深埋式桩板结构桥-隧过渡段动力响应特征分析

为了解深埋式桩板结构桥-隧过渡段的动力特性及过渡性能，在沪昆高铁某工点过渡区（含隧道口、过渡段及桥台）开展现场动力响应测试，分析不同车型、车速及行车方向等工况下过渡区的动力响应分布规律；并建立考虑车辆-轨道-路基耦合振动数值模型，研究过渡区的线路平顺性及桩板结构过渡段的动应力分布. 研究结果表明:不同车型列车激励下，过渡区振动加速度及动位移有效值的最大值分别为0.85 m/s2、0.034 mm，过渡段的振动水平要比隧道及桥台的更低；过渡段动力响应有效值随车速增大而增大，其增幅比隧道与桥台的更小；行车方向对过渡段与桥台连接区域的动力响应影响较大，对其他断面影响微弱；列车以300 km/h车速经过该过渡区时，过渡区钢轨挠度最大变化率约为0.149 mm/m，车体竖向加速度最大值为0.74 m/s2；桩板结构的存在能够将列车荷载传递至深部地基，使浅层地基土体承受的动力作用降低. 

Dynamic Response Characteristics of Bridge-Tunnel Transition Section with Deep Buried Pile-Plank Structures

To understand the dynamic characteristics and performances of bridge-tunnel transition sections with deep buried pile-plank structures (DBPPS), dynamic field tests were performed on a transition zone including a tunnel entrance, a transition section and a abutment in the Shanghai—Kunming high-speed railway to investigate its dynamic response distributions under running trains with different train types, speeds and driving directions. A numerical model considering vehicle-track-subgrade coupled interaction was then established to study the railway line smoothness along the transition zone and the vertical dynamic stress distribution of the DBPPS subgrade. Results show that under the train loads with different train types, the maximum effective values of acceleration and displacement along the transition zone are 0.85 m/s2 and 0.034 mm, respectively. The vibration level of the transition section is lower than that of the tunnel and the abutment. The effective values of dynamic response in the transition section increase with the increasing train speed, and its increase rate is smaller than that of the tunnel and the abutment. The driving directions have a significant influence on the dynamic responses in the connection between the transition section and the abutment, but have a weak influence on other sections. When the train passes through the transition zone at a speed of 300 km/h, the maximum change rate of rail deflection is approximately 0.149 mm/m, and the maximum vertical acceleration of the carbody is 0.74 m/s2. The pile-plank structure can transfer the train load to the deep foundation and reduce the dynamic effect on shallow soil of the foundation.