The Settlement Characteristics Of Modified Phyllite Filling Subgrade

A large number of weathered phyllite materials are distributed in the eastern section of Shiyan-Tianshuihighway in Ankang territory,Shaanxi province.Influenced by mineral composition and structure,the weathered phyllite is extremely sensitive to water.Poor weathering resistance,water stability,and anti-deformation ability often lead to the failure of phyllite filling subgrade.According to the investigation of highway and the existing research results,the paper studied the engineering properties and deformation characteristics of the modified phyllite filling subgrade through the methods of indoor test and finite element simulation.The following results are obtained.(1)The main mineral components of the phyllite are chlorite,mica,and quartz.The irregular mass structure of quartz and mica is the main reason for the poor strength of phyllite.Through field sampling analysis,the CBR of most original weathered phyllite is less than 3%,which is difficult to meet the requirements of subgrade filling.(2)Thecompaction characteristics of different coarseparticle contents of phyllite show that the coarse particlecontent of 55% is the optimum gradation for packing.Based on the optimum gradation,the effect of different cement and lime contents on the CBR value and unconfined compressive strength of the phyllite is analyzed.The results indicate the optimum content of cement is 4% and the lime is 5%.Then the indoor bearing plate tests and direct shear tests were carried out,and the change rules of resilient modulus and shear strength were analyzed,providing a parameter basis for the numerical simulation.(3)Combined with the mechanism of subgrade settlement,the vehicle load is simplified to semi-sine load,and the elastoplasticity of filler is considered in creep analysis.The MC(Mohr-Coulomb)plastic failure criterion is introducedin the Burgers creep modelto calculate the settlement and deformation of different phyllite filling subgrade under vehicle load.(4)Based on ABAQUS,a long-term settlement calculation model of modified phyllite filling subgrade is established to study the influence of modifier on its deformation.The results show that lime and cementadded to the phyllite fillers can effectively reduce the influence depth of vehicle loads and control the settlement of modified phyllite filling subgrade.