【摘要】 采用有限差分软件FLAC3D 3.0研究隧道洞口段的抗震设防长度和衬砌刚度对地震反应的影响,分析设置横向减震层、纵向减震层和加固围岩对衬砌结构的减震效果,并总结山岭隧道洞口减震的思路和措施。结果表明:一般进入洞内25~30 m后地震放大效应开始趋于平稳,该距离可为确定洞口抗震设防长度参考;衬砌刚度过大在一定程度上将加大震害;设置横向减震层和纵向减震层都能使地震反应明显减弱,使应力分布更趋均匀,且前者效果明显好于后者;通过设置锚杆增强围岩整体性,可有效减少作用在衬砌上的地震荷载,且对软质围岩效果更佳。最后,提出山岭隧道洞口必须综合减震,衬砌应该刚、柔平衡。更多还原

【Abstract】 The influence of the protecting length of tunnel portal and lining stiffness on seismic response was studied by using the finite difference software FLAC3D 3.0.The damping effect of setting buffer layer in lateral direction or axial direction and reinforcing the surrounding rock on the lining structure was analyzed.The keys and the synthetical measures for shock absorption of mountainous tunnel portal were summarized as well.The result shows that(1) the amplification effect of seismic wave gets stable after going deep into tunnel about 25～30 m,which can be used as a reference to specify the protecting length of tunnel portal for earthquake-resistance;(2) too large stiffness of lining will expand the seismic damage;(3) setting lateral bufferlayer or axial buffer layer can both significantly decrease the seismic response and make the stress evenly,and the effect of the former is obviously better than the latter;(4) enforcing wall rock with bolts can effectively reduce the seismic load on lining and this effect is better for weak wall rock.Finally,it is put forward that synthetical measures for vibration absorption should be adopted and the lining stiffness should be balanced for seismic safety design of mountainous tunnel portal.更多还原