絮凝–真空预压加固吹填淤泥试验研究

Experimental study of flocculation combined with vacuum preloading to reinforce silt foundation

针对目前真空预压法加固吹填土地基中存在的真空传递效率低,排水板易淤堵,深层土体排水固结困难,工期较长的问题,提出一种新型化学絮凝联合真空预压法,其方法在于加固前,先在吹填土样中加入一种化学药剂,通过有效的化学絮凝作用使细小土颗粒凝聚成团,同时降低土颗粒黏性,增大渗透性以利于排水,之后再采用真空预压进行加固处理。为此,设计一组絮凝剂在不同掺量下的真空预压室内模型桶试验,结果表明,掺入絮凝剂的吹填土土中真空度明显上升,孔隙水压力下降更多且消散速率更快,出水量趋于稳定所需时间大大缩短,十字板强度大幅度提升,且沿深度递减幅度大为减小,证明采用絮凝联合真空预压法能使吹填土获得更好的加固效果;絮凝剂的使用存在一个最佳掺量,掺量过多或过少都不能使吹填土加固效果达到最优;通过加固后的效果对比,得到温州地区吹填淤泥(含水量300%)的絮凝剂最佳掺量为1.5%。

The present method ofvacuurn preloading has low efficiency of vacuum transter ann me oralnage platen are easily clogged, so the deep soil is poorly consolidated and the hydraulically filled mud needs a long construction period. A new kind of vacuum preloading combined with flocculant method was proposed. A type of inorganic flocculant was added into the dredged slurry before the vacuum preloading. The effective chemical flocculation led to the aggregation of small particles into lager clusters. Meanwhile, the viscosity was decreased and the permeability was increased, leading to the improved drainage of the soil after the flocculation. A series of model tests of vacuum preloading combined with different dosages of flocculants were carried out. The test results showed that the degree of vacuum in the deep soil was increased significantly. Both the pore water pressure dissipation and the process of soil consolidation were accelerated. The overall vane strength was improved obviously and with low decrement along the depth. The test proved that vacuum preloading combined with flocculant method achieved better effect of reinforcement. An optimal value of the percentage of the added flocculant exists. The best dosage of the flocculant was 1.5% for the slurry in Wenzhou（water content is 300%）.