Study On Pore Pressure Dissipation And Settlement Calculation Under Low-energy Dynamic Vacuum Compaction

Since the new technology of dynamic compaction method combined with plastic drainage plate foundation treatment was invented,more and more engineering application arise at home and abroad,and the related theoretical research is deepening.On the basis of dynamic compaction method combined with plastic drainage plate foundation treatment technology,in order to adapt to the construction of soft soil foundation treatment with the first large area filled,the adjacent buildings and road facilities,low energy dynamic compaction vacuum drainage method comes into being.practice shows that the method has the foundation of good treatment effect,short construction period,low cost,wide application prospect.But the theory and engineering application research on pore pressure dissipation and settlement calculation of this method need to be further studied and strengthened.The results of previous research and engineering examples are used to study the dissipation of pore pressure and settlement calculation in this thesis.The main work and achievements are as follows:(1)Expounding the present situation of the research on low energy dynamic compaction and vacuum drainage method as compared with other traditional methods;basing on the theory of existing research dynamic compaction and consolidated settlement,the paper analyzes the reinforcement mechanism and characteristics of the vacuum drainage method with diagram.(2)Through the analysis of pore water pressure calculation and field monitoring data of pore pressure,low energy dynamic compaction forms soft double-layered ground of up rigidity and down weak.then the vacuum pump makes soft substratum and hard shell forming a pressure difference,the vertical plastic drainage plates make the pore water discharging,making the pore water pressure eliminating so that the soil can be compacted.(3)The theoretical values of pore pressure dissipation are calculated respectively without considering and considering the vacuum pressure in two cases.The results are compared with the field measured values of pore pressure:Considering the vacuum pressure calculation of pore pressure with the measured value is more consistent and closer,The pore pressure dissipation rate was fast followed by slow,The pore pressure disappeared rapidly first days after the end of the dynamic compaction,and the pore pressure relief was about 40%,and then the pore pressure dissipation degree gradually decreased until a certain limit was reached;reconsolidation volume compressibility of soil affects the dissipation rate of pore pressure,and the greater reconsolidation volume compressibility the faster the dissipation of pore water pressure;The negative pressure produced by the vacuum tube has precompression effect,the coupling action of dynamic compaction and vacuum pressure can accelerate the dissipation of pore water pressure and shorten the time interval between multiple dynamic compaction.(4)Settlement analysis of low energy dynamic consolidation by vacuum dewatering,basing on the formation mechanism of double layer foundation under impact loading,the calculation formula of foundation settlement of low energy dynamic compaction vacuum drainage method is put forward;The formula is applied to the settlement calculation of a case project.Compared with the measured settlement data,the deviation between the calculated value and the measured value is 6%?10%,which meets the requirements of engineering accuracy and can be used for reference of similar projects.