强震作用下隧道明洞段的减震机理及对策研究

In order to improve the stability of the mountain near the portal part of tunnel, the construction of tunnel should obey the discipline that 'enter earlier and out later'. To present precondition for subsurface excavation, the cut-cover part of tunnel is commonly applied. Under strong ground motion, the cut-cover part of tunnel is the weakest part for antiseismic. Currently, the countermeasure for the cut-cover part of tunnel under strong ground motion is one of the key issues for the antiseismic research of underground structures. In this proposal, based upon the field investigation in early period and the scientific classification of the damage genesis, the damage mechanism, the influence factors and the dynamic response discipline of the cut-cover part of tunnel will be analyzed. Based on the base seismic isolation method for the ground structures and the buffer layer method for the underground structures, two or more original shock absorption structures will be presented especially for the cut-cover part of tunnel. Applying the vibration mechanics, the wave mechanics, and the earthquake engineering knowledge, through the dynamic response properties of the cut-cover part of tunnel, the mathematical and mechanical model will be founded for the corresponding shock absorption structure. In the model, the interaction among the overlying strata, the tunnel liner and the shock absorption structure will be considered. The feasibility of the countermeasure will be verified by the related mathematical and mechanical model, through which the mechanism of the countermeasure will be discussed. Because of the complexity of the dynamic analysis, numerical simulation will be realized through secondary development of the existing finite element program, and verified by the indoor model test. Employing both numerical simulation and indoor model test, the effectiveness of the proposed shock absorption structures would be compared under special conditions, and the main influence factors of the damping effect will be optimized. The research of this proposal can provide important theoretical basis and design principles for the practical engineering.

为增强隧道洞口段的山体稳定性，需贯彻早进晚出的原则，但为了给暗挖进洞创造条件，往往需要接长一段明洞，而强震作用下的明洞段是抗震的薄弱环节，其灾害控制对策是目前地下工程抗减震领域亟需解决的关键问题之一。本项目拟基于前期的现场调查,在对明洞段震害形式进行科学分类的基础上，研究其破坏机理、影响因素和动力响应规律，参考地面建筑的基底隔震法和地下结构的减震层法，提出两种或多种针对明洞段的减震结构；依据振动力学、波动力学和地震工程学等理论，结合明洞段的动力响应特性，建立考虑上覆土层、隧道衬砌与减震结构相互作用的数理力学模型，从理论上验证减震结构的可行性，并剖析其减震机理；利用有限元程序进行二次开发，实现数理力学模型的程序化，在室内试验正确性验证的基础上，综合数值分析和模型试验等手段，比选特定条件下的减震结构，并优化影响其减震效果的主要因素，为将本项目研究内容应用于工程实践提供理论基础和设计依据。

随着地球地震活跃期的来临，在我国西部大开发建设的背景下，为了保证强震作用下隧道特别是抗震最薄弱部分的明洞段安全，亟需相应的减震机理与灾害控制对策研究。采用资料调研、数值模拟和模型试验等方法，本课题深入研究了隧道洞口段的地震响应机理及减震对策。.（1）通过文献资料的广泛搜集，明确隧道洞口段的破坏形式可分为：①边坡失稳破坏导致的崩塌、滑落造成其变形和压损；②隧道门墙壁的破损、倾斜、开裂等问题；③隧道过断层段的错动。.（2）结合模型试验和数值分析的方法，研究仰坡角度、衬砌刚度，减震缝间隔对隧道结构地震响应的影响，得出结论有：①过大的衬砌刚度对衬砌的受力不利，在保证静力荷载和变形的条件下，适当减小衬砌的刚度可以吸收地震荷载的能量，对隧道抗震更有利。②无配筋衬砌相比有配筋衬砌的峰值弯矩大，明洞以及洞口附近衬砌应予以配筋。③仰坡坡度越大，洞口段上覆土层越厚，其惯性力和主动压力越大，衬砌附加弯矩峰值越大。在洞口处可以通过接长明洞来减小仰坡坡度，从而减小衬砌的受力，同时还可以预防地震引起的滑坡、落石等次生灾害。④洞口附近设置减震缝可以改善衬砌的受力，降低受力集中，使衬砌受力更均匀。.（3）借助模型试验和数值方法研究上部滑移隔震、下部滑移隔震、下部碎石减震、全包减震、隔震层+下部碎石减震五种措施的减震效果，得出设置隔震层和下部碎石对衬砌的减震作用明显，下部碎石减震作用更为有效。洞门附近可以对基底进行处理，这不仅可以增加基底承载力并且可以起到一定的隔震作用。.本课题研究成果有助于提高隧道结构抗的抗减震，可为相关工程设计与施工提供指导，亦可为今后规范和标准的制定提供理论和技术支持。