公路隧道喷射混凝土套拱加固结构力学特性

Mechanical Characteristics of Shotcrete Arch Reinforcement Structure in Highway Tunnel

为研究喷射混凝土套拱加固前后二次衬砌与混凝土套拱的受力状况,依托陕西汉中至留坝段八里关隧道,运用有限元软件建立隧道混凝土结构套拱加固分析模型,并通过现场监测获取二次衬砌与套拱间的接触压力、套拱格栅拱架钢筋应力、套拱混凝土应力,将数值模拟结果与现场测试结果相结合,得出套拱结构的一般受力变化规律。结果表明:套拱加固前衬砌结构的最不利荷载位置位于施工缝附近的拱顶、拱肩与拱脚处;由于衬砌局部变形与温度应力的影响,套拱混凝土应力变化呈现反复“上升—下降—上升”最后趋于稳定的特点;套拱的作用是控制二次衬砌的进一步变形,套拱施作后所承受荷载较小,套拱反作用力远小于围岩作用于衬砌的应力,在应力计算中不应将衬砌与套拱作为整体计算;套拱结构数值模拟所得的结果与现场测试套拱结构内力(轴力、弯矩)的大小及分布相似度高,但在衬砌裂损严重部位,数值模拟所得结果误差较大,应以现场测试结果为准。

In order to understand the stress state of secondary lining and concrete arch before and after shotcrete arch reinforcement,based on the Baliguan tunnel from Hanzhong to Liuba in Shaanxi Province,the analysis model of the concrete structure of the tunnel concrete structure arch reinforcement was established by using the finite element software.Through field monitoring,the contact pressure between the secondary lining and the arch sleeve,the steel bar stress of the grid arch frame and the concrete stress of the arch were obtained.Combining the numerical simulation results with the field test results,the general stress variation law of the arch structure was obtained.The results show that the most disadvantageous load position of lining structure is located at the vault,arch shoulder and arch foot near the construction joint.Due to the influence of local deformation of lining and temperature stress,the change of arch stress presents the characteristics of“rise-drop-rise”and finally tends to be stable.The function of the arch sleeve is to control the further deformation of the secondary lining,and the load on the arch after construction is small.The reaction force of arch is far less than the stress of surrounding rock acting on lining,so the lining and arch should not be considered as a whole in stress calculation.The results of numerical simulation are similar to the distribution of the internal forces(axial force and bending moment)of the structure.The results of numerical simulation have a large error in the parts with serious lining cracks,so the field test results should be taken as the criterion.