Load-bearing performance of caisson-bored pile composite anchorage foundation for long-span suspension bridge: 1-g model tests

The caisson-bored pile composite anchorage (CBPCA) foundation, as a new form of gravity-type foundation for long-span suspension bridges, has been recently proposed and numerically studied by the authors. In this paper, the bearing performance of the CBPCA foundation under different working loads is further investigated by performing a series of 1-g model tests. Taking into consideration the traditional caisson foundation (CA foundation) and the CBPCA foundations with different pile diameters (i.e., d = 20 mm, 30 mm), pile spacing (i.e., S = 3.5 d, 4.5 d, 5.5 d) and pile lengths (i.e., l = 270 mm, 360 mm, 450 mm), seven working conditions were considered. The horizontal displacement, vertical displacement, earth pressures on the front surface and the bottom of caisson, as well as the induced bending moments in the piles, were analyzed to illustrate the bearing capacity of the CBPCA foundation. The test results show that compared to traditional CA foundation, the CBPCA foundation is feasible for long-span suspension bridges considering its smaller displacements and inclination angles under certain circumstances (i.e., pile diameter d >= 20 mm, pile length l >= 450 mm, and pile spacing S <= 4.5 d). Moreover, the bending moments in piles of different locations were also discussed, and the corner pile and edge pile located under the front caisson subject to the greatest bending moment.