Life-cycle dynamic analysis and probabilistic seismic risk assessment of cross-fault hydraulic tunnels considering AAR-induced deterioration

Abstract

The alkali-aggregate reaction (AAR) triggered the deterioration of the machinistic property of concrete materials is among the major negative factor that results in the reduction of structural serviceability and performance for concrete structures, especially for those hydraulic engineering in contact with water for service life-cycle. Hydraulic tunnels, being a vital component of hydraulic engineering, are frequently employed in various lifeline projects around the world. Once the AAR effect renders the hydraulic tunnel inoperable, the government and society will suffer enormous economic losses, delaying the achievement of carbon neutrality. However, current specification for seismic design does not account for the degradation of structural performance parameters induced by AAR effects, which cannot fully reveal the earthquake performance of AAR-affected tunnels during use. Having realized this challenge, this work presents a mechanical model of the AAR effect integrating the concrete elastic-plastic damage model to conduct the inelastic dynamic response and random earthquake risk assessment of AAR-affected cross-fault hydraulic tunnels with design life-cycle. To this end, a study of the AAR-affected hydraulic tunnels, which consider the fluid-structure-surrounding rock coupling systems throughout the service period, is undertaken to associate the structural reaction with the predefined evaluation index directly. Subsequently, The nonlinear dynamic assessment of cross-fault hydraulic tunnel is conducted by using increased dynamic method to generate several data. Besides, this research constructs the three-dimensional (3D) time-dependent fragility surfaces considering the AAR effect and seismic intensity level. The results of this study underscore this point that the AAR effect possesses the capability to aggravate the response of relative displacement and extend the cumulative damage cracking area of the cross-fault hydraulic tunnels (CFHTs) with the increase in service time. Similarly, the 3D time-varying fragility surfaces show that the longer the service time of AAR-affected cross-fault hydraulic tunnels, the more likely they are to collapse. The above phenomena demonstrate that the AAR effect can be recommended for the utilization in estimating the likelihood of the erosion of the building during service life-cycle and future seismic design code.