2017 – Steel Fibre Combined with Conventional Reinforcing Joint Free Spillway Chute–Key Elements for Durability and Serviceability

Tian Sing Ng, David Gardiner

Spillway structures play an important part in regulating the designed reservoir water level and are paramount to protect the structural integrity of the dam structure. Impermeability and tight crack control are prime importance in the design and construction of the spillway lining in order to minimise the potential failure modes of cavitation damage and stagnation pressure related failure. A spillway chute is essentially continuously restrained by the roughness of the rock surface and the ground anchors. The provision of control joints, i.e. expansion, contraction and movement joints,are therefore of little benefit due to the restraint as open cracks will still occur. Steel fibre reinforced concrete has been used for resisting erosion of the surface due to abrasion and/or cavitation. Steel fibres combined with conventional reinforcement also provide an amazing synergy to effectively reinforce concrete due to their ability to provide an effective restraining tensile force across open cracks. For the spillway chute,this means any concrete panel size or shape can be considered, even when the chute is fully restrained. Most importantly, this cost effective solution can be constructed joint free while maintaining watertightness. This paper presents some basic principles governing the design of joint free dam spillways employing steel fibre combined with conventional reinforcement. The focus of this paper describes the design and construction of the 400 m long Happy Valley Dam Outfall Channel together with overseas project examples.

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