为解决石砌体材料非均质的描述问题，提出一种基于Cohesive单元的石拱桥主拱圈两相数值模拟方法。视石砌体为两相材料(砌块和砌缝)，采用实体单元模拟砌块并引入非线性本构描述其破坏行为，在相邻砌块间插入Cohesive单元考虑砌缝砂浆的剪切和拉伸破坏。通过室内试验与数值模拟对比验证方法的有效性及适用性，分析了砌缝抗剪摩擦系数μ、加载位置等敏感参数对拱桥承载力的影响。结果表明：基于Cohesive单元的石砌体两相数值模型，可以有效描述石砌体材料的非均匀性及石拱桥的破坏过程(尤其是砌缝剪切滑移破坏行为)，可为石拱桥极限承载力评估提供重要信息，如荷载-位移曲线、破坏模式等。此外，研究结果还发现主拱圈破坏机制由拱的受弯、受剪特性决定，并与砌缝抗剪摩擦系数μ强相关。“,”To simulate the non-homogeneity of masonry materials, a two-phase numerical modeling strategy based on Cohesive elements is proposed. In the proposed method, masonry is considered as a two-phase material, which consists of stone blocks and mortar joints. Solid elements are used to simulate the blocks. A nonlinear constitutive model is introduced to describe their failure behavior. Cohesive elements are inserted between adjacent blocks to consider the shear and tensile failure of the mortar. The effectiveness and applicability of the method are verified by comparison of experimental tests and numerical simulation. The influence of sensitive parameters, such as the shear friction coefficient μ and loading position, on the strength of the arch bridge is analyzed by numerical simulation. The results show that the two-phase numerical model of stone masonry based on Cohesive elements avoided the difficulty in continuous numerical methods in simulating the non-homogeneity of masonry materials, and provided important information for the ultimate strength evaluation of stone arch bridges, such as the load displacement curves and failure modes. In addition, the failure mechanism of the main arch was determined by the bending and shear characteristics of the arches, especially the shear fiction coefficient of the mortar joints.