Research On Dynamic Characteristics Of Subgrade And Dynamic Construction Control Index On Changsha Round-the-city Expressway

The foundation of current asphalt design theory and regulation in our country is based on elastic half space of linear elastic layered systemIt treat the traffic load as static load out on the pavement structure calculation. But in fact,the pavement structure is not a uniform medium elastomeric. Treating high-speed mobile vehicle dynamic load as static load ignores the effect to pavement structure. Based on the analysis of the dynamic characteristics of subgrade soil, We get the roadbed compaction effect evaluation system which takes the dynamic modulus of subgrade soil as a parameter. We established the finite element analysis model of asphalt pavement.we has carried on the dynamic response simulation test on the silty clay which came from changsha highway. We realized the Rayleigh wave testing dynamic modulus of subgrade construction.the Concrete results are as follows:We detailed analysis the characteristics of subgrade soil under dynamic load.the soil Composed of subgrade has elastic-plastic and viscoelastic characteristics.Under the effect of cyclic loading,it showed off nonlinear,hysteresis characteristics and deformation accumulation.we obtained the changing rule of the stress and strain of the soil under the effect of cycling loading.On the basis of summary of asphalt pavement fatigue life model,We used the finite element to analysis fatigue life of three types pavement.they are Conventional subgrade,Half filling and half digging subgrade and Low fill subgrade.We found that the dynamic modulus of subgrade soil parameters has the important influence on the fatigue life of asphalt surface.We got three kinds of typical dynamic modulus of subgrade structure limits.We developed a method to test the dynamic modulus by the means of dynamic shear test.we got the dynamic modulus of standard specimen in known compaction degree and moisture content.the result provide a basis to use Rayleigh wave detection of subgrade construction qualityThe method that using Rayleigh wave method to measure the dynamic modulus of subgrade has been developed.we obtained dynamic mathematical relation model of Rayleigh wave velocity and modulus of subgrade.Comparing traditional detection method and Rayleigh wave, the latter is more Scientific and reasonable, nondestructive and fast.