重载铁路隧道内无砟轨道力学特性研究

Study on Mechanical Characteristics of Ballastless Track in Tunnel for Heavy Haul Railway

鉴于无砟轨道诸多优点,在重载铁路隧道内铺设无砟轨道是一种较好的选择,而国内外对于隧道内无砟轨道力学特性、选型设计的研究尚较少见。本文基于有限元理论建立了重载铁路隧道内无砟轨道空间耦合实体分析模型,系统分析了四种无砟轨道型式在车辆荷载、隧道口温度梯度作用下的力学特性,并对双块式无砟轨道轨枕块—道床结合面粘结强度问题进行了探讨。主要结论如下:(1)隧道口温度梯度作用下,CRTSⅠ型板式轨道存在诸多问题:1)钢轨、轨道板、底座板的纵向位移过大;2)轨道板易翘曲变形,带动钢轨变形致其纵向应力增大;3)轨道板胀缩挤压道床板导致道床板局部应力过大;4)凸台剪应力过大易被剪坏。故不推荐在重载铁路隧道中使用该种轨道型式。(2)CRTSⅠ型双块式无砟轨道对轨道结构限位能力较好,但轨枕块—道床结合面较为薄弱,不足以抵抗25t以上轴重车辆所产生的荷载;通过轨枕块侧面凿毛、植入外伸钢筋等方式可提高结合面的强度。故不推荐使用未经改进的CRTSⅠ型双块式轨道。(3)弹性支承块式和弹性长枕式无砟轨道中橡胶套靴的存在可以较好地保护轨枕结构,显著减小其纵向应力;同时套靴隔离了轨枕结构和道床,避免了类似CRTSI型双块式轨道中轨枕—道床结合面薄弱引起的一系列病害;但是这两种无砟轨道对钢轨及轨枕结构的垂横向限位能力略显不足。

In view of many advantages of ballastless track, it is a good choice to pave ballastless track in tunnel for heavy haul railway.But there are few researches on the mechanical characteristics and design of ballastless track in tunnel. In this paper, spatial coupling solid model of ballastless track in tunnel for heavy haul railway is established based on the finite element theory. The mechanical characteristics of four types of ballastless tracks are analyzed under vehicle loads and temperature gradient, and the issue of bonding strength of sleeper-ballast bed interface for CRTSI bi-block track is discussed. The following conclusions are drawn：①a lot of problems are exposed in CRTSIslab track under the temperature gradient of tunnel entrance： 1） longitudinal displacements of rail, track slab and bottom slab are overlarge;2） bucking deformation of track slab is easy to occur, which causes the deformation of rail and increases its longitudinal stress; 3） the expansion and shrinkage of track slab cause overlarge stress of bottom slab; 4） the bulgy abutment bears overlarge shear stress and is proneto be damaged. Therefore, CRTSI slab track is not recommended in tunnel of heavy haul railway. ②CRTSI bi-block track has good performance in keeping the position of track structure. But the sleeper-ballast bed interface is too weak to bear the loads caused by vehicleof 25t or larger axle load. The bonding strength of interface can be enhanced by some measures like roughening the surface of sleeper andimplanting steel bars in sleeper. Hence the unimproved CRTSI bi-block track is not recommended. ③For elastic bearing block track andelastic long sleeper track, the rubber boot can effectively protect the sleeper structure and decrease its longitudinal stress. Besides, therubber boot separates the sleeper from ballast bed, which avoids some damages caused by the weakness of sleeper-ballast bed interface likeCRTSI bi-block track. However, there is a slight deficiency in limiting the position of rail and sleeper for these two types of tracks.