铁路重载运输条件下钢筋混凝土涵洞受力特征试验研究

Mechanical Behavior of Reinforced Concrete Culvert under Railway Heavy Haul Transport Condition

为掌握铁路既有线钢筋混凝土涵洞实际的受力特征,评估其对重载运输的适应性,理论分析涵洞活载储备量以及货车参数、冲击作用、疲劳荷载对涵洞受力的影响;通过某重载线路的大轴重列车试验,测试大轴重试验列车和运营列车通过时钢筋混凝土涵洞的静、动力响应。结果表明:30t轴重货车对涵洞的作用效应超过运营列车;大轴重列车通过时,理论上小跨度涵洞的活载储备量明显不足,但实测状态良好涵洞的受力水平较低,仍具备一定的承载潜力;涵洞跨中挠度、钢筋应变与大轴重货车的轴重、邻轴距直接相关,而与列车运行速度、货车长度关系较小;实测涵顶填土厚度大于1.0m的涵洞仍受到活载的竖向冲击作用,但动力系数并未随着货车轴重的增加而明显增加,且实测列车活载在涵顶填土中的扩散范围大于按现行铁路规范计算的结果。需要对铁路涵洞动力系数、荷载分布等的计算理论开展进一步研究,以使其进一步地完善;在既有线上开行大轴重列车之前,应对涵洞进行综合评估,以确定其合理的改造范围。

In order to understand the actual mechanical behavior of reinforced concrete culverts on the existing lines and assess the adaptability of culverts to heavy haul transport, the influence caused by the live load reserve of culvert, the parameters of freight car, impact action and fatigue load was theoretically analyzed. A test of heavy axle load trairf was carried out on a heavy haul railway to obtain the static and dynamic response of reinforced concrete culverts under the loading of heavy axle load test trains and in- service trains. Results showed that the effect of the freight car with 30 t axle load was greater than that of in-service trains on the culverts. In theory, the live load reserve of culvert with small span was not enough obviously when heavy axle load train passed. But the actual stress level of culverts under good condition was lower, which still had a certain amount of potential load bearing capacity. The mid-span deflection and reinforcement strain of culvert were directly related to the axle load of heavy axle load train and adjacent wheel base, while had less relationship with train running speed and the length of freight car. The culverts were still impacted vertically by live load effect when the measured depth of backfill on the top of culvert was greater than 1.0 m, but the dynamic coefficient was not increased significantly with the increase of the axle load of freight car. The measured distribution area of live load in the backfill was greater than the results calculated according to the current railway code. Therefore, further research on dynamic coefficient and load distribution should be done and perfected. Before the operation of heavy axle load train on exist- ing lines, comprehensive evaluation should be performed for the culverts to determine the range of rein- forcement and reconstruction.