Experimental Investigation of Debris Damming in Transient Flow Conditions

Introduction: Extreme flooding events, such as tsunamis and tropical storms, have resulted in significant loss of life and extensive damage. The unexpected failure of critical infrastructure in these events has shown that improved structural design guidelines are necessary (Yeh et al., 2013). These standards require a more comprehensive review of the loading due to accumulations of debris, commonly referred to as debris damming. Debris dams form when entrained solid objects accumulate in-between or on the face of structures. Debris damming is generally considered a quasi-static load and can increase hydrodynamic loading due to an enlarged cross-sectional area exposed to the flow. In addition, debris damming has been known to result in overtopping and increased erosion (Pagliara and Carnacina, 2013). Due to several challenges related to assessing debris damming post-disaster, experimental investigations are required to develop a further understanding of debris damming loads under these complex hydrodynamic conditions. The following study examines loads and effects related to debris damming in transient flow conditions.

Experimental Setup: Experiments were conducted in the Dam-Break Flume at the University of Ottawa, Canada. Idealized debris dams were attached to a column and tested with a modified dam-break wave, which is commonly used to model an on-land tsunami bore (Chanson, 2006). Due to the random behaviour of debris dam formation, rectangular dams with various geometry were tested. The flow depths, velocities, and forces exerted on the column and debris dam were recorded utilizing various hydraulic instruments.

Results: This study analyzed the impact of debris geometry on the induced structural loads and the surrounding flow conditions. Additionally, the authors investigated the drag coefficient of the various debris dams related to various parameters including Froude number and debris dam geometry. The study concluded that debris dam geometry had a significant impact on loading and surrounding hydrodynamic conditions. Debris dams with increased height resulted in an increase in the associated forces acting on the column. Porous dams had reduced loading and drag coefficients due to a decrease in the aspect ratio. The implications of these findings are expected to be of significant interest to design engineers.

References: Due to space limitations, mentioned references are not listed.