Study On The Static And Dynamic Characteristics Of Remoulded Red Clay In Jiangxi Province

Red clay can be seen everywhere in Jiangxi Province.In recent years,railway transportation in Jiangxi Province has developed rapidly.Red clay will be used as subgrade filler in many sections.As an important part of railway engineering,subgrade directly bears the joint action of rail static load and train dynamic load.Under the action of various complicated loads,more and more scholars pay attention to the deformation and uneven settlement of red clay subgrade.In this paper,static and dynamic tests are carried out on Jiangxi saturated remolded red clay through GDS dynamic and static triaxial test systems.The effects of consolidation confining pressure,initial porosity and drainage conditions on the static constitutive relationship of soil and the effects of cyclic dynamic stress ratio,initial porosity,consolidation confining pressure and loading frequency on the dynamic deformation,dynamic pore pressure and softening characteristics of soil are studied respectively.The research contents and achievements of this paper are as follows:(1)Based on the indoor routine geotechnical tests,the basic physical properties tests and direct shear tests of Jiangxi red clay are carried out,and the basic physical indexes,composition and content proportion of red clay are obtained.According to the results of direct shear test,the failure mode of red clay samples,stress-strain relationship curve and the influence law of moisture content on the shear strength index of soil are analyzed.The strength failure mechanism of soil was revealed from the microstructure characteristics of the soil by scanning electron microscope.(2)Triaxial shear characteristics and nonlinear static constitutive model of saturated remolded red clay.The dynamic triaxial test principle is introduced in detail,and the strength characteristics of red clay under two test conditions of consolidated drainage and consolidated undrained are explored.The effects of consolidated confining pressure and initial porosity on shear strength,bulk strain and excess pore water pressure of soil are analyzed.Duncan-Chang constitutive model parameters are established,and the normalized equation of stress-strain relationship of red clay based on the asymptotic value of principal stress difference as the normalized factor is established.(3)Dynamic characteristics of saturated remolded red clay.Through dynamic triaxial tests,the dynamic characteristics of saturated remolded red clay under unidirectional cyclic loading are studied.The effects of dynamic stress ratio,initial porosity,consolidation confining pressure,loading frequency and other factors on the plastic cumulative strain,hysteresis curve,dynamic pore pressure ratio and softening index of soil are fully considered.Based on the existing test results,a more suitable plastic cumulative strain prediction model is established by comparing with the classical logarithmic function model,which comprehensively considers the influence factors of dynamic stress ratio,initial porosity,consolidation confining pressure,loading frequency and the like.