Test Analysis of Dynamic Reponse in Bridge Foundation and Subgrade under Train Loads

The distribution and propagating rules of dynamic responses in bridge foundation and subgrade under high-speed train loads has become an important aspect in studying and solving vibrating and settlement problems. A bridge on Zhe-Gan railway line was selected to test the vibration wave. Regardless of wheel-rail-bridge dynamic propagation process, vibration waves in foundation and subgrade are measured with velocity sensor with 3 meter interval along longitudinal and transverse direction, and the characteristics and propagation rules of vibration load are studied. Wave's spectrums are analyzed to study the propagating rules and damping characters. The results indicate that: the energy of velocity signals motivated by all kinds of trains were concentrated in low frequency less than 80Hz and reduced quickly with the distance in the foundation. The vibration amplitude increase with weight, decrease with performance. For goods train and passenger train, the energy of velocity signal concentrates on the similarly frequency band and the vibration amplitude increase with the speed, but for bullet train,it essentially unchanged. These results are useful to identify the dynamic load of high speed train and to analyze the dynamic response of bridge foundation and subgrade.