| With the vigorous construction of high-speed railways in western China and the gradual implementation of the medium and long-term railway construction planning network,China has also put forward some new requirements for the construction of high-speed railways.To ensure the safe and smooth operation of high-speed trains,the smoothness of the railway track and the long-term dynamic stability of the subgrade under cyclic dynamic loads are very important.Therefore,this paper relies on the National Natural Science Foundation project “Research on Accumulative Plastic Deformation and Long-term Dynamic Stability of Improved Loess Subgrade under Cyclic Loads for High-speed Railways”,combined with previous research results of the fund project,through indoor dynamic model tests,for Lanzhou area,remolded loess and 5% content cement are used to improve loess fill roadbed,the rule of long-term cumulative deformation of subgrade structure under cyclic loading is studied under different conditions.Finally,the vehicle-rail coupling model was established by UM software,and the wheel-rail interaction force was obtained.With Midas/GTS-NX software,the dynamic response of the high-speed railway ballastless track cement-improved loess roadbed was analyzed,and relevant conclusions were obtained.The main content and conclusions of this article are:(1)On the basis of consulting a large number of documents,the current research status of cement modified loess is summarized,and the relevant scheme of the indoor model test of cement improved soil is formulated,and the research content of this paper is put forward.(2)The static and dynamic characteristics of the remolded loess and 5% cement modified loess are studied.The results show that the unconfined compression strength,cohesive force,internal friction angle and dynamic strength are increased after the cement is added in the loess.(3)According to the requirements of mixing,filling and compaction of the improved soil subgrade in the standard,the remolded loess and 5% Improved Loess Subgrade models under different compactness conditions are filled.The model test boundary uses a 3 cm thick foam.Simulating the actual flexible boundary,the loading method uses two sets of vibration motors for combined loading,and the data acquisition uses the INV3018-USB dynamic tester for acquisition.The vertical and horizontal cumulative plastic deformation,elastic deformation and dynamic stress at different locations of the subgrade under different conditions were studied and analyzed with the changing rule of the number of loads.(4)Through the study of the variation law of the dynamic characteristics of the subgrade model under different working conditions with the number of loads,it can be known that the remolded loess filling subgrade presents a rapid-breaking ring form,and the deformation increases rapidly with the increase of the number of load actions;and 5% of the cement the modified loess will quickly stabilize after 1.5 million repeated loads.(5)A long-term cumulative plastic deformation prediction model for 5% cementimproved loess subgrade under cyclic loading was established,and the predicted results were compared with the modified Power model calculation results,and 5% cement modified loess subgrade under different experimental conditions was obtained.Long-term cumulative plastic deformation calculation empirical formula.(6)A coupled dynamic analysis model for vehicle track subgrade of high-speed railway is established based on UM software.The track irregularity is calculated by Chinese spectrum,and the wheel and rail force time histories under different speed conditions are calculated.Then,MIDAS GTS-NX is used to model and analyze the ballastless track single track railway subgrade,a wheel-rail time history of two pairs of bogies is applied to the rail,the distribution of dynamic displacement,dynamic acceleration and dynamic stress in different parts of roadbed is analyzed. |
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