重载铁路路基基床不同改良厚度的动力响应研究

重载列车荷载对路基基床的影响较为显著,为探究北方风沙地区选择水泥改良的粉细砂作为基床填料后路基体的变形及动力稳定性。通过动三轴试验对比分析了不同掺入率水泥改良土临界动应力大小及不同围压下回弹模量的变化规律,进一步结合FLAC3D建立三维动力仿真模型,重点探讨了列车激励荷载作用下路基基床换填不同厚度的5%水泥改良土时动应力、沉降变形、振动加速度的变化分布规律。结果表明:5%水泥改良土临界动应力、回弹模量较原状土提高幅度最大;路基体竖向动应力、位移、加速度峰值均随深度增加而逐渐减小;路基基床对动应力的扩散抑制作用较强,动荷载传递经基床后平均衰减约83.5%;路基沉降主要产生在中上部,且随基床底层改良厚度增加路基顶部最大竖向位移逐渐减小,最大减小约45.6%;此外,振动加速度传播经改良后的路基基床衰减幅度较明显,约为69.4%。

Study on Dynamic Response of Different Improvement Thickness of Subgrade Bed of Heavy Haul Railway

Heavy-haul train load has a significant impact on the subgrade bed. In order to explore the deformation and dynamic stability of the subgrade with cement modified fine sand as the base bed filler in wind-sand region of north China, this paper analyzes the changes of critical dynamic stress and elastic modulus of the soil under different confining pressure conditions of cement stabilized soil with different incorporation rates based on dynamic triaxial test. In addition, a three-dimensional simulation dynamic model is established with FLAC3 D, and the variation distribution rules of dynamic stress, settlement deformation and vibration acceleration of subgrade base bed of 5% cement soil with different thicknesses under the action of train excitation are discussed. The results show that the critical dynamic stress and the modulus of resilience of 5% cement soil are improved most. The vertical dynamic stress, displacement and acceleration peak of the roadbed decrease with the increase of depth. The effect of subgrade bed on dynamic stress diffusion is strong and the average attenuation of dynamic load is about 83.5%. The settlement of subgrade mainly occurs in the middle and upper part, the maximum vertical displacement at the top of the bed decreases gradually up to about 45.6% with the increase of the thickness at the bottom of the bed. Finally, the attenuation amplitude of the vibration-acceleration propagation of the improved subgrade bed is about 69.4%.