柔性垂直防渗技术膨润土-黏土密封材料防渗性能研究

董洋; 张文; 李大伟; 姚兰; 初文磊; 王海东; 殷晓东

doi:10.12153/j.issn.1674-991X.20210286

柔性垂直防渗技术膨润土-黏土密封材料防渗性能研究

doi: 10.12153/j.issn.1674-991X.20210286

中科鼎实环境工程有限公司

详细信息

作者简介:
董洋(1992—)，女，工程师，硕士，主要从事污染场地修复与控制研究，dongy0825@163.com

通讯作者:
张文（1985—），女，高级工程师，博士，主要从事污染场地修复与风险管控研究，zhangwen@bjdshj.net

中图分类号: X53
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出版历程
- 收稿日期: 2021-07-01
- 网络出版日期: 2022-06-07

Research on the impermeability of the bentonite-clay sealing materials in the flexible vertical impermeability technology

China State Science Dingshi Environmental Engineering Co., Ltd.

摘要

摘要:
以长沙某厂区内天然黏土为主要原料，采用水溶液聚合法，在室温条件下，通过聚丙烯酰胺改性膨润土与黏土混合，制备密封材料，用于柔性垂直防渗墙建设工程底部区域密封，以防止地下水从高密度聚乙烯(HDPE)土工膜底绕流。通过室内试验研究3种不同改性剂以及膨润土添加量对密封材料渗透系数的影响以及密封材料对六价铬的阻滞吸附作用。结果表明：聚丙烯酰胺改性膨润土能够减小密封材料的渗透系数，而羟丙基甲基纤维和聚乙烯醇在一定程度上导致密封材料渗透系数增大；随着改性膨润土掺入量的增加，密封材料的渗透系数逐渐减小。在模拟柱迁移试验中，密封材料对污染物的截留率可达68.5%。基于长沙某柔性垂直防渗墙工程，对建成防渗墙区域进行示踪剂弥散迁移试验，在下游接收井中均未检测到示踪剂，说明该密封材料在工程应用上能有效防止底部地下水绕流。
- 柔性垂直防渗技术 /
- 改性膨润土-黏土密封材料 /
- 六价铬 /
- 渗透系数 /
- 工程应用
Abstract:
Taking the natural clay in an enterprise in Changsha as the main raw materials, using the experiment method of water solution polymerization at the room temperature, a new type of sealing material was prepared by mixing bentonite and clay modified with polyacrylamide (PAM), which was used to seal the bottom area of flexible vertical impervious wall construction projects to prevent the groundwater from flowing around the bottom of the high-density polyethylene (HDPE) geomembrane. The influence of three different modifiers and the amount of bentonite on the permeability coefficient of the sealing material and the blocking and adsorption of hexavalent chromium were studied by laboratory experiments. The results showed that the permeability coefficient of the sealing material could be reduced when the bentonite was modified with PAM, while, to a certain extent, the hydroxypropyl methyl fiber and polyvinyl alcohol increased the permeability coefficient of the sealing material. With the increase of the amount of modified bentonite added, the permeability coefficient of the sealing material decreased gradually. In the simulated column migration experiment, the retention effect of the sealing material on pollutants could reach 68.5%. Based on a flexible vertical impermeability wall project in Changsha, no tracer was detected in the downstream receiving well in the tracer dispersion and migration experiment on the area of the built impermeability wall, indicating that the sealing material could effectively prevent groundwater from flowing around the bottom on the engineering application.
- flexible vertical impermeability technology /
- modified bentonite-clay sealing materials /
- hexavalent chromium /
- permeability coefficient /
- engineering application

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图 1 砂柱试验装置示意

Figure 1. Schematic diagram of sand column experimental device

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图 2 监测井布设点位

Figure 2. Setting points of the monitoring well

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图 3 3种聚合物对密封材料渗透系数的影响

注：T1为不掺入膨润土；T2为掺入5%PAM改性膨润土；T3为掺入5%HPMC改性膨润土；T4为掺入5%PVA改性膨润土。

Figure 3. Effect of three kinds of macromolecular compound on the permeability coefficient of sealing materials

