Experimental study on ground vibration induced by double-line subway trains and road traffic

Rail transit and highway transportation have flourished in the process of urbanization by virtue of their respective advantages, facilitating people’s travel but also producing harmful environmental vibrations. For an accurate analysis of source characteristics and propagation laws of train-induced vibrations, a field measurement was carried out in Shenzhen, China, where a double-line subway passes directly under the main urban road. The rail acceleration at the straight track and the point of fixed frog in the tunnel as well as ground vibrations caused by double-line subway and road traffic under different operating conditions were measured. A special attention was paid to the vibration response of each measurement point on the ground when the subway train and road vehicles passed through simultaneously. Measurement shows that horizontal acceleration cannot be ignored in the area close to the subway line, and vibration amplification phenomenon exists in the free field, due to the difference of the local geological conditions that leads to different vibration levels. Compared with the ground vibration caused by only the near-line train passage, when a near-line train passes the test section with a far-line train is about to arrive, the ground vibration intensifies in the frequency band of 50–63 Hz. When a far-line train passes the test section with a near-line train just left, the vibration level of each measuring point shows different degrees of reduction in various frequency bands, and reduction amount of horizontal acceleration in the frequency 10–16 Hz reaches 12 dB. Ground vibration aggravates significantly when the near-line train and bus pass simultaneously, the horizontal vibration is more sensitive to the superposition influence of road traffic. The measured data can not only guide the work of vibration environment assessment in the stage of subway design and planning but also can validate possible numerical models for predicting train-induced vibrations.