基岩软化条件下仰拱结构疲劳寿命的预测分析

Fatigue life prediction of tunnel base structure under the softening surrounding rock conditions

由于隧道施工期间扰动及重载列车荷载的长期循环作用,造成底部基岩出现一定范围的软化和围岩力学参数降低,引起拱底围压的不均匀分布,并影响基底结构的疲劳寿命。通过引入重载列车振动荷载函数和Miner线性累积损伤理论,建立了考虑基底软化仰拱结构疲劳寿命的预测方法,研究列车振动荷载作用下基底软化因素对铁路隧道底部结构疲劳寿命的影响。计算结果表明:在基岩不同软化条件下,隧道底部结构动应力响应分布规律相似,隧道底部结构各部位动拉应力和动压应力增幅较大,仰拱结构疲劳寿命明显减小。隧道底部结构仰拱中心处出现拉应力最大值,仰拱与边墙连接处出现压应力最大值。在仰拱结构的应力计算结果的基础上,结合混凝土疲劳寿命原理,论述了基底软化条件下隧道底部结构疲劳寿命预测值。

Due to the tunneling construction disturbance and the long-term cyclic heavy haul train loading, the softening of the surrounding rock will appear at the bottom of the tunnel. The softening and the stress distribution of the loose surrounding rock will affect the fatigue life of the tunnel base structure. In the article, the softening of surrounding rock at the bottom of heavy-haul tunnel is introduced into the fatigue life analysis and dynamic response of the base structure by using the finite ele- ment method. Based on the vertical load induced by train vibration and the linear cumulative damage theory, the fatigue life prediction of the tunnel base structure is established to study the influence of the bed situation on the force status of railway tunnel base structure. The results show that the distributions of dynamic responses of the base structure are similar under dif- ferent surrounding rock conditions. With the increase of softening distance and softening extent, the tensile stress and pressure stress amplitude of the base structure increases, and the fatigue life of the base structure reduces greatly. The maximum value of tensile stress emerges at the center of the invert, so does the compressive stress at the junction of the sidewall and invert. According to the fatigue life principle and the stress data, this paper discusses the prediction methods of the fatigue life time of tunnel base structure under the softening surrounding rock conditions.