高铁运行引起的高架桥群桩基础地面振动衰减分析

采用多质点弹簧-阻尼模型模拟列车,将板式轨道运动学方程引入到桥梁模型中,推导了桥梁振动半解析模型,结合群桩基础模型,建立了列车-轨道-桥梁-桥墩-群桩基础半解析耦合模型。基于傅里叶变换和频域内弹性半空间Green函数求得高铁高架桥群桩基础地面波动场,研究了上软下硬和上硬下软地基环境振动规律,分析了桩径、桩长对地面振动衰减的影响。结果表明:车速较低时,轨道中心处上硬下软地层比上软下硬地层振动大;上软下硬地层,车速较高时因接近表层软土剪切波速而增大地面振动,故应避免车速接近表层土的剪切波速;群桩基础地面振动随桩长和桩径增大而增大,且车速越大地面振动增速越快;桩体具有好的减振效果,群桩范围内地面振动由于几何阻尼和桩体散射作用迅速衰减,且桩径越大振动衰减速度越快,但受桩长影响较小;群桩基础外上硬下软地层比上软下硬地层的地面振动幅度小,表明上硬下软地层减振效果好;合理设计桩基可控制轨道中心处地面振动,并能有效降低高架桥远处的环境振动。

Ground vibration attenuation of viaduct and pile-group foundation induced by moving high-speed train

The train is simulated by a multiple-mass-spring-damper model, and the bridge vibration is solved by incorporating the slab track kinematic equations into the bridge model. Combined with pile-group foundation model, a semi-analytical coupling model of train-rail-bridge-bridge pier-group pile foundation is established. Based on the Fourier transform and the Green function of elastic half-space in the frequency domain, the ground wave field caused by the moving train on viaduct is obtained. The vibration laws of the upper stiff-layer and lower soft-layer ground and the upper soft-layer and lower stiff-layer ground are studied. Moreover, the effects of pile diameter and pile length on ground vibration attenuation are analyzed. The results show that the vibration of the upper stiff-layer and lower soft-layer ground at the center of the track is larger than that of the upper soft-layer and lower stiff-layer ground at lower vehicle speed; but the vibration of the upper soft-layer and lower stiff-layer ground increases significantly when the vehicle speed is close to the shear wave velocity of the surface soft soil, which indicate that the speed of the train should be avoided to approach the shear wave velocity of the surface soil. The vibration at the center of the track increases with the increase of the pile length and pile diameter, especially when the vehicle speed is large. The pile has a good damping effect, and the ground vibration attenuates rapidly due to the geometric damping and pile scattering effects within the pile-group area. The vibration attenuation speed is faster when the pile diameter is larger, but it is less affected by pile length. The ground vibration amplitude of the upper stiff-layer and lower soft-layer ground on the outside of the group pile foundation is smaller than that of the upper soft-layer and lower stiff-layer ground, which indicates that the effect of the upper stiff-layer and lower soft-layer ground on vibration attenuation is better. Rational design of pile foundation can meet the vibration control requirements at the center of the track and effectively reduce the environmental vibration around the viaduct.