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图 4 膨润土掺入量对密封材料渗透性的影响

Figure 4. Effect of bentonite amount on the permeability of sealing materials

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图 5 六价铬在模拟柱中的穿透曲线

Figure 5. Penetration curve of hexavalent chromium in the simulated column

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图 6 模拟柱中各物质层对六价铬截留情况

Figure 6. Interception of hexavalent chromium by each material layer in the simulated column

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图 7 黏土微观结构^[33]

Figure 7. Microstructure of the clay

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图 8 膨润土微观结构^[33]

Figure 8. Microstructure of the bentonite

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图 9 对照区监测井内地下水电导率变化

Figure 9. Conductivity variation of groundwater in monitoring wells in the control area

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图 10 试验区B1和B2监测井内地下水水位和电导率变化

Figure 10. Variation of water level and conductivity of groundwater in monitoring wells B1 and B2 in the test area

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图 11 试验区C1和C2监测井内地下水水位和电导率变化

Figure 11. Variation of water level and conductivity of groundwater in monitoring wells C1 and C2 in the test area

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图 12 试验区D1和D2监测井内地下水水位和电导率变化

Figure 12. Variation of water level and conductivity of groundwater in monitoring wells D1 and D2 in the test area

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表 1 黏土土样粒径占比

Table 1. Particle analysis of the clay %

粒径/mm					塑性指数
0.075~0.25	0.05~0.075	0.01~0.05	0.005~0.01	<0.005	塑性指数
3.7	3.5	54.1	4.7	34.0	29.9

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表 2 钠基膨润土性质

Table 2. Properties of sodium bentonite

蒙脱石占比/%	含水量/ %	滤失量/ mL	黏度计600 r/min 读数	−75 μm湿筛余量/%
60.0	9.5	14.0	22	2.6

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表 3 模拟柱配置参数

Table 3. Configuration parameters of the simulation column

模拟柱规格	填充介质	孔隙度/ %	渗透系数/ （cm/s）	六价铬浓度/ （mg/L）
长15 cm，内径5 cm	上下层中砂（粒径0.25~0.5 mm）各5 cm，中层密封材料5 cm	30	≤1.0×10⁻⁷	100

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表 4 监测井参数

Table 4. Parameters of monitoring wells

区域	编号	类别	开孔深度/m
对照区	A1/A2	注入井/接收井	20~40
对照区	A3/A4	注入井/接收井	10~20
试验区	B1/B2	注入井/接收井	10~20
	C1/C2	注入井/接收井	10~20
	D1/D2	注入井/接收井	20~40

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表 5 监测井各指标背景值

Table 5. Background value of various indicators in monitoring wells

监测井	pH	色度	浊度/NTU	总硬度/（mg/L）	电导率/（mS/cm）	硫酸盐浓度/（mg/L）	六价铬浓度/（mg/L）	总铬浓度/（mg/L）
A1	7.41	15	3.9	169	0.865	55.5	<0.004	<0.03
A2	10.93	15	31.2	165	3.080	39.6	<0.004	0.20
A3	6.97	15	0.5	155	0.822	251	<0.004	<0.03
A4	6.07	15	10.1	102	0.275	26.9	<0.004	<0.03
B1	7.64	10	38.1	184	4.820	42.2	<0.004	<0.03
B2	7.45	15	4.9	147	0.574	105	<0.004	<0.03
C1	6.36	5	8.1	143	0.425	51.0	<0.004	<0.03
C2	5.73	10	4.1	86.3	0.344	80.2	<0.004	<0.03
D1	6.81	15	10.1	133	1.060	162	<0.004	<0.03
D2	6.44	10	6.3	120	0.704	164	<0.004	<0.03

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