为解决现有基坑上跨开挖诱发既有盾构隧道纵向变形简化解中往往忽略其横截面椭圆化的不足问题，借助两阶段分析法基于修正Mindlin应力解计算开挖卸荷引起的附加应力，并将既有隧道建模为Pasternak地基上的Euler短梁-弹簧模型，同时基于严格的隧道横截面椭圆化参数方程推导其环间接头转动刚度计算公式，提出考虑横截面椭圆化的上跨基坑开挖诱发在役盾构隧道纵向非连续变形差分解。通过2个工程案例对纵向非连续变形差分解的合理性进行验证，并进一步研究隧道环间接头刚度和纵向加固环数对其纵向变形的影响。研究结果表明： 1）纵向非连续变形差分解预测的隧道隆起变形与实测值间具有较好的一致性；忽略隧道横截面椭圆化会导致对其隆起位移和环间张开量的低估以及环间错台量的高估，但当基坑开挖面积较大时，截面椭圆化对隧道隆起位移影响较小，对环间变形影响不变。2）接头转动刚度的增加会减少隧道隆起位移和环间张开量，并增加环间错台量；而接头剪切刚度的增加会减少隧道隆起位移和环间错台量，并增加环间张开量。3）纵向加固能够有效降低上方开挖引起的隧道隆起位移，但加固环数的增加对进一步减少隧道隆起影响有限。

The cross-sectional ovalization of tunnels is often neglected in the analysis of longitudinal deformation in existing shield tunnels caused by the excavation of an overlying foundation pit. The authors propose a discontinuous deformation differential solution that accounts for the influence of cross-sectional ovalization. A two-stage analytical approach is adopted. First, the additional stresses due to excavation unloading are computed using a modified Mindlin solution. The existing tunnel is then modeled as a short Euler-Bernoulli beam on a Pasternak foundation. The rotational stiffness of tunnel joints is derived from a parametric expression considering cross-sectional ovalization. The proposed method is validated through two engineering case studies. Furthermore, the influence of joint stiffness and the number of longitudinal reinforcement rings on the tunnel′s longitudinal deformation is analyzed. The results show that: (1) The proposed solution aligns well with measured tunnel uplift, while ignoring cross-sectional ovalization underestimates uplift displacement and joint opening and overestimates joint dislocation. For large excavation areas, ovalization has a diminished effect on uplift displacement but still significantly affects joint deformation. (2) Increasing joint rotational stiffness reduces uplift displacement and joint opening but increases joint dislocation. Increasing shear stiffness reduces both uplift displacement and joint dislocation but increases joint opening. (3) Longitudinal reinforcement effectively mitigates tunnel uplift due to overcrossing excavation; however, the marginal benefit decreases as the number of reinforcement rings increases.