Piles are largely back-rotated in sliding slope or subjected to lateral spreading. This paper reveals for the first time that response of these piles (e.g., displacement, rotation, bending moment, and shear force) is amplified against forward rotating piles. In particular, magnification is detrimental, once normalized rotational stiffness (NRS) of the piles is around a singularity value (i.e., normalized singularity stiffness, NSS). New expressions are developed to gain the NSS value, the magnification degree, and the sliding depth to incur the singularity. The NRS is assessed using 1g model tests. The solutions are adopted to capture the response of the model piles, to detect new failure mechanism of Showa Bridge, and to check the safety of Christchurch bridges. The main conclusions are as follows: (i) piles are prone to response amplification, when subjected to lateral spreading or in sliding slopes. (ii) The NRS is only slightly affected by soil movement profiles and sliding depths. (iii) Showa Bridge collapsed from displacement amplification of back-rotated piles. Finally, (iv) the roller connections between girder and piers, and an integral abutment and piers are proved to be effective to curb the amplification. The amplified response needs to be assessed in practice to lessen failure of back-rotated piles.
Model Tests on Single Piles Subjected to Lateral Soil Movement
