铁路下穿式结构施工受轮轨作用力的影响分析

针对既有线下隧道施工引起的轨道变形而加大轮轨作用力的情况,以在建地铁南京站为例,通过弹塑性动力有限元法分析行车动荷载对轨下施工中隧道的影响,同时分析了由于轨下构筑物的存在对路基内动应力的影响。分析中采用轨枕—道床全支承模式,土体采用理想弹塑性动本构模型,分别考虑了轨道不加固情况和采用D24型便梁加固两种情况,计算得到了隧道上覆土体及隧道初衬结构的动力响应。对两种情况的计算结果进行比较,表明对线路采取便梁加固后,隧道拱部土层的附加动应力减小了76%,而初衬的附加动应力减小了58%,便梁加固时减小了列车动荷载对施工期隧道的影响,有利于初期支护的施工;轨下构筑物的存在将减弱列车动应力往深层传递的衰减,在既有线路的地下构筑物施工中应引起重视。

Dynamic Analysis of Wheel/Rail Interaction During Construction of Tunnel under Railway

In consideration of the increased force brought about by the deformation of track due to the excavation of tunnel, taking the subway station of Nanjing railway station as an example, the influence of wheel/rail interaction on tunnel construction is analyzed with the elastic-plastic finite element method. At the same time, the influence to dynamic stress in subgrade is also analyzed because it is a tunnel under railway. In the analysis, the full support mode of sleeper-ballast and the ideal elastic-plastic soil dynamic model of the soil condition are adopted. The two instances of the unreinforced track and reinforced track by D24 temporary steel beam are considered. The dynamic response of the covered soil and the initial lining of the tunnel are obtained. The two calculation results are compared, indicating that the influence of additional train force acting on the arch soil is decreased by 76% when the temporary steel beam is adopted and that on the initial lining by 58%. Since the temporary steel beam reinforcement helps reduce the impact of the train dynamic loading on tunnel under construction, it facilitates the initial lining work. The under-track structure impedes the transmission of the train dynamic force further down, which should call the attention of builds structures under rail on the existing railway.