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为探明铁路隧道基底刚度对仰拱混凝土疲劳损伤的影响,研制了一种可变换基底刚度并模拟仰拱力学环境的加载装置,结合MTS疲劳试验机进行了仰拱混凝土疲劳损伤的试验研究,揭示了静动载耦合作用下隧道仰拱混凝土的疲劳损伤机理,构建了引入抗力系数的仰拱混凝土疲劳损伤计算模型,阐明了基底刚度对仰拱混凝土动态应变特征及疲劳损伤的影响程度.结果表明:隧道基底刚度对仰拱混凝土疲劳损伤和累积应变增长影响显著;随着基底刚度的降低,混凝土动应变及损伤值快速增长并发生疲劳破坏;混凝土损伤演化曲线与动应变曲线相似,均具有明显的三阶段变化特征;基于疲劳损伤拟合公式和抗力系数表达式,量化了基底刚度对混凝土疲劳损伤的影响程度;均布弹簧基底有利于混凝土抗疲劳性能的提高,其疲劳寿命约为三点弯折条件下混凝土疲劳寿命的10倍.
In order to find out the effect of basement stiffness of railway tunnel on the fatigue damage of inverted arch concrete, a loading device that can change the stiffness of the basement and simulate the mechanical environment of the inverted arch was developed. The fatigue tests of the inverted arch concrete were carried out with MTS fatigue tester. The fatigue damage mechanism of inverted arch concrete under static and dynamic loads was revealed, and the fatigue damage calculation model of inverted arch concrete with introduced resistance coefficient was established, and the effect of base stiffness on the dynamic strain characteristics and fatigue damage of inverted arch concrete was demonstrated. Results The results show that: the stiffness of tunnel foundation has a significant influence on the fatigue damage and cumulative strain growth of inverted concrete; the dynamic strain and damage value of concrete rapidly increase and fatigue damage occurs with the decrease of the stiffness of foundation; the evolution curve of damage of concrete is similar to that of dynamic strain curve Obvious three-stage variation characteristics; based on fatigue damage fitting formula and resistance coefficient expression, the effect of base stiffness on concrete fatigue damage was quantified; the uniform spring base is conducive to the improvement of anti-fatigue performance of concrete, and its fatigue life is about three Point bending conditions of concrete fatigue life of 10 times.