Centrifuge shaking table study on the hydrodynamic effects on a pile foundation bridge pier in soft soil under earthquakes

Abstract

Previous investigations have shown that water-pier interaction has a considerable effect on the seismic response of bridge piers in deep water. However, most of those studies assumed that the foundation is rigid and there are few studies on the hydrodynamic effects on the piers considering soil-structure interaction under earthquakes. To investigate the hydrodynamic effects on bridge piers built on soft ground, series of centrifuge shaking table tests were conducted. In the tests, a pile foundation bridge pier was scaled down by a factor of 1:50. The height of the pier was 340 mm, and the length of the pile was 200 mm. The pile foundation pier was installed in soft soil contained in a laminar shear box. Three depths of water, i.e., no water, 150 mm and 300 mm, were considered. The dynamic responses of pier displacement, acceleration and bending moment of the pier and piles, hydrodynamic pressure on the pier, soil pressure on the pile and pore-water pressure in the soil were measured. The results show that the natural frequency of the pier decreases as the water depth increases, and the displacement of the pier with a water depth of 300mm is significantly reduced in comparison with that of no water. However, water increases the acceleration and bending moment of the pier and the pile. The results also show that as the water depth increases, the hydrodynamic pressure acting on the pier and the dynamic soil pressure exerted on the pile both increase under earthquakes.