Soil Plugging Effect Of PVD Consolidation In High Water Flow Mud Under Vacuum Pressure

In China,dredged clay are often used to form reclamation sites and vacuum preloading combined with plastic vertical drains(PVDs)is adopted to improve the site.Because of high water content and consolidation distance,soil column with low permeability around the PVD arise in the consolidation process of dredged clay under vacuum preloading,which postpones the whole consolidation procedure and weakens the improvement efficiency.So,study on the formation and effect of soil column is helpful to the understand of consolidation theory,also is significant to soil improvement engineering.First,vacuum preloading test of dredged clay is carried on a two-buckets model.Variation in water and void ratio near the PVD is studied and a soil column with certain dimension is obtained.Based on the drainage water and drainage rate,permeability of soil column and its effect on consolidation procedure of outer soil is analyzed.In the following,the consolidation model of soil is divided into soil column and outer soil parts.Considering clogging effect of soil column,a non-linear consolidation model of dredged clay is established based on the e-logk and e-logp.Influence of permeability of soil column,dimension,compression index and permeability index is analysed.This paper considers the tightness during vacuum preloading,Study the clogging of drainage boards near PVD,Specifically,the influence of the size of the soil column on the clogging effect of the high water volume dredging soil column is studied.Method of using soil column seepage,Through the soil sample that can easily obtain the soil column,Furthermore,it is possible to carry out an indoor test to determine the variation of the permeability coefficient during the seepage process.Secondly,relying on the sealing of the dredging mud itself,PVD consolidation test of dredging mud under vacuum preloading without seal film,Sampling at a different location from the boundary of the plastic drainage board,The variation of different water content and pore ratio of the dredged mud near the drainage board with the consolidation time was studied.It is found that under the vacuum load,the void ratio of the dredging mud at the boundary of the drainage board is reduced rapidly,and the consolidation is basically completed.At this time,the flow of the mud flowing away from the drainage board has not been consolidated,and the uneven consolidation phenomenon is extremely obvious.Finally,the pressure control valve was used to adjust the vacuum pressure,different vacuum loads were applied,and the PVD consolidation test of the dredging mud under different vacuum loads was carried out.The variation of water content and void ratio of the dredging mud near the drainage board was studied.Under different vacuum pressures,the clogging conditions are different.