In both design and research, the model configuration of an isolated concrete segment working under the solely action of longitudinal jack forces is generally adopted as representative of the most onerous loading scenario borne by the segments of concrete segmental linings (CSLs) during tunnelling. The influence of TBM transverse actions, i.e. tail seal pressures and the transverse component of jack forces, on the ring deformations and structural damage typically recorded on site during the tail seal passage is thus systematically overlooked. In this paper, the segment interactions and stress concentrations experienced by the last erected ring, which is subjected simultaneously to the TBM ram loads and the advance of the sealing pressures, are analysed in detail via a suite of multiring finite element (FE) models. In this first part, the axisymmetric scenarios representative of concentric tail seal passage are examined. Non-axisymmetric scenarios are discussed in the second part. It was found that during the axisymmetric TBM advance, the segments rotate radially, i.e. about their tangential axis. Regardless of the cause of rotation, the maximum in-plane angularities, gasket gaps and gasket offsets in the longitudinal joints exhibit a strong linear correlation with the peak rotations and can become excessive under unfavourable loading or irreversible with joint plasticisation. The wider side of the keystone joints is the most critical area for groundwater leakage. The sealing pressures can increase spalling stresses at the packer extrados by 50% and hoop spalling stresses at the ram pad interspaces by threefold. The rear corners of the rotated segments are susceptible of radial bursting and shear failure in either convex-convex longitudinal joints or when differential radial rotations are very pronounced. The keystone joints can also undergo non-radial spalling at the rear of their bearing surfaces. Based on the numerical outputs, guidelines for tunnelling operations and joint design are provided.

在设计和研究中，单独在纵向千斤顶力作用下工作的孤立混凝土管片的模型配置通常被用作隧道开挖过程中混凝土管片衬砌（CSL）管片所承受的最繁重载荷情况的代表。因此，TBM 横向作用（即尾封压力和千斤顶力的横向分量）对尾封通过期间通常在现场记录的环变形和结构损坏的影响被系统地忽略了。在本文中，通过一套多环有限元 (FE) 模型详细分析了最后一个竖立的环所经历的段相互作用和应力集中，该环同时受到 TBM 冲压载荷和密封压力的提高。在这第一部分，检查了代表同心尾密封通道的轴对称场景。非轴对称场景将在第二部分讨论。发现在轴对称 TBM 推进期间，段径向旋转，即围绕它们的切线轴。不管旋转的原因如何，纵向接头中的最大平面内角度、垫片间隙和垫片偏移与峰值旋转具有很强的线性相关性，并且在不利载荷下可能变得过大或在接头塑化时不可逆转。基石接缝较宽的一侧是地下水渗漏的最关键区域。密封压力可使封隔器外背处的剥落应力增加 50%，并使闸板垫间隙处的环向剥落应力增加三倍。旋转节段的后角在凸-凸纵向接头中或当径向差异旋转非常明显时容易发生径向破裂和剪切破坏。梯形接头的支承面后部也可能发生非径向剥落。根据数值输出，提供了隧道施工和接头设计的指南。