Reinforcement Effect Of Cotton Straw Bales With Preloading Vacuum In Dredger Soft Soil Foundation

Because of the city construction and development needs,large-scale land reclamation projects spread around.The special engineering properties of dredger fill soft soil determine the defect of soft soil foundation.In order to solve the problems of settlement and stability of soft foundation,it is necessary to choose an appropriate technology to reinforce it.At present,the method of vacuum preloading is one of the most popular methods for the reinforcement of soft soil foundation.The vacuum preloading method cannot do without the vertical drainage system effectively,plastic drainage plate which is widely used has the problems of clogging and bending.The high performance anti clogging plastic drainage is facing the problem of high costs in such large-scale application conditions.To solve the above problems not only need to innovate the drainage technology,but also need to reform in the material selection.Therefore,combined with the actual situation of China's current agricultural development,cotton straw bales are considered to be the vertical drainage body.Cotton straw has excellent natural characteristics of skeleton,hollow,adsorption and so on.Cotton straw can be obtained locally and has low cost.The application of cotton straw bales to the temporary reinforcement of soft soil foundation will have significant economic benefits and alleviate the problem of straw waste incineration.In order to study the feasibility and the drainage consolidation effect of the cotton straw bales as vertical drainage in vacuum preloading,a series of experiments were carried out.The main contents are as follows:(1)The basic physical and mechanical properties of soil samples were tested,including the soil moisture content,void ratio,internal friction angle,cohesion and so on.(2)Through a single cotton straw and cotton straw bales laboratory model test,the drainage mechanism,drainage performance and rules of cotton straw drainage system were analyzed.It included:Study on drainage mechanism and performance of cotton straw drainage system;Based on the sand well symmetric consolidation theory,the effective drainage range of the straw bale,the ratio of the effective diameter and the straw bale diameter and the range of "s" were determined.The drainage model of straw drainage system was established to study the drainage rules.Meanwhile,the influencing factors of cotton straw about the drainage effect were studied quantitatively,and the intrinsic relationship between the initial density,diameter,spacing and the drainage consolidation effect of cotton straw bales was established.The results show that the drainage consolidation effect of large diameter and small density(p=0.0637g/cm3,d=45cm)straw bale is the best,and the drainage consolidation effect is obvious in the large and sparse arrangement.