Research On Dynamic Characteristics Of High Fill Subgrade Under Vehicle Load

Under the background of western development,the construction of expressways in Shanxi Province is in full swing,and the loess gullies in the province are widely distributed.Expressway lines often cross high valleys by building high-fill roadbeds.However,after the highway is put into operation,the high-fill roadbed often suffers from settlement deformation,sliding instability and other diseases under the load of the vehicle,which seriously affects the driving safety and service life.Therefore,it is very urgent and necessary to study the dynamic characteristics of the high-fill roadbed under vehicle load.Based on the Taiyuan East Second Ring Expressway construction project,this paper uses a combination of on-site investigation,indoor testing,numerical simulation and theoretical analysis to carry out the vehicle load on the high-fill roadbed filled with Shanxi Lishi Loess Research on the dynamic characteristics.(1)Carry out a series of laboratory tests to obtain physical and mechanical properties indexes such as density,dry density,water content,limit water content,maximum dry density,optimal water content and shear strength of loess filler.Among them,the GDS triaxial test results show that the undisturbed loess in this area has a more obvious liquefaction trend when the drainage is poor,and an effective drainage system should be ensured during the design and construction of the subgrade project to prevent the subgrade from being unstable.(2)Use FLAC3 D to establish a numerical calculation model to study the dynamic response characteristics of the high-fill roadbed under the dynamic load of the vehicle.The research shows that under the load of vehicles,the vertical stress of each soil layer of the high-fill subgrade increases significantly,and the dynamic stress at the top of the subgrade changes the most drastically.As the depth increases,the dynamic stress changes gradually.As the height of the soil increases,the settlement deformation of the soil increases,but the contour of the settlement deformation is not horizontal,but bulges upwards.This may be because the "coupling" effect of the original valley slope limits the development of deformation;Under the dynamic load of vehicles,the deformation of high-filled subgrade can be divided into elastic deformation and plastic deformation.Plastic deformation is represented by the cumulative subsidence of the subgrade;the overall horizontal displacement of high-filled subgrade is small,but concentrated on the original valley slope And the top surface of the roadbed above it.(3)With the increase of the dynamic load amplitude,the vertical stress,vertical displacement and horizontal displacement of each soil layer of the high-fill subgrade will increase with a linear relationship.Among them,the increase in the amplitude of the vertical displacement of the top surface of the roadbed with the following dynamic load is the most obvious.As the depth increases,the increase in the amplitude of the vertical displacement with the increase of the dynamic load decreases.(4)The number of vehicle dynamic load effects on the settlement of high-fill subgrade is very obvious: with the increase of the number of dynamic load effects,the settlement of high-fill subgrade gradually increases,but the growth rate gradually decreases.