模拟路基动力响应的原位激振试验研究

In-situ dynamic experimental study for simulating dynamic response of subgrades

动荷载下路基动力响应规律是研究路基长期动力稳定性的基础。采用自行研制的分离式变频激振器,开展铁路路基动力响应的模型试验,研究不同激振频率、动载水平下铁路路基本体的动力响应规律,掌握石灰改良土+粉质黏土填筑的铁路路基本体的共振频率约为25 Hz,路基表层的振动加速度、动应力随着激振频率的增加而显著增大;弄清了振动加速度、动应力沿深度和水平方向的变化规律,两者在主要影响深度1.5 m处已衰减90%,表明其沿深度方向的衰减速度较无砟轨道路基情况下快,而两者沿水平方向的变化受到应力扩散效应的影响,在浅层水平面会迅速衰减,而一定深度(0.7 m)处反而比较稳定,反映了路基动力响应的空间变化特征。

The dynamic response rule of subgrades under dynamic loads is the basis for studying the long term dynamic stability of the subgrades.The self-developed separated variable frequency vibration exciter was used to carry out full-scale model tests to study the railway subgrade dynamic response.The dynamic response rules of the railway subgrade under different excitation frequencies and dynamic load levels were studied.The test results show that the resonance frequency of the railway subgrade which was filled with lime improved soil and silty clay is 25 Hz and the vibration acceleration and dynamic stress of the subgrade surface increase significantly with increasing the excitation frequency.The vibration acceleration and dynamic stress along the depth and horizontal direction were researched.It is revealed that the vibration acceleration and dynamic stress in the depth of 1.5 m reduce by 90%,which indicates that the vibration acceleration and dynamic stress along the depth attenuates faster than those of the ballastless track subgrade.The changes of the vibration acceleration and dynamic stress in the horizontal direction are affected by the stress diffusion effect.To be specific,the vibration acceleration and dynamic stress decay rapidly in the shallow horizontal plane while keep relatively stable in the depth of 0.7 m.The research results reveal the spatial variation characteristics of the subgrade dynamic response.