Study On Creep Characteristics And Constitutive Model Of Geogrids

The long-term creep property of geogrids is the main factor to affect the stability of geogrids reinforced soil structure.The paper studies the creep property and constitutive model of geogrids under different temperature and confined conditions through indoor creep tests,theoretical analysis and numerical simulation.The research results can provide theoretical for the optimization of geogrids reinforced soil structure design.The main contents are as follows:(1)The high and low temperature creep tests of geogrids under different temperature conditions were carried out to analyze the isochronous creep curve,the isostrain creep curve and the secant modulus curve of geogrids.With the increase of temperature,the time for the geogrid to reach the allowable strain value decreased,and the creep rate increased.The creep of geogrid can be accelerated by increasing temperature.(2)The confined creep test of geogrids under different confined conditions was carried out.When the load level was the same as the confined normal load,the strain of geogrids increased sharply with time,and then tend to be gentle.Friction and embedment occurred between soil particles and geogrids,and lateral restraint can limit the deformation of geogrids.(3)Based on the indoor creep test of geogrids,the variation of stress and strain of geogrids was analyzed by using COMSOL finite element software.At the same load level,with the increase of temperature,the stress and strain of geogrids increased gradually.With the increase of lateral normal load,the stress and strain of geogrids gradually decreased.During the creep process of the geogrids,the stress and strain in the middle of the longitudinal rib was the largest,the part of the longitudinal rib connecting the transverse rib took the second place,and the stress and strain in the transverse rib was the smallest.(4)Based on the indoor creep test of geogrids,the typical creep model of geogrids is analyzed.The power function model can accurately reflect the creep behavior,but it only considers the time effect.In order to comprehensively consider the time and stress effects,a three parameter viscoelastic constitutive model is studied.It can be accurately applied to the creep test results under different load levels,but it is not applicable to the creep of geogrids under confined conditions.Therefore,the modified constitutive model with coefficients a and b is introduced.