盾构穿越对圆形风井结构的变形内力影响分析——以南京纬三路过江通道工程盾构穿越梅子洲风井为例

盾构进出工作井是盾构安全施工的关键。以南京市纬三路过江通道工程梅子洲圆形风井盾构穿越为研究背景,建立复杂的大型三维计算模型,对盾构穿越区域采用实体单元模拟、土弹簧释放开挖荷载的特殊模拟方法,首先对盾构破除素混凝土强度的选取进行优化分析,建议采用C15混凝土,既能减小盾构穿越施工的难度,又能保证围护结构的安全稳定;然后对盾构穿越前后风井地连墙、内衬墙和冠梁等重要围护结构的变形和内力变化规律进行了研究分析,盾构穿越前后,地连墙的变形和内力变化很大,最大增幅分别为45%和228%,内衬墙的环向弯矩和竖向最大正弯矩均存在较大变化,环向弯矩最大增幅200%,竖向弯矩最大增幅54%,冠梁的最大环向弯矩变化很大,最大增幅为1 160%。因此,工程设计时应对地连墙、内衬墙和冠梁内力较大区域加强配筋,以保证盾构安全顺利地通过。

Analysis on Deformation and Stress of Ventilation Shaft Influenced by Shield Crossing:Case Study on Meizizhou Circular Shaft of Weisanlu River-crossing Tunnel in Nanjing

Shield departure and reception is one of the most important issues when shield crosses working shaft. In the paper, complex 3D calculation model is established, with shield crossing Meizizhou circular ventilation shaft as background，and numerical simulation is conducted by using solid elements and soil spring releasing excavation load. Firstly, the grade of the plain concrete that the shield will cut is analyzed. Conclusion is drawn that C15 concrete, which can not only decrease the difficulty of shield crossing, but also can guarantee the safety and stability of the retaining structures, should be adopted. Secondly, the deformation and internal forces of the retaining structures, including the diaphragm wall, the inner wall and the ring beam, are analyzed. Conclusion is drawn as follows: Compared to those before shield crossing, the maximum deformation and internal force of the diaphragm wall after shield crossing increase by 45% and 228% respectively, the maximum circumferential moment and the maximum vertical positive moment of the inner wall increase by 200% and 54% respectively, and the maximum circumferential moment of the top beam increases by 1 160%. Therefore, during the design of the works, the reinforcement for the zones of the diaphragm wall, inner wall and top beam with large stress shall be strengthened so as to ensure the successful crossing of the shield.