强震作用下工法对接变刚度隧道振动台试验研究

Drill-and-blast tunnel method and TBM tunnelling are commonly used in divisional excavation when a tunnel passes through rock and soil strata. A transition tunnel is generally built to connect the drill-and-blast tunnel and the TBM tunnel. As a result，the stiffness of the tunnel changes suddenly due to different cross sections and types. The transition tunnel becomes precarious under earthquake loadings，which should be paid significant attentions in seismic design. Regarding to the anti-earthquake issue of the tunnel passing through the rock-soil strata in seismically active areas，a shaking table test is carried out to study the seismic response of the transition tunnel under strong earthquake loadings. Accelerations at different tunnel portions，pressures between rock and lining，and joint extensions of the TBM tunnel are analysed based on the shaking table test. Furthermore，the influence of the stiffness change on the dynamic response of tunnel is discussed. Results show that the acceleration amplification factor of tunnel decreases with the increase of input ground motion intensity. The tunnel with larger stiffness leads to larger amplification factors. The rock-lining pressure increases with the increase of earthquake intensity；while the pressure shows a slow increase when the PGA reaches to 0.5 g. It is speculated that tunnel structure and rock show regional damages. Also，higher earthquake intensity shows larger joints extensions of shield tunnel. It is noted that the joint extension close to the inner lining is five times to the extension at normal area due to the sudden change of stiffness at the inner lining area. The research is able to provide guidance for the seismic design of the transition tunnel with changing stiffness.