Experimental And Numerical Simulation Study On Dynamic Properties Of Saturated In-Situ Loess Under Traffic Load

Most of the studies on the dynamic properties of loess consider the effects of seismic action,the traffic vibration loads that act on the pavement repeatedly and many times at a certain frequency,and their effects have a long-term nature,and there are fewer studies on the dynamic properties of saturated in-situ loess under the action of traffic loads.The seismic action is usually analyzed by sine waves,while the actual action of traffic loads is in the form of half-sine waves.In order to further study the dynamic characteristics of saturated primary loess under repeated traffic loads,this paper takes saturated primary loess in Xi’an,Shaanxi Province as the research object,and uses literature research,indoor vibration triaxial test and numerical simulation to study the dynamic response characteristics of saturated primary loess under semi-sinusoidal traffic loads,which is of obvious theoretical and engineering application value for analyzing engineering problems in loess areas and reducing the adverse effects of traffic load vibration.The main research contents of the thesis are as follows:（1）The basic physical properties of the loess were determined by conventional indoor tests,and the characteristics of the dynamic pore pressure of saturated in-situ loess under semi-sinusoidal traffic loads were analyzed by vibration triaxial tests with respect to the vibration times and different surrounding pressures,and the development of dynamic strain and dynamic residual strain of saturated in-situ loess under different amplitude traffic loads were explored.（2）The evolution of the dynamic strength of saturated in-situ loess under traffic loading was investigated with vibration times,and the dynamic stress-strain relationship of saturated in-situ loess after the application of half-sine traffic loading was analyzed.The E_d toε_d relationship of saturated loess under traffic load was investigated,and it was found that theσ_d toε_d and E_d toε_d relationship of saturated loess under traffic load could be fitted by Hardin-Drnevich hyperbolic model.（3）The effects of dynamic strain and enclosing pressure on the dynamic modulus and damping ratio of saturated in-situ loess under traffic loading were analyzed,the characteristics of the variation of dynamic residual modulus of saturated in-situ loess were investigated,and the relationship between the variation of dynamic shear modulus ratio and dynamic shear strain ratio of saturated soil samples under traffic loading was studied;the relationship betweenλ/λ_max～1-G_d/G_dmax of saturated in-situ loess was analyzed,and the depth of influence of half-sinusoidal traffic loading was found to be up to 12 m below ground level.（4）Numerical modeling analysis of the stress and deformation of typical projects under different frequencies and amplitudes of traffic loads shows that the changes of stress and displacement caused by dynamic vehicle loads are greater than the adverse effects caused by static vehicle loads;the overall trend of displacement and stress in a loading cycle with time under semi-sinusoidal traffic loads shows an"inverted bell shape";higher frequencies do not cause excessive effects on stress and displacement.