High-speed Railway Culvert Adjacent Transition Roadbed Dynamic Response Of The Interaction Analysis

The Wuhan-Guangzhou passenger line is a high speed railway paved with ballastless tracks on the whole line, compared with common railway of ballast tracks, it is faster operation and higher design standard. So, it is stricter reguirement in deformation of the subgrade, and the deformation of the culvert-subgrade (or bridge-subgrade, or tunnel-subgrade) transition section is one of the most important researches. Thus, it is the key of subgrade design to make stiffness change smoothly and to control the differential settlement and the bending of rail top and so on, which ensures a smooth line. The thesis which is supported in part as a program of National Natural Science Foundation of China (No:50678177) has studied the dynamic response characteristics of the different conditions'culvert-subgrade transition sections under the train load influence. It has adopted the combination of numerical simulation and field measuring, on the ground of the Wuhan-Guangzhou passenger railline and on the basis of lots of relevant research at home and abroad. It has gained many valuable research results, which provide some reference value for design and construction of the ballastless tracks. The main research work of this dissertation gained can be summarized as follows.(1) By the long-term monitoring of the settlement on passenger railline DK1252+679-+731,we have got the settlement value at different positions between the culvert-sungrade transition sections, the predicted final settlement of the transition subgrade is between 3.86mm and 4.15mm, the differential settlement is 0.29mm.(2) It has been gained on parameter obtainment tests that the average Ed of grading macadam mix with 5% cement, A,B fillers of soil classification, clay layers were 1714.6MPa,765.6MPa,616.7MPa,and the average Gd of grading macadam mix with 5% cement, A,B fillers of soil classification,clay layers were 655.5MPa,282.0MPa,227.3MPa. Measured by field vibration test,the vertical compressive stiffness of the top of the culvert, culvert lateral, normal section between transition section of the roadbed subgrade were 162.5kN/mm,135.5 kN/mm and 121.3 kN/mm, the stiffness ratio was 1.34:1.12:1.(3) Using ADAMS/Rail software to set up vehicles-rails coupling model, combining with the Wuhan-Guangzhou Passenger Dedicated practical engineering parameters, the dynamic response analysis of the transition sections close by culverts shows that:Irregularity in the existing circumstances, the common security, stability and comfort of trains of 350km/h passing through the transition sections can be guaranteed, but when the speed reaches 400km/h, both the train body security and stability change into adverse; The stiffness of both ends of transition section is not the controlling factor; Transition Angular greater than 1‰, the vehicle operation safety and stability can not be guaranteed, it should be strictly controlled that Transition Angular is less than 1‰; the length of separate culvert -road transition section should not be smaller than 15m, while the distance between culverts of intensive culvert-road transition section should not be less than 40m; when the culvert spacing is greater than 80m, its basically eliminated the interaction can be treated as two separate culvert-road transition.(4) Using ANSYS software to set up track-foundation finite element analysis model, combining with the Wuhan-Guangzhou Passenger Dedicated practical engineering parameters, the dynamic response analysis of the intensive culvert-road transition sections shows that:in the speed of 350km/h, the dynamic stress amplitude and the displacement amplitude of top of the transition section subgrade bed are much smaller than specification limits; as setting transition section, the dynamic response of the amplitude of the rigid-flexible transition section appears a ladder-type region gradual process, which greatly smooth the differences brought about by the stiffness irregularity; the dynamic response amplitude along the depth direction of the base suffered from decay, in which the dynamic stress and vibration acceleration attenuate obviously, while dynamic displacement attenuates a little.(5) Introduced the wavelet analysis theory to deal the measured dynamic signal with wavelet threshold filtering, and effectively eliminated the noise of dynamic signal, and provided a more accurate data for amplitude analysis and statistical analysis. Through the time-frequency analysis of field measurement data, it has been obtained either embankment or transition section, the base surface of the vibration bed velocity frequency spectrum is different, but the first frequency main focus on 3～60Hz(6) The extreme dynamic stress value appeared in the two culverts at the top, while the extreme value of dynamic displacement appeared in common embankment section between the two culverts, analysis showed that all above were associated with the stiffness of the structures. The measured dynamic stress and displacement values were smaller than simulation, but the overall trend along the vertical lines and the foundation depth of transition section were basically the same.