Evaluation and analysis of the ductile dynamic response of mountain tunnels based on shaking table tests

Abstract

Dynamic response tests using a shaking table were conducted to directly measure the time-history relationship of ductile displacements in cast-in-place horseshoe-shaped mountain tunnels. These tests provided displacement and maximum deformation rate (MDR) control indices for the tunnels. Shaking table tests on such tunnels have typically focused on seismic mechanisms, primarily through measurements of acceleration, strain, strength, and internal forces. However, research on ductile displacements and deformation rate control indices remains limited. In this study, a novel experimental methodology was developed and utilized to directly quantify the time-history relationship of ductile displacements in mountain tunnels. A series of shaking table tests were conducted to evaluate the seismic performance, influence extent, and impact range of the tunnels. The seismic response characteristics and damage assessment under various conditions were systematically investigated. The primary conclusions are summarized as follows: (1) The practicality and effectiveness of the method for directly measuring the time-history relationship of ductile displacements were validated through testing and analysis. (2) Recommended MDR thresholds for ductility indicators in mountain tunnels are proposed, with values of 8.27 ‰, 6.09 ‰, and 4.85 ‰ for shallow-buried, medium-buried, and deep-buried tunnels, respectively. (3) Burial depth is identified as a critical factor influencing the seismic performance of mountain tunnels, with both displacement and MDR showing a decreasing trend as burial depth increases. (4) Based on the seismic response characteristics and damage patterns of cast-in-place horseshoe-shaped mountain tunnels, four distinct damage patterns were identified: elastic, elastoplastic, plastic-critical, and critical-collapse. These findings provide a foundation for predicting damage and failure, as well as for developing probabilistic seismic demand models for cast-in-place horseshoe-shaped tunnels under seismic loading, thus offering valuable references for the establishment of relevant industry standards and guidelines.