Hydro-mechanical behaviour of reinforced concrete linings in hydraulic tunnels: steady state

Abstract

Existing literature covers the behaviour of reinforced concrete (RC) tunnel linings in hydraulic tunnels during filling and steady-state conditions. However, certain aspects remain insufficiently addressed, risking the under-dimensioning of structures, particularly concerning transient behaviour. This paper introduces a comprehensive analytical framework for the design of RC linings in hydraulic tunnels, clarifying conditions that lead to a water-filled gap between the lining and rock mass, significantly impacting system behaviour. The presence or absence of this gap notably affects the number of cracks in the lining, with a substantial increase in cracks when the gap is absent. Contrary to prior assumptions, the paper highlights that the cracking process of the lining is progressive and can stabilize before reaching a fully cracked state, resulting in fewer cracks. Understanding these phases is crucial for setting realistic initial conditions for transient events, particularly concerning lining stiffness. Accurate stiffness determination is essential for evaluating the lining’s response during transients and its fatigue performance. This becomes increasingly significant with the rise of pumped storage schemes for grid stabilization, posing challenges in resistance and fatigue verification of hydraulic tunnel RC linings.