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当前地下岩石工程地震响应研究中,缺乏对近断层地震动的影响机制的研究,也较少考虑地下岩石工程赋存环境中的地质结构。采用一种非线性节理本构模型模拟不利地质结构面,结合从NGA-West2数据库中选取的近断层脉冲型、近断层无脉冲型、及远场地震记录,分析近断层地震动对不利地质结构地震破坏现象的影响机制,并讨论、提出不利地质结构的地震动潜在破坏势,最后针对受层间错动带C2切割控制的白鹤滩水电站左岸尾水系统1#尾调室,揭示其在近断层脉冲型、无脉冲型、远场地震动作用下的动力响应与稳定性的差异。初步研究结果表明:(1)仅有近断层脉冲型地震动才具有较大的速度、位移峰值和反应谱长周期值的特点,而近断层无脉冲型地震动特性与远场地震动近似;(2)相对于近断层的大幅值,速度脉冲才是导致近断层地震动具有较大破坏能力的根本原因,速度脉冲使得岩体结构面两盘产生不可接受的剪切位移,成为洞室在近断层地震动作用下独特的失稳机制;(3)对于地下工程中的不利地质结构而言,相比最常用的地震动强度参数PGA,PGV,PGD和PGV/PGA是为更理想的地震动潜在破坏势,且近断层/远场地震动可适用一种破坏势;(4)提出的潜在破坏势参数在白鹤滩尾水系统1#尾调室的地震响应分析中得到了较好的验证,若受近断层脉冲型地震动的影响,洞室可能处于不稳定状态,可能需要针对性的抗震支护措施。结论可供地下洞室的抗震设计与分析参考。
In the current research on seismic response of underground rock engineering, there is a lack of research on the influence mechanism of near-fault ground motions and less consideration of the geological structure in the underground rock engineering environment. A nonlinear joint constitutive model was used to simulate the unfavorable geological structure. Based on the near-fault pulse type, near-fault pulseless type and far-field seismic record selected from the NGA-West2 database, the effect of near-fault ground motions on the adverse geological structure Finally, in view of the potential tailing potential of the left bank tailrace system of Baihetan Hydropower Station under the control of C2 cut between layers, Difference of dynamic response and stability of fault pulse, pulseless and far-field ground motions. Preliminary results show that: (1) Only the near-fault impulsive ground motion has the characteristics of large velocity, displacement peak and long-period response spectrum, while the near-fault impulsive ground motion is similar to the far-field ground motion; 2) Compared with the near-fault large amplitude, the velocity pulse is the fundamental reason that causes the near-fault ground motions to have a greater damage ability. The velocity pulse causes unacceptable shear displacements on both sides of the rock mass structure plane, (3) PGA, PGV, PGD and PGV / PGA are the most suitable ground motion parameters for the geotechnical structures in underground engineering, compared with the most common ground motion parameters (4) The proposed potential damage potential parameters are well verified in the seismic response analysis of the tailrace 1 # tailrace of Baihetan tailrace system, If subjected to near-fault impulsive ground motions, the caverns may be unstable and may require targeted seismic support. Conclusion It is a reference for seismic design and analysis of underground caverns.