无砟轨道混凝土弯曲疲劳性能提升方法及其机理

Improving Methods and Mechanism of Bending Fatigue Performance of Ballastless Track Concrete

为提升高速铁路无砟轨道的疲劳寿命,以直接承受列车高频疲劳荷载的无砟轨道混凝土为研究对象,通过Weibull分布函数对弯曲疲劳寿命进行统计分析,采用图像分析、孔结构分析等手段,对提高强度、乳液改性及增韧三种改性方法分析混凝土弯曲疲劳性能的提升效果及其提升机理。结果表明,与基准C60相比,C80混凝土疲劳寿命提升12.7%~29.7%,其原因是混凝土孔隙率降低6.9%,疲劳破坏前能量吸收能力提高40.3%,但峰值应变降低了7%,耗散能量的占比下降到9%,表明混凝土脆性增加限制其疲劳性能提升效果;聚合物改性混凝土疲劳寿命提升21.0%~57.5%,疲劳破坏时断面裂纹未完全连通且宽度仅为0.7 mm,其原因是聚合物能够填充混凝土的孔隙、改善浆体韧性、增加浆体与骨料的黏结,使聚合物改性混凝土变形能力与吸能能力提升27.0%和74.2%;玻璃纤维混凝土疲劳寿命提升18.6%~41.1%,疲劳破坏形态证明玻璃纤维的桥接与应力分散作用是其疲劳性能提升的主要原因。

In order to improve the fatigue life of ballastless track concrete within the designed service life,in this paper,ballastless track concrete bearing the high-frequency fatigue load of trains was studied,and the bending fatigue life was statistically analyzed by Weibull distribution function.The effects and mechanism of strength grade,polymer-modified technology,and alkali resistant glass fiber bridging on the fatigue resistance of concrete were investigated,by means of image analysis and pore structure analysis.The results show that compared with the benchmark C60 concrete,the fatigue life of C80 concrete is increased by 12.7%~29.7%,due to a 6.9%decrease in concrete porosity and a 40.3%increase in energy absorption capacity before fatigue failure.However,the peak strain is reduced by 7%,with the proportion of dissipated energy being reduced to 9%,indicating that the increase in concrete brittleness affects the further improvement of its fatigue performance.The fatigue life of polymer-modified concrete is increased by 21.0%~57.5%,with section cracks being not completely connected during fatigue failure,with the width of only 0.7 mm.The reason is that polymers can fill the pores of concrete,improve the toughness of the grout and the bonding performance between grout and aggregate,so that the deformation and energy absorption capacity of polymer modified concrete are increased by 27.0%and 74.2%.The fatigue life of glass fiber reinforced concrete is increased by 18.6%~41.1%,and the fatigue failure mode proves that the bridging and stress dispersion effects of glass fiber are the main reason for the improvement of its fatigue life.