Abstract
This paper proposes a new design of bridge-subgrade transition sections in high-speed railways, in attempt to avoid typical defects observed in such sections. Field observations show that two types of defects tend to occur at bridge-subgrade transition sections of high-speed railways: ① the stiffness of the transition is usually too high so that tensile stress and even tensile cracks occur at the top surface of reserved trapezoid transition section and ② the compaction quality cannot be guaranteed within the first two meters from the abutment, which leads to excessive differential deformation within the transition section. For solving the above defects, a new design of the transition is proposed here: the section of the first 2 m from the abutment is filled with a graded gravel that is mixed with fly ash and cement to achieve specific stiffness and strength requirement, and the rest of the transition section is filled with roller-compacted concrete. For this new type of transition section, its dynamic performance is evaluated with on-site tests and numerical analysis. The results show that the bending angle of rail surface is almost constant along the route and the settlement of the rail surface along the route is in a linear distribution, which verifies the smoother transition from the rigid abutment to the flexible subgrade. Meanwhile, this new type of bridge-subgrade transition section has been successfully applied in the 680 km-long third bidding section of the Beijing-Shanghai high-speed railway, which provides valuable experiences for promoting and popularizing it in future construction of high-speed railways. In addition, the construction cost of the new type of bridge-subgrade transition section is verified by an economical efficiency analysis.
Highlights
One of the core requirements for high-speed railway is the route smoothness, which is the precondition for train safety and passenger comfortability [1,2,3]
This paper proposes a new design of bridge-subgrade transition sections in high-speed railways, in attempt to avoid typical defects observed in such sections
At the bridgetransition joint section (0–6 m from the bridge) and the transition-subgrade joint section (27–3 m from the bridge), the settlement difference of the new design is much smaller than that of the original design, which was considered the reason of the tensile stress occurring at the top surface of the inverted trapezoid transition
Summary
One of the core requirements for high-speed railway is the route smoothness, which is the precondition for train safety and passenger comfortability [1,2,3]. For both existing and new-built routes, transition sections between bridge and subgrade or between culvert and subgrade are always the key locations that affect the smoothness and evenness of the route. It is regulated in some specifications [4, 5] that a trapezoid structure should be adopted for the transition from rigid abutment (culvert) to flexible subgrade. The performance of the new design is evaluated against field monitoring and numerical analysis of the Beijing-Shanghai high-speed railway
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