桩承式高速铁路路基的地震反应特性研究

桩承式路基在我国高铁路基中广泛应用,因此,论文建立地震荷载作用下轨道-路基-地基三维数值计算模型,研究地震荷载作用下桩承式路基的地震反应特性,分析桩径、桩长、桩间距、桩身弹性模量等计算参数对路基地震反应的影响,并与自由式路基的地震反应对比。自由式路基地震反应特性表明,地震荷载作用下水平x方向钢轨振动位移幅值最大,是z方向的5倍,路基坡脚处振动位移幅值是基床表层的25.2倍,轨道、路基频谱曲线主频单一,且主频范围为2.5～7.5 Hz;与自由式路基相比,桩承式路基对轨道水平方向位移幅值、加速度幅值有增大作用,但减小了轨道竖向位移幅值、加速度幅值;对路基各结构层位移幅值、加速度幅值都有明显减小作用。综合考虑,桩承式路基抗震性能最佳桩径为0.8 m,最佳桩长为8～10 m,最佳桩间距为2 m,最佳桩弹性模量为20 GPa。

Seismic Response Characteristics of Piled High-speed Railway Subgrade

As a country with frequent earthquakes, the high-speed railway network in China is more and more intensive, and many railways are located along the seismic belt, thus endangering their operation safety. Pile-supported subgrade is widely used in high-speed railways in China. Therefore, the seismic response characteristics of pile-supported subgrade under seismic load were analyzed through a three-dimensional numerical model of track-subgrade-foundation, and the influence of calculation parameters, i.e., pile diameter, pile length, pile spacing, and elastic modulus of pile body on the seismic response of subgrade were discussed and contrasted with those of free subgrade. The seismic response characteristics of free subgrade showed that the vibration displacement amplitude of rail in the horizontal x direction is the largest under seismic load, which is 5 times of that in the z direction; the vibration displacement amplitude at the foot of subgrade slope is 25.2 times of that at the surface of subgrade bed. Compared with the free subgrade, pile-supported subgrade has an increasing effect on the horizontal displacement amplitude and acceleration amplitude of the track, but it reduces the vertical values. It also obviously reduces the displacement amplitude and acceleration amplitude of each structural layer of subgrade. It is concluded that the optimal pile diameter, pile length, pile spacing, and elastic modulus of pile-supported subgrade are 0.8 m, 8-10 m, 2 m and 20 GPa, respectively.