机械法联络通道管片切削下主隧道力学行为研究

Study on Mechanical Behaviors of Main Tunnel during Segment Cutting of Connection Channel by Mechanical Method

为了解机械法联络通道破洞过程中主隧道管片结构响应变化,依托宁波市轨道交通5号线海晏北路站—民安东路站区间工程,采用动力显式有限元法,建立全刀盘三维精细化模型并引入材料累进破坏失效准则,对不同施工阶段下主隧道管片力学行为进行研究,得到了施工初始阶段、预撑阶段及刀盘切削阶段下全切削环和半切削环管片衬砌变形图、弯矩图和轴力图,绘制了主隧道管片在3种切削阶段下应力云图,并与原型管片加载试验结果对比验证了模拟结果的准确性。主要研究结论如下:内支撑体系可为主隧道分担水土压力,有效减小管片整体内力与竖向变形;联络通道破洞后,切削区管片洞口表现出悬臂效应,最大位移位于全切削环洞口下侧,在破洞后应尽快施作强支护加固,限制管片开口处变形进一步发展;刀盘磨削管片过程中,半切削环弯矩变化相对于全切削环具有滞后性,两者均在靠背侧拱腰部位产生弯矩最大值,轴力总体上则从拱腰至拱顶底较为平滑地减小;在切削阶段,管片洞口外壁与靠背侧中部存在应力集中,半切削环与标准环的交界处发生了应力突变,应适当加大钢隔舱管片与普通混凝土管片之间的连接螺栓强度,避免螺栓破坏引起主隧道管片错台。

To investigate the structural response of the main tunnel segments during the mechanical excavation of a connection channel,this study takes the construction project between Haiyan North Road Station and Minan East Road Station of Ningbo Metro Line 5 as a case study.A detailed three-dimensional model of the full cutterhead was established using dynamic explicit finite element method,incorporating material progressive failure criteria.The mechanical behaviors of main tunnel segments at different construction stages were analyzed.The deformation,bending moment,and axial force diagrams of the fully-cut and half-cut segmental linings were obtained for the initial construction stage,pre-support stage,and cutterhead cutting stage.Stress cloud plots for the main tunnel segments under the three cutting stages were generated,and the accuracy of the simulated results was validated by comparing them with the results from prototype segment loading tests.The main conclusions were as follows:the internal support system could alleviate the water and soil pressure on the main tunnel,effectively reducing the overall internal force and vertical deformation of the segments.After the connection channel was excavated,the segment opening at the cutting zone exhibited a cantilever effect,with the maximum displacement occurring at the underside of the fully-cut ring opening.Therefore,it was crucial to implement strong support reinforcement promptly after excavation to prevent further deformation at the segment opening.During the cutterhead grinding process,the bending moment changes in the half-cut ring lagged behind those of the fully-cut ring,with both reaching maximum bending moments at the arch waist on the back side.The axial force generally decreased smoothly from the arch waist to the top of the arch.During the cutting stage,stress concentration occurred at the outer wall of the tunnel segment and the middle of the back side,with a stress mutation observed at the junction between the half-cut ring and the standard ring.It was advisable to enhance the strength of the bolts connecting between the steel interspace segments and the ordinary concrete segments to prevent misalignment of the main tunnel segments due to bolt failure.