倾滑断层动态破裂下衬砌隧道动力响应宽频高效模拟

Broadband and Efficient Simulation of Dynamic Response of Lined Tunnels under Dynamic Rupture of Dipslip Faults

摘要:

与远场地震动相比，近断层地震动具有上盘效应、速度脉冲等特征，将加剧地下结构震害。提出一种可高效模拟倾滑断层动态破裂—隧道反应全过程的快速多极间接边界元—有限元混合方法（FMM?IBEM?FEM）：采用快速多极间接边界元（FMM?IBEM）模拟断层破裂和大尺度场地地震动，发挥其求解精度高、计算存储量小的优势； 采用有限元（FEM）精细化模拟隧道及周围近地表场地域，通过施加黏弹性人工边界，将断层错动激发的地震动转化为施加在边界节点上的等效节点力，实现 FMM?IBEM 计算域和 FEM 计算域的应力和位移传递。基于所建方法，研究了断层距和断层倾角对近倾滑断层衬砌隧道地震响应的影响。结果表明：地震响应水平分量作用下衬砌隧道环向应力峰值出现在拱肩和拱脚，地震响应竖向分量作用下衬砌隧道环向应力峰值出现在拱腰和拱顶，且存在较大残余应力。当断层距为 2 000 m 时，地震响应水平分量作用下隧道拱脚内壁环向应力峰值相较断层距为 0 m 对应结果降低 54%；90°倾角断层产生的地震动对衬砌隧道影响最为显著，但同时要特别关注小于 45°的倾滑断层场地中衬砌隧道的动力响应。

Abstract:

Compared with far-field ground motions, near-fault ground motions exhibit characteristics such as hanging wall effects and velocity pulses, which can significantly exacerbate seismic damage to underground structures. The fast multipole method–indirect boundary element methodfinite element method (FMM-IBEM-FEM) was proposed to simulate the entire process of dip-slip fault dynamic rupture and tunnel response. The FMM-IBEM was employed to simulate fault rupture and large-scale site ground motions, leveraging its advantages of high solution accuracy and low computational storage requirements. The FEM was used for refined simulation of tunnels and surrounding near-surface domain. By applying viscoelastic artificial boundaries, the ground motions excited by fault dislocation were converted into equivalent nodal forces imposed on boundary nodes, enabling the stress and displacement transfer between the FMM-IBEM and FEM computational domains. Based on the proposed method, the effects of fault distance and fault dip angle on the seismic response of lined tunnels near dip-slip faults were investigated. The results showed that under the horizontal component of seismic response, peak circumferential stress in the tunnel lining occurred at the spandrel and arch foot, while under the vertical component, the peak appeared at the haunch and crown, with significant residual stress observed. When the fault distance was 2 000 m, the peak circumferential stress on the inner wall of the tunnel arch foot under the horizontal component of seismic response decreased by 54% compared to that at a fault distance of 0 m. Ground motions generated by faults with a dip angle of 90° had the most significant impact on the lined tunnel. However, special attention should also be paid to the dynamic response of lined tunnels in sites with dip-slip faults of less than 45°.