“See” groundwater flow by using a Hele-Shaw cell. The Hele-Shaw cell consists of two parallel transparent walls with a small gap between them that is filled with a viscous liquid that moves in response to a pressure difference along the plates. The pattern of flow between the walls of the cell is equivalent to groundwater flow in a plane. This video shows the groundwater flow pattern below a dam from a headwater reservoir on the left to a tailwater reservoir on the right. A cutoff wall protruding below the base of the dam increases the flow path below the dam, decreasing the flow velocity, thus reducing the potential for the groundwater flow to erode the porous material at the toe of the dam. (2 minutes)
A discussion of the material in this video provided in Section 2.6 “The “Hear See Do” of Flow Nets” of the Groundwater Project book “Graphical Construction of Groundwater Flow Nets”. Section 2.6 can be read online, or the entire book can be read online or a PDF of the book can be downloaded.
Citation: Jiao, J.J., Liang, W.Z. & Poeter, E. (2020). Hele-Shaw demonstration of groundwater flow under a dam with a cutoff wall. Video of The Groundwater Project, Guelph, Ontario, Canada.