Dynamic response and reliability of tunnel under earthquakes Yue, Qingxia; Ang, Alfredo H. S.
The damages of tunnels under earthquakes showed that soil/rock deposits around a tunnel have significant effects on its response to earthquake excitations, including the effects of the spatial variability and correlation of the soil properties which may properly be modeled as a random field. This paper studied these effects through modeling the surrounding soil as a random field on the dynamic response of a tunnel. A 2D finite element model of the tunnel-soil system was examined and the corresponding random field was simulated by the stochastic harmonic function of the first kind. The results revealed that under the design earthquake, the static load effect will initially dominate but as the earthquake intensity increases, the earthquake influence will dominate. The reliabilities of a tunnel for the design limit-state function was considered. The equivalent extreme events were formulated for the limit-state function, from which the tunnel system reliability can be evaluated. The probability density evolution method (PDEM) was employed to calculate the reliability of the tunnel under its design limit-state when subjected to a strong earthquake. This shows that the tunnel is adequately designed by the existing Chinese code under the design earthquake.
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