Study On Rheological Properties And The Model Of The High-Speed Railways Deep Excavation Roadbed Red Mudstone

In order to cooperate with the related research on the deformation mechanism of the upper arch of the red bed soft rock subgrade,relying on a typical red bed soft rock deep excavation subgrade project of a high-speed railway in the southwest region,the combination of experimental research,theoretical analysis and numerical simulation was used to analyze the red bed.The creep characteristics of mudstone have been studied in depth.The main research work completed and the results obtained are as follows:（1）Based on the design and processing of the sampling device in the preliminary project and the red mudstone original samples obtained and processed on the site of the high-speed railway deep excavation,the conventional geotechnical test of the red mudstone was carried out,and the basic physical properties of the red mudstone were obtained.characteristic parameter.（2）According to the incremental multi-stage loading passive triaxial creep test data of red mudstone,the axial creep strain,creep rate and isochronous stress-strain curve characteristics of mudstone in the original state were studied.The results show that the creep deformation of red bed mudstone mainly includes two stages of deceleration creep and constant velocity creep,and the accelerated creep stage does not appear due to the strong lateral restraint.The stress has a significant effect on the creep deformation characteristics of mudstone.With the increase of stress level,the creep deformation of mudstone gradually increases,and the initial creep rate and steady-state creep rate also show a decreasing trend.Under the loading stress level,the mudstone produces recoverable transient elastic strain,viscoelastic strain and irreversible transient plastic strain and viscoplastic strain,indicating that the red bed mudstone has viscoelastic-plastic properties.（3）Using the Cvisc function in the FLAC^3D software,a simulated numerical experimental study on the creep characteristics of red mudstone under passive triaxial compression is carried out.The confinement constraints and the size of the samples were studied to influence the rheological properties of the mudstone.（4）Based on the creep test value-time scatter plot,the creep trend of mudstone was identified,and after repeated calculation and comparison,it was finally confirmed that the creep characteristics of mudstone conformed to the Burgers rheological model.The multi-level analysis of model parameters at stress values was obtained by using the L-M nonlinear mathematical tool.（5）According to the characteristic that the parameters of the Burgers model change with the axial stress of the mudstone,the Burgers nonlinear rheological model is improved,and the relationship between the parameters of the mudstone rheological model and the stress value of the mudstone is established through regression analysis.Improved and developed the Burgers rheological model to describe the nonlinear rheological characteristics of red mudstone.