| When vacuum preloading technology is used to treat dredged clays with high water content,the clogging problem of vertical drains often occurs,resulting in the phenomenon of "soil pile".Aiming at the transmission and attenuation of vacuum degree in dredged clay,the law of vacuum transfer and attenuation in soil samples with different initial water content and different pre-compression strength in different paths was studied by the self-developed device.The key factors affecting vacuum transmission and the mechanism of vacuum transmission are revealed,and based on the attenuation law of vacuum degree in soil samples with different pre-compression strength,the damping coefficient of vacuum degree is proposed.The main work and results of this study are as follows:(1)A device for measuring the rate of vacuum transfer and attenuation in soil has been developed independently,which can flexibly control the height of sample and realize the transfer distribution of vacuum degree in soil samples with different initial water content and different pre-compression strength.The self-developed soil sample pre-compaction preparation device was used to carry out pre-compaction consolidation tests of dredged clays with different initial water content,and soil samples with different pre-compression strength were obtained.(2)The average transfer rate of vacuum degree in dredged clays with different initial water content was measured.The results show that the final vacuum value of the clays with higher water content is also higher.The path hinders the transmission of vacuum degree obviously,and the extension of the path can make the difference between the average transmission rate of vacuum degree in dredged clays with different water content remarkable.Increasing the initial vacuum load can accelerate the transmission of vacuum degree and narrow the gap between the average transmission rate of vacuum degree in dredged clays with different water content.When the water content is low,one-off vacuum loading can accelerate the transmission of vacuum degree.(3)The distributing law of vacuum transfer in soil samples with different pre-compression strength was studied.The results show that with the increase of undrained shear strength of soil,the average transfer rate of vacuum degree decreases obviously.Combining the consolidation-permeability properties of soils with different initial water content,it is revealed that void ratio is the key factor affecting the vacuum transfer distribution,and the mechanism of vacuum transfer distribution is expounded.(4)The law of vacuum attenuation in soil samples is analyzed.The results show that void ratio directly affects the loss value and the average attenuation rate of vacuum degree.The smaller the void ratio is,the larger loss value of vacuum degree is,and the faster the average attenuation rate of vacuum degree is.Through the analysis of the stress conditions of the soil column,it is found that the self-weight of the soil has limited effect on the transmission of vacuum degree.There is an obvious linear relationship between loss value of vacuum degree and transfer path,and a quantitative mathematical description between vacuum damping coefficient and void ratio is proposed. |
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