Experimental Study On Vibration Liquefaction Of Low Embankment Structure Based On Saturated Silty Soil From Guangxi Marine Sediments

Based on the study of the physical and mechanical properties of saturated silt soil deposited in Guangxi,this paper studies the method of vibration liquefaction test for the low embankment structure of coast Highway from the aspects of model selection,test scheme design and engineering example verification.Due to the limitation of construction conditions on site,it is difficult to carry out tests and long-term observations on different combinations of low embankment structure models to obtain the parameters such as stress,strain and pore water pressure,because of the time limit,cost,geological conditions and the representability of the test section.According to the principle of simple,convenient,practical and easy to operate,and grasping the three main factors of stress,strain and anti-liquefaction,this paper establishes an analytical method for optimizing the low embankment structure with safety,speed,economy and system.ABAQUS finite element analysis software was used to establish 10 low embankment structure models and optimize the low embankment structure model.FLAC^3D finite element software test analysis of saturated silt subgrade,laboratory physical model test and dynamic triaxial test of samples were designed.The feasibility of the test design scheme was verified by the application of Guangxi coast Highway engineering example.The research results have important practical significance for guiding the selection of low embankment structure under similar conditions in coastal highway projects,effectively improving the utilization rate of resources and saving costs,ensuring the quality of highway construction,and promoting regional economic development.The main research results of this paper are as follows:1.On the saturated silty soil liquefaction discrimination standard generally adopts the effective stress principle of direct method,indirect method and experience on the basis of the seismic method for judging,and these methods are derived from different sides to liquefaction,and all the questions have limitations in different degrees,low embankment structure optimization analysis and comprehensive methods of liquefaction.The method of comprehensive determination of liquefaction standard solves the limitation of liquefaction criteria such as direct method,indirect method and empirical method.The results of structure optimization and liquefaction analysis show that the method is safe,rapid,economical and systematic to analyze the liquefaction problems,especially for the saturated silt subgrade under low frequency vibration of vehicle load.2.According to the idea of changing the rigidity of low embankment structure,increasing the ability of diffusing stress and reducing strain of embankment structure,the method of optimizing structure model is designed.Multiple low embankment structure models established in ABAQUS are applied with simplified stress to calculate the stress and strain of each low embankment structure model under the action of vehicle load.The structural model is optimized with stress magnitude,concentration and dispersion and settlement deformation on the subgrade as the main objectives.The results show that FLAC^3D test scheme achieves the purpose of pre-testing and judging whether liquefaction occurs in low embankment structure and saturated silt foundation.3.FLAC^3D test scheme was designed to obtain the simulated data of dynamic strain,dynamic stress and pore water pressure before and after the treatment of low embankment structure through finite element calculation.The development and dissipation law of pore water pressure of saturated silt and the size of overhole pressure ratio were sorted out and analyzed to determine the liquefaction potential and settlement of soft soil foundation of low embankment structure.The results show that FLAC^3D test scheme achieves the purpose of pre-testing and judging whether liquefaction occurs in low embankment structure and saturated silt foundation.4.The laboratory test scheme was designed to analyze the liquefaction potential and settlement of saturated silt soil foundation of low embankment under the action of vehicle load through the relationships among boundary conditions,cyclic load,water level height,dynamic stress,total stress,pore water pressure and deformation.Laboratory test results show that the test scheme can judge whether liquefaction occurs in the low embankment structure model and verify the results of FLAC^3D simulation operation.5.The dynamic characteristics of saturated sandy soil foundation with low embankment structure under different consolidation ratio,consolidation pressure and frequency simulated traffic load were studied.Through the triaxial test carried out by step loading,the backbone curve,hysteresis curve,damping ratio curve and dynamic elastic modulus were studied,the dynamic strength,dynamic deformation and pore water pressure of saturated silt were analyzed,and the anti-deformation and anti-liquefaction effects of low embankment structure were summarized.The dynamic triaxial test scheme of the sample obtained the effect of judging whether the model sample of low embankment structure is liquefied and verifying with the simulation results of FLAC^3D.6.The test and calculation results of an engineering example show that the selected low embankment structure model meets the requirements of stress strain and anti-settlement and anti-liquefaction,which indicates that the research method of vibration liquefaction test of low embankment structure in saturated silt with Marine sediment in Guangxi has achieved the expected purpose and is feasible.