强震区穿越多破裂面破碎带隧道动力特性试验研究

Experimental Study on Dynamic Characteristics of Tunnels Crossing Multi-fault Fracture Zones in Strong Earthquake Regions

  • 摘要: 依托我国西部强震区某穿越活动断裂带的隧道工程,基于弹性地基理论建立集中质量力学与滑动模型,对穿越多破裂面破碎带隧道结构的受力与破碎带滑动特征开展研究。利用有限元软件结合无限元人工边界建立隧道与断层耦合模型,通过振动台试验对加速度响应进行分析,揭示地震时穿越多破裂面破碎带隧道围岩的动力响应规律及多破裂面破碎带的滑动规律。结果表明:围岩加速度放大效应随着PGA增大而减小,数值模拟与试验结果中围岩加速度峰值相差6.7%~13.6%;围岩纵向同高度处,破碎带与上下盘交界面附近土体加速度峰值最大,在PGA=0.4g时数值模拟与试验结果最小相差为0.8%,说明试验方法能够较好地模拟地震作用;采用破碎带相对滑动率γ对滑动位移进行评价,从上盘至下盘方向破碎带内各个破裂面之间的相对滑动率在理论解析、数值模拟与试验中从30.9%、33.46%、30.63%减小至16.5%、16.17%、15.3%,各破碎带内滑动量及破裂面处积累剪应力逐级减小。

     

    Abstract: Based on a tunnel project crossing an active fault zone in a strong earthquake region in western China, the stress of the tunnel structure and the sliding characteristics of the fracture zone in multi-fault fracture zones were studied. The research employed an elastic foundation-based lumped mass mechanical and sliding model. A coupled tunnel-fault model was established using the finite element software combined with infinite element artificial boundaries. Through shaking table experiments, the acceleration response was analyzed to reveal the dynamic response patterns of the surrounding rock and the sliding behavior of multi-fault fracture zones during earthquakes.Results show that the amplification effect of surrounding rock acceleration decreases as the peak ground acceleration (PGA) increases. The difference in peak acceleration values between numerical simulations and experimental results ranges from 6.7% to 13.6%. At the same height along the longitudinal direction of the surrounding rock, the peak acceleration of the soil near the boundary between the fracture zone and the hanging wall or foot wall is the largest. When PGA = 0.4g, the minimum difference between the numerical simulation and the experimental results is 0.8%, indicating that the experimental method can accurately simulate seismic actions. The relative sliding rate γ of the fracture zone was used to evaluate sliding displacement. From the hanging wall to the foot wall, the relative sliding rates between fault surfaces in the fracture zone decreased in theoretical analysis, numerical simulations, and experiments from 30.9%, 33.46%, and 30.63% to 16.5%, 16.17%, and 15.3%, respectively. Sliding displacements within the fracture zones and accumulated shear stresses at fault surfaces decrease progressively.

     

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