隧道工程地震动响应研究综述:从岩体动力特性到结构抗震分析

Review on seismic response of tunnel engineering: From dynamic characteristics of rock mass to structural earthquake-resistant analysis

  • 摘要: 尽管隧道工程结构被周围地层所约束,地震荷载作用下结构与地层之间的相对运动并不明显,抗震性能显著优于地面结构,但其并不是完全“免震”的。伴随隧道及地下工程建设的深度和广度持续拓展,结构抗震设防面临着日益严峻的挑战,深入研究地下工程结构的抗震性能并提升其抗灾韧性具有重要意义。首先,回顾了国内外已建立的隧道震害数据库,结合典型的隧道震害案例,归纳了震害的主要特征,并分析了震害影响因素及震害机理。其次,为有效认识工程岩体地震动特性,从岩石和节理的速率效应和循环加卸载下的力学行为、应力波在节理岩体中传播规律等3个方面进行综述。再次,围绕地下工程结构抗震分析方法,深入开展调研,探讨模型试验、动力时程分析法、简化抗震分析法、波动解析法、地震易损性评估取得的研究进展及亟待解决的关键问题。最后,梳理了目前常见的地下工程的地震防护措施,以期为隧道及地下工程抗震设防提供借鉴。研究表明:在地震烈度达到一定级别后,衬砌结构不可避免地出现不同程度的损伤。典型破坏类型主要包括轻微裂缝、剥落、渗漏水甚至错台、垮塌,破坏特征与地震动参数、结构特征、地质条件密切相关;工程岩体表现出很强的速率敏感性,循环加卸载条件下的应力−应变曲线呈现明显的滞回特性,形成封闭的塑性滞回环,并出现不可逆的累积损伤,开发可表征岩土和混凝土材料速率效应和循环荷载性质的动态本构模型并嵌入数值仿真中值得重视;不良围岩条件会加剧衬砌结构的加速度、动土压力与应变响应,穿越断裂带等部位的衬砌结构动力响应更趋剧烈,强震与断层错动、高地应力等多因素耦合下结构响应规律研究值得关注;由于刚度突变和应力集中效应,隧道群之间的连接节点以及空间上交叉、重叠的复杂部位往往是隧道抗震薄弱环节,考虑群洞效应的简化抗震分析方法需深入探索;融合地下结构的地震易损性与使用功能恢复能力是实现其抗震韧性提升的关键途径;多重防护策略融合、新材料和新型结构体系的引入是未来抗震防护设计的重点。

     

    Abstract: Although tunnel structures are confined by the surrounding strata, and relative movement between the structure and strata is not obvious under seismic loads, resulting in significantly superior seismic performance compared to surface structures, they are not entirely “seismic-free”. With the continuous development of the construction of tunnels and underground engineering, it is a major challenge for structural earthquake-resistant fortification design. Therefore, it is of great significance to conduct in-depth research on the seismic performance of underground structures and to promote their seismic resilience. First of all, the established tunnel seismic damage databases worldwide are reviewed. Based on the typical tunnel seismic cases, the main seismic damage characteristics are summarized, and the damage influencing factors and mechanisms are analyzed, respectively. Then, to effectively recognize the ground motion features of a rock mass, an extensive literature review is performed to explore the rate-dependent effect and the mechanical behavior under cyclic loading and unloading of rock and joint, and stress wave propagation principles in jointed rock. Additionally, from the perspective of seismic analysis of underground engineering structures, research progress and urgent key issues to be solved in the physical similarity experiment, dynamic time-history analysis, simplified seismic analysis method, wave analysis method, and seismic vulnerability analysis. Finally, the current common seismic protection countermeasures of underground structures are sorted out to provide a reference for seismic reinforcement of tunnels and underground projects in the future. It can be seen that tunnel lining will emerge with different degrees of damage during a certain level of earthquakes, such as slight cracks, spalling, leakage, dislocation, and collapse, which are related to ground motion parameters, structural characteristics, and geological conditions. Engineering rock mass exhibits a very strong rate-dependent effect. When it is subject to cyclic loading and unloading, the stress-strain curve will exhibit closed plastic hysteresis loops, and irreversible cumulative damage occurs. It is worthy of attention to develop a dynamic constitutive model that can characterize the rate effect and cyclic load properties of geotechnical and concrete materials and embed it into numerical simulation. Poor surrounding rock conditions will aggravate the acceleration, dynamic earth pressure, and strain response of the lining structure. Considering that the dynamic response of the lining structure crossing the fault zone is more intense, the study of structural response under coupling strong earthquake, fault dislocation, and high ground stress may be necessary. Since the sudden change of stiffness and the effect of stress concentration, the structural junctions and spatially overlapping sections between tunnel groups are often the weak links of tunnel seismic resistance. The simplified seismic analysis method considering the group cavities effect needs to be further explored. Integrating seismic vulnerability and functional recovery capacity of underground structures is a critical approach to enhancing seismic resilience. The combination of multiple protection strategies, the introduction of new materials, and new structural systems is the focus of future seismic protection design.

     

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