黄土无衬砌隧道破坏机制振动台试验研究——隧道稳定性分析讲座之二

Shaking Table Test Studies of Failure Mechanism of Unlined Loess Tunnel under Earthquake

在参考相关文献以及做了一定数值模拟分析后进行了黄土无衬砌隧道的大型振动台试验的研究。振动台试验的研究结果表明:埋深越深峰值加速度越小,埋深浅的隧道和地下结构要加强抗震措施;隧道洞口部由于刚性变化较大峰值加速度相比沿隧道其它位置要大,在隧道洞口部一定范围内要提高抗震水准;隧道直墙中下部是最易破坏的部位,而隧道仰拱会出现拉裂缝,最终这两处会形成贯通的破坏区,在输入0.8 g的峰值加速度后测得的加速度峰值曲线变缓,在0.8g的峰值加速度处出现拐点,表明此时隧道围岩进入塑性。进行振动台试验的数值模拟分析表明:在输入0.9 g的峰值加速度计算得到的隧道安全系数为1.07,而在输入1.0g的峰值加速度时隧道的安全系数低于1.0,隧道破坏。试验和数值模拟都说明黄土无衬砌隧道具有很强的抗震性能。

A large-scale shaking table test of loess unlined tunnel is done after relevant literature consulting, and numerical simulation analysis. Shaking table test results show that： the deeper the depth the smaller peak accelera- tion, the tunnels and underground structures with shallow depth need to reinforce earthquake resistance measures; tunnel entrance department will have greater change in peak acceleration dueto its rigidity. Compared to other loca- tions along the tunnel the seismic standards, in the tunnel entrance area within a certain range; should been hanced tunnel in the lower part of vertical wall is the most easily damaged parts and the tensile cracks of tunnel invert will ap- pear at first, and eventually the two parts will be formed connected destroyed areas;the measured peak acceleration curve is more smooth when the input peak acceleration is more than 0.8 g, the surrounding rock is plastic when a turning point appears at the input peak acceleration in 0.8 g. The numerical simulation analysis of the shaking tabletest shows that ： the safety factor of the tunnel is 1.07 when the input peak acceleration is 0.9 g, but the safety factor of the tunnel is less than 1.0 when the input peak acceleration is 1.0 g, then the tunnel damaged. The shaking table test and numerical simulation all show that loess unlined tunnel has strong anti-seismic performance.