非均匀地层盾构隧道纵向抗震分析

Longitudinal Aseismic Analysis of Shield Tunnels in Inhomogeneous Ground

盾构隧道纵向刚度相比于横向刚度小,地震作用下容易因过大的变形而产生震害,特别是在地层或结构本身发生突变的部位,纵向抗震问题更加值得关注。文章采用地层-结构模型,基于纵向等效刚度模型计算了不同地震作用下隧道纵向动力响应,并对纵向转角、管片及接头螺栓应力等抗震指标进行了验算。计算结果表明:软硬突变地层是盾构隧道纵向抗震薄弱部位,软土侧结构内力显著增大的区域达到隧道外径的4倍;当地震波横向激振时,纵向弯矩起控制作用,而纵向输入时,则是较高的轴力对结构起控制作用;相同水平地震作用下,地震波纵向激振对结构的受力影响与横向相比更加不利。

As the longitudinal stiffness of shield tunnels is less than that of transverse sections, it is likely to suffer from seismic damage caused by excessive deformation, especially at places where the ground or the structure chang- es suddenly, and so the longitudinal aseismic study is worthy of attention. Based on the ground-structure mode, this paper uses a longitudinal equivalent stiffness model to simulate the longitudinal dynamic response of shield tunnels under different seismic actions and to verify the aseismie indicators of the longitudinal rotation angle, segment and joint bolt stress. The results show that： the areas with abrupt changes between hard and soft ground are the weakest parts of shield tunnels regarding the longitudinal aseismic design, and the areas where the internal forces of the tun- nel structure increase obviously at the soft ground side are four times the areas covered by the tunnel external diame- ter; when the seismic wave spreads in a lateral direction, the longitudinal moment plays a control role, and when the seismic wave is input vertically, the higher axial force plays the control role; and the tunnel structure is in a more un- favorable condition with longitudinal seismic excitation as compared to lateral excitation under the same level of seismic action.