Abstract: To study the influence of the underground tubular structure on the seismic subsidence of shallow raft foundations in the soft soil site, a method for analyzing the seismic subsidence of the shallow raft foundation in soft soil was established based on the FLAC3D finite difference analysis platform and vibration softening model. By comparing the simulated and measured values of seismic subsidence and damage of typical building foundations in soft soil of Tanggu Port in Tianjin during 1976 Tangshan earthquake, the rationality of the proposed method was verified. Numerical simulation was carried out for analyzing the influence of different burial conditions and cross-sectional dimensions of square-sectional (for example) underground tubular structures on seismic subsidence of shallow raft foundation. Results show that the underground tubular structure has a more significant impact on the seismic subsidence of the superstructure with a lighter self-weight, affecting the design and construction of workshop structure. The seismic subsidence decreases with the increase of the relative size of the underground tubular structure, and tends to be steady after it exceeds the width of the foundation. Seismic subsidence increases with the increase of the burial depth of the underground tubular structure, and eventually tends to be the result without underground tubular structures. The seismic subsidence initially increases with the increase of the burial distance between the underground tubular structure and building, and decreases afterwards. In terms of seismic subsidence control, the distance from the underground tubular structure to the existing building needs to be controlled.

Key words: soft clay seismic subsidence, vibration-induced softening model, shallow raft foundation, underground tubular structure, FLAC3D numerical model