下伏隧道层状岩质边坡地震响应特性的大型振动台试验研究

Large-scale shaking table model test study of seismic response characteristics on layered rock slope with tunnel

针对下伏隧道水平层状岩质边坡,设计并完成比尺1∶10的大型振动台试验。试验选取汶川波、Kobe波和大瑞人工波作为台面输入地震波,研究下伏隧道水平层状岩质边坡的加速度和动位移响应变化规律及地震动参数对边坡动力响应特性的影响。研究表明:在地震荷载作用下,下伏隧道水平层状岩质边坡的加速度响应随着地震波类型、激振强度、激振方向、岩层相对位置等因素呈现出非线性变化特征;在X向或Z向单向激振下,边坡主要在地震波激振方向上产生动力响应;边坡的竖直加速度放大系数沿坡高呈"U"型变化,最小值出现在软弱夹层与上部弱风化岩层的分界面处,软弱夹层对边坡的竖向加速度响应有较大影响。边坡的动位移响应整体上表现为:对于不同类型地震波,Kobe波双向激振下最大、大瑞波次之、汶川波最小;对于同一种地震波,双向激振时较强、单向激振时较弱。边坡软弱夹层与上部弱风化岩层的分界面在耦合地震作用下易发生剪出破坏,应采取相应的预加固措施。

A large scale shaking table experiment with a scale of 1:10 is designed and completed for a horizontal layered rock slope under a tunnel. A series of tests are performed with different seismic waves including Wenchuan, Darui and Kobe. The dynamic acceleration and dynamic displacement response of a horizontal layered rock slope in a submerged tunnel are studied, and the influence of ground motion parameters on the dynamic response characteristics of the slope is studied. Results show that the dynamic response of seismic acceleration presents obvious nonlinearity amplification trend with seismic waveform, earthquake amplitudes, excitation direction and the transducer locations. With the unidirectional seismic wave excitation, the dynamic response of rock slope is mainly generated from the same direction of inputted seismic wave. The vertical acceleration amplification coefficient of rock slope evolves with the trend as a type of "U" along the foot to the top of slope and becomes the minimum at the separatrix of weak rock and upper weakly weathered rock.The soft rock has a significant effect on the vertical acceleration response of rock slope. As a whole, the seismic displacement response amplitude of rock slope is K-XZ > DR-XZ > WC-XZ and bidirectional excitation is stronger than unidirectional. The position near the separatrix of weak rock and upper weakly weathered rock is easy to generate a shear failure under the coupled excitation. The interface between soft slope and upper weak weathered rock is prone to shear failure under coupled seismic actions, so the corresponding pre-reinforcement measures should be adopted.