弹射冲击荷载下高速铁路路基振动加速度时频特性

高速铁路具有运营时速快、平顺性高等特点，将其作为列车机动发射站坪具有一定的优势，其振动加速度作为高铁路基结构破坏的关键参数有重要的研究价值.借助ANSYS有限元分析软件，结合弹塑性理论并引入三维一致粘弹性人工边界及其边界单元，建立半无限长无砟轨道-路基-地基非线性耦合静力学分析模型；在此基础上进行模态分析，得到了模型系统的振型、固有频率，进而建立了动力分析模型，并对比弹性地基梁板模型进行模型验证；基于上述动力分析模型，结合弹射冲击荷载得到了各结构层加速度时域信号；最后，基于EEMD-HHT变换对加速度信号进行时频分析.研究结果表明：各结构层加速度在荷载突变处取得瞬时加速度峰值，在0.17 s处取得加速度幅值；各结构层加速度成分主要分布在0～20 Hz，其中，2 Hz及10 Hz两处有明显峰值，且在2 Hz附近分布最为集中；自密实混凝土层、底座板、基床表层几乎没有发生加速度成分的吸收，而基床底层及以下有较大幅的吸收，因此，应重点关注0～20 Hz超低频范围内的基床表层及以上结构层的动力响应.

Time-Frequency Characteristics of Vibration Acceleration of High-Speed Railway Subgrade Under Ejection Impact Load

high-speed railway is characterized by fast operation speed and high smoothness, and has certain advantages when used as a platform for train launching. Its vibration acceleration can be used as a critical parameter to assess the structural damage in high-speed railway subgrade. Using the finite element analysis software ANSYS, a semi-infinite ballastless track-subgrade-foundation nonlinear coupling static analysis model is established by elastic-plastic theory and introducing the three-dimensional uniform viscoelastic artificial boundary with its boundary element. The modal shape and natural frequency of the model system are obtained by modal analysis, and then a dynamic analysis model is established. The dynamic model is verified by comparing with the beam-slab model on an elastic foundation. Based on the dynamic analysis model, the time-domain acceleration signals of each structural layer under ejection impact load are obtained. Finally, the acceleration signals are analyzed through EEMD-HHT transform. The results show that the peak instantaneous acceleration occurs at the time of sudden change of load, and the amplitude of acceleration is obtained at 0.17 s. The acceleration components of each structural layer are mainly distributed in the range of 0–20 Hz, and there are two prominent peaks at 2 Hz and 10 Hz, most concentrated in the vicinity of 2 Hz. The three structural layers including the self-compacting concrete layer, the pedestal plate and the subgrade surface layer almost do not absorb any vibration acceleration components, but the subgrade bottom layer and the zone below it have significant absorption. Therefore, more attention should be paid to the dynamic response of the subgrade surface layer and upper layers in the ultra-low frequency range of 0–20 Hz