Research Of The Deformation Characteristics Of Reinforced Subgrade Under Repeated Vehicle Loading

With the development of economy and transportation in China, traffic volume, vehicle speed and vehicle loading are increasing. So automobile load plays an impotant part in dynamic property of pavement and subgrade. The differential settlement of subgrade makes asphalt pavement yielded. The occurrence may reduce the driving safety and comfortablity of riders. At the same time, the incredible maintenace cost of road is added. In practice of engineering, geogrids are laid in subgrade to reduce the differential settlement. But some questions have not been solved. For example, how is the effect, what is the mechanism of action, how to design it reasonably? To solve these problems, a three-dimention finite element interface model is presented, which may predict the dynamic interaction behaviors of the geogrid and subgrade, in order to study the reduction effect of the differential settlement in the subgrade and pavement reinforced with the geogrid due to the cyclic automobile loading. And the dynamic reinforcement principal is particularily illuminated.A serial of consolidated undrained dynamic triaxial tests on silt are conducted to study the dynamic behaviors of sugrade soils using DDS-70 dynamic triaxial instrument. These tests are carried out to discuss the influences of dynamic strain, cofining stress and layer of reinforcements on the dynamic characteristics of subgrade respectively.Adopting the general-purpose finite program ANSYS, the transient dynamic response analysis of geogrid-reinforced pavement and subgrade through the three-dimensional finite element method is carried out in this paper. Druker-Prager model is chosen to consider the nonlinear propertities of soil, the nonlinear relation of the interface is considered by surface-to-surface contact element and the geogrid is moduled by the membrane element. The comparative dynamic response analysis of reinforced road models, which include several layers of geogrids and unreinforced road model is studied to illuminate the reinforcement effect under the automobile loadings. The layer location of geogrid has an important role in reducing the settlement,which the geogrid layers are more, then the settlement are fewer.