Seismic Performance of Bridge Pile Foundations in Karst Areas

The current bridge pile foundation design specifications in China provide only general principles for karst areas and do not provide a method to calculate the safe cave roof thickness or the vertical displacement of the pile foundation. Additionally, previous studies have not adequately considered the interaction between bridge pile foundations and caves under seismic loads. Therefore, the national design code does not provide an effective basis or reference for calculating the seismic performance of pile foundations in complex karst areas. This study establishes a numerical model of the pile-foundation-cave interaction system. The dynamic responses of the pile foundation displacement, stress, plastic strain, and bending moment subject to ground motion after inversion are analyzed. The effects of different factors on the safe cave roof thickness and vertical displacement of the pile foundation are investigated, and multiple regression models are obtained and optimized. Finally, parametric sensitivity analysis is conducted for each influencing factor. The results demonstrate that the safe cave roof thickness is between 2.5[Formula: see text]m and 5.7[Formula: see text]m and the vertical displacement is between 0.0075[Formula: see text]m and 0.06[Formula: see text]m. The sensitivity factors for the safe cave roof thickness in the case where the cavern shape is simplified to a rectangle, in descending order, are the rock cohesion, pile diameter, initial load at the top of the pile, cave size, and the peak value of ground motion. The sensitivity factors for the vertical displacement of the pile foundation, in descending order, are the peak value of ground motion, initial load at the top of the pile, cave size, and pile diameter. The conclusions provide valuable insights into the design optimization of rock-socketed pile foundations in karst regions.