衬砌脱空对隧道地震响应影响的振动台试验研究

Shaking table tests for investigating the effect of void behind lining on the seismic responses of a tunnel

以某两车道高速公路隧道为原型,针对隧道衬砌完好且背后无空洞、拱顶衬砌完好但背后有空洞、拱顶衬砌厚度不足且背后有空洞3类情况开展振动台模型试验,研究既有隧道衬砌背后空洞及衬砌厚度不足对隧道地震响应的影响。试验结果表明:衬砌背后空洞及衬砌厚度不足对隧道地震响应的影响很大,显著降低了隧道结构的抗震性能,改变了隧道地震破坏模式,衬砌厚度不足处和空洞处成为抗震薄弱部位。随着空洞范围和衬砌厚度不足程度的增加,这种影响随之增大。相比较而言,空洞对抗震性能的影响更明显,衬砌厚度不足的影响呈非线性变化。对于无缺陷情况,衬砌开裂部位为与隧道中轴线约成45°角的拱腰和墙脚位置;当存在拱顶衬砌背后空洞时,衬砌拱顶部位首先出现裂缝,以拱顶、墙脚和仰拱部位开裂为破坏特征;当拱顶衬砌厚度不足且存在空洞时,衬砌破坏均以拱顶及墙脚开裂为主。

Taking a two-lane highway tunnel as the engineering background,shaking table model tests were carried out under three different conditions,including a normal tunnel,a tunnel with the defect of void behind lining and a tunnel with the defects of both void behind lining and insufficient thickness of lining. The influences of the defects on the seismic responses of tunnel were analyzed. The model tests show that the defects of lining significantly affects its seismic behavior.The seismic performance of the tunnel structure is obviously reducesd,the failure mode of the tunnel is changed,and the parts of lining thinning and void behind lining become the regions with weak tunnel seismic resistance. The effect increases with the increase of void range and thinning degree,the influence of the void on the seismic performance is greater than the lining thinning,and yet it is of non-linearity. For the model test condition one,cracks appear in the conjugate 45° directions with the central axis of the lining structure. For the model test condition two,the cracks first appear on the vault,and the failure mode of the lining is characterized by the cracks on the vault,at the corner and on the invert of tunnel. For the model test condition three,the crack damages of lining appear mainly on the vault and at the corner.