山岭隧道洞口段设置减震层的振动台模型试验研究

Shaking table test for dynamic response in portal section of mountain tunnel with shock absorption layer

为了解减震层在地震过程中对隧道衬砌及围岩仰坡动力响应的影响,针对山岭隧道洞口段开展振动台物理模型试验研究,模型试验按有无减震层分为两组工况。试验结果表明:减震层的存在可以有效减弱洞口段衬砌加速度与位移的放大效应,减弱围岩振动向衬砌的传递;衬砌的应变反应在设置减震层后明显减小,特别是应变反应较大的两侧拱肩和拱脚位置,减震层的设置使衬砌的动应变接近均匀,随着地震次数的增加,减震层并不会失效,减震效率反而会有所增强;而减震层的设置不能改变围岩的加速度反应,坡面随高程的放大效应依然明显,较易发生局部的滑塌破坏,特别是高位滑塌,但坡面均为浅层破坏,不会对衬砌产生附加荷载作用,但需要注意的是滑塌的围岩会掩埋洞口,将严重影响隧道的正常使用。

Big scale shaking table model tests are performed on tunnel portal parts, in order to learn about the effect of shock absorption layer on the dynamic response of lining and front slope during earthquakes. In this modeling test, two cases with and without shock absorption layer respectively, are executed to analyze the behaviors of shock absorption layer. The analysis results show that： the shock absorption layer can weaken the amplified effect of acceleration and displacements of tunnel structures exist at the area which is of some distance from the entrance of the tunnel, and reduce the vibration of lining transmitting from the surrounding rock. The strains of lining are reduced during the earthquake because of the shock absorption layer, especially on arch waist and arch feet, which could be seen as strain concentration zone, and the shock absorption layer can make strain of lining uniformity. As the increasing of the PGA of input seismic wave. there is no invalidation, but will be improved on damping efficiency. Whether or not the shock absorption layer is installed, there is not much differences on the acceleration response of surrounding rock, and the amplified effect along the slope surface is still obvious, which make the slump on the slope easier to occur, especially on the top of the slope. But there is the surface failure, and we should focus on that the tunnel openings are usually partially or completely buried, which severely affect the normal use of tunnel.