考虑进洞高程效应的黄土隧道洞口段地震动力响应特征研究

Seismic Dynamic Response Characteristics of Loess Tunnel Portal Section with Consideration of Tunneling Elevation on the Slope

摘要:

通过大型振动台模型试验并采用Midas-GTS有限元软件进行模拟计算，研究黄土隧道洞口段在地震作用下的动力响应特征、破坏过程和地震波在模型中的传递规律，分析影响黄土隧道洞口段地震动力响应的主要因素。结果表明：边坡沿弧形开裂面的垮塌受坡脚剪切和坡顶拉裂的共同作用；边坡会对其卓越频率内的地震波产生明显放大效应，且在1/2 坡高以上放大效应出现饱和现象；隧道临空面是影响隧道洞口段地震动力响应的主要因素。考虑进洞高程效应时隧道洞口段抗震设防长度可取距洞口5倍洞径范围。振动台模型试验与数值计算在位移、加速度、应力三个响应特征上吻合较好，证明二者结果合理可靠。研究成果可为隧道工程设计和地下结构抗震理论研究提供有益参考。

Abstract:

In this study, we conducted a large-scale shaking-table model test and a numerical simulation using Midas-GTS finite element software to obtain the dynamic response characteristics and failure process of a loess tunnel portal section under earthquake action and the transmission law of the seismic wave. We then analyzed the main factors influencing the dynamic response of the loess tunnel portal section. The results reveal that the collapse of the slope along the arc fracture surface is affected by the coupled effect of shearing at the toe and cracking at the top of the slope. The slope will have a significant amplification effect on the seismic waves at the predominant frequency. The tunnel free surface was found to be the main factor affecting the seismic dynamic response of the tunnel portal section. The length of the anti-seismic section at the tunnel opening should be five times the portal diameter with the consideration of tunneling elevation on the slope. The results obtained from the shaking-table model test and numerical calculation agree well with respect to the three response characteristics: displacement, acceleration, and stress, which verifies the results as being reasonable and reliable. These research results provide useful reference information for tunnel engineering design and the anti-seismic theoretical research of underground structures.