京张高铁东花园长大明挖隧道衬砌结构变形特征研究

为解决长大明挖高铁隧道施作衬砌结构时养护不充分、拆模较早等引起的衬砌结构容易裂缝问题,防止衬砌结构在自重应 力作用下对隧道运营期的防水及结构安全造成影响,基于京张高铁东花园长大明挖隧道工程,采用有限元分析和在衬砌结构典型 断面上的拱肩、拱腰不同位置布设钢筋计、混凝土应变计、土压力计、表面应变计,对衬砌结构的内力变形进行现场监测。分析得 出: 衬砌结构容易出现塑性应变的位置是拱腰处大于拱肩处,裂纹均出现在1/2 截面附近的矮边墙以上及起拱线以下位置,且均为 环向裂纹;对于矮边墙以上、起拱线以下的混凝土来说,其降温产生的收缩变形会受到矮边墙钢筋剪力的约束,使其不能发生水平 位移。最后,给出控制衬砌结构受力变形和加快施工进度的建议。

Deformation Characteristics of Lining Structure of Long-and-Large Open-cut Donghuayuan Tunnel on Beijing-Zhangjiakou High-speed Railway

The lining structure is prone to cracks due to insufficient maintenance and early demoulding of the lining structure of large open-cut high-speed railway tunnel. In order to prevent the lining structure from affecting the waterproofing and structural safety of the tunnel during the operation period under the effect of dead weight stress, finite element analysis and site monitoring are carried out by setting bar gauges, concrete strain gauges, earth pressure gauges and surface strain gauges on arch shoulders and haunch of typical cross-section of lining structure of long-and-large opencut Donghuayuan Tunnel on Beijing-Zhangjiakou High-speed Railway. The analytical results show that: (1) The plastic strain is easier to occur on arch haunch than arch shoulder of lining structure, the cracks appear above the short side wall near the one-half cross-section and the arch line, and the cracks are circumferential ones. (2) For the concrete above the low side wall and below the arch line, the shrinkage deformation caused by the cooling will be restricted by the shear force of the low side wall steel bar, which would not lead to horizontal displacement. Finally, suggestions for controlling the deformation of the lining structure and shortening the construction schedule are provided.