Investigation On Dynamic Performances And Reasonable Form Of Elevated Pile-board Structure Under High-speed Train Loading

When constructing high-speed railway embankments in karst area,karst grouting or traditional pile-plank structure is often used for foundation treatment.However,the effectiveness of the treatment is hard to be guaranteed and the project investment is tremendous.When filling the high-speed railway embankments in the central and eastern plains of China,poor geological conditions that require far-distance transportation of qualified fills are often encountered,in which case the bridge-replacing method is extensively adopted in the engineering practice due to the cost and freight of filling materials,which leads to a high bridge-to-tunnel ratio of high-speed railways in China.To overcome the aforementioned problems,a new type of subgrade structure,named the elevated pile-board structure,is proposed.In this study,the mechanical behavior and the adequate type of the elevated pile-board structure are investigated,which provides a theoretical reference for its application in China's high-speed railways.This paper presents extensive literature review of the research status of pile-slab structure.Then,the classification,mechanical characteristics and design methods of pile-slab structure are summarized.Combined with the application status and evaluation criteria for the traditional pile-slab structure and rigid bridge frame structure,the design load and governing factors of the elevated pile-board structure are investigated,which provides engineering guidance for the subsequent design and calculation of the structure.In this work,the dynamic model of vehicle-track-elevated pile-board structure is established by adopting the finite element code ABAQUS.The modeling process of the coupled vibration model is detailedly introduced.Using the design parameters of high-speed railway pile-slab structure,the sensitivity analysis of the elevated pile-board structure is performed,and the adequate geometric parameters of each component are obtained.Based on the results of the sensitivity analysis,the engineering design of the testing section on Guinan line is carried out.The dynamic calculations for the most unfavorable conditions are performed,and the results are compared with the specification standards.The results show that the elevated pile-board structure can effectively decrease the settlement of foundation in karst area.The design scheme of this site conforms to the current standards.In view of the lack of reports on the application of elevated pile-board structure,further research is needed for in-situ experiments to investigate the mechanical characteristics and failure modes of the structure.Based on the engineering data of the Guinan Railway,the programme of the field test,in-situ excitation test,driving test and long-term monitoring test of the testing section are designed.