Abstract: Foundation of Wudu gravity dam has the complex geological conditions, developed many adverse geological structures including faults and interbed shear zones. The stability of dam foundation is very serious due to the potential natural sliding paths formed by these interlaced planes. In order to study the impacts of multi-structural planes on foundation stability and reinforcement measures, a 3D numerical computation is conducted to analyze the typical dam section #19 of Wudu project by means of finite element method(FEM). First, the sensibility analysis is performed to study the impacts of various weak structural planes on stability. It reveals that the dam stability is severely affected by faults 10f2 and F31 incline downstream from dam heel, and the reinforcement measures should be taken and focus on the faults 10f2 and F31. On this basis, another sensibility analysis of concrete replacement depth is also conducted. Through varying the concrete replacement depths for faults 10f2 and F31, the corresponding safety factors are obtained. Results show that the reasonable replacement depth for faults 10f2 and F31 is about 19 m which can achieve favorable reinforcement effect; deformation and stress of dam have been improved; plasticity states of the dam foundation has been significantly reduced; the safety factor of anti-sliding stability is significantly improved; and the requirement of design specification is satisfied simultaneously. These research results provide an important scientific basis for the reinforcement of Wudu project, and also have the reference value for the stability analysis and reinforcement treatment of other similar projects.

Key words: stability of gravity dam foundation, multi-structural planes, concrete replacement, sensibility analysis, finite element calculation