TBM隧洞管片衬砌受力与连接螺杆的必要性研究

Stress Analysis of Segmental Lining with or without Connecting Screws

结合某TBM有压引水隧洞,建立了包含管片衬砌与外部围岩的三维数值计算模型,运用有限元法模拟分析衬砌在不同工况下的应力和变形特性,探索使用连接螺杆的必要性。结果表明:施工完建期在开挖释放荷载和豆砾石灌浆压力单独作用下螺杆对衬砌的受力影响甚微;运行期在内水压力作用下,采用螺杆的方案衬砌环向拉应力较大且在与螺杆连接位置处出现局部应力集中。未采用螺杆的方案使得管片衬砌具有柔性结构的特征,承担的内压较小因而环向拉应力较小,表明螺杆对衬砌的环形拉应力不利。未采用螺杆的接缝处最大张开位移由原来的0.635 mm增加为0.731 mm,表明螺杆对于减小接缝处张开位移有利。基于接缝处张开位移不大于4 mm即可满足要求,具有较高的安全裕度,螺杆的优势不明显。鉴于此,从螺杆的不利角度出发,建议螺杆在管片安装期间完成功能后放松螺杆连接,以避免管片局部被动拉裂而影响结构整体的安全性。

A three-dimensional numerical model is established for a pressure diversion tunnel by TBM, in which the seg- mental lining and surrounding rocks are simulated. Then, finite element stress and deformation analyses of the segmental lining under different working conditions are carried out. Effect of the connecting screws are also studied. Results show that during the completion period, connecting screws are of little effect on the stress of segmental lining under the exca- vation released load and the grouting pressure in surrounding pea gravels. During the operation period when the tunnel is subjected to internal water pressure, the circumferential tensile stress of screw-connected lining is larger and local stress concentrations are observed at the lining-screw connection points. While the lining without connecting screws shows a flexible structural characteristic, which bearing a smaller internal pressure and thus of smaller circumferential tensile stress. It indicates that the connecting screw is of negative effect in respect of lining stresses. On the other hand, the maximum opening displacement in the lining joints increases from 0. 635 mm to 0. 731 mm for non-screw lining, showing that the screw is helpful in reducing the opening displacement. But the effect is rather small. It suggests that the con- necting screws should be released after the lining segment installation to avoid the screw-induced tensile cracks in lining segments which may affect the overall safety of the structure.