盾构隧道衬砌结构计算若干问题研究与探讨

Research and Discussion of Several Issues on Structural Calculation for Shield Tunnel Lining

研究目的:目前广泛应用的盾构隧道衬砌结构计算方法中,衬砌结构单元长度划分和衬砌单元四周约束弹簧的作用形式比较随意,将地面超载直接施加在衬砌结构上,忽略了地面超载在应力转变过程中的折减,因此需要提出明确的单元长度划分原则与弹簧作用方式,并根据地面超载的作用机理与影响程度,提出相应的理论计算方法。研究结论:(1)衬砌结构单元长度对结构内力计算结果影响不大,但相对精细的衬砌单元有利于得出更加准确的计算结果;(2)可采用水平向与竖向弹簧取代法向与切向弹簧,实现与地勘报告相对应的弹簧参数取值;(3)地面超载可根据松弛土压力或塌落拱高度折减,并提出了相应的荷载折减系数,指出了超载对衬砌内力的影响与其荷载水平正相关;(4)应根据局部超载作用范围及其与隧道间的相对位置关系,以及荷载在地层中的应力扩散角综合确定其对衬砌结构内力的具体影响,提出了不同范围局部超载作用下的衬砌结构附加荷载计算模型;(5)该研究结论可为正确的地下隧道工程结构计算模型与计算理念提供借鉴与指导。

Research purposes： As for the popular methods adopted in structure calculation for shield tunnel lining, random size division of lining element and random function mode of constraint spring acted on lining are always found. And ground overload are always directly applied on shield lining without considering stress reduction during its transformation process. So, concrete principle of lining element division and the function mode of ground spring should be put forward, and corresponding calculation theory should be put forward based on the mechanism and influences of ground overload. Research conclusions：Form the study, it is concluded：（ 1 ）Little influences on lining stresses for different element length. Relatively fine lining element division is beneficial to lead a more accurate result. （2）The normal and tangential spring can be substituted by horizontal and vertical spring, then the spring value can be corresponded with geology survey report. （3）Ground overload can be proportionally reduced based on the loosed earth pressure or earth pressure arch, and the reduction factor is put forward correspondingly. Then, the positive relationship between ground overload and lining stress is made clear. （4） The scope of local ground overload and its relative positional relationship with tunnel, and the diffusion angle of ground overload should be considered together for the determination of the concrete influences on lining stresses. And different lining structure calculation models based on different scope of additional ground overload are put forward correspondingly. （5）This study can lead a reference for the calculation model and calculation theory in underground engineering.