Seismic Performance of Tunnels in Rock

A significant number of tunnels in the US are excavated in rock. Many of these tunnels have suffered moderate to heavy damage during a strong earthquake, primarily due to a lack of robust seismic design principles when they were initially constructed. This award supports research to improve understanding of the interaction mechanisms between rock and tunnel support, identify the sources of damage and failure in tunnels, and develop tools that practitioners can use for the safe seismic design of tunnels. The outcomes of this work will improve the resilience of our civil infrastructure against earthquake hazards. The award also supports workforce development, enhancing engineering education and participation in STEM fields. Undergraduate, graduate students and practitioners will be engaged with the project. The lack of established criteria for their seismic design of tunnels has created deficiencies in the current seismic performance of tunnels in rock. This research aims to address these challenges through analytical and computational studies of concrete tunnel liners in different rock mass structures. Analysis of test results will be used to obtain verified computational algorithms and models with predictive capabilities and enable technology transfer. The experiments consist of subjecting a circular concrete structure to the displacements imposed by seismic loading. The goal of the experiments is to monitor the response of the structure, from initial damage to final failure to identify and quantify the mechanisms of damage to the structure, compile data for assessment and/or refinement of numerical and analytical models, and assess the potential for damage from concentrated loads and loss of support confinement due to relative movement of blocks and rock stiffness that may facilitate the creation of gaps behind the support. The results will produce high quality data on rock-structure interaction and extensively verified models to be used in practice. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.