热荷载作用下高速铁路纵连式轨道板屈曲上拱机理研究

Aiming at the problem that, on high speed railway, buckling of longitudinal continuous track slab has adverse effect on stability and safety of high speed train, a basic theory research of stability of longitudinal continuous track slab under thermal load is carried out. This project focuses on the mechanism of buckling of the longitudinal continuous track slab due to the excessive axial thermal pressure. It mainly includes that, firstly, mechanical models of buckling of straight and hinged longitudinal continuous track slab are established. Based on the mechanical models, equilibrium and stability equations of longitudinal continuous track slab under thermal load are derived by the energy method which comes from elastic theory of Timoshenko. Secondly, curved surface function and analytical formula of axial thermal pressure are deduced by perturbation method and critical axial thermal pressure is obtained when longitudinal continuous track slab buckling. Then, the safe temperature increase to prevent buckling is proposed after the relational curve of temperature increase and maximum buckling displacement being drawn out. Thirdly, the shear resistance is obtained by carrying out an experimental study, and then, the mechanism of shear resistance acting on thermal buckling of longitudinal continuous track slab is revealed by discussing the relationship between shear resistance and safe temperature increase. Finally, by analyzing the upper and lower boundary of safe temperature increase, the reasonable value of temperature increase of joint construction is proposed.

针对热荷载作用下纵连式轨道板屈曲上拱给高速行车稳定性和安全性带来不利影响的问题。本项目围绕高速铁路纵连式轨道板在整体温升荷载作用下的稳定问题开展基础理论研究，重点探索纵连式轨道板因轴向热压力过大造成屈曲上拱的机理。主要包括：建立平直和铰接的纵连式轨道板屈曲上拱力学模型，并基于铁摩辛柯的弹性理论，采用能量法推导热荷载作用下纵连式轨道板的平衡方程和稳定方程；采用摄动法求解稳定平衡方程，推演出纵连式轨道板屈曲后平衡的挠曲面函数和轴向热压力解析式，求得屈曲上拱的临界热压力，绘制出温度增量和最大上拱位移的关系曲线，并提出防止纵连式轨道板屈曲上拱的安全温度增量；建立模型试验，对轨道板底的剪切阻力进行试验研究，结合稳定平衡方程求得剪切阻力与安全温度增量之间的关系曲线，揭示剪切阻力对纵连式轨道板热屈曲上拱的影响；在分析安全温度增量上下限值的基础上，提出轨道板间接缝施工的合理温度增量建议值。

CRTSⅡ型板式无砟轨道结构是一种纵向连续结构，大规模应用于我国高速铁路建设中。通过对多条CRTSⅡ型板式无砟轨道线路的现场调研发现，个别区段出现不同程度的轨道结构伤损，其中以某病害段的纵连式轨道板屈曲上拱现象最为严重，最大上拱量位于接缝处，达到20mm，导致高速列车限速为200km/h。本课题重点关注板式无砟轨道层间界面的力学行为，向前推进，发现问题、不断深入，探索层间力学薄弱面在热荷载作用下纵连式轨道板因轴向热压力过大导致的屈曲上拱机理。根据对平直的纵连式轨道板在热荷载作用下必然出现微小伤损现象的观察，创新性地提出以铰接接头表征轨道板间接缝的微小伤损思路，建立平直和铰接的纵连式轨道板屈曲上拱力学模型，作为深入研究的基础；根据平直和铰接的纵连式轨道板屈曲上拱力学模型，并基于铁摩辛柯的弹性理论，采用能量法推导出屈曲上拱后平衡状态下的解析公式，获得最大上拱位移与整体温升和轴向热压力的关系曲线，得到防止纵连式轨道板屈曲上拱的安全温度增量；利用实尺和缩尺模型试验，获得纵连式轨道结构层间界面关键参数，并结合推导出的考虑层间界面损伤情况下的无砟轨道竖向、水平推板试验解析解及有限元分析，揭示层间界面关键参数对层间变形协调能力的影响，为研究数据的合理性及机理探究提供坚实基础；探明层间界面离缝模式，并确定层间损伤及离缝的判断准则，建立板式无砟轨道层间损伤至离缝的演化机制；揭示轨道板在“单元→纵连（未服役）→服役”全过程中的离缝发生、发展过程及演化机理；进一步建立含轨道周期性不平顺与单元轨道板正温度梯度翘曲变形的车辆-轨道系统动力学模型，分析正温度梯度及自重导致的轨道板静力变形趋势及高速列车作用下的轨道板层间脱空演化规律。上述在基础理论、仿真分析、模型试验三方面的研究成果是对高速铁路纵连式轨道板热屈曲上拱机理认知的推进和完善，是进一步保障高速列车安全性、舒适性的坚实基础。研究过程中发现并提炼了一些新的问题，值得今后继续深入。