道砟抗破碎性能变化规律的冲击试验研究

Impact Test Study on the Change Law of Crushing Resistance of Ballast

道砟铺设于轨枕之下用于传递列车荷载,其抗破碎性能对于铁路的安全运营具有重要的影响。道砟在实际服役过程中会产生劣化,且雨水会显著改变其含水状态,该含水状态又会反作用于道砟,影响道砟的抗破碎性能。为研究劣化及劣化后饱和含水状态对道砟抗破碎性能影响规律,本文采用洛杉矶磨耗产生不同劣化程度的道砟,运用综合图像分析量化道砟劣化的颗粒形态特征变化,测量不同劣化程度道砟集料的饱和含水率,进而开展一系列不同劣化程度以及干燥、饱和两种含水状态道砟的落锤冲击荷载试验;分析劣化道砟集料颗粒破碎规律和永久变形特性,定义适用于劣化道砟集料的抗破碎性能指标,量化分析劣化道砟抗破碎性能变化规律。研究结果表明:随着劣化程度的增加,道砟颗粒形状系数和圆度增大,表面质地系数减小,形态逐渐圆润;细粒含量显著上升,级配更加均匀。在重复冲击荷载作用下,道砟集料的最大竖向变形呈现先减小后增大再减小的变化规律;相较于干燥道砟集料,饱和道砟集料竖向变形更大而破碎更少;干燥和饱和状态道砟的抗破碎性能指标分别从12.81和9.54下降至4.44和3.92,下降速度呈现先快后慢的规律,说明道砟劣化和含水状态对于道砟的抗破碎性能影响是显著且不能忽视的,应在铁路运维过程中密切关注。

The ballast is laid under the sleepers to transmit the load of the train,and its anti-crushing performance has an important impact on the safe operation of the railway.The ballast will be degraded in the actual service process,and rain water will significantly change its water content.This water content will react on the ballast and affect the crushing resistance of the ballast.In order to study the influence of deterioration and saturated water content state after deterioration on the crushing resistance of ballast,this paper adopts ballast of different degrees of deterioration generated by Los Angeles abrasion,uses comprehensive image analysis to quantify the change of particle morphology characteristics of ballast deterioration,and measures the saturated moisture content of ballast aggregates of different degrees of deterioration.Furthermore,a series of drop hammer impact tests of different deterioration degrees and dry and saturated water-bearing states were carried out.The particle breakage law and permanent deformation characteristics of degraded ballast aggregate was analyzed,the anti-crushing performance index suitable for degraded ballast aggregate was defined,and the variation law of broken performance of degraded ballast aggregate was quantitatively analyzed.The results show that with the increase of deterioration degree,the shape coefficient and roundness of ballast particles increase,the surface texture coefficient decreases,and the shape is gradually rounded.The fine grain content increased significantly and the gradation became more uniform.Under the action of repeated impact load,the maximum vertical deformation of Ballast aggregate decreases first,then increases and then decreases.Compared with dry ballast aggregate,the vertical deformation of saturated ballast aggregate is larger and the crushing is less;The anti-crushing performance indexes of ballast in dry and saturated states decreased from 12.82 and 9.55 to 4.45 and 3.95,respectively,and the decreasing speed showed a law of first fast and then slow,indicating that the impact of deterioration and water content cut on anti-crushing performance of ballast is significant and cannot be ignored,which should be paid close attention to in the process of railway operation and maintenance.