There is a large terrain gap to some sections of cut-off wall for Daning reservoir

on both sides of wall and the top of lower wall

which affected by construction significantly

need a large amount of backfill soil. A three-dimensional numerical simulation is adopted based on experiment and monitoring data to analysis the effect of backfilling construction. The interaction between cutoff wall and backfilled soil is considered in the simulation. The stresses and deformations of the wall forms affected by different distances and contact are analyzed; the distribution of internal deformation and stress along the construction proceeding is obtained at the same time. The analysis shows that the upper wall tilts toward inside of reservoir

and the maximum principal stress appears at top of transfer position of the two walls. The inclination of the lower wall is very small and its maximum principal stress appears at the bottom of guide wall. No tensile stress exists in the lower wall. The stress and deformation of the wall have some variances along the wall

and the greatest change presents at the corner. The simulation results are comparatively close with the monitoring results.