地铁盾构隧道内径扩增对结构抗变形能力影响研究

Influence of Inner Diameter Enlargement of Metro Shield Tunnel on Anti-deforming Capability

隧道内径扩增是盾构隧道工程的发展趋势,而内径扩增后的管片抗变形能力仍值得探讨。基于南京地铁9号线工程,通过几何相似比为1∶10的模型试验,研究内径由5.5 m扩增至5.8 m对隧道结构抗变形能力影响,并提出内径扩增后的管片厚度优化建议。结果表明,正常加载阶段内,管片的收敛变形、应变和拱顶弯矩近似线性变化且增速较低,而在超载阶段内则均表现为非线性迅速增加;管片内径增大导致其整体变形、局部应变和弯矩均增大,且在超载阶段内尤为明显,使管片处于偏不利的受力状态,深埋条件下管片内径由5.5 m扩增至5.8 m导致其水平、竖向收敛值均增大了14.94%;增大管片厚度可有效控制收敛,尽管导致结构弯矩和偏心距增大,但最大结构拉应变/应力下降,在控制变形方面有较好的效果,也使管片整体处于更安全的受力状态。

The increase in the inner diameter of the tunnel lining is an indisputable development trend in shield tunnel engineering. By now, the structure size optimization of the lining segment after its inner diameter enlargement is still a subject to be explored. Based on the project of Nanjing Metro Line 9, the variation of the anti-deforming capability of the lining structure after its inner diameter expanded from 5.5 m to 5.8 m is studied through model tests with a geometric similarity ratio of 1: 10. Considering the condition of surcharge, the optimization of the segment’s thickness after the inner diameter enlargement is also discussed. The test results show that the convergence deformation, strain and bending moment of the segment approximately grow linearly and slowly during the normal step loading, and they grow nonlinearly and rapidly in case of overloading. The increase of the inner diameter of the lining leads to the increase of the convergence deformation, strain, and bending moment, especially during the surcharge stage, which renders the lining segment into an adverse stress state. The convergence can be effectively reduced by increasing the lining’s thickness, which, though, increases bending moment and eccentric distance of the structure, but its maximum surface tension strain/stress decreases, resulting in effective deformation control and safer stress state of the lining segment.