Experimental study on dynamic response of rock tunnel subjected to train moving load

Abstract

With the rapid development of transportation engineering, it is increasingly common for railways to closely pass over tunnels. The tunnels might be suffered from damage and destruction under the dynamic loads generated by trains moving on railways, which can in turn threaten the safety of the upper railways. Therefore, it is essential to well understand the dynamic response of tunnels subjected to the upper train moving load. However, there is currently a lack of relevant research on this topic, especially regarding model experiments. To investigate the dynamic response of tunnels subjected to train moving load, physical model experiments were carried out on the train-rail-bridge-shaking table test system, where train moving load was applied through moving of a model train along model tracks. The testing results showed that the train moving speed (vtr) significantly impacts the dynamic response of the tunnel and the surrounding rock mass. Except for the peak particle velocity (PPA) at tunnel vault, the PPAs at other locations and the vibration dominant frequency (f0) at all locations increase as the train moving speed increase. The average PPAs at tunnel spandrels undergo more significant changes compared to the PPAs at tunnel vault, tunnel invert, and inside the surrounding rock mass when the vtr increases. With the exception of some special cases, the average PPAs on tunnel spandrels are generally less than that on the tunnel vault and greater than that on the tunnel invert. As vtr increases, the average f0 on tunnel wall changes more obviously compared to average f0 inside the surrounding rock mass. When the vtr exceeds 10.54 m/s, corresponding to the prototype train moving speed of 120 km/h, the average f0 on tunnel wall are noticeably larger than those inside the surrounding rock. The high coefficients of determination obtained from the nonlinear regression analysis indicates a power relationship between the PPA and vtr, while the f0 shows an exponential association with vtr. The findings of this study hold great importance in ensuring the safe operation of tunnels and railways.