A New Concrete Spillway Chute Concept that Addresses Flow Induced and Seepage Potential Failure Modes

Recent spillway chute incidents during spill events such as at Oroville Dam in 2017 (France, J.W., et al, 2018), and at Toddbrook Dam in 2019 (Balmforth, 2020) highlight the need for spillway chutes that are reliable, resilient and robust. Consequently, structural failure mechanisms for spillway chutes need to be understood and addressed for new spillways and rehabilitation of existing spillways. The main failure mechanisms for concrete spillway chutes can be classified into four broad categories (Daly & Pavlov, 2022): 

• Structural failure due to excessive uplift 

• Structural failure due to loss of support and undermining 

• Structural failure due to excessive or unaccounted dynamic actions 

• Structural failure due to concrete deterioration, cracking or corrosion of reinforcement 

Past spillway chute failures indicate that the first two structural failure mechanisms account for the majority of chute failures for that portion of the chute above maximum tailwater (USBR and USACE, 2019) (ICOLD, 2024). Design of spillway chutes and energy dissipaters below maximum tailwater must also address structure floatation due to submergence and hydrodynamic failure mechanisms. This new concept for concrete spillway chutes was developed for use above maximum tailwater but could be considered for those portions of the spillway chute below maximum tailwater with additional assessment.