Study On Dynamic Response Characteristics Of Subgrade System For Heavy Haul Railway Under Launching Impact Load

With the in-depth implementation of China’s railway civil-military integration development strategy,the construction of railway mobile launch system has been put on the agenda.The heavy-haul railway can be used as a strategic missile launch base because of its strong transportation and carrying capacity.When the heavy-duty railway subgrade structure bears the launching impact load,its dynamic response is an important index to evaluate the stability of the launching base,and the stability of the launching base will inevitably affect the stability of the upper launching system.In addition,after the launching load,the residual response of the subgrade structure will affect the subsequent use of the line.In view of the above problems,this paper combined numerical simulation,field test,theoretical analysis and other methods to study the dynamic response characteristics of heavy-load railway subgrade under launching impact load.Firstly,in order to expand the geotechnical material model base of ANSYS software,the Drucker-Prager hardening constitutive model was developed by using USERMAT subroutine in ANSYS-UPFS.The compiled USERMAT subroutine was linked to generate a custom version of ANSYS software.With the help of this software,the simulation model of track-roadbed-subgrade system of heavy-haul railway was established and the transient dynamic solution was carried out.The accuracy of the simulation model was verified by the full-scale model test and the Boussinesq theory.Then,based on the calculation results of the simulation model,the time-history variation law of dynamic stress of heavy-haul railway single track subgrade under the launching impact load was studied,and the spatial distribution law of dynamic stress in the subgrade was revealed.According to the principle that the ratio of dynamic stress to subgrade dead weight stress is 0.2and 0.1,the overall thickness of foundation bed and the depth affected by load were determined respectively.Based on the analysis of the dynamic strength of subgrade under the launching impact load,the ultimate load value of gravel roadbed and the suggested value of subgrade coefficient K₃₀ when the subgrade filling under the roadbed meets the dynamic strength requirements were given.Then,based on the calculation results of the simulation model,the time-history variation law of dynamic displacement of heavy-haul railway single track subgrade under the launching impact load was studied,and the spatial distribution law of peak displacement and residual displacement in the subgrade was revealed.Through fitting,the function relations between the plastic deformation of subgrade and the launching impact load,the elastic modulus of subgrade and the thickness of subgrade were obtained,which can be used to predict the plastic deformation of subgrade under different loads,different elastic modulus of subgrade and different thickness of subgrade.Finally,based on the study of single-track subgrade,the dynamic simulation model of track-subgrade and subgrade system of double-track heavy-load railway was established.The application of launching impact load was divided into single-track load and double-track load.The dynamic stress and dynamic displacement response characteristics of double-track subgrade under the two loading schemes were studied.The research results provide reference for safe operation,maintenance and maintenance of heavy-haul railway in case of accidental launching load.