Experimental study on the improvement of sludge by vacuum preloading-stepped electroosmosis method with prefabricated horizontal drain

To improve the defects of low electroosmosis efficiency in the later stage and high energy consumption of conventional vacuum preloading combined with electroosmosis, the vacuum preloading-stepped electroosmosis method (VP-SEO) with prefabricated horizontal drain (PHD) was proposed for dredged sludge in this paper. In the test, waste concrete fine aggregate was used as the horizontal drainage cushion to alleviate the clogging of the PHD. The results showed that compared to vacuum preloading combined with electroosmosis (VP-EO), more drainage channels throughout the soil were produced after VP-SEO treatment, and VP-SEO could maintain a higher drainage efficiency in the later stage of treatment with improved final drainage and consolidation. The sludge treated by VP-SEO showed a significant increase in vane shear strength and a reduction in water content. Furthermore, the water loss and shrinkage of the soil surface after VP-SEO treatment were more uniform than that of VP-EO treatment, and the electroosmotic energy consumption and anode erosion were also lower. This study provides an effective improvement scheme for solidifying sludge with a high water content by conventional vacuum preloading combined with electroosmosis method.