A combined dam structure using different concrete materials offers many practical benefits.There are several real-world cases where large-volume heterogeneous concrete materials have been used together.From the engineering design standpoint,it is crucial to understand the deformation coordination characteristics and mechanical properties of large-volume heterogeneous concrete,which affect dam safety and stability.In this study,a large dam facility was selected for a case study,and various design schemes of the combined dam structure were developed by changing the configurations of material zoning and material types for a given dam shape.Elastoplastic analysis of the dam-foundation-reservoir system for six schemes was carried out under dynamic conditions,in which the concrete damaged plasticity (CDP)model,the Lagrangian finite element formulation,and a surface-to-surface contact model were utilized.To evaluate the mechanical properties of zoning interfaces and coordination characteristics,the vertical distribution of the first principal stress at the longitudinal joint was used as the critical index of deformation coordination control,and the overall deformation and damage characteristics of the dam were also investigated.Through a comparative study of the design schemes,an optimal scheme of the combined dam structure was identified: large-volume roller-compacted concrete (RCC) is recommended for the dam body upstream of the longitudinal joint,and high-volume fly ash conventional concrete (CC) for the dam body downstream of the longitudinal joint.This study provides engineers with a reference basis for combined dam structure design.