黄土隧道仰边坡及洞口段地震动响应试验研究

随着西部大开发的进一步深入,国家对该地区的抗震减灾工作提出更高的要求。以郑西客专和宝兰客专线上比较典型的黄土隧道为工程背景进行振动台模型试验,本次试验加载的地震波形为正弦波(3~50 Hz)、汶川卧龙波和EL-Centro波,通过对试验过程中边坡和隧道洞口段的失稳破坏形式以及得到的实验数据研究分析,得出以下结论:(1)试验过程中模型在坡顶、坡面、拱顶以及拱脚处分别出现不同程度的裂缝,坡顶中部出现错台和震陷。随着地震动峰值加速度的增大边坡鼓出现象更加明显,同时存在隧道一侧滑塌破坏程度大于纯边坡一侧。(2)隧道的存在会加大坡面的加速度,坡顶边缘处的动力放大效应比较明显,当台面峰值加速度增大时会出现放大效应趋于"饱和"现象。(3)随着地震动峰值加速度的增大,仰拱和拱顶的最大土压力值位置逐渐向隧道洞内延伸,洞口段衬砌加速度和土压力沿隧道轴向一般先增大再减小,洞口段的抗震设防长度建议为5倍的最大洞径。

Experimental Study on Seismic Responses of Slope and Portal of Loess Tunnel

With the continued and rapid development of the Western Region of China,the state puts forward higher requirements for earthquake resistance and disaster reduction.In this paper,shaking table model tests are conducted based on typical loess tunnels on Zhengzhou-Xi ' an and Baoji-Lanzhou dedicated passenger railway lines.The loaded seismic waveforms in the tests are sine wave(3 ~ 50 Hz),Wenchuan,Wolong and EL-Centro waves.The analysis and research on the slope and tunnel portal failure and experimental data collected in the process of tests draw the following conclusions:(1) In the process of model test,the top of slope,slope face,vault and arch foot witnessed cracks in different degrees and top middle faulting and subsidence.With the increase of the peak acceleration of the ground motion,the slope bulge is more obvious,and the damage degree of one side of the tunnel is larger than that of the pure slope.(2) The presence of tunnels may increase the acceleration of slope,the top edge of the power amplification effect is more obvious,and the increase of the peak acceleration may result in"saturation"of the magnification effect.(3) With the increase of seismic peak acceleration,the inverted arch and vault of the maximum stress position gradually extends into the tunnel,theacceleration of portal lining and the stress along the tunnel axis increase first and then decrease,and the length of tunnel seismic fortification is recommended to be 5 times the maximum tunnel diameter.