地震动作用下隧道洞口段破坏特征试验研究

Experimental Study on Failure Characteristics of Tunnel Portal under Ground Motion

为研究山岭隧道洞口段在地震动力作用下对边坡变形特征及其二者之间的相互影响,以宝兰客专某黄土隧道为工程背景,开展了大比例尺的黄土隧道洞口段大型振动台模型试验,输入不同类型的地震动参数,分析在地震动力作用下黄土隧道洞口段的动力响应及变形破坏特征。结果表明:(1)随着地震动强度的增大,模型表观和内部经历了弹性阶段、弹塑性阶段和破坏阶段;(2)阿里亚斯强度(Arias Intensity)的水平与垂直分量的放大系数云图呈现颜色区域互补状态,能量衰减区集中在洞口拱顶附近的围岩,仰拱底部1~4.50倍洞径和拱顶2.50~4倍洞径围岩范围则为能量加强区;(3)不同地震波形、相同加载方向,加速度水平、垂直分量的峰值连线线形相似,个别测点的加速度峰值突出到线形之外,峰值出现时刻明显提前或滞后,说明围岩发生较大的塑性变形或破坏;(4)单向加载时,拱顶、仰拱底部围岩沿隧道进深方向的加速度放大效应基本一样,沿垂直方向的放大系数连线的台阶式变化更为明显。双向耦合加载时,拱顶、仰拱底部围岩的放大系数连线的台阶式变化都较为明显。

In order to study the slope deformation characteristics and mutual influence between the entrance section of the mountain tunnel under the action of seismic dynamics, a large-scale shaking table model test was conducted with a loess tunnel of Bao-Lan passenger dedicated line as the engineering background. During the test, seismic waves of different waveforms, loading directions and peak ground accelerations were applied to study the dynamic response, deformation, and failure characteristics of the loess tunnel and slope system. The test results indicated that:(1) with the increase of seismic intensity, the apparent and internal longitudinal sections of the model have experienced the elastic stage, elastic-plastic stage, and failure stage.(2) The contour lines of horizontal and vertical components of the Arias Intensity showed a complementary trend in colors. The local energy degradation area was mainly concentrated in the surrounding rocks near the arch of the portal, while the energy concentration area was mainly distributed beneath the inverted arch about 1~4.50 times of the tunnel radius and above the vault about 2.50~4.50 times of the tunnel radius.(3) With different seismic waveforms and the same loading direction, the peak value line of horizontal and vertical components of acceleration was similar. However, the peak values of acceleration of some measuring points protruded out of the line, and the peak value appeared obviously in advance or lag, indicating that the surrounding rock experienced large plastic deformation or failure.(4) Under unidirectional loading, the acceleration amplification effect of the surrounding rock at the top and bottom of the invert was basically the same along the tunnel deepening direction. The step change along the vertical amplification coefficient line was more obvious. When the two-way coupling loading was applied, the step-by-step variation of the amplification coefficient of the surrounding rock at the top and bottom of the arch was obvious.