摘要
目前专门针对隧道初期支护的结构设计并未形成规范,实际施工过程中初期支护拱架参数的选择主要依赖于以往的施工经验,涉及到结构计算也往往将拱架简化为理想单轴杆件。为提供初期支护拱架的精细化设计理论基础,整理了常见初期支护拱架的结构形式,给出了三弦、四弦格栅拱架以及型钢拱架的常用几何参数;通过建立拱顶沉降与围岩压力的关系,提出了初期支护拱架支护刚度的概念;充分考虑拱架锁脚的约束作用,建立了均布向心荷载作用下的无铰拱模型、两铰拱模型;分析了两种模型中初期支护拱架的失稳机理,给出了无铰拱架、两铰拱架模型的稳定系数确定方法,认为其临界荷载可以作为拱架系统稳定性的判据;在此基础上解析了Pratt型和Warren型两种格栅拱架基本布置方式中斜腹杆对拱架抗压刚度、抗弯刚度的影响。从研究成果可以看出,相对于理想状态,在充分考虑格构单元剪切形变时,格栅拱架的支护临界荷载有所下降;建立“8”字结钢筋的力学结构模型,对其受力进行分解投影,进而给出针对无弦杆交叉格构单元的轴压刚度、抗弯刚度以及剪切刚度的计算方法。通过工程案例的数值仿真计算认为解析公式能够较为准确地计算支护拱架的失稳荷载与支护刚度。
By now,no standard has been established for structural design of initial support of tunnels.During actual construction,selection of the parameters of initial support arch mainly relies on previous construction experience,and the structural calculation often simplifies the arch as an ideal uniaxial member.In order to provide the theoretical basis for fine design of the initial support arch,the common structural forms of initial support arch are gathered in this paper,and the common geometric parameters of three-string and four-string lattice girder and section steel arch are presented.After the relation between crown settlement and surrounding rock pressure is established,the concept of support rigidity of initial support arch is proposed.With the restraining action of arch feet lock adequately considered,the hingeless arch model and two-hinged arch model under the action of uniform centripetal load have been built.The instability mechanism of initial support arch in the two models has been analyzed,and the method to determine the stability factor of hingeless arch and two-hinged arch has been given;it is believed that the critical load can be used as a criterion for determining the stability of arch system.On this basis,how the diagonal web member will affect the compressive stiffness and flexural stiffness of arch in the basic configuration of Pratt type and Warren type lattice girders has been analyzed.As the results suggest,compared with the ideal state,when the shear deformation of lattice unit is considered,the critical load of the support with lattice girder decreases.The mechanical structural model of steel reinforcement with"8"-shaped knot has been built,decompositional projection of the forces on the structure has been conducted,and the methods to calculate the axial compressive stiffness,flexural stiffness and shear stiffness of the crossed lattice unit of chord-free member has been put forth.After numerical simulation and calculation of engineering cases,it is believed that the analytic formula can be used to accurately calculate the destabilization load of support arch and the arch stiffness.The study results are helpful for scientifically understanding the bearing characteristics and stability of initial support of tunnel,and are valuable reference for selection and operation of initial support structure.
作者
孙毅
SUN Yi(China Railway 16th Bureau Group Co.,Ltd.,Beijing 100018)
出处
《现代隧道技术》
CSCD
北大核心
2023年第3期34-43,共10页
Modern Tunnelling Technology
基金
国家自然科学基金高铁联合基金重点支持项目(U1934210).
关键词
隧道工程
格栅拱架
型钢拱架
承载特性
稳定性
Tunnel works
Lattice girder
Section steel arch
Bearing characteristics
Stability
