Experimental Investigation On Treatment Of High Water Content Dredged Sediment Using The Combined Method Of Horizontal Vacuum And Solidification

Dredged sediment is an important by-product from coastal engineering,land reclamation,port channel deepening and dredging of inland rivers and lakes.Because of its high water content and poor mechanical properties,it is difficult to directly use the dredged sediment in construction projects.At present,the widely used physical treatment method,chemical solidification method and vacuum preloading method are not efficient in the treatment of dredged sediment with very high water content.In order to improve the treatment efficiency of dredged sediment,this thesis proposes a method that combines the prefabricated horizontal drain(PHD)-facilitated vacuum preloading and the solidification to treat the dredged sediment with high water content.The vacuum preloading method is used to reduce the water content of dredged sediment,and cement is used as the solidifying agent to improve the strength of dredged sediment.The feasibility and effectiveness of the proposed method are demonstrated by model tests,which provide a practical,economic and environmentally way of dredged sediment utilization for engineering practice.The main research work of this thesis includes:(1)Compared with the PHD-vacuum preloading method and the cement solidification method,the feasibility of the combined method of PHD-vacuum preloading and solidification for the treatment of dredged sediment is verified through the model tests.It is found that under the condition of high water content and low cement content,the treatment effect of the combined method of PHD-vacuum preloading method and solidification is far better than that of the PHD-vacuum preloading method and the cement solidification method;(2)Through the study of the microstructure and mineral composition of the soil samples treated by the PHD-vacuum preloading method,the cement solidification method and the combined method of PHD-vacuum preloading and solidification,it is concluded that the mechanism of the combined method of PHD-vacuum preloading and solidification is not only due to the cementation of soil particles and filling of pores by cement solidification products,but also due to the rearrangement,filling and compacting of soil particles under vacuum preloading;(3)Parameter analysis was carried out to study the influence of initial water content,duration of vacuum preloading,magnitude of vacuum load,and cement content on the effect of the combined method of PHD-vacuum preloading and solidification.It was proved that the combined method of PHD-vacuum preloading and solidification reduced the influence of initial water content and cement content on the strength of solidified soil,and the duration of vacuum preloading and vacuum load affect the strength of soil by reducing the water content and increase the compactness of the sediment.