隧道二衬结构安全性评估及改进方案

为解决较长段深埋隧道二衬钢筋缺失情况下结构安全性问题,基于破损阶段法理论,运用ANSYS有限元软件建模分析隧道二衬结构受力情况,综合分析隧道埋深、围岩级别、围岩水平竖直荷载、初支二衬荷载分担比,并引入结构抗拉抗压安全系数来评定二衬结构安全状况,计算出隧道断面各点处弯矩值、轴力值,进而得出钢筋缺失段安全系数。以石家庄地区某隧道为例,经计算,钢筋缺失段抗拉抗压安全系数未达到对应规范值(3.6、2.4),抗拉安全系数较全截面钢筋降低70%以上,判定二衬结构安全性不合格。并针对较长隧段二衬结构钢筋缺失问题提出了可靠的处理措施。

Safety Assessment and Improvement Schemes of the Secondary Tunnel Lining Structure

In order to analyze safety problems of the secondary lining of long deep-buried tunnel with steel bars missed,based on the theory of damage stage method,ANSYS finite element software was used to model and analyze the stress conditions of the secondary lining structure.Tunnel depth,surrounding rock level,load sharing ratio of the primary two lining,structural tensile and compressive safety factor were adopted to assess the safety of the secondary lining structure.Bending moment and axial force values at each points of the tunnel section were calculated.The safety factor of the section with steel bars missed was obtained.Taking a tunnel in Shijiazhuang area as an example,after calculation,the tensile and compressive safety factor of the missing steel bar did not reach the corresponding standard value(3.6,2.4),and the tensile safety factor was 70%of the tunnel with full-section steel bars.The safety of the second lining structure was determined as unqualified.Reliable treatment measures were presented for tunnel with reinforcement missed in the second lining structure.