为探究立体交叉隧道在地震荷载作用下的动力响应并对立体交叉隧道的抗震设计提供理论参考，通过大型振动台试验，分别研究加载X单向及XZ双向El-Centro波时，斜交型立体交叉隧道的上跨和下穿隧道及交叉区段坡体内部加速度峰值的分布规律。试验结果表明： 1）上跨及下穿隧道拱顶加速度峰值在交叉段中心断面处最大，影响区段两侧断面较小，呈现出“抛物线”分布，表明拱顶易成为立体交叉隧道抗震的薄弱环节； 2）由于下穿隧道及空间效应的存在，导致上跨隧道交叉断面仰拱处的地震响应较拱顶而言明显减弱，同时下穿隧道仰拱交叉段中心断面处动力响应最小，即仰拱破坏模式表现为影响区段两侧断面—交叉段中心断面的传递演化形式； 3）坡体内部交叉中心段的加速度响应存在叠加效应，导致该点的地震响应最为强烈，且其余测点的加速度放大系数随着埋深的增大而逐渐减小； 4）在加载XZ双向地震波时，其同一测点的动力响应相较于只加载X单向时显著增长，且在高地震烈度（0.4g~0.6g）时这种增长现象的变化幅度较大； 此外，地震波加载方向的改变对立体交叉隧道仰拱处的地震响应产生不同影响。
To explore the
dynamic response of overlapped tunnels under the action of seismic loads and
provide a theoretical reference for the seismic design of overlapped tunnels,
the distribution laws for peak acceleration values of upper and lower tunnels
and crosssection of oblique overlapped tunnels are studied using a largescale vibration test platform under X unidirectional and XZ bidirectional ElCentro waves,
respectively. The results show that: (1) The peak acceleration at the central
crosssection of the overlapped tunnels is the highest,
whereas those at the crosssections of the ends of the
tunnels are significantly less; as such, the peak acceleration curve has a
parabolic shape, indicating that the crown of the overlapped tunnel would be
the weak point during earthquake resistance. (2) The seismic response of the
invert at the crosssection of the upper tunnel is
significantly weaker than that of the crown because of the undercrossing tunnel and spatial effect. Moreover, the dynamic response
at the central crosssection of the invert of the undercrossing tunnel is the lowest, indicating that the failure mode of
the invert shows a transmission evolution from both sides of the affected crosssection to the central crosssection. (3)
Superposition effect is observed in the acceleration response of the central
crosssection soil, leading to the strongest seismic
response at this point. However, the acceleration amplification factors of
other points decrease with increasing buried depth. (4) The dynamic response of
a point under the XZ bidirectional seismic wave is much higher than that under the X unidirectional [HJ]seismic wave,
especially when the seismic intensity is between 0.4 g and 0.6 g. Seismic
waves with different loading directions diversely affect the seismic response
at the invert of the overlapped tunnels.
