Abstract: The concrete cutoff wall is the main anti-seepage structure of the rockfill dam resting on the deep overburden foundation, and is the key to ensuring the dam safety. Therefore, it is of great significance to accurately simulate the stress state of cutoff wall for evaluation of the rockfill dam resting on the deep overburden. Combining the incremental iteration method and the finite element-scaled boundary finite element coupling method (FEM-SBFEM), this paper realizes the trans-scale refined numerical analysis of the stress and deformation of the rockfill dam, which overcomes the low precision of the conventional midpoint increment method in solving local strong nonlinear problems. The characteristics of local large strain in band-shaped connected zone between cutoff wall and core wall and the bottom of cutoff wall are found. The overestimate of cutoff stress is due to the failure of conventional methods to describe local large strain of soil. The three-dimensional efficient refined analysis of cutoff wall of high asphaltic core dam on the super-deep overburden is performed by setting thin-layer elements to simulate the local large strain. The proposed trans-scale analysis method based on FEM- SBFEM-incremental iteration method-embedding thin-layer elements provides theoretical and technical support for the safety evaluation and design optimization of cutoff wall of rockfill dam resting on deep overburden.

Key words: cutoff wall, refined analysis, deep overburden, rockfill dam