高铁隧道内地下水作用下双块式无砟轨道道床板裂缝扩展研究

Research on Crack Growth of Double-block Ballastless Track Roadbed Slab Under the Action of Groundwater in High-speed Railway Tunnel

针对我国高速铁路隧道内CRTSⅠ型双块式无砟轨道施工阶段道床板开裂问题,运用有限元软件建立隧道-无砟轨道三维实体模型,研究地下水作用下隧道内无砟轨道各结构层位移隆起变化规律,并结合FRANC3D软件,在道床板结构受力最不利位置插入不同形状的预制三维裂缝,分析水压、裂缝长度对道床板裂缝扩展的影响。研究结果表明:(1)三角形荷载作用相较于均布荷载作用时,道床板位移隆起量虽有所减小,但地下水压的反复作用始终会影响轨道结构的平顺性,甚至导致道床板与仰拱填充间出现离缝;(2)裂缝长度是裂缝失稳扩展的控制因素,在排水系统完全堵塞时,建议将裂缝长度控制在200 mm以内;(3)水压为裂缝扩展的关键影响因素,同等条件下水压越大,道床板裂缝扩展越迅速,均布荷载下道床板裂缝尖端应力强度因子是对应三角形荷载下的1.2~1.4倍。

Aiming at the problem of bed plate cracking during the construction of CRTSⅠ double-block ballastless track in high-speed railway tunnels in China,a three-dimensional solid model of tunnel and ballastless track is established by using finite element software.The change law of displacement and uplift of each structure layer of ballastless track in tunnel under the action of groundwater is studied.Combined with FRANC3D software,prefabricated three-dimensional cracks of different shapes are inserted into the most stressed position of the roadbed slab structure,and the influence of water pressure and crack length on the crack growth of the roadbed slab is analyzed.The results show that:(1) Although the displacement uplift of the roadbed slab is somewhat decreased when the triangular load is applied compared with the uniform load,the repeated action of underground water pressure will always affect the track structure smoothness,and even lead to the separation of the track bed plate and the invert arch filling.(2) Crack length is the controlling factor of crack instability and growth.When the drainage system is completely blocked,it is recommended that the crack length be controlled within 200 mm.(3) Water pressure is the key influencing factor of crack growth.Under the same conditions,the larger the water pressure is,the more rapid the crack growth will be.The stress intensity factor at the tip of the crack of the roadbed slab under uniform load is 1.2~1.4 times of that under the corresponding triangular load.