隧道火灾下衬砌结构安全性能研究

【作者】 汪洋；

【导师】 赵望达；

【作者基本信息】 中南大学 ， 防灾减灾工程及防护工程， 2008， 硕士

【摘要】 由于隧道火灾事故的不可避免性和高危险性,隧道火灾研究已引起各方的高度重视。衬砌结构的安全性能是隧道防火的一个重要领域,因此对衬砌结构火灾下安全性能的评定已成为了重要课题。本文参照国内外的火灾案例及试验结果,采用理论分析和数值模拟相结合的方法,对火灾下衬砌结构的安全性能进行了深入研究,自主建立了一套基于数值分析的评定体系。研究内容主要包括:(1)提出根据隧道火灾时的烟气分布规律拟定高温荷载曲线,运用地层结构法建立围岩与衬砌的整体模型,进行有限元求解。在温度场分析结果的基础上,计算温度最高截面的刚度折减,从而判明衬砌烧伤程度。工程实例分析表明拱顶的烧伤最为严重。(2)应用了传统的温度—应力耦合理论,探索了火灾下衬砌结构强度评定的新思路:初始应力场分析→高温应力场分析→高温内力场分析→强度安全系数检算。初始应力场的分析是进行后续分析的基础,内力场可通过对高温应力场的积分获得,强度检算可根据受弯或偏心受压截面进行计算。工程实例分析表明,拱顶是受力最为薄弱的区域,可能出现较大的塑性区域。(3)根据圆拱结构稳定理论,采用有限元法进行非线性屈曲分析。分析中对拱顶截面可能出现的塑性铰区域采用添加一个单向铰模拟,衬砌断面根据等效抗火截面法进行折减。分析采用荷载逐步累加法,直至结构失稳,得出极限屈曲荷载,然后对比火灾下衬砌结构的内力值,判断其稳定性。(4)借鉴一般地面建筑物安全性能的评定方法,提出了火灾下衬砌结构安全性能的评定流程体系,将其应用于苍岭隧道火灾后衬砌结构的安全性能评价中,从衬砌烧伤程度、结构强度、结构稳定性三方面给出了相应的评价结果,为日后该领域的工程咨询评估及科研工作的开展提供了参考。更多还原

【Abstract】 For the ineluctability and high fatalness of tunnel fire accident, the research in tunnel fire has drawn great attention from academia and engineering department. Because the safety of tunnel liner is an important part of tunnel fire-resistant performance, the assessment of liner safety in tunnel fire has become an important task now.According to the fire cases and experiment results, the liner safety in tunnel fire is studied by the method combined with theory analysis and numerical simulation. Based on numerical analysis, the assessment system is established, and carried out using ANSYS according to the engineering case. The main conclusions are as follows:1) The high temperature load curve is studied out according to the distribution rule of smoke in tunnel fire, and the finite element method of temperature field is introduced to establish an integrated model combined with liner and wall rock. Then, on the basis of temperature field result, the stiffness of the highest temperature section is deduced, so as to ascertain the burnt degree of liner. The case simulation indicates that the burnt degree of vault is the most serious.2) The new method of liner intensity assessment is explored according to thermal-mechanical coupling theory: initial stress field analysis→high temperature stress field analysis→high temperature internal force field→the check-calculation of safety factor. The thermal-mechanical coupling analysis should be done after the initial stress field analysis, and then internal force could be calculated through stress integral. The check-calculation of safety factor could be followed with the criterion of section in bonding or eccentric compression. The case simulation indicates that the vault is the weakness of the liner, and plastic deformation occurs seriously.3) Based on the stabilization theory of arch structure, the mathematical model is presented, and the nonlinear finite element buckling analysis method is proposed. A single-orientation hinge is supposed to simulate the plastic hinge of vault section, and the whole liner cross-section could be calculated according to the equivalent fire-resistant section. The load is applied step by step until the structure lost stability to get the buckling load. And then, according the buckling load with the internal force of liner structure in fire, the stability of liner structure is assessment.4) According to the assessment method of ground buildings, the assessment system of liner structure safety performance is proposed, which contains section stiffness, structure strength and structure stability. The system could provide reference for the engineering consultation or assessment and scientific research on the field of tunnel fire-resistant.更多还原