CRTSⅡ型板式轨道的纵连特征对板下离缝的影响研究

Research on Under-Slab Gap Caused by Longitudinal Connection Characteristics of CRTSⅡ Slab Track

针对CRTSⅡ型板式轨道板下离缝问题,建立包括钢筋、预裂缝等轨道板主要特征的有限元模型,分析轨道板在整体升温40℃和温度梯度-50~100℃/m作用下, CRTSⅡ型板的纵连特征造成的板间接缝初始受力不均匀对板下离缝和钢轨不平顺的影响。结果表明:若宽接缝硬化时窄接缝存在较大的初始压应力,板温较高时窄接缝被挤碎的概率大幅增加;对板下离缝和钢轨不平顺影响最大的是窄接缝被挤碎,其次是仅宽接缝承力,而窄接缝处存在一定的初始压应力对其影响较小;由接缝处初始受力不均匀引起的板下离缝值虽然较小(增加0.5~1 mm),却会大幅增加运营维护后期砂浆层离缝的维修工作量;施工中应采取措施减小宽、窄接缝硬化时的板温差,使宽接缝硬化时的板温T_k高于窄接缝硬化时的板温Tz不超过10℃。

Aiming at the problem of the under-slab gap of CRTSⅡSlab track, the element model, which is characterized by such main features of track slab as rebars, pre-splitting cracks and so on, is established. As the temperature of track slab increases 40 ℃ and at the temperature gradient of-50~100 ℃/m, the impacts on both under-slab gap and rail irregularity by initially uneven loading of joints caused by the longitudinal connection characteristic ofⅡslab are analyzed. The results show that: if the initial compression stress of narrow joints is larger when wide joints are hardened, the possibility of the crush of narrow joints can be increased greatly when the temperature of track slab is high, the biggest impact on both under-slab gap and rail irregularity is the crush of narrow joints;secondly when wide joints only bear the force, the impact caused by initial compression stress of narrow joints is very small;although the value of the under track slab gap caused by the uneven initial stresses of joints is small(increased by 0.5~1 mm), it will greatly increase the maintenance work of the mortar layer during later operation and maintenance period. It is suggested to take measures to reduce the difference of track slab temperature when narrow joints and wide joints are harden so as to maintain the slab temperature of hardened wide joints not higher than that of the hardened narrow joints by 10 ℃.