Research On Improvement Of Dredged Slurry By Combined Of Vacuum Preloading And Dynamic Consolidation Method

In recent years,many reclamation projects in coastal areas are carried out with dredged slurry,which often has poor geotechnical properties.Vacuum preloading-only cannot meet the requirements of construction period and bearing capacity,so vacuum preloading combined with other construction methods has become a trend.In recent years,vacuum dynamic consolidation method has been put forward,which combines the characteristics of vacuum preloading method and dynamic consolidation method.This method is a consolidation process of vacuum load,dynamic load and drainage system,which introduces the idea of drainage consolidation into the dynamic reinforcement method,and makes it suitable for the reinforcement of soft foundation.It has the advantages of short construction period,low cost and remarkable reinforcement effect.In practical application,the design and construction of this method are still in the stage of application while testing.Further exploration of vacuum dynamic consolidation method and its application in soft soil foundation treatment engineering have important promotion value.In this paper,the reinforcement mechanism of vacuum preloading method,dynamic consolidation method and vacuum dynamic consolidation method is described and discussed.Then,dredged slurry is taken as the research object,and vacuum dynamic consolidation method are comprehensively explored through indoor model test,direct shear test,unconfined compressive strength test,consolidation test,scanning electron microscope image combined with Image-Pro Plus 6.0 software analysis and mercury intrusion test.The main work is as follows:(1)Through the indoor model test,this paper explores the mitigation effect of different tamping methods of vacuum dynamic consolidation method on the silting effect around the PVD.For the blow sequence,the results show that the best consolidation effect is achieved by using the method of first blowing the outer soil and then blowing the inner soil.For the blow energy,it is better to use the blow method of external heavy and internal light,which is conducive to the consolidation of dredged slurry more evenly.(2)The vacuum dynamic consolidation characteristics of dredged slurry under different blow counts were studied by model test.Then,the law of soil mechanical parameters under different blow counts was discussed,and the influence law of different blow counts on the stress-strain curve,unconfined compressive strength,cohesion,internal friction angle,compression curve,compression index and pore index of dredged slurry is analyzed.According to the suggestions of 12 groups of model test indexes and mechanical parameters,the recommended blow count is 5,accounting for 46%,and other parameters are scattered.(3)The microstructure of soil samples corresponding to different blow counts was analyzed,and the structural state adjustment rules of soil samples under different blow counts of vacuum dynamic consolidation method were explored.The effects of different blow counts on porosity,flatness,fractal dimension,shape coefficient,porosity,increment of mercury intake and pore size distribution of dredged slurry were analyzed.Among the 8 groups of proposals,after comprehensive consideration,the recommended blow count is 5.