火灾下热传导-蒸汽压耦合作用对隧道衬砌受力特性与灾变机理影响研究

A large number of domestic and foreign cases demonstrate the significantly deteriorated mechanical performance and easily occurred spalling of tunnel lining in fire. This problem is directly related to the coupled heat conduction and vapor pressure in the tunnel lining exposed to fire, which has become the domestic and foreign academic research focus. However, almost all of the existing model test, theoretical and numerical analysis are difficult to accurately reflect the tunnel lining’s mechanical characteristics under coupled heat conduction and vapor pressure, resulting the disaster mechanism of tunnel lining in fire remains unclear and lacking systematical and in-depth study. This project aims to the tunnel lining’s mechanical characteristics under coupled heat conduction and vapor pressure in fire. The study on influence of tunnel lining's mechanical behavior and disaster mechanism under coupled heat conduction and vapor pressure in fire, will be carried out using the research platform of nonlinear analysis method for structure damage combined with the mass transfer theory. The action mechanism of coupled heat conduction and vapor pressure in tunnel lining exposed to fire will be analyzed in three-dimensional space. The numerical analysis method for tunnel lining’s mechanical characteristics in fire will be developed, taking account of the coupled heat conduction and vapor pressure, and the influence of tunnel lining’s mechanical characteristics and disaster mechanism due to coupled heat conduction and vapor pressure in fire will be disclosed, provided a theoretical basis for the study of lining structure’s fire resistance in tunnels and underground engineering, which has very important theoretical significance and wide application prospect.

国内外大量隧道火灾案例表明，火灾将极大劣化混凝土衬砌结构力学性能并易导致其产生爆裂。该问题与火灾高温下衬砌内部热传导-蒸汽压耦合作用直接相关，这已成为当前国内外学术界研究热点。然而，现有模型试验、理论与数值分析均难以准确反映热传导-蒸汽压耦合作用对火灾下衬砌结构受力特性影响，致使火灾下隧道衬砌灾变机理尚不明确，且缺乏系统深入研究。本项目针对火灾下隧道衬砌处于热传导-蒸汽压耦合作用受力特点，以与物质移动理论相结合的结构破坏非线性分析方法为研究平台，开展火灾下热传导-蒸汽压耦合作用对隧道衬砌受力特性与灾变机理影响研究，分析衬砌结构在三维空间热传导与蒸汽压耦合作用机理，建立火灾下考虑热传导-蒸汽压耦合作用的隧道衬砌受力特性数值分析方法，揭示热传导-蒸汽压耦合作用对隧道衬砌受力特性与灾变机理影响规律，预期成果将为隧道与地下工程衬砌结构耐火性能研究提供理论基础，具有十分重要理论意义和广泛应用前景。

火灾高温将极大劣化隧道混凝土衬砌结构力学性能。然而，火灾高温下混凝土衬砌内部出现热传导、蒸汽压移动等现象，表现出热传导-蒸汽压耦合作用的受力特点，使得火灾高温下隧道混凝土衬砌受力特性尤为复杂，且缺少有效分析方法。本项目在研究表征混凝土单向热传导与蒸汽压移动规律的杆单元特性、表征裂缝对混凝土结构蒸汽压移动影响的杆单元模型基础上，构建了适应隧道衬砌热传导与开裂前后蒸汽压不同移动规律的三维杆单元网络模型。在优化已有的用于混凝土结构受力性能分析数值模型基础上，研究了将三维杆单元网络模型嵌入受力性能分析数值模型，形成了火灾高温下考虑热传导-蒸汽压耦合作用的隧道混凝土衬砌受力特性数值分析方法，为隧道与地下工程混凝土衬砌结构耐火性能研究提供分析工具。此外，开发了一种具有高力学性能、高延性、表面保护功能、可持续等优势的应变硬化水泥基复合材料（Strain Hardening Cementitious Composite，简称SHCC），其用于损伤隧道混凝土衬砌加固，可以显著提高衬砌结构的承载能力及耐久性。在研究混凝土衬砌既有裂缝引起SHCC加固层延性变化机理、SHCC加固混凝土衬砌剪力传递机理基础上，形成用于分析SHCC加固混凝土衬砌受力性能的精细化数值方法。本项目的完成有助于推动隧道与地下工程混凝土衬砌结构耐火性能提升。