Improvement of silty clay by vacuum preloading incorporated with electroosmotic method
Improvement of silty clay by vacuum preloading incorporated with electroosmotic method
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DOI：
10.3724/sp.j.1235.2010.00365
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发表时间：
2010-12
影响因子：
7.3
通讯作者：
Baotian Wang;Manh Quang Vu
中科院分区：
文献类型：
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作者：
Baotian Wang;Manh Quang Vu
为评价真空预压结合电渗(EOM)处理粉质粘土的效果，进行了一项实验室试验，以评估真空预压与电渗(EOM)联合处理在粉质粘土上的效果，如新的处置池，其中土层下的水平电极配置是可能的，排水管道和预制垂直排水系统(PVD)在从海床或河床拖来的污泥进入现场之前可以很容易地预先安装。中国，对南京秦淮河粉质粘土进行了三组试验。该模型能够同时在土层底部施加真空压力和直流电场。它还可以测量土柱不同深度处的孔压，以及沉降和体积随时间的变化。本研究采用真空预压法，即底部真空预压法(VAB法)，将阴极安装在土层下。结果表明，与真空预压相比，含水率显著降低，干密度和不排水剪切强度增加，特别是在靠近阳极的位置。该组合方法利用了电渗透产生的垂直引流，整合了主要由真空压力产生的水平引流。总排水量可以由电渗法的垂直排水量和真空预压法的水平排水量来计算。结合法中阴极和阳极的放置方式也克服了EOM法本身存在的缺陷，即阳极与周围土壤之间出现裂纹。此外，真空预压在前期对自由孔隙水的提取起主要作用，而电渗法在后期对扩散双层土的吸水效果更好。
A laboratory test was performed to assess the effectiveness of vacuum preloading incorporated with electroosmotic (EOM) treatment on silty clay (combined method) for reclamation projects like new disposal ponds, where the horizontal electrode configurations beneath the soil layer were possible and the drainage pipes and the prefabricated vertical drains (PVDs) system could be easily installed in advance before the sludge dragged from sea bed or river bed was filled into the site. Three groups of tests were conducted on the silty clay from Qinhuai River in Nanjing, China. The model is able to apply vacuum pressure at the bottom of the soil layer and a direct current electric field simultaneously. It is also possible to measure the pore pressures at different depths of soil column, and the changes in settlement and volume with the elapsed time. In this study, the vacuum preloading method, vacuum preloading applied at the bottom (VAB method), was applied and the cathodes were installed beneath the soil layer. The results obtained indicate substantial reduction in water content, and increases in dry density and undrained shear strength in comparison with those obtained by the vacuum preloading only, particularly at the positions close to the anode. The combined method utilizes the vertical drainage flow created by the electroosmosis integrating the horizontal drainage flow created mostly by the vacuum pressure. The total drainage flow can be calculated as a result of the vertical drainage flow by electroosmosis only and the horizontal drainage flow by the vacuum preloading only. The way of placement of the cathode and the anode in the combined method also overcomes the disadvantage of EOM method itself, i.e. the appearance of cracks between the anode and the surrounding soil. Moreover, it is observed that the vacuum preloading plays a primary role in earlier stage in deduction of free pore water; meanwhile, the electroosmotic method is more efficient in later stage for absorbing water in the diffused double layers of soil.