小型TRD工艺在有机污染场地垂直阻隔工程的应用研究

    Application of small-scale TRD method in constructing vertical barriers at an organic compounds-contaminated site

    • 摘要: 以某有机污染场地垂直阻隔工程为依托,以垂直切割搅拌器为主体施工设备,采用小型TRD工艺和原位垂直切割搅拌工艺建造了长度为70 m,深度为7.0,5 m的垂直阻隔屏障。通过现场试验与室内试验结合的方法,研究了膨润土材料的施工和易性。结果表明,水固比为4∶1时,有机黏土改良膨润土材料无法充分水化,活性炭改良膨润土材料的马氏黏度和流动度无法满足小型TRD工艺施工要求,六偏磷酸钠改良膨润土材料可满足小型TRD工艺施工要求。垂直阻隔屏障施工14 d后沿屏障深度方向取样,在室内开展颗分、含水率、液塑限、pH、特征元素(Na)全量分析和柔性壁渗透等试验,研究垂直阻隔屏障材料的土工参数沿深度方向的均匀性。结果表明,在清洁自来水渗透下,小型TRD工艺段屏障材料的渗透系数(1.3×10-10~2.4×10-10 m/s)低于原位垂直切割搅拌工艺段屏障材料的渗透系数(7.5×10-10~9.3×10-10 m/s)。对比分析了小型TRD工艺段、原位垂直切割搅拌工艺段两类屏障材料的含水率、液限、特征元素(Na)全量、pH沿屏障深度方向的变异系数。结果表明,小型TRD工艺段屏障材料上述4个参数的变异系数低,沿深度方向的均质性更好。

       

      Abstract: A vertical cutting equipment is used as the main equipment to construct vertical barriers at an organic compounds- contaminated site. The vertical barriers with a length of 70 m and depths of 7.0 m and 5 m are constructed by the small-scale TRD and the cutting-backfilling-mixing method. The workability of bentonite materials is studied through a combination of field and laboratory tests. The results show that the organo clay-enhanced bentonite material can not be effectively hydrated, and the viscosity and slurry fluidity of the activated carbon-enhanced bentonite does not meet the construction requirements of the small-scale TRD method with a liquid-solid ratio of 4:1. In contrast, the sodium hexametaphosphate-enhanced bentonite slurry prepared well meets the construction requirements of the small-scale TRD method. The barriers are sampled and the coring samples are subjected to a series of testing programs including grain-size distribution, water content, liquid limit, pH, characteristic element (sodium) content and flexible-wall hydraulic conductivity tests after construction of 14 days. The test results are used to assess the uniformity of geotechnical parameters along the barrier depths. The hydraulic conductivity test results reveal that the vertical barriers constructed by the small-scale TRD method exhibit lower hydraulic conductivity (1.3×10-10~2.4×10-10 m/s) as compared to that constructed by the conventional construction method (7.5×10-10~9.3×10-10 m/s), indicating that the SHMP-SB possesses superior hydraulic conductivity. The barrier materials constructed by the small-scale TRD method have superior uniformity in terms of lower coefficient of variation values of water content, liquid limit, sodium content and pH along the depths.

       

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