Based On The Fractional Order Calculus To Study The Dynamic Mechanical Properties Of Soil Subgrade Vibration Compaction

In order to fundamentally solve the problem of pavement damage caused by the increase in load and speed, the road must be built with a higher quality. And the reasonable compaction effect directly determines the bearing capacity of the road subgrade and pavement and the life expectancy. Whether the dynamic mechanical properties of the job objects can be fully considered in the process of compaction construction work has a very significant influence on the final compaction effect.In this paper, based on the fractional calculus theory, the dynamic mechanical properties of the compacted soil in the vibrating compaction process were studied by establishing several classical and fractional order models. Based on the finite element theory, this paper established the dynamic equilibrium equation of the vibrating compaction system.This paper respectively established classic Maxwell model, Kelvin-Voigt model, three elements model and fractional Maxwell model, Kelvin-Voigt model, three elements model and on this basis analyzed and studied the dynamic mechanical properties-storage modulus, loss modulus, loss factor and dynamic modulus. The simulation results show that, compared to the classical models, the fractional order models are closer to the experimental results, so the fractional order model can be used to describe the dynamic mechanical properties of the soil.Through further comparison between the fractional Maxwell model, fractional Kelvin-Voigt model and fractional three elements model, it was found that the fractional three elements model can better describe the dynamic mechanical properties of the soil. But the simulation results of the storage modulus are not ideal, so the least square method is used to optimize the fractional three elements model.The soil was considered as an isotropic material and using the Ritz-Galerkin algorithm and space discrete, the dynamic equation of fractional order viscoelastic material was introduced and then based on the finite element method and the numerical algorithm for the fractional order dynamic equations of viscoelastic materials, the finite element equations of the fractional order three elements soil dynamics were established.At the same time, with the consideration of the soil system and the vibrating compactor system, this paper combined the fractional order three element soil dynamic finite element equation with the dynamic model of vibrating compaction and thus established the finite element equation of vibrating compaction-soil system. This method can effectively overcome the shortcomings of the traditional method, which considers separately the dynamic mechanical properties of the soil and studies the vibratory roller and the compacted soil as a whole, consequently, the evaluation quality can be greatly improved.This paper is related to the basic theory of cross disciplines. The research work can not only reveal the subgrade vibration compaction mechanism, and supplement and enrich the theory system of compaction, also can guide the engineering practice. In conclusion, it has a very important theoretic value and practicality in engineering.