碱、锌污染淤泥质黏土的压缩与渗透特性试验研究

Experimental study on compression and infiltration characteristics of silt clay contaminated by alkaline and zinc

城市生活垃圾随意堆放或未经卫生填埋导致淋滤液下渗造成地基土污染,场地污染范围、污染土性变化及污染机理等问题引起了广泛关注。针对宁波地区的典型软土,人工制备不同程度的碱污染土和锌污染土,通过室内试验和微观测试探讨了污染土的物相成分和微观结构,分析了污染土的渗透特性以及压缩特性的变化规律以及相应的变化机理。研究表明,受到污染液腐蚀后,原状土的微结构变化明显,随着污染液浓度的增大,污染土孔隙面积比增大而丰度减小;碱和锌污染对土体的渗透性影响较大,且与渗透时长有关;碱污染土的压缩系数随着污染液浓度的增大而逐渐降低,而锌污染土的压缩系数变化不大;机理分析认为,造成上述土性变化的主要原因在于污染离子侵入土体后胶结物质溶蚀与新物质生成之间的平衡以及结合水膜厚度变化等。

The municipal solid waste dump or non-standard landfills lead to the infiltration of leachate and cause soil contamination.The geotechnical engineering problems such as the contamination scope of the site,the changes of the physical and mechanical properties of contaminated soils and the corresponding pollution mechanism have attracted the wide attention.The typical soft soil in Ningbo region is selected to artificially prepare the different concentrations of alkali-contaminated soil and zinc-contaminated soil.The phase composition and microstructure of the contaminated soils are analyzed,and the seepage characteristics and the changing law of compression characteristics and the corresponding pollution mechanism are studied by using laboratory tests and microcosmic tests.The study shows that:the microstructure changes of undisturbed soil after the corrosion of contamination are obvious,with the increase of the concentration of contaminated solution the pore area ratio of the contaminated soils increases and the abundance decreases;alkali and zinc pollution has great influence on soil permeability,and the permeability is related to the duration of infiltration;the compression coefficient of the alkali contaminated soil decreases with increasing concentration of contaminating fluids,and the compression coefficient of zinc contaminated soil has little change.The mechanism analysis suggests that the main reasons for the above changes include the balance between the cementing material dissolution and new material generation after the contaminated ions invade the soil,and the variation of water film thickness.