隧道初期支护型钢格栅节点受力性能影响研究

初支二衬连拱隧道新型支护体系支护结构中钢架连接节点处为钢架的受力薄弱点,在隧道施工中应加强关注,但是,目前节点连接对于隧道初期支护钢架整体受力性能的影响仍不清楚,需要通过试验进行研究。基于此问题,按照初支二衬连拱隧道初期支护形式设置型钢、格栅分节及不分节四类构件,进行室内加载试验,研究设置节点对初期支护结构的力学性能影响,得到如下结论:设置节点会导致减小结构极限承载力,降低结构的强度、刚度,构件整体性下降;削弱型钢、格栅自身性能,降低型钢、格栅与混凝土间的协同作用,混凝土提前脱离工作;开裂提前,裂缝开裂、构件变形程度加重,构件出现斜拉破坏;对型钢混凝土类初期支护构件的影响要更显著,从结构内部来看,该影响体现在对钢架的影响。

Study on Influence of Mechanical Performance of Steel Grid Joints for Initial Support of Tunnel

In the supporting structure of the new supporting system of the double-arch tunnel with primary support and secondary lining, the joint of the steel frame is the weak point of the steel frame, which should be paid more attention in tunnel construction. However, the influence of the joint connection on the overall mechanical performance of the initial supporting steel frame of the tunnel is still unclear and needs to be studied through experiments. Based on this, four types of structural members, i.e. section steel, grid section and non-section members are set up according to the initial support form of the double-arch tunnel with primary support and secondary lining. Indoor loading tests are carried out to study the influence of setting joints on the mechanical properties of the initial support structure. The following conclusions are obtained: setting joints can lead to:(1) Reduction of the ultimate bearing capacity of the structure, reduction of the strength and rigidity of the structure, and reduction of the integrity of the members.(2) Weakening the self-performance of section steel and grid and reducing the synergistic effect between section steel, grid and concrete separate the concrete from work in advance.(3) The cracking is advanced, the cracking and deformation degree of the components are aggravated, and the components suffer diagonal tension failure.(4) The impact on steel reinforced concrete primary support members is more significant. From the inside of the structure, the impact is concentrated on the steel frame.