乔家山隧道粘土岩大变形及支护结构稳定性分析

Study on Large Deformation of Claystone and Support Stability in Qiaojiashan Tunnel

在大西客运专线乔家山隧道粘土岩地层前期施工中,支护结构出现大变形现象和混凝土开裂。为了寻求粘土岩地层隧道的有效支护方案,采用室内外试验对粘土岩物理特性展开了调查。物相分析和微观结构试验结果表明,该粘土岩中含有较多的片状粘土矿物绿泥石和伊利石,致使现场围岩具有流变特性。针对围岩流变大变形,优化调整了支护结构参数。选取典型断面进行支护结构内力监测,结果表明,初期支护钢拱架和二次衬砌混凝土基本上呈受压状态,钢拱架均有部位压应力达到或接近于钢材的屈服强度。然而,在初期支护强度充分发挥基础上,及时施做二次衬砌。二次衬砌受力较小,有效地保证了粘土岩地层的隧道结构安全。本研究可望为粘土岩地层隧道设计和施工提供借鉴,具有一定的工程应用价值。

There were large deformation and concrete crack appeared during the initial construction for Qiaojiashan Tunnel. To obtain effective support design in the claystone ground of the tunnel,the physical properties of the claystone were investigated by laboratory and field tests. The investigation of mineral and microstructure of the claystone indicated that there were a lot clay minerals,mainly including chlorite and illite,resulting in a creep behavior of adjacent rock. The parameters of tunnel support were optimized due to the creep behavior of the rock. The internal forces in the support were monitored in several typical cross-sections of the tunnel,indicating that the whole primary and secondary supports were compressed basically. The compression pressure of steel arch reached to or very close to its yield strength for the primary support. However,the stress in secondary supports was little,thanks to the timely construction of secondary support after the primary support reached its strength,and the safety of tunnel support in the claystone ground was ensured. This study can be referenced for design and construction of tunnels in claystone ground.