Performance of rubber-concrete composite periodic barriers applied in attenuating ground vibrations induced by metro trains

Recently, the use of periodic vibration isolation barriers (PVIBs) has emerged as a significant method for attenuating environmental vibrations along the propagation path. Previous studies have indicated that periodic infilled trenches and piles can effectively isolate low-frequency surface waves. However, a considerable number of these periodic structures require full-size shipments or cast-in-place construction, thus increasing the shipment difficulty or construction period. In addition, few experimental studies have reported on the performance of PVIBs under underground excitation. To solve these problems, this study proposes a novel periodic composite rubber-concrete barrier (PCRCB) with prefabricated assembly characteristics. A laboratory test was performed, in which the calculated frequency band gap (FBG) and attenuation zones of the optimised PCRCB were validated under ground-borne and underground hammering excitations. Then, a numerical model was developed to analyse the vibration mitigation effect of the optimised PCRCB considering the metro train loads. The results of the laboratory study demonstrated that the depth of the impact load affects ground vibration attenuation. The optimised PCRCB has been proven to exhibit good vibration isolation performance. The results of the numerical study demonstrate that the vibration mitigation effect of the PCRCB on the ground surface is good under underground metro train loads. The insertion loss (IL) increases, but its value is less than 2 dB, with the ratio of burial depth to tunnel base depth increases from 1 to 2 times. Accordingly, the ratio of the burial depth to the tunnel base depth is recommended to be 1 in the vibration isolation project of an underground metro train.