可液化地层叠落盾构隧道抗震分析及对策

Aseismic Analysis and Measures of Shield Tunnel in Liquefiable Soil

饱和砂土地层的盾构隧道可能因液化影响产生变形及内力变化引起隧道破坏,地层液化对叠落隧道的影响可能因结构间的相互影响而加剧。基于工程实例,采用有限元分析软件Midas GTS建立三维模型,对可液化地层叠落隧道进行水平和竖向抗震动力时程分析,分析了液化地层在隧道不同位置以及不均匀分布情况对隧道的不同影响,对液化与非液化情况的隧道结构内力及变形进行对比,研究了地层加固对液化地层的处理效果。液化情况下隧道内力及变形均有一定程度的增加,其中液化地层处于隧道底部、液化地层分布不均匀对隧道影响程度较大,竖向地震作用主要影响隧道的竖向变形。综合考虑多种加固方案,中等液化程度时盾构隧道采用径向注浆加固地层有较好的效果。

The deformation and internal force of a shield tunnel in a saturated sandy soil layer may change owing to liquefaction,which may lead to tunnel failure. However, the influence of liquefied strata on overlapped tunnels may be aggravated by the interaction between structures. Thus, based on an engineering example, a three-dimensional model was established using the Midas GTS software to analyze the horizontal and vertical seismic dynamic time history of the tunnel with liquefiable soil.The study analyzed the different influences of different positions and uneven distributions of liquefied strata on the tunnel.The internal force and deformation of the tunnel structure under liquefiable and non-liquefiable conditions were compared.The treatment effect of stratum reinforcement on the liquefied stratum was studied. The internal force and deformation of the tunnel in liquefiable conditions increased to a certain extent. A significant impact was observed when the liquefied strata were located at the bottom of the tunnel or were not uniform. Vertical seismic action mainly affected the vertical deformation of the tunnel. Therefore, radial grouting is recommended to reinforce the ground when the liquefaction degree is moderate.