Study On The Difference Of Subgrade Filling For Widened Road

With the continuous increase of traffic demand,China’s expressway four lanes of traffic have reached saturation,and widening subgrade is a relatively direct and effective treatment measures to solve the problem of road congestion and gradually becomes the inevitable trend of the development of the transportation industry.Because of the different stress history of old and new subgrade,widening subgrade is easy to appear uncoordinated deformation,which affects pavement smoothness and greatly reduces the comfort and safety of driving.And the research on the Reconstruction and expansion project of scholars at home and abroad focuses on the analysis of the influence of filling height,widening width and so on,and there is less research on the difference of new and old Subgrade fillers,which is easy to cause engineering waste or the overall damage of subgrade when the material selection of subgrade filling materials is not appropriate.Therefore,it is of great theoretical significance and practical value to study the influence of the difference of new and old Subgrade fillers on the uncoordinated deformation of embankment,which is helpful to the rational material selection of the project.Firstly,this paper analyzes the characteristics and main ways of disease prone to the expansion of highway,and studies the mechanism of differential settlement,and analyzes that the diseases prone to widening subgrade are the collapse of embankment,the breakage of pavement and the decrease of the overall performance of Subgrade,and the main causes of these diseases are widening the uneven settlement of Subgrade and improper handling of joint parts.Then it is determined that the differential settlement control standard can be accepted under the condition of driving safety and comfort,and the different settlement control standards based on the reference standard are not the same.Secondly,the parameters characterizing the properties of subgrade filler are classified,and the correlation between five parameters(heavy γ,viscoelastic c,internal friction angle Φ,elastic modulus E,Poisson’s ratio μ)is analyzed by SPSS software on the basis of investigating the established engineering data,and it is concluded that the five parameters are not mutually exclusive random variables.Then the sensitivity of filler parameters to widen the differential settlement of Subgrade surface is analyzed by orthogonal test,and the influence of five factors on widening the surface differential settlement of Subgrade is analyzed from large to small: severe(γ)> elastic modulus(E)> Poisson’s ratio(μ)> friction angle(Φ)> adhesion(c).Then combined with the typical section type of the old and new subgrade,the finite element model is established by using ABAQUS to study the law of the occurrence and development of the uneven settlement of the old and new embankment,and the internal law between widening the uneven settlement of Subgrade and the parameters of embankment filler is analyzed.It is concluded that there is a linear relationship between the weight of the new embankment filler and the maximum difference settlement on the surface of widening subgrade,and the influence is significant and the influence of the other four filler parameters is small.Finally,this paper mainly studies the control measures of differential settlement by filling high quality filler,soil foundation treatment and adding geotextile grille three treatment techniques.The main conclusions are as follows:(1)The way of the new embankment layered filling high quality filler is different,the number of layers is different,and its effect on widening the differential settlement control of subgrade surface is obviously different;(2)changing the elastic modulus of soft Foundation can obviously reduce the influence of uncoordinated deformation of old and new embankment,but when it increases to a certain limit,the improvement effect of widening subgrade settlement deformation is weakened;(3)the geotechnical grille has little effect on widening the surface subsidence of subgrade,whether it is single layer reinforcement or multi-layer reinforcement.