地震作用下有砟轨道路基动力响应规律振动台试验

Shaking table test of dynamic response law of subgrade with ballast track under earthquake

以京沪高铁CRH380BL高速动车组为原型,根据相似定律设计完成了1:10比尺的铁路有砟轨道路基振动台模型试验,研究分析了路基的加速度、土压力和位移响应规律。模型尺寸为9.6 m×3.5 m×1.0 m(长×宽×高),包括列车、有砟轨道和路基部分。试验结果证明:随高程增加,水平加速度峰值放大系数逐渐增大,基本上稳定在1.0~2.5,竖向加速度峰值放大系数则呈现先增加后减小的规律,基本稳定在1.5以内。随着输入地震动强度的增大,水平加速度峰值放大系数与高程成正比例关系,非线性关系逐渐增强,竖向加速度峰值放大系数最大值位于距离底部H/3处向2H/3处转移(H为路基高度),在输入峰位加速度(PGA)为0.3g时,水平、竖向加速度峰值放大性均达到最强;随着输入地震动强度的增大,填料中峰值土压力强度逐渐增大,在输入波PGA为0.4g时,土压力强度达到最大,路基中心截面土压力强度随高程增加有先增加后减小的趋势,最大土压力逐渐由距离路基底部H/3向2H/3位置转移;在输入地震波PGA为0.05g时,路基表面、路基底部的土压力强度沿着路基体水平方向呈线性分布,前者离路基越远、土压力越大,后者则是基本不变。在输入地震波PGA为0.15g、0.30g、0.40g时,土压力强度在道砟边缘处最小,在路基中心下土压力强度其次,整体沿着路基体水平方向呈三角形分布;路基坡面中部和顶部的水平位移逐渐增大,前者小于后者,呈近似线性分布,且两者差值逐渐减小。在路基顶部位置,坡面上的位移与路基中心线顶部的位移差值随着输入地震动强度的增大,两者差值逐渐增大,最后区域稳定;地震波在路堤底部时主频集中在5~15 Hz,随着高程增加,路基对30~40 Hz频段有强烈的放大效应,在其余频段的影响不明显。

Taking the Beijing-Shanghai high-speed railway CRH380BL EMU as the prototype,a 1:10 ratio railway ballast track subgrade shaking table model test was carried out based on the law of similarity to analyze the acceleration,earth pressure and displacement response of the subgrade.The model is 9.6 m×3.5 m×1.0 m(length×width×height),including the train,ballasted track and subgrade part.Some findings are as follow.As the altitude increases,the amplification factor of peak horizontal acceleration increases gradually,and the value is basically stable between 1.0 and 2.5;while the amplification factor of peak vertical acceleration firstly increases and then decreases,and the value is basically stable within 1.5.As the input ground motion intensity increases,the amplification factor of the peak horizontal acceleration is directly proportional to the elevation,and the non-linear relationship is gradually strengthened.The maximum amplification factor of vertical peak acceleration is shifted from the bottom H/3 to 2 H/3 and the peak magnification of horizontal and vertical accelerations reach the maximum when the input seismic wave PGA is 0.3 g.As the input ground motion intensity increases,the peak earth pressure intensity in the filler increases gradually.When the input seismic wave PGA reaches 0.4 g,the earth pressure intensity reaches the maximum.The earth pressure intensity at the center section of the subgrade tends to increase firstly and then decrease with the increase of elevation,and the maximum earth pressure gradually shifts from H/3 to 2 H/3 at the bottom of the subgrade.When the input seismic wave PGA is 0.05 g,the earth pressure intensity on the subgrade surface and the subgrade bottom is linearly distributed along the horizontal direction of the subgrade.The farther the former is from the subgrade,the greater the earth pressure,and the latter is basically unchanged.When the input seismic wave PGA is 0.15 g,0.30 g and 0.40 g,the earth pressure intensity is the smallest at the edge of the ballast,followed by the earth pressure intensity at the center of the subgrade,and the earth pressure presents a triangular distribution along the horizontal direction of the subgrade;the horizontal displacement of the middle and top of the subgrade slope gradually increases,and the former is smaller than the latter,showing an approximately linear distribution and the gradual reduction in the difference between them.At the top of the subgrade,the difference between the displacement on the slope and that on the top of the center line of the subgrade increases gradually with the intensity of the input ground motion intensity,and the difference between both gradually increases,and the stable finally;When the seismic wave is at the bottom of the embankment,the main frequency is concentrated in 5-15 Hz.As the elevation increases,the subgrade has a strong amplification effect on the 30-40 Hz frequency band,but the influence on the remaining frequency bands is not significant.