黄土隧道结构的振动台模型试验研究

Shaking Table Model Test of Loess Tunnel

为了研究黄土隧道结构在不同地震波及降雨条件下的地震响应和橡胶减震层的减震效果,按相似理论分别设计制作了缩尺比为1∶40的减震黄土隧道及非减震黄土隧道,在总降雨量50 mm,降雨强度10 mm·h-1的条件下,分别加载近、远场地震波El-Centro波和Taft波,对比了地震波不同加速度条件下黄土隧道各测点的地震响应情况及土压力变化情况,通过减震模型和非减震模型各测点的应变变化情况分析了黄土隧道的减震效率。结果表明:在调幅和持时一致的情况下,黄土隧道结构对于不同的地震动具有明显的选择性,El-Centro地震动条件下的动力响应大于Taft地震动条件下的动力响应,说明黄土隧道结构的动力响应不仅取决于地震动的强度及持时,也与地震波的频谱特性有关,黄土隧道结构对近场地震波的响应大于远场地震波;对模型横向加载,模型各点的横向加速度和竖向加速度均有变化,横向的加速度响应大于竖向的加速度响应;拱顶位置的土压力较大,拱脚位置虽然土压力较小,但应变变化较大,应力集中现象明显;通过设置减震层可使衬砌不同部位的应变值均有所减小,且应变越大的部位减震率越高,不同工况下拱顶及拱脚的应变减震率接近50%,设置减震层不但可以减小衬砌结构的变形,而且能吸收地震能量,发挥围岩结构和衬砌结构的协同作用,减小土体的裂缝宽度及深度。

To study the seismic response of the loess tunnel structure and the damping effect of the rubber damping layer under different seismic fields and rainfall conditions, a 1∶40 damping loess tunnel and non-damping loess tunnel were designed and constructed according to similar theories. Under the conditions of a total rainfall of 50 mm(a rainfall intensity of 10 mm·h-1), the near seismic wave(El-Centro wave) and far-field seismic wave(Taft wave) were applied. The changes in the seismic response and earth pressure around the loess tunnel measuring points under different acceleration conditions of the seismic wave were compared. The damping efficiency of the loess tunnel was analyzed through the strain changes at each measuring point of the damping and non-damping models. The results demonstrate that when the amplitude modulation and duration are the same, the loess tunnel structure exhibits obvious selectivity for different seismic motions. The dynamic response under the El-Centro seismic motion condition is greater than that of the Taft seismic motion condition, indicating that the dynamic response of the structure around the loess tunnel depends not only on the intensity and duration of the seismic motion, but also on the spectral characteristics of the seismic wave. The response of the loess tunnel structure to near-field seismic waves is greater than that of far-field seismic waves. When the model is loaded laterally, the lateral and vertical acceleration of each model point are changed, and the lateral acceleration response is greater than the vertical acceleration response. Moreover, the earth pressure at the vault position is relatively large. Although the earth pressure at the arch foot position is relatively small, the strain changes significantly and the stress concentration is obvious. The strain values of different parts of the lining are reduced by setting the damping layer, and greater strain results in a higher damping rate. The strain damping rate of the vault and arch foot is close to 50% under different working conditions. Setting the damping layer can reduce the deformation of the lining structure, absorb seismic energy, exert the synergistic effect of the surrounding rock structure and lining structure, and reduce the crack width and depth of the soil.