A typical profile of the cross-river section of Nanjing Metro Line 10 near the North Yangtze River dike was taken as an example.Single running scenario and three typical meeting scenarios
namely 8-s meeting
12-s meeting
and 16-s meeting scenarios were considered
and a tunnel-soil finite element model was developed to analyze the dynamical response of the silty fine sand layer beneath the single-hole double-track tunnel.Results showed that the peak acceleration values of the fine silty sand decayed exponentially with almost the same value when reaching a depth of 23 mfor all the four scenarios.The maximal displacements of the soil layer beneath the tunnel decreased linearly along the depth.The maximal vertical displacement was observed for the 8-s meeting scenario
followed by the 16-s
12-s meeting
and the 8-s single running scenarios.Moreover
the excessive pore water pressure induced by the dynamic load of the subway train was only a hundredth of the static pore water pressure.The maximal pore water pressures also exhibited an exponential attenuation trend.Finally
the ratio of the maximal pore water pressure to the total stress was less than 1
meaning that liquefaction would not occur in the fine silty sand layer beneath the tunnel.The investigation results can be used to regulate the dynamic response and the liquidability of the fine silty sand layer beneath the tunnel at controlled sections.
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