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Hardening of hydraulic fill dredged from rivers & lakes and its ecological treatment effect
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摘要: 河湖清淤吹填土含水率高，流动性大，具有污染性。无砂真空排水预压法在固结硬化吹填土，提高其强度和承载力方面效果显著。受环形流道、落淤分选的影响，同一堆泥场内不同区域的地基沉降和超静孔压的变化存在一定差异性。无砂真空预压法具有较好的阻隔、过滤、吸附有机污染物等净化功能，经历堆置沉淀、负压抽吸、尾水沉淀和水生植物过滤吸附后排放的水体中有机质和总磷(TP)含量大幅减小，污染综合指数由0.8~1.0降到0.7，基本满足地表水Ⅲ类水质标准要求。固结后吹填土中的有机质、总氮、总磷含量大幅度降低，有机污染指数提高了1个等级。重金属含量符合土壤环境质量Ⅲ类标准，重金属的浸出毒性指标低，对地表水无污染，重金属污染程度的计算评价结果总体为轻微。Abstract: The hydraulic fill dredged from rivers and lakes is generally characterized by high water content, large fluidity, and greater pollution. The sand-free vacuum preloading method has a remarkable effect in consolidating and hardening the hydraulic fill, and improving its strength and bearing capacity. Due to the influences of the annular channel and the sedimentation separation, there are some differences between the foundation settlement and the change of the excess pore water pressure in the different areas of the same mud pit. This method performs an important purification function in barrier, filtration and adsorption of the organic pollutants. After the stacking and precipitation, the negative pressure suction, the tailwater precipitation, the filtration and adsorption of the aquatic plant, the content of organic matter and total phosphorus (TP) are decreased significantly, and the pollution index P is reduced from 0.8~1.0 to 0.7, which basically meets the requirements of the class Ⅲ water quality standard of the surface water. After consolidation, the content of organic matter, total nitrogen and total phosphorus in the soil had decreased greatly, and the organic pollution index OI is improved by one grade. The content of the heavy metal element in the soil meets the class Ⅲ environment quality standard for soils, and the leaching toxicity of the heavy metals is low, thus producing no pollution to the surface water. The calculation results show that the heavy metals pollution degree is slight.
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Key words:
- hydraulic fill /
- vacuum preloading /
- ecology treatment /
- organic pollution /
- heavy metal
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图 6 不同阶段吹填土主要物理性质指标
Figure 6. Histogram comparison of physical indexes of filled mud at different improvement time
图 7 水质指标含量柱状分布
Figure 7. Histogram comparison of water quality indexes of filled mud in different phrase
图 8 水质指标含量变化率曲线
Figure 8. Rate curves of water quality indexes of filled mud at different improvement time
表 1 天然堆置吹填土主要物理性质
Table 1. Physical indexes of filled mud before improvement
含水率w/% 密度/(g·cm-3) 液限wL/% 塑限wp/% 塑性指数Ip 颗粒分析/% ＞0.075 mm 0.075~0.005 mm < 0.005 mm 122.8 2.69 42.4 20.5 21.9 6.1 75.5 18.4 
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表 2 硬化前后土体有机污染物含量
Table 2. Organic pollutants in soil mass before and after hardening
项目 取样深度/m 有机质OM含量/% 总氮TN含量/% 总磷TP含量/% 自然沉淀 0~0.4 6.27 0.14 0.06 固结硬化后 0~2.1 3.03~4.86(3.89) 0.006~0.120(0.080) 0.040~0.065(0.050) 变化率(%) 22.5~51.7(38.0) 13.6~95.7(41.4) 1.6~34.4(14.8) 注：括号内数值为该项的平均值。
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表 3 土体重金属污染性计算评价结果
Table 3. Calculation and assessment results of heavy metals pollution in soil mass
重金属元素 Cd As Pb Cr Cu Ni Zn 检测平均值(mg/kg) 3区 0.92 9.50 2.35 16.23 23.35 18.10 138.56 5区 0.44 30.17 5.88 17.31 45.02 25.35 198.23 Ⅲ级标准值(mg/kg) 1 40 500 300 400 200 500 内梅罗污染指数 3区：NI=0.95，警戒级，尚清洁；5区：NI=0.80，警戒级，尚清洁 地累积指数 3区 -0.71 -2.66 -8.32 -4.79 -4.68 -4.05 -2.44 清洁 清洁 清洁 清洁 清洁 清洁 清洁 5区 -1.77 -0.99 -6.99 -4.70 -3.74 -3.56 -1.92 清洁 清洁 清洁 清洁 清洁 清洁 清洁 Hakanson
潜在生态
风险指数Eri(3区) 27.60 2.38 0.02 0.11 0.29 0.45 0.28 RI(3区) 31.10(轻微) Eri(5区) 13.20 7.54 0.06 0.12 0.56 0.63 0.40 RI(5区) 22.50(轻微)
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