Holding Back the Flow: Designing Cutoff Walls to Prevent Potential Dam Failure

Overview

ABSTRACT Holding Back the Flow: Designing Cutoff Walls to Prevent Potential Dam Failure The California Central Valley has four dams that are classified as High Urgency due to water seepage causing erosion, according to the United States Army Corps of Engineers. Currently, the cutoff walls used to control seepage are 90-degree angles from the ground and are attached or next to the dam. The purpose of this experiment answers if I design a cutoff wall that is not 90-degrees, will it extend the water seepage flow away from the dam farther, which is crucial for preventing the destruction of a dam due to erosion? My hypothesis is that if I design a cutoff wall attached to a dam model with a 45-degree angle on the toe side, then the water seepage flow will extend farther from the dam model than identical dam models with cutoff walls of a 90-degree angle from the ground or a 45-degree angle on the heel side. Four dam models were constructed out of bricks. The Control Dam model had no cutoff wall attached. Cutoff walls of foam board were attached to three dam models. One cutoff wall attached to the dam model was at a 90-degree angle from the ground. I designed one cutoff wall attached to the dam model with a 45-degree angle on the toe side, and one cutoff wall attached to the model with a 45-degree angle on the heel side. For each trial, one liter of water was poured on the upstream side of the dam model. The distance of the water seepage was measured from the toe of the dam to the exact location where the water surfaced on the downstream side. The results of the 40 trials were compared. The Control Dam model had an average distance of 1.1 cm. The dam model with a 90-degree angle cutoff wall had an average distance of 5.4 cm. The dam model with a 45-degree angle cutoff wall attached on the heel side had an average distance of 7.8 cm. The dam model with a 45-degree angle cutoff wall attached on the toe side had an average distance of 14.15 cm. My hypothesis was correct, a cutoff wall attached to the dam model with a 45-degree angle attached to the base of the dam model on the toe side extended the water seepage flow 14.15 cm , which exceeded the results of the identical dam models with cutoff walls of a 90-degree angle or a 45-degree angle on the heel side. These results are applicable when designing cutoff walls to protect dam structures.

Competition history

• CSEF 2026 Applied Mechanics (Senior Division) · Entry S-02-01

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