Displacement Modeling of Earth Dams During the Construction of a Cutoff Wall

Abstract

Cutoff walls play a crucial role in reducing seepage through the foundation and increasing dam stability. However, impacts from other factors, such as soil movement around the cutoff wall during construction, must also be considered. Hence, this study investigated the movement behavior of a 33-meter-high earth saddle dam with a 408-meter-long, up to 67-meter-deep cutoff wall and a complex weathered rock foundation, which previously faced issues related to high pore pressure and settlement. The objective was to simulate the movement behavior using a 2D Finite Element model (SIGMA/W) under various cases to evaluate the impacts from the cutoff wall construction process and the intrusion of bentonite slurry in collapse voids. Analysis results during the trench excavation stage showed maximum movement in the embankment and residual soil, approximately 1-8 centimeters upstream and 1-6 centimeters downstream. In the backfilling stage, the cutoff wall showed a tendency to move downstream approximately 1-2 centimeters. Comparison with field lateral movement data revealed that the magnitude of movement in the original soil in the field was less than that predicted by the analysis, which may be a result of the difference in elastic modulus between the original soil and the embankment soil. Investigation into the effect of bentonite slurry intrusion in collapse voids demonstrated that slurry quantity has a direct and significant impact on movement, with maximum associated movement potentially reaching 0.6 centimeters, depending on the location, void characteristics, and failure pattern. These findings provide important guidance for construction control, dam defect assessment and repair, as well as long-term dam behavior monitoring.