火灾下盾构隧道衬砌结构受力与抗火措施模拟分析

Simulation Analysis of the Forces on Lining Structure of Shield Tunnels and Fire Resistance Measures during Fire

以甬舟铁路金塘海底隧道为工程背景,采用数值模拟手段分析RABT标准升温曲线下盾构隧道衬砌结构受火后的应力、变形以及劣化情况,研究火灾高温下大直径盾构隧道管片衬砌结构的耐火性能以及抗火措施。结果表明,在RABT升温曲线下受火120 min后,混凝土衬砌受火面处最高温度达到1119℃,衬砌结构无法满足抗火设计要求;混凝土衬砌在受火5.3 min时开始劣化,且随着受火时间增加破坏区继续发展,受火结束时最大劣化深度超过12 cm;受火结束时,隧道竖向和水平方向净空收敛量较受火前均有所减小,减小量绝对值分别为11.5 mm、0.12 mm;设置管片混凝土耐火层、设置防火板以及施作防火涂料3种措施均能较好地提高衬砌结构的抗火性能,综合考虑实际工程适用性等因素,建议采用8 cm及以上厚度的C40混凝土耐火层或导热系数小于0.15 W/(m•K)的防火涂料。

As for the Jintang Subsea Tunnel on Ningbo-Zhoushan Railway,the numerical simulation method is used to analyze the stress,deformation and deterioration of shield tunnel lining structure induced by fire under the RABT standard heating curve,and to investigate the fire resistance of segmental lining structure of large-diameter shield tunnel under high temperature of fire and the fire resistance measures.As the results suggest,after 120 min of exposure to fire under the RABT heating curve,the fire heated surface of concrete lining reaches 1,119℃,so the lining structure cannot meet the fireproofing design requirements;the concrete lining starts deterioration after 5.3 min of exposure to fire,the failure zone continues expanding as the duration of fire increases,and when the fire stops,the maximum deterioration depth is greater than 12 cm;in addition,when the fire stops,the clearance convergence of the tunnel in both vertical and horizontal directions decreases as compared with that before the fire,and the absolute value of the decrease is 11.5 mm and 0.12 mm respectively;the 3 techniques,i.e.installing concrete refractory layer on segments,installing fire board and applying fire-resistant coating,will effectively enhance the fire resistance of the lining structure,but with comprehensive consideration of the factors such as suitability in practical engineering,it is recommended to use the C40 concrete refractory layer with≥8 cm thickness or the fire-resistant coating with thermal conductivity<0.15 W/(m·K).