Overburden treatment for concrete face rockfill dams and its application in Hekoucun project

The concrete face, toe-slab, connecting slab, cut-off wall are usually used as the anti-seepage system of concrete face rockfill dams (CFRDs) on deep overburden. As the toe slab and dam body are built on the overburden, the deformation caused by filling and impoundment significantly affects the joint displacement of the anti-seepage system. Therefore, the quality of overburden treatment is the key to ensure the safety of the CFRDs. Aiming at the problem of overburden treatment, considering the Hekoucun project, several treatment schemes for dam foundation, such as dynamic compaction, consolidation grouting and high-pressure rotary spray, are proposed. Using the non-linear finite element method, the effects of various foundation treatment schemes on the joint deformation of anti-seepage system are systematically studied. The results show that consolidation grouting and high-pressure jet grouting pile can meet the design requirements. However, the consolidation grouting scheme is difficult to implement and difficult to achieve the design goal. Finally, the high-pressure jet grouting pile scheme is employed, and a new type of partition gradient layout is proposed. The on-site monitoring results show that the infiltration zone can effectively reduce the deformation of anti-seepage system. After reinforcement, the deformation of the overburden decreases significantly.