Liquefiable Concrete Tunnel-Sand-Pile Interaction Response Under Seismic Excitations

This paper presents the concrete tunnel-sand-pile interaction (TSPI) phenomenon in liquefiable sand considering various relative densities and seismic excitations. The novel shake table test for the TSPI model was performed to evaluate the excess pore pressure ratio (EPPR) surrounding the tunnel body and interactive tunnel and pile moments. The relative densities are taken to be 27, 41, and 55% in the local sand of Bangladesh. Similarly, the peak ground acceleration (PGA) of the Kobe and Loma Prieta earthquakes are considered to be 0.05, 0.10, 0.15, and 0.20 g. The shake table was calibrated based on similar variations of the input and output PGA. The 3D finite element concrete TSPI model has been performed by Plaxis considering the UBC3D-PLM (two yield surfaces consisting of kinematic hardening rules) constitutive model of sand. Therefore, experimental and numerical results vary closely, which may inform the possibility of the application of the concrete TSPI model on a large scale. The maximum SRSS (Square Root Sum of Squares) tunnel moment has been found to be 18.7 kN-m from the experimental results for 27% relative density of the Kobe earthquake with a PGA of 0.15 g. Also, the maximum SRSS moments of front and rear piles vary (0.10-0.14) % of the tunnel moment. So, the tunnel moment always shows a higher value in liquefiable ground based on the experimental results because of the larger volume and stiffness than a series of piles. However, the present study may be enhanced in the future by varying geometric properties.