Scour of rock in dam foundations and spillways during flood events is an important issue for dam safety. A new approach using Block Theory to evaluate erodibility of 3D rock blocks has been developed using physical hydraulic model and prototype testing. The use of high-resolution remote sensing technology for 3D site characterization of the rock mass (e.g., photogrammetry and LiDAR) in combination with the Block Theory Rock Erodibility (BTRE) method has permitted a more detailed, site-specific, examination of rock erodibility than previously attainable. This includes delineation/analysis of site-specific 3D rock blocks, monitoring/change detection of scour over time, and rapid collection of thousands of discontinuity measurements for probabilistic scour analysis.
Scour of rock foundations for dams and spillways during normal and extreme flood events is an important issue for dam safety. This was highlighted during the 2017 events at Oroville Dam in California where concerns arising from scour in the spillways lead to the evacuation of nearly 200,000 downstream residents. Removal of rock blocks is a dominant mechanism by which scour occurs, however, tools for assessment of rock scour have historically been hydraulically focused with limited or no parameters to represent the rock mass (e.g., Mason & Arumugam 1985) or based on empirical relationships to characterize rock potential to resist scour (e.g., Annandale 1995, 2006, Pells 2016). More recently, physics-based approaches have attempted to simulate the mechanics of the scouring process (e.g., Bollaert 2002, George 2015). Prior to George (2015), however, all block studies focused on cubic or rectangular block geometries. Extension of these simplified block shapes to actual sites can be challenging when rock mass discontinuities yield non-cubic block geometries.
A new approach using Block Theory is presented to evaluate erodibility of 3D rock blocks has been developed. The Block Theory Rock Erodibility (BTRE) method provides a systematic approach to assess block removability, kinematics, and stability for rock masses subject to hydraulic loading associated with dam overtopping and spillway flows.
