Location

Madrid, Spain

Session

Session 3

Start Date

11-30-2022 4:20 PM

Description

Flood events generating potential risk for dam overtopping may become more frequently in the future, especially because of increasing climate change. Crest overflows at arch dams generally impact the downstream rock mass very close to the dam foundation. As such, any scour of the rock mass generated by this phenomenon may potentially endanger the stability of the dam and its appurtenant structures. Hence, pertinent assessment of this scour formation through space and time is becoming increasingly relevant to dam safety. This paper presents a novel computational method for detachment of prismatic rock blocks from their mass when impacted by high-velocity jets during dam overtopping. The method makes use of the average flow velocities and of block protrusion at the water-rock interface to determine the net uplift pressures and the potential for detachment. Block movements are described based on 1-degree-of-freedom rigid body kinematics applied to submerged bodies and account for the most relevant forces such as quasi-steady and fluctuating lift forces, submerged weight, added mass during block acceleration and potential frictional forces along lateral joints. The paper details the mechanism of block detachment and the way it is accounted for in the computations. Furthermore, an application example of the presented novel approach is outlined through site observed scour formation downstream of a spillway flip bucket.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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Nov 30th, 4:20 PM

A Novel Computational Method to Compute Rock Scour Due to Dam Overtopping

Madrid, Spain

Flood events generating potential risk for dam overtopping may become more frequently in the future, especially because of increasing climate change. Crest overflows at arch dams generally impact the downstream rock mass very close to the dam foundation. As such, any scour of the rock mass generated by this phenomenon may potentially endanger the stability of the dam and its appurtenant structures. Hence, pertinent assessment of this scour formation through space and time is becoming increasingly relevant to dam safety. This paper presents a novel computational method for detachment of prismatic rock blocks from their mass when impacted by high-velocity jets during dam overtopping. The method makes use of the average flow velocities and of block protrusion at the water-rock interface to determine the net uplift pressures and the potential for detachment. Block movements are described based on 1-degree-of-freedom rigid body kinematics applied to submerged bodies and account for the most relevant forces such as quasi-steady and fluctuating lift forces, submerged weight, added mass during block acceleration and potential frictional forces along lateral joints. The paper details the mechanism of block detachment and the way it is accounted for in the computations. Furthermore, an application example of the presented novel approach is outlined through site observed scour formation downstream of a spillway flip bucket.