5 0.5 抗拉强度** 径向/(kN·m-1) ≥10 ≥16 垂直渗透 系数 ≥2×10-2 cm/s 纬向/(kN·m-1) ≥8.0 ≥12.8 极限延伸度 径向/% ≥60 ≥60 有效孔径≤0.14 mm 纬向/% ≥60 ≥60 撕裂强度/kN ≥0.3 ≥0.5 CBR顶破强度/kN ≥2.0 ≥3.0 ≥0.5 注: *在2 kPa压力条件下的厚度;**按5 cm宽试样折算。表 2 左、右岸围堤土石坝测压管水位特征值统计
Table 2 Characteristic values of piezometric level of earth-rock dam
编号 最大值及库水位 最小值及库水位 最大年变幅/m 测压管/m 库水位/m 年份 测压管/m 库水位/m 年份 GZ2-2 82.66 86.56 2003 80.02 83.19 2000 2.35 GZ3-1 84.12 86.22 2000 81.73 83.19 2000 2.39 GZ4-1 83.98 85.97 2000 79.92 83.19 2000 4.06 GZ5-1 86.54 86.53 2007 82.03 83.19 2000 4.44 GZ6-2 86.23 86.35 2017 84.20 86.02 2018 1.85 GY2-1 82.44 86.32 2011 80.10 83.19 2000 1.88 GY3-1 82.47 86.32 2011 80.28 83.19 2000 1.81 GY4-2 82.46 86.35 2003 80.82 83.19 2000 1.50 GY5-2 83.12 86.35 2003 80.85 83.19 2000 2.14 GY6-2 84.71 86.23 2000 80.27 83.19 2000 4.44 GY7-2 85.50 86.47 2006 81.48 83.19 2000 3.46 表 3 GY5断面测压管水位特征值统计
Table 3 Characteristic values of piezometric level of GY5 section
编号 最大值及库水位 最小值及库水位/m 最大年变幅/m 测压管/m 库水位/m 年份 测压管/m 库水位/m 年份 GY5-1 83.12 86.02 2001 82.23 84.79 2000 0.88 GY5-2 83.12 86.35 2003 80.85 83.19 2000 2.14 GY5-4 83.25 86.24 2000 82.63 86.39 2006 0.49 GY5-5 82.80 86.35 2003 82.00 85.81 2001 0.60 GY5-6 82.54 86.35 2003 81.85 86.36 2006 0.44 GY5-7 82.70 86.48 2005 81.89 86.39 2006 0.57 表 4 渗流场各分区渗透系数初始值
Table 4 Initial values of permeability coefficient of each zone in seepage field
符号 渗透系数分区 渗透系数/(cm·s-1) ky kx k1 复合土工膜 1.00×10-11 1.00×10-11 k2 坝体砂砾石 3.40×10-2 3.40×10-2 k3 坝基砂壤土 2.20×10-3 2.20×10-3 k4 坝基中细砂层 2.40×10-2 2.40×10-2 k5 坝基砂砾石层 3.40×10-2 3.40×10-2 k6 基岩 5.00×10-5 5.00×10-5 表 5 反演训练样本
Table 5 Inversion training samples
样本数 渗透系数/(cm·s-1) 测压管水位计算值/m k1/10-11 k2/10-2 GY5-1 GY5-2 GY5-4 1 8.00 2.72 82.793 82.672 82.916 2 8.00 3.40 82.736 82.622 82.854 3 8.00 4.08 82.689 82.573 82.801 4 8.00 4.76 82.380 82.542 82.781 ··· ··· ··· ··· ··· ··· 13 14.00 2.72 82.800 82.675 82.919 14 14.00 3.40 82.741 82.623 82.855 15 14.00 4.08 82.693 82.572 82.801 16 14.00 4.76 82.380 82.539 82.778 表 6 检验样本计算成果
Table 6 Calculated results of test samples
检验样本渗透系数/(cm·s-1) 反演渗透系数/(cm·s-1) 相对误差/% k1/10-11 k2/10-2 k1/10-11 k2/10-2 10.00 3.06 9.72 3.05 2.78 0.48 10.00 4.25 9.63 4.20 3.69 1.20 10.00 4.42 9.70 4.33 3.04 2.09 10.00 4.59 10.20 4.59 1.90 0.05 -
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