Cushioned pile-raft foundation (Cushioned-PR) is a new type of foundation for sea-crossing bridges in deep water (more than 50 m in depth). Cushioned-PR is able to tolerate a certain amount of slide that occurs between the raft and the piles under strong earthquakes. This characteristic could reduce the seismic motion transmitted to the superstructure to maintain the integrity of the bridge. Thus, Cushioned-PR has become popular for bridges under the threat of strong earthquakes. However, the dynamic responses of the Cushioned-PR under various earthquake intensities in soft clay have not been thoroughly understood. It is essential to better evaluate the isolation effect of Cushioned-PR to improve the design. In this study, the non-linear behavior of Cushioned-PR and the isolation effect of its interposed layer are evaluated using centrifuge tests. A series of dynamic centrifuge tests are performed with a 3 × 3 pile group foundation embedded in soft clay under different earthquake motions. Both the cushioned pile raft foundation system (Cushioned-PR) and the connected pile raft foundation system (Connected-PR) are tested in the centrifuge tests. Acceleration and residual displacement of the super-structure, and bending moment of columns and piles, are monitored during the experiments. The results show that the interposed layer in Cushioned-PR has a significant impact on the bending moment and residual displacement of the pile-raft system. Based on the observation from this study, the maximum bending moment of the column in the Cushioned-PR is around 28%–54% of the values from the Connected-PR. On the other side, the maximum horizontal displacement of Cushioned-PR is about 2–10 times larger than that of the Connected-PR. The results show that Cushioned-PR can effectively reduce the seismic excitation transmitted to the super-structure if the seismic intensity is high. However, the benefit of Cushioned-PR is marginal under low-intensity earthquakes.

缓冲桩筏基础（Cushioned-PR）是一种用于深水（深度超过50 m）的跨海桥梁的新型基础。在强烈地震下，Cushioned-PR能够承受木筏和桩之间发生的一定量的滑动。该特性可以减少传递到上部结构的地震运动，以保持桥梁的完整性。因此，在强烈地震的威胁下，Cushioned-PR在桥梁中变得很流行。但是，对于软土中各种地震烈度下的Cushioned-PR的动力响应尚未完全了解。更好地评估Cushioned-PR的隔离效果对改进设计至关重要。在这项研究中，Cushioned-PR的非线性行为及其插入层的隔离效果通过离心测试进行评估。在不同地震运动下，将3×3桩组基础埋入软粘土中，进行了一系列动态离心试验。缓冲桩筏基础系统（Cushioned-PR）和连接桩筏基础系统（Connected-PR）均在离心机测试中进行了测试。在实验过程中，监测上部结构的加速度和残余位移，以及桩和桩的弯矩。结果表明，Cushioned-PR中的插入层对桩筏系统的弯矩和残余位移有很大影响。根据这项研究的观察结果，Cushioned-PR中柱的最大弯矩约为Connected-PR值的28％–54％。另一方面，Cushioned-PR的最大水平位移约为Connected-PR的2–10倍。结果表明，如果地震烈度较高，Cushioned-PR可以有效地减少传递到上部结构的地震激励。但是，在低强度地震下，Cushioned-PR的好处微不足道。