抛石挤淤法在沿海高等级公路地基处理中广泛应用，但对加固机理研究较少，通过建立弹塑性有限元力学模型，对抛石挤淤处理的路基应力变形性状进行了分析。计算结果表明：①抛石挤淤处理后的地基能有效提高地基的模量，减小路基沉降和地基浅部水平位移，加速地基孔隙水压力的消散，因此抛石挤淤的加固机理在于人工硬壳层效应和加速排水固结效应；②抛石挤淤体厚度越大，路基沉降越小，而抛石挤淤体模量和宽度对路基沉降的影响较小，因此施工时应采取有效工程措施增大抛石的沉底深度；③填筑速率越大，路基工后沉降越大，预压期越短，路基沉降越大，因此施工时应严格控制施工速度，并保证足够的预压期使路基沉降满足工程要求。深入了解抛石挤淤的加固机理、应力变形性状和影响因素，有助于为设计和施工提供参考和指导。

The method of silt extrusion by dumping riprap has been widely applied in the foundation treatment of coastal high-grade highway. However, the reinforcement mechanism is rarely researched. Elastic-plastic finite element numerical simulation was performed to analyze the stress and deformation behavior of subgrade treated by dumping riprap to extrude silt. The results indicate that the foundation modulus after riprap treatment can be increased effectively, the settlement and horizontal displacement can be decreased and the dissipation of pore water pressure can be accelerated, which suggest that the reinforcement mechanism lies in artificial shell effect and accelerated consolidation effect. The settlement of subgrade decreases with the increase of riprap thickness, but is influenced little by riprap modulus and width. Therefore, effective measurements must be taken to increase the depth of riprap in construction. The quicker of subgrade filling, the bigger of subgrade settlement; and the shorter of preloading period, the bigger of subgrade settlement, therefore the filling speed must be controlled strictly and sufficient preloading period must be assured so as to meet the requirements. Understanding of the reinforcement mechanism, the stress and deformation behavior and the influencing factors is conducive to providing reference and guidance for the design and construction of riprap silt extrusion. 