Case Studies of Liquefaction-Induced Damages to Two Pile-Supported River Bridges in China

Abstract

Pile-supported river bridges continue to collapse after most major earthquakes in the event of liquefaction. The identified failure mechanisms of piles in liquefied soil are (1) bending failure due to inertial loads of the superstructure and kinematic loads due to the lateral spreading of soil; (2) shear failure due to shear loads; (3) buckling instability failure due to vertical loads and associated imperfections; (4) settlement failure due to loss of effective stress in the liquefied zone; and (5) failure due to the effects related to elongation of the natural period of the piers (also referred to as dynamic failure). This paper revisits the collapse of Shengli Bridge (Tangshan, China) (due to the 1976 Tangshan earthquake) and Panshan Bridge (Panjin, China) (due to the 1975 Haicheng earthquake) based on the aforementioned failure mechanisms. It has been concluded that pile-supported bridges in liquefiable soil can collapse due to each of these five failure mechanisms or due to a suitable combination thereof. It is therefore quite imperative to take all the failure mechanisms into consideration when designing pile foundations in liquefiable soil. The simplified calculation procedure presented in this paper can also be used to carry out the design of bridge piles in liquefiable soil.