有轨电车嵌入式轨道路基荷载动应力特性分析

掌握有轨电车交通荷载下路基动力响应特性是设计嵌入式轨道路基结构的关键技术前提.首先,考虑车体间铰接形式、轨道支承特点与路基阻尼影响,构建有轨电车-嵌入式轨道-土质路基耦合动力学模型;然后,以中国普通干线铁路轨道谱为激励,进行动力学仿真;最后,分析路基面承受车辆荷载特点,并讨论动应力放大系数的概率分布特征与沿深度衰减规律.研究表明：嵌入式轨道结构路基面动应力的幅值受轨道随机不平顺影响服从正态分布规律;在有轨电车轴重11 t、设计速度100 km/h、90%干线轨道谱条件下,路基面动应力放大系数服从正态分布N(1.008, 0.100²),超越概率30%的常遇动力系数为1.058,保证率为99.9%的极限动力系数为1.308;受路基材料阻尼影响,动应力放大系数沿深度线性衰减,阻尼增大,衰减趋势加剧;随着深度增加,动应力放大系数均值逐渐减小,由动力作用增大区略大于1过渡到动力作用减弱区小于1.

Analysis on Load Dynamic Stress Characteristics of Embedded Track Subgrade of Tram

Determining the dynamic response characteristics of a subgrade under tram traffic loads is a key technical prerequisite for the design of embedded rail roadbed structures. First, a tram-embedded track-soil subgrade coupling dynamics model is established by considering the articulation forms between the car bodies, track support conditions, and damping effect of the subgrade. Then, dynamics simulations are performed using the track irregularity PSD of the China railway (CR) as excitation. Finally, the vehicle load characteristics on the subgrade surface are analyzed and the probability distribution characteristics of the dynamic stress amplification factor and its decay law with depth are discussed. The results show that the dynamic stress amplitude on the embedded track subgrade surface is subject to a normal distribution resulting from random track irregularities. Under the conditions of a tram with an 11 t axle, a design speed of 100 km/h, and a 90% CR track spectrum, the dynamic stress amplification factor on the subgrade surface obeys a normal distribution N (1.008, 0.1002), the frequent dynamic factor with a 30% exceedance probability is 1.058, and the limit dynamic factor with a 99.9% guarantee rate is 1.308. Influenced by the damping of the subgrade material, the dynamic stress amplification factor decays linearly with depth, and when the damping increases, the decay trend accelerates. With increasing depth, the mean dynamic stress amplification factor gradually decreases, from the dynamic action increasing zone slightly greater than 1, and to the dynamic action weakening zone less than 1.