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Effect of deep unloading zone on working performance of arch dam and abutment: A case study in the Yebatan Hydropower Station

WithWen Zhang, Yuan Chen, Lin Zhang, Bao-quan Yang, Chong Zhang, Xiao-qiang Liu

A large number of dam projects have been built in the southwest mountainous area of China. Many projects are located on large rivers with complicated geological conditions, which may cause some adverse effects. The deep unloading zone is a special geological structure caused by unloading fracture of deep rock mass, which is broken and weak. In the Yebatan Hydropower Project, the deep unloading zones develop seriously in the mid-low elevation of each abutment. The working performance of the project is a critical problem needs to be further studied. In this paper, the geomechanical model test and numerical analysis are carried out to study the working performance of dam and abutment affected by the deep unloading zone at EL. 2750 m. According to the research, the deformation properties and failure patterns of the arch dam, the abutment and the deep unloading zone are obtained, and the effect degree of the deep unloading zone is studied. The research results indicate that the deep unloading zones have significant effect on the working performance of dam and abutment. The effect degree is not only related to the position of the strong relaxed rock mass IVS in the deep unloading zone, but also related to the combination with faults near the arch abutments. The strong relaxed rock mass IVS in left abutment has a great effect on the deformation performance of the arch dam and abutment. The stability of right abutment is affected by the fault f29 (f74) in the right abutment. In addition, some reinforcement measures have also been proposed.