火灾中混合温场下隧道管片受力分析

对于以盾构方式修建的地铁，其隧道管片是主要的受力构件。在实际的火灾中，管片所在的温场往往是热对流及热辐射两种形式的混合温场。不同位置管片受热不均匀，整周管片内部将产生非均匀的热力荷载，与地应力荷载共同作用使模型中的应力分布更为复杂。从热量的角度进行温场融合，分别计算每个单元在两种温场下的温度及热量，将每个单元的两种热量分别相加求得每个单元的总热量，根据总热量再反算单元温度，从而确定这个混合温场。使用FLAC3D在模拟过程中随温度升高实时调整材料参数，使模拟结果更加准确。结果表明：当温度较低（〈500℃）时混合温场中以热辐射为主的均匀温场势力较强，当温度升高（〉500℃）后以热对流为主的非均匀温场势力较强。

Internal forces analysis for tunnel segment under fire in mixed temperature field

The tunnel segment of the shield construction subway is the main hearing structure. In the actual fire, the segment is often subject to heat convection and thermal radiation, which correspond to two kinds of temperature fields. In such temperature fields, the circle segments will produce non-uniform thermal load, as well as the ground stress load, which causes complex stress distribution. The two temperature fields are integrated in consideration of heat. The temperature and heat of each unit are calculated respectively in the two kinds of temperature fields. The two kinds of heat of each unit are summed up to obtain the total heat, by which the integrated temperature field is calculated inversely. FLAC3D is used to simulate the stress distribution and deformation characteristics of the segment. Since the material properties depend on the temperature, the parameters are adjusted real-timely to achieve more accurate simulation results. The results show that for lower temperatures （〈 500 ℃）, the integrated temperature field is uniform, mainly dominated by the thermal radiation, while for higher temperatures （〉 500 ℃）, the integrated temperature field is non-uniform, mainly dominated by convection.