3D valley effect mechanism and damage behavior of the concrete cut-off wall in overburden

The performance of concrete cut-off walls in overburden of earth dam foundation is crucial important to dam design and safety evaluation. However, it is difficult to carry out in-depth study because the traditional numerical methods are limited to nonlinear elasticity theory. In this paper, a systematic numerical simulation by 3D nonlinear FEM is firstly conducted to study the three-dimensional valley effect mechanism, focusing on the deformation mode and the spatial characteristics of stress distribution in the wall. Then, a 3D plastic-damage model for concrete and an adaptive-incremental iterative algorithm for collaborative analysis with rock-fill were developed, the damage-stress characteristics of the wall was revealed. Finally, The analysis methods for evaluating the performance of concrete cut-off walls were discussed. This re- search indicated that the 3D valley effect on the wall is outstanding due to the combined effect of bending deflection of the wall and negative resistance aroused by overburden. The direction of the tensile stress is orients axially, trends to the vertical gradually with the increasing deflection. In addition, there exists critical valley slope and valley depth of tensile stress. It is good to understand the force-deformation-stress rule of the wall with elastic analysis, but has no application to evaluate the performance of the wall in complex conditions. The material behavior of concrete and the damage features can be described and captured with damage analysis. Moreover, the damage index has the ability to build connections with anti-seep- age performance. It is more reasonable and accurate to evaluate the performance of cut-off walls with dam-age analysis. © 2019, China Water Power Press. All right reserved.