Test analysis of metro induced ground vibrations at interval

In-situ tests of metro induced ground vibrations were carried out at Dongdan-Jianguomen interval in Beijing, in order to study the law of metro induced ground vibrations. Vertical ground vibrations induced by the normal operation of metro and ground traffic were tested using a high sensitive acceleration sensor and 24-bit dynamic signal collection system. All 95 records of 354 times histories were transformed into 1/3 octave band frequency spectrum through Hanning window and linear average technology. The frequency domain data were averaged according to metro style, thereby obtaining the averaged 1/3 octave band frequency spectrum of both G style metro and S style metro. Analysis results show that the main factors influencing metro induced ground vibrations are distance and background vibration. There exists a joining frequency for ground vibrations. When smaller than the joining frequency, metro induced ground vibrations are mainly dominated by background vibration, while effect of distance is very weak. When bigger than the joining frequency, they are mainly dominated by distance, but the effect of background vibration is only inferior to the distance. Superposition of metro induced ground vibrations and ground traffic causes the response within 1-30 Hz to increase.