Numerical simulation of land subsidence caused by subway train vibration using PFC

Subsidence induced by human activity and urbanization is distributed in an area or along a line. In Shanghai, China, land subsidence is distributed along the belt near a subway line. The subsidence is caused by train vibration as well as regional land subsidence and other engineering activity. In order to figure out the mechanical response of the tunnel surroundings, the PFC2D software based on a discrete element method is introduced to simulate a section of the metro tunnel. The linear contact bond model was employed to reflect the characteristics of clay. Based on the analysis of stress and settlement caused by dynamic cyclic loading, the mechanical response law and subsidence mechanism were investigated. In addition, the influence of frequency on settlement was also analyzed: the greater the frequency, the more particles were rearranged and the larger the settlement. The fraction of sliding contacts was introduced to explain this phenomenon. The results can be used to understand, predict and control land subsidence to protect the geological environment.