为实现工程弃土的资源化利用和降低工程投资，以苍南县安澜工程（南片海塘）护塘河开挖产生的淤泥质土为研究对象，将附近绿能小镇三澳核电站工程弃土作为粒径改良用土，并采用水泥作为固化剂，通过不固结不排水（UU）三轴剪切试验研究水泥与粗颗粒工程弃土复合改良淤泥土的物理力学性能，并得到既符合工程设计要求又具较好经济性的改良土配合比。试验结果表明：影响改良土物理力学性能因素主要为粗颗粒弃土占比、水泥掺量、养护龄期，其中水泥掺量与养护龄期影响最为显著；单掺改良时，粗颗粒掺量对改良土的力学性能影响较小，改良效果不佳。淤泥土、粗颗粒土、水泥掺量分别为40%、60%、15%，养护龄期为56 d时淤泥质土的改良效果最佳，最大偏应力和黏聚力分别为2 897.87、567.63 kPa。改良后的土作为海塘闭气土方用土能够满足工程设计要求。研究成果能够为海塘工程设计和施工提供理论依据和指导。

To realize the resource utilization of engineering spoil and reduce the project investment, taking the muddy soil generated from the excavation of the protective river of the Anlan Project (southern seawall) in Cangnan County as the research object, the abandoned soil from the nearby green energy town San'ao Nuclear Power Plant project was used as soil for particle size improvement, and cement was used as a solidifying agent. The physical and mechanical properties of the composite improvement of silt soil with cement and coarse particle engineering abandoned soil were studied through unconsolidated undrained (UU) triaxial shear tests, and an improved soil mix ratio that met the engineering design requirements and had good economic efficiency was obtained. The experimental results show that the main factors affecting the physical and mechanical properties of the improved soil are the proportion of coarse particle waste soil, cement content and curing age, the cement content and curing age have the most significant impact. When single addition is used for improvement, the amount of coarse particles has little impact on the mechanical properties of the improved soil, resulting in poor improvement effect. When the content of the mucky soil, coarse grained soil and cement is 40%, 60% and 15%, respectively, and the curing period is 56 days, the improvement effect of muddy soil is the best, with the maximum deviator stress and cohesion being 2 897.87, 567.63 kPa, respectively. This improved soil can meet the engineering design requirements as a soil for enclosed air in seawalls. The research results can provide theoretical basis and guidance for the design and construction of the seawall engineering.