Shaking table test study of large-scale (1/15) nuclear containment vessel supported by pile group foundation in a layered ground

This paper investigated the seismic response of nuclear containment vessel supported by pile group foundation in a non-rock site through a series of large-scale shaking table tests. The test model was 1/15 scaled nuclear containment vessel (outer diameter 2.96 m, height 5.38 m) supported by a pile group foundation, which was fixed at the bottom of the newly developed large-scale laminar soil box (5 m × 5 m × 2 m). The pile group foundation was modeled by 19 piles with diameter of 0.2 m and height of 1.5 m, and the layered ground was represented by 0.75 m thickness sand layer over 1.05 m thickness silty clay layer. The tests were conducted at the National Facility for Earthquake Engineering Simulation (NFEES) of Tianjin University and the input motions included the RG 1.60, safety evaluation wave, and Chi-Chi wave with peak accelerations ranging from 0.1g to 1.0g. The failure phenomenon, dynamic characteristics, acceleration, displacement, and strain responses were recorded and analyzed. Findings reveal that the containment vessel maintains its integrity even under loading cases exceeding safe-shutdown earthquake (SL-2). The pile group foundation exhibits a seismic resistance effect on the containment vessel, compared with the rigid foundation. The pile group foundation sustains significant damage at the pile heads. Notably, the pile heads on the outer ring experience approximately 20 % higher bending moments than those on the inner ring. Under three-directional (3D) loading, the containment vessel exhibits an approximately 20 % rise in peak concrete tensile strain and a 50 % elevation in peak acceleration amplification factor compared with one-directional (1D) loading. The results indicate that the pile group foundation can serve as an effective and reliable foundation for nuclear containment vessel constructed on complex non-rock sites.