大直径盾构铁路隧道火灾温度荷载及结构内力特性研究

Study on Temperature Loads and Structural Internal Force Characteristics of Large-diameter Shield-driven Railway Tunnels in a Fire Scenario

为了得到大直径铁路盾构隧道非均匀火灾场景下的温度荷载及结构内力特性变化规律,文章首先运用火灾动力学软件FDS建立考虑火区通风的列车火灾模型,研究衬砌受火面温度荷载分布;其次通过有限元软件ANSYS建立考虑内部结构的热力耦合模型,着重研究隧道衬砌及内部结构的变形、温度分布以及内力变化。结果表明:考虑火区通风的单洞双线铁路隧道列车着火为非均匀火灾场景,火灾温度荷载(20 MW)最高不超过500℃,受火120 min后,受火面衬砌混凝土最高温度达到256℃;火灾工况下隧道拱顶及底部的竖向位移较非火灾工况均减小,结构水平方向的位移略微增大,轨道板的竖向位移减小,结构部分截面的内力发生较大变化,最大增幅接近1倍;衬砌受火面截面呈现出复杂的应力状态,在温度影响的局部范围内存在较大的温度应力。

In order to obtain the change laws of the temperature load and structural internal force of a large-diameter shield-driven railway tunnel in uneven fire scenarios, first, using the software FDS the train fire model with ventilation in the fire area considered is established to research the distribution of temperature loads on the fired lining surface. Then using the software ANSYS the thermal mechanical coupling model with internal structure considered is established to focus on researching the deformation, temperature distribution and internal force change of the tunnel lining and internal structure. The results show that the fire occuring to the train in a single-tube double-track railway tunnel with ventilation in the fire area considered is an uneven fire scenario where the fire temperature load is at most 500 ℃ and the highest concrete temperature of the fired lining surface is up to 256 ℃ after being exposed to fire for 120 m. The vertical displacements of tunnel vault and bottom in fire conditions are smaller than those in non-fire conditions, the horizontal structural displacement increases slightly while the vertical displacement of track slab decreases, and the internal force of the partial structural sections changes significantly with maximum increase being nearly 1 times. The sections on the fired lining surface present a complex stress status with larger temperature stress in the local range influenced by the temperature.