盾构竖井垂直顶升作用下隧道变形响应及控制

Deformation Responses and Control of Tunnel under Shield Shaft Vertical Jacking

研究目的:为揭示盾构竖井垂直顶升过程隧道变形响应特征,研制盾构隧道内垂直顶升工艺的模型试验装置,开展顶升过程试验研究,探索顶升阶段上覆土层的合理破坏范围、所需顶升反力及隧道变形规律。借助有限元法分析盾构竖井垂直顶升阶段隧道的变形,与试验结果对比分析,并讨论隧道变形对不同加固方案的敏感性,提出隧道变形合理控制思路。研究结论:(1)垂直顶升阶段上覆土层破坏特征不遵循现有研究的经验假定,现有研究对上覆土层破坏机理和形态的认识存在不足,提出的顶升力经验计算法也存在明显误差;(2)顶升反力作用使管片环缝外侧张开及剪切错动,纵缝内侧张开,管片纵向特性受顶升反力的影响更大;(3)开口环用特殊管片可减小张开量,但加剧了环间剪切错动趋势,实际工程不适合用特殊管片;(4)管片变形与环缝接头刚度呈反向非线性关系,刚度增大5倍后变形趋于稳定,实际工程仅需增大环间底部接头刚度;(5)管片外侧注浆加固能有效抑制顶升施工诱发的隧道变形,合理加固范围为管片底部30°,现有成果提出环向120°或全周加固不妥,造成浪费且增加了施工风险;(6)本研究成果可为盾构竖井垂直顶升施工法的应用和推广提供借鉴和参考。

Research purposes:In order to reveal the deformation response characteristics of the tunnel during the vertical jacking process of the shield shaft,the vertical jacking model test device was developed,and the jacking test was carried out to explore the reasonable damage range of overburden soil,the jacking reaction force and the tunnel deformation law in the jacking stage.The finite element method is used to analyze the deformation of the tunnel in the vertical jacking stage of the shield shaft,and the results are compared with the test results.The sensitivity of tunnel deformation to different reinforcement factors is discussed,and the idea of tunnel deformation control is proposed.Research conclusions:(1)The failure characteristics of the overlying soil layer in the vertical jacking stage do not follow the empirical assumption of the existing research,and the understanding of the failure mechanism and shape of the overlying soil layer in the existing research is insufficient,and the empirical calculation method of the jacking force proposed also has obvious errors.(2)The jacking force causes the outer opening and shear dislocation of the segment circumferential seam,and causes the inner opening of the longitudinal seam,and the longitudinal characteristics of the segment are more affected by the jacking force.(3)The opening amount can be reduced by using special segment in the open ring,but the shear dislocation trend between rings is aggravated,and the special segment is not suitable for practical engineering.(4)The deformation of the segment is inversely nonlinear with the stiffness of the ring joint,and the deformation tends to be stable when the stiffness increases by 5 times.In practical engineering,only the stiffness of the bottom joint between the rings is increased.(5)The grouting reinforcement outside the segment can effectively inhibit the tunnel deformation induced by the jacking construction,and the reasonable reinforcement range is 30°at the bottom of the segment.The existing results suggest that the circumferential reinforcement of 120°or all-round reinforcement is unreasonable,which causes waste and increases the construction risk.(6)The research results can provide reference for the application and promotion of vertical jacking construction method of shield shaft.