絮凝−真空−电渗联合加固滩涂软土的模型试验研究

针对真空预压作用下排水板淤堵与排水条件受限等问题，提出絮凝−真空−电渗联合加固法。首先通过沉降柱试验确定合适的有机絮凝剂，然后采用该絮凝剂，分别在 48 h（开始介入真空预压，固结度为0 ）、60 h（排水速率明显下降，固结度为60%）及 84 h（排水速率近乎 0，固结度为 80%）时介入电渗，开展不同电渗介入时间的絮凝−真空−电渗联合加固试验。试验从排水量、十字板剪切强度、含水率与孔压等对比分析联合加固的有效性，确定其最佳电渗介入时间。试验结果表明：当固结度为 80% 时介入电渗，絮凝−真空−电渗联合加固法能够有效地抑制排水速率减小的趋势，增长有效排水时间。同时，土体的抗剪强度和承载力亦得到大幅提升，孔压消散更加均匀。此外，在阳离子聚丙烯酰胺絮凝剂的作用下，初始排水速率快，在一定程度上使土体的渗透性得到提升，有效地解决了排水板淤堵问题，说明絮凝−真空−电渗联合加固法具有较强的优越性。

Laboratory study of consolidation of marine soft soil using flocculation-vacuum preloading-electro-osmosis

To solve the technical issues in vacuum preloading method, including the sediment clogging of drains and the limitation of drainage conditions, this study investigated vacuum preloading combined with flocculation and electro-osmosis consolidation for marine soft soil. A series of column settling tests was conducted to determine the optimal organic flocculant for the combined method. With the selected organic flocculant, laboratory tests were performed on the soil samples using the combined consolidation method, in which the electro-osmosis was added at different time moments. The tests considered three representative cases at different time moments: (i) at 48 h, i.e., the initial stage of vacuum preloading with the consolidation degree of 0; (ii) at 60 h, i.e., the obvious reduction in the dewatering speed with the consolidation degree of 60%; and (iii) at 84 h, i.e., the dewatering speed of 0 with the consolidation degree of 80%. The effectiveness of the combined method was evaluated using the tested results, including water discharge, soil vane shear strength, water content, and pore water pressure, along with the determination of the best time for adding the electro-osmosis. The results indicated that the combined method effectively delayed the decrease of dewatering efficiency and significantly increased dewatering duration. Also, the shear strength and load-bearing capacity of the consolidated soil were clearly improved, with the evenly dissipated pore water pressure. In addition, the cationic polyamide was the optimal flocculant for the combined method, which enhanced the initial dewatering speed and improved the permeability of the soft soil to solve the sediment clogging in the plastic board during the vacuum preloading. This research demonstrated the effectiveness of vacuum preloading combined with flocculation and electroosmosis consolidation for soil improvement.