人工冻结法协同竖井淋洗原位修复污染黏性土的可行性试验  

Feasibility of remediating polluted clayey soil in situ by artificial freezing and PVD-enhanced system

作　　者：陈雄志 毋文涛 张军[2] 芮大虎[2,3] 李国玉 伊藤譲 CHEN Xiongzhi;WU Wentao;ZHANG Jun;RUI Dahu;LI Guoyu;ITO Yuzuru(The Third Geological Brigade of Jiangxi Geological Bureau,Jiujiang 332000,Jiangxi,China;School of Civil Engineering,Henan Polytechnic University,Jiaozuo 454000,Henan,China;State Key Laboratory of Frozen Soil Engineering,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;Department of Civil Engineering,Setsunan University,Osaka 572-8508,Japan)

机构地区：[1]江西地质局第三地质大队,江西九江332000 [2]河南理工大学土木工程学院,河南焦作454000 [3]中国科学院西北生态环境资源研究院冻土工程国家重点实验室,甘肃兰州730000 [4]摄南大学土木工学科,日本大阪572-8508

出　　处：《冰川冻土》2021年第5期1489-1497,共9页Journal of Glaciology and Geocryology

基　　金：国家自然科学基金项目(41771070);冻土工程国家重点实验室开放基金项目(SKLFSE201917)资助。

摘　　要：针对黏性土淋洗效率低下问题,提出了人工冻结法协同竖井淋洗原位修复污染土壤的方法。通过垂直布设冻结板,水平冻结土体的竖井淋洗模型试验,研究冻结过程中土中温度场、水分场分布及融解期的排水方式,探讨了人工冻结法协同竖井淋洗原位修复污染黏性土的可行性。研究表明:利用人工冻结法,使未冻土侧水分或淋洗液在“冻吸力”作用下向冻结锋面迁移,然后利用塑料排水板完成融化水(淋出液)与土壤分离的方案可行,能够解决抽液过程中抽液井和注液井之间土体容易形成渗流通道出现优先流,导致淋洗效率低下的问题。在分步冻结模式下,未冻土侧水分在“冻吸力”作用下向冻土侧迁移,冻结-吸水量为22.78 L,融化-排水量为24.60 L;经历一次冻融循环后,相同冻结模式下冻结-吸水量达到30.40 L,在负压抽吸模式下排水量达到44.21 L。该研究结果为今后原位修复污染黏性土提供了新的思路。In view of the low washing efficiency of clayey soil,the method of artificial freezing and prefabricat⁃ed vertical drains(PVD)enhanced soil flushing was put forward to remediate polluted soil in situ.In this study,the temperature field and moisture field distribution in the soil during the freezing process and drainage way dur⁃ing the thawing period were studied via the shaft leaching model test of vertically setting freezing plate with hori⁃zontally freezing soil.Furthermore,the feasibility of artificial freezing method cooperating with PVD-enhanced system for remediation of polluted clayey soil was discussed.The results show that it is feasible to use the artifi⁃cial freezing method to transfer the water or eluent on the unfrozen side to the frozen front under the action of“freezing suction”,and then use the plastic drainage plate to separate the melting water(leachate)from the soil.On the basis of this method,the problem of the soil between the pumping well and the injection well is easy to form seepage channel and preferential flow,which results in the water or eluent can not fully contact with the pollutants adsorbed on the soil particles and the washing efficiency is low can be solved.the stepwise freezing mode,the moisture on the unfrozen side migrates to the frozen front under the action of“freezing suction”,the water absorption is 22.78 L,while the thawing-discharge volume is 24.60 L.After a freeze-thaw cycle,the wa⁃ter absorption in the freezing period under the same freezing mode reached 30.40 L,and the water discharge was 44.21 L,in the negative pressure suction mode.This technology provides a new idea for in-situ remediation of polluted clayey soil in the future.

关 键 词：人工冻结法 竖井淋洗 冻结板 负压抽吸 

分 类 号：P642.14[天文地球—工程地质学]