Abstract
Pile-plank structures are widely applied for high-speed railway built in soft ground in China. It can be used as a reinforcement to improve the behavior of subgrade by providing vertical confinement to increase their stiffness and strength and reduce the subgrade settlement of ballastless track. However, the use of pile-board structure for soft ground reinforcement of high-speed railway is hindered by the existing gap between applications and theories. To verify vibration characteristics and long-term performance of pile-plank-supported low subgrade of ballastless track and the benefit of pile-board structure, an experimental study was conducted on low subgrade of pile-board under excitation loads using both in situ frequency sweeping and cyclic loading experiments. The frequency sweeping experimental results show that the pile-plank-supported low subgrade has smooth stiffness along the longitudinal subgrade and can effectively control the progressive effects of train speed on dynamic stiffness of the subgrade, which ensures driving safety and comfort. The cycle loading experimental results show that the pile-plank-supported low subgrade has favorable long-term dynamic stability, and its dynamic response is uniform along the longitudinal subgrade.
Highlights
With the increasing speed of trains, there is a requirement for more analyses of train-induced vibrations
The results show that the flexible subgrade bed weakens the effect that any stiffness differences of the pileplank structure along the longitudinal subgrade have on the subgrade surface stiffness, ensuring the uniform distribution of dynamic stiffness of ballastless track in the longitudinal direction
This paper presents an experimental study to investigate vibration characteristics and long-term performance of pileplank-supported low subgrade of ballastless track under excitation loads
Summary
With the increasing speed of trains, there is a requirement for more analyses of train-induced vibrations. The railway engineering community has researched vibrations of the ground and structures (e.g., subgrade structures and tracks) induced by high-speed train (HST) passage on ballasted and ballastless tracks. Japan Railway’s Railway Technical Research Institute (JR) conducted a repeated impact test of track subgrade with an excitation force range of 9.8–98.0 kN under a fixed frequency of 7 Hz, as shown, and performed several experiments to analyze the dynamic characteristics of ballastless track subgrade [8, 9]. We describe the method of investigating the vibration characteristics of the pile-plank-supported low subgrade of the ballastless track on a high-speed railway to confirm safe operation. Dynamic performance of the subgrade during operation via application of simulated high-speed train dynamic loads on the foundation slab of the ballastless track
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