基于低场核磁共振技术PVC-P土工膜细观渗透机理研究

张宪雷; 尹春杰; 马仲阳; 谷晓雨

doi:10.11779/CJGE20221546

基于低场核磁共振技术PVC-P土工膜细观渗透机理研究 English Version

华北水利水电大学水利学院, 河南郑州 450045

基金项目:

国家自然科学基金项目 52009045

详细信息

作者简介:
张宪雷(1984—)，男，博士，副教授，主要从事膜防渗结构方面研究工作。E-mail: zhangxianlei@ncwu.edu.cn

中图分类号: TU43
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出版历程
- 收稿日期: 2022-12-15
- 网络出版日期: 2023-06-01
- 刊出日期: 2024-03-31

Micropermeation mechanism of PVC-P geomembranes by low-field NMR technology

North China University of Water Resources and Electric Power, Zhengzhou 450045, China

摘要

摘要: PVC-P土工膜的防渗性能是膜防渗结构乃至工程安全运行的关键。为避免传统上用渗透系数表征其渗透性能的弊端，运用多组渗透压力下土工膜垂直渗透试验数据和基于低场核磁共振技术获取的孔隙度，构建了渗透流量-孔隙度数学模型，结合孔隙和孔径动态分布探讨了用孔隙度评价其垂直渗透性能的适用性。结果表明：以¹H原子为探针的低场核磁共振技术能够准确量测膜内孔隙和孔径分布；依据T₂特征谱弛豫时间划分的微孔隙、中孔隙和大孔隙的占比以及孔隙范围内孔径的萎缩或发育是孔隙度变化的根本原因；孔隙度与渗透流量关联性较强，利用量测的饱和PVC-P土工膜孔隙度和构建的模型能够准确预测渗透流量。研究成果表明基于低场核磁共振技术测得的孔隙度可用于PVC-P土工膜防渗性能评价。
- PVC-P土工膜 /
- 渗透流量 /
- 孔隙度 /
- 低场核磁共振技术 /
- T₂特征谱
Abstract: The impermeability of PVC-P geomembranes is of significant importance to the safe operation of a project. To avoid the drawbacks of adopting the permeability coefficient to characterize permeability traditionally, a mathematical model for porosity and seepage discharge is proposed based on the results of the vertical permeability tests and the porosity obtained from the low-field NMR tests, and the applicability of porosity to evaluate the permeability is explored. The results show that the low-field NMR technology with 1H atoms as the probe can accurately measure the distribution of pores and pore radiis. The proportions of the micropores, mesopores and macropores and the shrinkage and development of the pore radii are primarily responsible for the variation of the porosity. The porosity is closely correlated with the seepage discharge, and the proposed model can accurately predict the seepage discharge. Furthermore, the porosity can evaluate the impermeability of PVC-P geomembranes.
- PVC-P geomembrane /
- infiltration flow /
- porosity /
- low-field NMR /
- T₂ characteristic spectrum

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图 1 土工膜垂直渗透仪示意图

Figure 1. Schematic diagram of geomembrane vertical penetrator

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图 2 低场核磁共振试验示意图

Figure 2. Schematic diagram of low-field NMR tests

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图 3 单位体积信号强度与孔隙度关系曲线

Figure 3. Relationship between signal intensity per unit volume and porosity

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图 4 PVC-P土工膜渗透量与渗透流量曲线

Figure 4. Curves of permeable water and seepage discharge of PVC-P geomembranes

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图 5 0.8 MPa渗透压力PVC-P土工膜低场核磁共振成果

Figure 5. Results of low-field NMR test for PVC-P geomembrane at 0.8 MPa

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图 6 所有PVC-P土工膜T₂特征谱

Figure 6. T₂ characteristic spectra of all PVC-P geomembranes

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图 7 同一试样不同压强下T₂特征谱

Figure 7. T₂ characteristic spectra of same sample under different pressures

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图 8 不同渗透压力下PVC-P土工膜孔径变化

Figure 8. Variation of pore radius of PVC-P geomembranes with percolation pressure

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图 9 试验压力下PVC-P土工膜3类孔隙占比

Figure 9. Proportions of three types of pores in PVC-P geomembranes under test pressures

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图 10 孔隙信号总强度-渗透压力分布趋势

Figure 10. Variation of total signal intensity of pores with percolation pressure

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图 11 孔隙度和渗透流量的分布趋势

Figure 11. Distribution of porosity and seepage discharge under different pressures

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图 12 渗透流量q与孔隙度n关系

Figure 12. Relationship between seepage discharge q and porosity n

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表 1 PVC-P土工膜主要参数

Table 1 Main parameters of PVC-P geomembranes

技术指标	执行技术标准	横向	纵向	单位
厚度	ASTM D 5199-12^[22]	2.0±0.2	2.0±0.2	mm
单位面积质量	ASTM D 5261-10^[23]	1.77	1.77	g/cm²
断裂强度	ASTM D 6693M-04^[24]	9.65	10.10	MPa
断裂延伸率	ASTM D 6693M-04	310.04	289.99	%
屈服强度	ASTM D 6693M-04	2.57	3.39	MPa
屈服延伸率	ASTM D 6693M-04	49.85	49.10	%

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表 2 渗透流量-孔隙度数学模型拟合成果

Table 2 Simulated results of mathematical model for permeability flow-porosity

渗透流量模型公式	拟合参数值	相关系数R²
式（15）	$\zeta$ =32.28	0.929
式（16）	$\lambda$ =38.55，m=3.971	0.992
式（17）	$\chi =10.97，C=0.862$	0.980

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