| It is requested to paved by ballastless track on the whole line of Wu-Guang express railway engineering, compared with common railway of ballast track, it is stricter in deformation of subgrade. The subsidence of post construction on high-speed railway is required less than 3cm, even of road foundation no settlement. Seen from the datum of Japan, French, etc., good materials are required as filling materials of roadbed in high-speed railway, while the embankment below the roadbed, many kinds of materials can be used, except those soils, such as weathered soft rock, whose properties are unstable and mechanical properties have been changed greatly, influenced by various factors. But currently, there are few mature technologies of embankment filling with soft rock in express railway. Based on the present research on soft rock fillings at home and abroad and the integrated analysis, the dissertation combines the research projects supported by railway ministry, by means of the research on the characteristics of embankment filling with soft rock and ballastless track-roadbed system for high speed railway with theory analysis, indoor test, model test and numerical simulation, the research work has been accomplished with following achievements:(1) Based on variational (or weak) form of the equilibrium equations for the ballastless track-roadbed system in Galerkin method and total Lagrangian form, a semi-infinite tri-dimensional spatial timing coupled dynamic model has been founded, which involves the ballastless track and roadbed system. In the model, the roadbed and track structure are dispersed to different elements and infinite element method is applied to eradicate boundary effects. There is relative restricted coupling between contact interfaces of various materials of the system. It can provide dynamic responses of the system with changes of wheel load, vehicle velocity, frequency, irregularities, and distribution of dynamic responses in the subgrade; also be used to select parameters, optimize designs and forcast dynamic properties of the system, etc.(2) Based on Timoshenko beam and geostatic theory, coupling restricted equations of various finite elements are founded firstly. Therestricted equations have been dealt with by penalty parameters or lagrange multipliers. By this way, the difficult problem of the coupling between the contact interfaces of various materials of the ballastless track-roadbed system has been solved effectively.(3) Based on deformation characteristics of materials, the dissertation adopts analysis models, such as linear, nonlinear elasticity, Drucker-Prager, visco-plasticity constitutive model, etc. The coupling between vehicles system and the track-roadbed system is affected by putting external simplified force on the plane of the rail vertically. The global matrices equations have been solved, using implicit time integration of Newmark. Because there are many restricted equations in the dynamic model, Frontal solution is adopted to modal analysis, and reduced solution is adopted to transient dynamic analysis.(4) The engieering geological condition, physics and mechanics characteristic of soft rock in the section of the express railway have been traversed by detailed exploring and indoor test, intensity and deformation characteristics were mastered, characteristics of roadbed filling with soft rock as embankment material discussed. Based on deformation observed results of the model test in loading period, the settlement rules of the model roadbed were studied. Combining with local geological conditions and similarity rule, the calculating model of the model test was founded and were numerically simulated by FEM. The simulating results and observed results were compared, many influencing factors were studied by founding all kinds of roadbed models and FEM numerically simulating. The future settlement was forecasted by some common forecasting models, fit precision and results were evaluated and analyzed. The most suitable forecasting model was selected to guide future construction and optimize designs.(5) Based on K30 tests, the strength and deformation properties of the soft rock fillings have been studied. It was demonstrated that the fillings can satisfy the requirements provision of ballastless track and embankment for express railway and standards of high-speed railway roadbed design in German on the aspects of strength and stiffness properties.(6) Applying the track-roadbed dynamic model above-mentioned, the influences of wheel load, vehicle velocity, frequency, irregularity and material parameter on the dynamic response of the system were studied systematically, some results were stated as folio wings:(D The settlement displacement, velocity and acceleration on the top of the rails have been decreased quickly through the fasteners, rubber pads below the rails, slab, concrete roadbed layer to the graded crushed stone subgrade , the amplitude of the dynamic response on the top of the rails is about 10-12 times as many as that on the top of the subgrade filling with graded crushed stone, when the wheel load of design is 250kN, or abnormal wheel load is 334kN. When the wheel load is 122kN and the velocity of a moving vehicle is 350km/h, the amplitude of the settlement displacement of the rails and the vertical stress on the top of the subgrade filling with graded crushed stone are 0.74mm and 42kPa. These studies show that the results are in good agreement with the datum from tests. It proves that the dynamic model is practical and reliable.(2) The dynamic responses of the system were changed with the changes of velocity, wheel load of a vehicle and frequencies of excitation forces. But when the velocity of a vehicle is accelerated to above 250km/h, the dynamic respondency had nothing to do with velocity. The amplitude of the dynamic response on the top of the rails and roadbed is mainly ascertained by static wheel load, excitation forces of medium and high frequencies. The wave of dynamic response is controlled by excitation forces of low frequencies. The amplitude of dynamic responses with dynamic load is about 1.35-1.65 times as many as that of the static load, which equals dynamic load in numerical value.(3) The spring-damping properties of fastener-rubber pads system and CA layer have influenced greatly on the dynamic characteristics of the track structure and roadbed system. The dynamic properties of the track and roadbed can be improved to reduce the stiffness of the fastener-rubber pad structures, or increase the thickness of the CA layer.
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