Settlement And Deformation Characteristics Of High Embankment Based On Unsaturated Theory

The settlement and deformation of fill embankment has become one of the most important problems in highway construction.Based on the research status of the fill embankment filled settlement deformation indoor and outdoor.The paper finds that the existing research only stays in the research of the low filling height or saturated filling.Therefore,this paper takes the high embankment in the Sanming section of Xiasha high-speed road as the research background and its fill soil as the main research object to study the settlement deformation of embankment from the unsaturated theory.Based on indoor and outdoor experiment,the paper grasps the geological background of the study area and the basic physical and mechanical properties of embankment filling.Through these it determines the maximum dry density and optimal moisture content of embankment filling and other key parameters.Using temp pressure plate apparatus,GDS unsaturated back pressure shear apparatus for embankment filling soil properties and deformation characteristics of unsaturated strength has carried on the detailed research,the quality of different initial conditions,the matrix suction and moisture content,the multiple regression analysis between the unsaturated strength parameters for solving the embankment filling,unsaturated embankment filling creep model is established,and analyses the influence of matrix suction of unsaturated strength deformation of embankment filling effect.Creep model for the construction of the unsaturated embankment packing for secondary development is based on the numerical simulation analysis of Flac^3D Xiasha high-speed road embankment filling stage and operation stage of settlement deformation on,compare the simulation results and field monitoring results,the validation of numerical simulation analysis method and the precision of the secondary development,analysis of matrix suction and compaction effect on high embankment settlement deformation characteristics.The main research results are as follows:1.This paper has proved that the study area Sanming Xiasha high-speed road section of high embankment engineering geology background,through indoor physical experiment,mineral chemical composition analysis,microstructure analysis test,compaction test,penetration test to obtain the basic properties of embankment filling in the study area,and set the embankment filling key parameters such as maximum dry density and optimum moisture content.2.Using ultrahigh pressure plate gauge test on Xiasha high-speed road embankment filling soil characteristics of research,combined with the unsaturated soil mechanics often used to describe the soil water and soil characteristics of three kinds of models,respectively,this paper discusses the different initial moisture content and different degree of compaction influence on embankment filling soil characteristics,through the analysis found that VG model fitting out of the water and soil characteristic curve and test data is more merger can fully reflect the way the boundary of the dike packing under different matrix suction effect area,transition area and the residual area three phase characteristics.In order to better research of unsaturated embankment filling and soil features,this paper also the quality of different initial conditions,the matrix suction and moisture content has carried on the multiple regression analysis,draw the different initial moisture content and the embankment filling under different compaction degree of surface soil characteristics,Marquardt with established global optimization algorithm for packing is suitable for high embankment soil characteristics of multivariate nonlinear regression model,and its parameter inversion.3.The unsaturated strength test was carried out by using GDS unsaturated back pressure shearing instrument to study the effect of different matric suction and different compactness on embankment strength.4.Using GDS unsaturated back pressure shear apparatus to Xiasha high-speed road high embankment in unsaturated creep test,the matrix suction was studied the influence of creep property of embankment fillers,the creep mechanism of unsaturated embankment filling is analyzed,to solve the long-term strength of unsaturated embankment filling,calculate the loss rate of the strength of the under long-term load.Burgers was classic model is established to analyze unsaturated creep properties of embankment filling,Burgers was not through the study found that the classic model can better fit with test data,but it is in the initial stage of creep are often short of creep of the variables in the actual test will have entered the stage of constant creep,and when the soil is in a stable creep stage of creep rate and the creep rate is greater than the actual test.Therefore,the basic components based on the analysis of the features of creep of unsaturated embankment filling creep model is established and its results are compared with Burgers this classic model,through analysis and comparison this paper builds the unsaturated embankment filling Burgers was not creep model and the classic model of the law of the model parameters changing with matrix suction is consistent,and unsaturated embankment constructed in this paper packing creep model not only fitting results with the experimental data can be a good fit,but also can well reflect the way embankment fillers in the initial stage of creep and constant speed characteristics of the creep stage.In order to construct unsaturated embankment filling creep model applied to numerical simulation of the ultra high embankment,this paper deduced the unsaturated finite difference form of embankment filling creep model,based on the Visual Studio development environment using C++language to constitutive model for secondary development,to generate the dynamic link library files and run successfully loaded in FLAC^3D.5.The site monitoring of the super high fill embankment of Xiasha high-speed road is carried out,and obtained the data of post-construction settlement data of the super high fill embankment.According to the data of filling period,the layered settlement of embankment filling increases with the progress of filling process,but the settlement rate decreases.From the data of post-construction settlement monitoring,the post-construction settlement stage experienced accelerated settlement and stable settlement,which was similar to the creep law of unsaturated soil.6.Based on FLAC^3D finite difference software builds the high embankment of Xiasha high-speed road is entity of geological model,respectively using the software built-in Mohr Coulomb model with unsaturated embankment filling creep model of the secondary development of the actual field of ultra high embankment filling process and filling 300 days after the completion of the settlement of embankment deformation,numerical simulation analysis to compare the analysis results with the field monitoring data,to verify the numerical analysis method and the applicability of the secondary development.7.Based on the results of the numerical simulation analysis of the super high fill embankment,it is concluded that the stress of the fill embankment is mainly caused by the dead weight of the packing,the ground stress is nonlinear distribution with embankment height,and gradually increases from top to bottom,while the shear strain of embankment is mainly concentrated on both sides of the embankment slope.The vertical displacement at the filling stage is significantly greater than the horizontal displacement.The law of layered settlement is closely related to the progress of the filling process.The cumulative settlement law of 300 days after construction is to form an elliptical concentrated settlement area with the center of the top of the embankment as the center of the circle downward,while the horizontal displacement is mainly concentrated around the slope surface and the foot of the embankment filling part.In addition,the matrix suction and compaction have great influence on the settlement deformation of the super high fill embankment.The effect of different matric suction on the filling of the bottom layer of embankment is obvious while the effect of compaction on the surface layer is obvious.Different matric suction leads to great difference in post-construction settlement deformation of high fill embankment.The smaller the matric suction is,the more likely the uneven settlement will occur and the lower the stability of embankment slope.Based on the above research,some Suggestions and references are put forward for the maintenance of the high fill embankment and the prevention and treatment of subsidence deformation.