Study On The Construction Technology Of Clay Subgrade In Riverine Plain Region

The full implementation of the highway network in china has brought to greater prominence the contradiction between the environment and constraints of resources.Hence, it is crucial to take into consideration of both conservation of land resources and environmental protection when constructing highways.Highway subgrade is severely restricted by land resources on riverine plain region. Filling height of subgrade is very low. Traffic loads cause severely permanent deformation of subgrade.Through repeated loading and dynamic triaxial laboratory of clay subgrade on riverine plain region, this study elucidated the change law, prediction model, overall characteristics of clay subgrade.The control method of permanent deformation of subgrade was proposed.The achievements of this study included:1. Resilient modulus laboratory experiments of clay subgrade were conducted.When water content less than optimal water content, the resilient modulus increased with the increase of water content. When water content more than optimal water content, the resilient modulus decreased with the increase of water content. The results demonstrated that, with the decrease of subgrade strength, the pavement surface deflection, the subgrade surface deflection, the subgrade surface strain, and base bottom tensile stress all increased. Maximum shear stress was decreased.2. The calculation results for permanent deformation, based on the strip-wise and layer-wise summation method,indicated that under the effect of traffic load, the factors affecting the permanent deformation of subgrade were(in descending order):soil plasticity index >moisture content>vehicular overloading>degree of compaction.In terms of the permanent deformation characteristics of subgrade surfaces, maximum deformation occurred at the middle lane, with gradual reduction towards the lanes on both sides, similar to a U-shaped distribution.3. A systematic summary was made of existing technical measures for the treatment of highway subgrades, which was then integrated with the inherentcharacteristics of clay subgrade on riverine plain region, leading to methods for controlling subgrade permanent deformation. A definition of man-made crust of clay subgrade was proposed, together with a qualitative description of the structure and function of that layer. A quantitative analysis was also made of changes in the thickness, elastic modulus and position of man-made crust of clay subgrade.