Numerical Analysis And Test Study On The Statical And Dynamical Characteristics Of High-speed Railway Transition Section Reinforced By Geogrid

The precondition of the development of high-speed railway is safety, reliability and ride comfort that are decided by the high quality and high reliability of all aspect of the railway system. When the vehicle passes road-bridge (culvert) transition section, the phenomenon that "bump" occurs frequently, which reduces the safety and ride comfort of the vehicle in motion greatly. With the rapid development of the high-speed railway in our country, these problems of transition section become more and obvious than before. Basing on the research status of the transition section at home and abroad and coordinating the item tackling key problem of railway ministry, this dissertation is comprehensively analyzed and studied by theory study, test in-situ, and numerical analysis. The main research work of this dissertation gained can be summarized as below.(1) Basing on the elastoplastic incremental theory, and introducing the contact surface element to simulate the interaction between the longitudinal ribs, transverse bars and the soils; accordingly, a dynamic elasto-plastic constitutive model of reinforced earth by geogrid is established for numerical calculating.(2) According to the vehicle-track coupling dynamics theory [1], ballastless track slab dynamics theory, and combining the finite element and infinite element method, a vehicle-track spatially dynamics contact model of transition section is established.(3) Computerizing the well-done vehicle-track dynamics finite element analysis program and comparing the calculating results of elasticity theory with those field measured data, therefore, the reliability and applicability of the program are checked up.(4) Basing on the "spatial field "point of view, studying on statical vector field characteristics of track-roadbed structure subject to train load of in transition section, the following conclusions have been observed:① the distribution characteristics of statical vector field in the longitudinal direction, transverse direction and in the depth direction;② the good improvement to statical vector field distribution of reinforced roadbed by geogrids behind abutment in transition section;③ the force vector field distribution characteristics of reinforcedroadbed by geogrids behind abutment in transition section;④ The sensitivity analysis of the vector field of roadbed-ballast structure subject to such factors as geogrids, train statical axle-load, K30 modulus of surface layer of foundation bed.⑤ Basing on the "time and spatial field" point of view, under the moving load of train, simulating and analyzing the effects of the vehicle-rail-roadbed system subject to such factors as run direction, train speed, reinforcement behind abutment, track vertical profile irregularity, and etc... At the same time, the dynamic control indexes of the vehicle system about stabilization and comfort are proposed.⑥ By time and frequency domain analysis of a great deal of field measured data, and by studying on dynamic response of bedding of roadbed, a brand "critical speed" conception at which the dynamic response trend of roadbed will change is proposed. The variation coefficient formula of axle-load is put forward to forecast general change trend of the dynamic response of transition section roadbed, in the mean time, a design idea that"excess height" of embankment fill can reduce the differential settlement and the dynamic response of transition section roadbed is advanced.⑦ By studying on the settlement observation data of three field test spots, the special settlement curve characteristics of transverse section and longitudinal section of roadbed are gained.⑧ By analyzing the standard of design and treatment of railway road-bridge transition section, the construction skills for the structures of grading macadam (sandy gravel) and soils reinforced by geogrids are specialized.