大地震主震发生之后通常伴随强余震，多次余震下大坝的结构损伤破坏累积效应明显。为了解复杂地基上重力坝在主、余地震联合作用下的变形和稳定性，以紧邻汶川地震震中的某大型水利工程重力坝典型坝段A#坝段为研究对象进行研究分析。首先，仅考虑主震作用的影响，采用拟静力法模拟地震主震荷载，运用地质力学模型试验方法，研究主震作用下A#坝段坝与地基的变形特征和模型最终破坏形态；再考虑主、余地震联合作用的影响，采用动力法（即时程分析法）基于ANSYS有限元软件进行计算。研究结果表明，主震作用下模型试验与有限元计算结果基本一致，坝与地基均发生了大变形，且通过模型试验得到了A#坝段最终破坏形态；在主、余地震联合作用下，A#坝段坝与地基的变形的累积增加效应明显，变位特征值比主震作用下明显增大，其坝体最大变形处（坝顶）变位值增幅约为37%，对坝与地基稳定性影响较大。因此，对位于地震高发带复杂地基上的重力坝，应考虑主、余地震联合作用的影响，这样更利于工程的安全。

Aftershock often takes place in the wake of a main shock, and the cumulative damage effect of dam structure can become significant after several aftershocks. To explore the deformation and stability of a gravity dam with a complex foundation under the combined effect of main shock and aftershock, a dam section #A of a large-scale hydraulic project close to Wenchuan-epicenter is adopted for a case study. Firstly, only the main shock only is considered, which is simulated using the pseudo-static method in the geomechanical model test, and through experiments the deformation characteristics and the final failure pattern of dam section #A and foundation are studied. Then based on this, the time history analysis is performed, and the combined effect of main shock and aftershocks is analyzed using the 3D FEA software ANSYS. The results show that the model testing results are consistent with calculations. Under the effect of main shock, both the dam and foundation generate large deformation; and the final failure pattern of dam section #A is obtained. Under the combined effect of main shock and aftershock, the cumulative deformation effect of dam and foundation becomes more significant, and the displacement is significantly larger than that induced by the main shock only. The maximum displacement amplification of dam is about 37% which has a significant impact on the stability of dam and foundation. Therefore, the gravity dam on complex foundation in highly seismic region should take into account of the combined effect of main shock and aftershock so as to ensure the project security.