大直径盾构隧道拼装过程管片力学响应研究

通过对拼装阶段管片衬砌进行荷载分析,建立了管片拼装阶段的有限差分模型,结合佛莞城际铁路狮子洋盾构隧道全断面岩层段的现场实测数据深入研究了管片拼装过程的环向内力响应规律,结果表明：①拼装过程中管片轴力实测值以受压为主,但在拼装初期存在局部受拉的情况,而计算值均为受压状态,弯矩实测值和计算值呈现出明显的正弯趋势;②拼装成环后管片轴力、正弯矩及负弯矩实测最大值分别约为计算值的1.5,1.28和1.36倍;③拼装过程引起管片弯矩的响应较轴力更为敏感;④相邻块拼装对管片轴力和弯矩的影响最显著,其次是F块插入,其他拼装步的影响较小,且距相邻块和F块越近的截面,其内力响应越大;⑤拼装成环后,管片轴力和弯矩计算值与实测值大致沿封顶块径向中轴线对称分布,计算值空间分布的对称性比实测值明显;⑥拼装过程中管片轴力实测最大值达到正常使用阶段梁-弹簧模型计算最大值的43.5%,而最大正弯矩、负弯矩则达到正常使用阶段的188.89%,447.84%,表明全断面岩层段管片拼装过程引起的内力响应显著、管片处于弯矩大而轴力小的不利受力状态,设计和施工应予以重视。

Mechanical response of large-diameter shield tunnels during assembly

Based on loading analysis of shield tunnel segments during the assembly phase, a finite difference model is established for segmental lining structure in assembly stage. The mechanical response of segments during assembling is analyzed regarding the in-situ test results of Shiziyang Intercity Railway Tunnel Project from Foshan to Dongguan. The results show that: (1) The measured values of axial force of segment monitoring section are mainly under compression during assembling process, but in the initial stage of assembling, the local tension exists and the calculated values are under compression. The measured and calculated values of bending moment show obvious positive bending trends. (2) The maximum measured values of axial force, positive bending moment and negative bending moment of segments after the ring is formed are about 1.5 times, 1.28 times and 1.36 times the calculated values, respectively. (3) The response of segment bending moment is more sensitive to assembly process than that of axial force. (4) The adjacent block assembly has the most significant effects on the axial force and bending moment of the segment, and the effects of F block insertion are subordinate. Other assembly steps have less influences, and the closer to the adjacent block and F block, the greater the internal force response. (5) The calculated and measured values of segment axial force and bending moment are approximately symmetrical along the radial central axis of the capping block after assembly, and the symmetry of the calculated values is more obvious than the measured values in the assembly process. (6) During the assembling process, the maximum measured axial force reaches 43.5% of the maximum calculated value of the beam-spring model in the serviceability limit stage, however, the maximum positive and negative bending moments reach 188.89% and 447.84%. It is indicated that the internal force response during assembling process is at a higher level during construction, which makes the segment often in a disadvantageous condition of large bending moment and small axial force when tunneling in full-face rocks. It is rational to pay more attention in design and construction.