Experimental Study On Dynamic Characteristics Of Western Loess Subgrade Based On Shakedown Theory

It is a critical period to promote the national economic construction and the rapiddevelopment of science and technology during the Twelfth Five-Year Plan. China willcontinue to accelerate the construction of highway. As the development and utilization ofland, mining, geology and the tourism resources in western, it puts forward more needsabout the region’s transportation. However, because of the special mechanicalcharacteristics of loess which is widely distributed in the western region, severe challengeswill be faced in the west construction of highway.In the design specifications of roadbed, the select and compaction of subgrade filler isthe main consideration. Yet the deformation characteristics of subgrade filler have notconsidered with the long-term vehicle cyclic loading action. The purpose of this paper is toprovide the theoretical basis for the design of the loess subgrade through the dynamictriaxial experiment research.Based on the typical Pavement-Subgrade structure form of the western highway, anumerical simulation is conducted to study the stress transmission law between thepavement structure layer and the subgrade by using FLAC5.0software. Firstly, the effectsof vehicle load on stress transmission are analyzed for subgrade fillers with differentphysical and mechanical properties. Secondly, the effects of vehicle load on stresstransmission are analyzed for various degrees of stiffness and thickness of pavementstructure layers when subgrade filler is certain. And then, the concept of the stress transfercoefficient is put forward. When vehicle load transfers via the general pavement structureform in the western region of China, the stress transfer coefficient is used to analysis theeffect of equivalent thickness and equivalent stiffness for stress transfer. Furthermore, themodel for stress transmission be established, which provides the basis for the study on themechanical behavior of interaction of the pavement-subgrade system.Based on the study of stress transfer model, dynamic triaxial test is conducted toanalysis the shakedown of loess roadbed and research the dynamic stress, the dynamicstrain and the diffusion rule of the internal subgrade. Using shakedown theory, we canbuild the relationship between the shakedown limit (plastic shakedown limit and plasticcreep shakedown limit) and the vehicle load, the vehicle flow-rate, the static wheel load, the driving speed, and the physical and mechanical characteristics of loess subgrade filler.Moreover, the shakedown of loess subgrade under the long-term vehicle cyclic loading actionis researched. The influence caused by the vehicle load, the speed, the vehicle flow-rate,the water content of the loess can be concluded to provide the theoretical guidance for thedesign of loess subgrade.