隧道洞口含软弱夹层仰坡振动台试验研究

SHAKING TABLE TEST ON TUNNEL FRONT SLOPE WITH WEAK INTERCALATION

为研究地震作用下含软弱夹层隧道洞口仰坡的动力响应特性,针对含软弱夹层隧道洞口仰坡开展大型振动台试验研究,通过分析水平和竖向激振作用下洞口段仰坡和衬砌模型动力响应和破坏特征,得到以下结论:水平向激振作用下,仰坡沿坡面向上存在明显加速度放大效应,软弱夹层对竖向加速度激振时仰坡动力响应有显著影响;越接近临坡面,衬砌结构加速度响应和越大,并且洞口段隧道衬砌拱顶加速度峰值最大,仰拱最小,衬砌结构受力状态复杂;竖向加速度激振时,软弱夹层上覆模型土出现松动,坡脚土体出现挤压、掉块,仰坡整体上保持稳定;在水平向激振作用下,而含软弱夹层仰坡则在坡脚土体先被挤压破碎,然后坡顶表面沿软弱夹层位置出现张拉裂缝,上覆土体沿软弱夹层滑动,最后土体大规模崩塌、滑落。竖向和水平激振力作用下,衬砌45°方向应变幅值最大,衬砌洞口段设防长度为25 m。该研究成果可以为山岭隧道洞口段边坡抗减震研究和设计提供参考。

Large-scale shaking table experiment was carried out to study the dynamic response of the front slope of tunnel entrance with weak layer has,and general conclusions were obtained through analyzing the acceleration and failure modes of front slope of tunnel entrance and tunnel lining under the horizontal and vertical excitation. The results showed that the front slope had an obvious acceleration magnified effect under the horizontal excitation and the weak layer produced a significant impact on the dynamic response of the front slope under vertical excitation;The peak acceleration of the tunnel lining at the entrance was larger than that far from the slope surface,at the entrance the maximum peak acceleration occured in the vault while that minimum occured in the invert,the forced state of the lining was complicated;With vertical acceleration excitation,the overlying soil model of the weak intercalation loosed,the soil at the toe of slope squeezed and fall-block,however the slope remained stable overall;Under the action of horizontal excitation,the soil at the toe of the front slope crushed first,and then the slope surface location along weak intercalation cracked,the overlying soil layer along weak intercalation slided,at last large-scale dilapidation and fall occured;Under the vertical and horizontal vibration force,the maximum strain amplitude occured in the 45°of the lining,the fortified length of tunnel portal section is 25 m. These conclusions can be reference for design,construction and study on the tunnel seismic study.