Experimental investigation on the treatment of different typical marine dredged sludges by flocculant and vacuum preloading

The properties of the marine dredged fill in different zones are different, especially the flocculation and consolidation properties, which are related to the choice of treatment method and procedure. This paper conducts a comprehensive study on mineral composition, particle composition, flocculation, and vacuum consolidation properties of dredger fillers in four specific regions in Shandong province, China, representing the four most typical slurries. The results are as follows: (1) Yantai and Weifang dredges contain little or no clay minerals. In contrast, the Dongying and Rizhao dredges contain about 33.7% and 53.09% clay minerals, respectively, and grain analysis shows the same conclusion. The settlement column test shows that Yantai and Weifang dredged slurry do not require flocculation. Still, at Dongying and Rizhao dredged slurry, a flocculation agent is necessary to accelerate the solid–liquid separation. (2) The use of quicklime to adjust the backfill of the dredger of the Rizhao district can increase the soil particle size and increase the sludge particle proportion. With the increase of quicklime from 0.2 to 0.8%, the content of large particles gradually increased. The settlement column test results show that the stable time of solid–liquid separation is positively correlated with the content of large particles and the amount of lime added. The results of this study for the chemical flocculation agents of the standard vacuum preloading method have important directional implications for engineering practice.