Research On The Performance Of The Prefabricated Vertical Drains In Reinforcement Dredger Fill Sludge In Vacuum Preloading

Recent years,Using vacuum preloading in combined with the prefabricated vertical drains(PVDs)reinforcement dredger fill sludge has been widely use in coastal areas.Especially in Tianjing,Shangdong,Jiangsu,Zhejiang and Guangdong.Due to the PVDs has the advantages of low price,convenient construction and other factors,the method has gradually replaced the traditional Manholes or bagged manholes and become the preferred method of reclamation in port construction and reinforcement of soft foundation in all coastal ares.At first,the article is focuse on the research of the performance of the membrane.Through the gradient ratio test and the membrane pore size optimization selection test show that the aperture value is 120?m of the filter membrane with the surrounding soil particle consist of the anti filtration system are obvious less siltation than the aperture value 40?m of the filter membrane under the high hydraulic gradient,and in the process of reinfocement dredger fill sludge with several different membrane pore size of the PVDs,the monitoring and detecting indexs of the PVDs that membrane pore size 120?m are obviously superior than others,it also indicate that use the PVDs with membrane pore size120?m reinforcement dredger fill sludge is best in Wenzhou area.Next,this article through the PVDs water test and Vacuum preloading singe-well model test analysis the discharge capacity of the PVDs,the experimental results show that with the increasing in the number of the bending,the discharge capacity of the PVDs is decrease significantly.In addition,the discharge capacity of the PVDs also influenced by bending form,through the research for the several bending forms like the vertical type,zigzag type,S type and Z type,we can found the different bending forms of the PVDs has the different influence on soil reinforcement,but compared with them,the S type has a minimum influence on discharge capacity.Thereforce,we should set out from the selection of the materials,and optimize the design of the PVDs in order to reduce the influence of the bending effect.Then,this article carried on the comparison experimental study on the different width of the PVDs,through reinforcement of two groups of different water content of the silt,we can found that the width of the PVDs is proportional with the vacuum time that the consolidation of the soil to achieve stability,the widther of the PVDs,the less time of the vacuum pumping.In addition,in the case of the same width of the PVDs,the high moisture content of the model need more time,therefore,when we use the vaccumpreloading method to reinforce the uneven moisture content of the filling silt,we can arrange the PVDs with the different width according to the moisture content,in order to achieve good reinforcement effect to the soil in the same vacuum pumping time.