隧道设置减震层减震机制研究

 通过Fourier-Bessel函数展开法，推导平面SV波垂直入射下半无限弹性介质中圆形双层衬砌结构、围岩–减震层–衬砌洞室的动应力集中系数级数解，分析入射波频率、减震层弹性模量和厚度对动应力集中系数的影响，并结合数值模拟分析结果对比，深入研究减震层减震机制。研究结果表明：入射频率对衬砌动应力集中系数有显著影响，减震层对低频波具有较好的减震效果；由于减震层剪切模量低，围岩和隧道可以剪切变形，从而减小了作用在衬砌外部的法向作用力，降低了衬砌内侧最大动应力集中系数，但围岩和衬砌外侧切向应力增大；随着减震层与围岩弹性模量之比减小，减震层厚度增大，二次衬砌动应力集中系数变小，减震层与围岩的弹性模量比宜低于1/10～1/20，和减震层弹性模量对应，存在一个最优的减震层厚度值。以一公路隧道为背景，开展隧道减震层结构大型振动台试验研究，结果表明：隧道衬砌设置减震层后，可以显著降低衬砌内力，减小衬砌裂缝的数量。

Damping mechanism and shaking table test on mountain tunnel linings with buffer layers

With Fourier-Bessel function expansion，the dynamic stress concentration factor of the cylindrical composite-lining cavity subjected to vertically incident plane SV waves was derived for an half elastic space with double lining and buffer layer，named as rock-buffer layer-lining. The factors affecting the dynamic stress characteristic of the lining structure such as the incident wave frequency，elastic modulus and thickness of the buffer layer were discussed. The damping mechanism of the buffer layer was studied with the solution and the numerical simulation. The results showed that the frequency of the incident SV waves played an important role in the dynamic stress concentration factor of the combined-lined cavity，and the dynamic stress concentration factor of the lining decreased effectively with the buffer layer subjected to low incident frequency waves. Because of the low shear modulus of the damping layer，the shear deformation of surrounding rock and tunnel was generated， so that the normal force on the lining decreased and the dynamic stress concentration factor of the inner lining decreased. But the tangential stresses in the wall rock and outer part of the lining increased with buffer layer. With the lower elastic modulus and lager thickness of the buffer layer，the dynamic stress concentration factor of the secondary lining decreased. The optimum elastic modulus ratio of the buffer layer to surrounding rock was proposed to below 1/10–1/20，and there is an optimal thickness of the buffer layer for one specific elastic modulus. Then the shaking table tests were accomplished based on a road tunnel，and the results showed that the dynamic internal forces of the tunnel decreased and the crack number of the lining reduced with buffer layers.